CRAT — Certified Rhythm Analysis Technician — Questions and Answers

Question 1: When attaching cardiac monitoring electrodes, which skin preparation step is most important to reduce artifact?

Cleaning and lightly abrading the skin to remove oils and dead cells before electrode placement (Correct answer)
Placing electrodes over hairy areas without preparation
Using cold water to clean the skin
Applying additional electrode gel over the electrode

Correct answer: Cleaning and lightly abrading the skin to remove oils and dead cells before electrode placement

Proper skin preparation by cleaning with an alcohol swab and lightly abrading the skin significantly reduces electrode-skin impedance, improving signal quality and reducing artifact.

Question 2: What is the intrinsic firing rate of the AV node if it serves as the escape pacemaker?

60-100 bpm
20-40 bpm
40-60 bpm (Correct answer)
100-150 bpm

Correct answer: 40-60 bpm

The AV junction has an intrinsic escape rate of 40-60 bpm, slower than the SA node but faster than ventricular escape rhythms.

Question 3: The secondary R wave (R') seen in lead V1 during RBBB represents delayed depolarization of which cardiac structure?

Right ventricle (Correct answer)
AV node
Left ventricle
Interventricular septum

Correct answer: Right ventricle

The R' in V1 during RBBB represents delayed activation of the right ventricle, which depolarizes late after normal left ventricular activation has already occurred.

Question 4: To troubleshoot a wandering baseline artifact on an ECG, which of the following is the LEAST likely to be a corrective action?

Unplugging a nearby fan or cell phone charger. (Correct answer)
Checking that lead cables are not pulling on the electrodes.
Moving electrodes from bony areas to fleshier locations.
Ensuring the patient's skin is clean and dry before electrode application.

Correct answer: Unplugging a nearby fan or cell phone charger.

Unplugging a nearby electrical device is the primary solution for AC (60-cycle) interference, not a wandering baseline. Wandering baseline is typically caused by poor electrode-to-skin contact, patient movement (including breathing), or tension on the lead wires. Therefore, checking skin prep, electrode placement, and cable tension are all appropriate corrective actions.

Question 5: Magnesium sulfate is the treatment of choice for:

Torsades de Pointes (Correct answer)
Junctional escape rhythm
First-degree AV block
Sinus bradycardia

Correct answer: Torsades de Pointes

IV magnesium sulfate is the first-line treatment for Torsades de Pointes because it stabilizes the cardiac membrane and shortens the QT interval.

Question 6: Mobitz type II second-degree AV block differs from Mobitz type I primarily because it has which characteristic?

Constant PR interval with sudden unexpected dropped beats (Correct answer)
Variable PR intervals
Progressively lengthening PR intervals
No visible P waves

Correct answer: Constant PR interval with sudden unexpected dropped beats

In Mobitz type II, the PR interval remains constant and QRS complexes are dropped suddenly without warning, indicating infranodal disease and higher risk of complete heart block.

Question 7: A patient's 12-lead ECG shows ST depression in leads V1 through V4 with tall R waves in V1-V2. Which condition should be suspected?

Right bundle branch block
Hyperkalemia
Posterior wall STEMI with reciprocal changes in anterior leads (Correct answer)
Anterior STEMI

Correct answer: Posterior wall STEMI with reciprocal changes in anterior leads

ST depression with tall R waves in V1-V2 is the mirror image (reciprocal changes) of posterior STEMI — the posterior wall is not directly viewed by standard leads but appears as reciprocal anterior changes.

Question 8: A QRS complex measuring 0.14 seconds is considered:

Wide or abnormal (Correct answer)
Normal
Slightly prolonged
Absent

Correct answer: Wide or abnormal

A QRS duration greater than 0.12 seconds is considered wide and suggests a bundle branch block or ventricular origin.

Question 9: Which heart valve is responsible for preventing the backflow of oxygenated blood from the left ventricle into the left atrium?

Aortic valve
Pulmonary valve
Mitral valve (Correct answer)
Tricuspid valve

Correct answer: Mitral valve

The mitral valve, also known as the bicuspid valve, is located between the left atrium and the left ventricle. Its function is to close during ventricular contraction (systole) to prevent blood from flowing back into the left atrium.

Question 10: What does the ST segment on the ECG represent?

Ventricular filling
AV nodal delay
Atrial repolarization
The period between ventricular depolarization and repolarization (plateau phase) (Correct answer)

Correct answer: The period between ventricular depolarization and repolarization (plateau phase)

The ST segment corresponds to the plateau phase of the ventricular action potential when all ventricular cells are depolarized and no net electrical current flows.

Question 11: A CRAT notices a patient in sustained stable monomorphic VT. After confirming the patient is stable, the next appropriate intervention is:

Immediate unsynchronized defibrillation
Increase IV fluids
Vagal maneuvers
Synchronized cardioversion or antiarrhythmic therapy per protocol (Correct answer)

Correct answer: Synchronized cardioversion or antiarrhythmic therapy per protocol

Stable monomorphic VT is treated with synchronized cardioversion or antiarrhythmics (e.g., amiodarone or procainamide) per ACLS protocol.

Question 12: Aberrant ventricular conduction most commonly produces a morphology resembling which bundle branch block?

Left anterior fascicular block
Left bundle branch block
Bifascicular block
Right bundle branch block (Correct answer)

Correct answer: Right bundle branch block

Aberrant conduction most commonly mimics RBBB morphology because the right bundle branch has a longer refractory period than the left and is therefore more susceptible to rate-related block.

Question 13: The refractory period of the AV node serves which primary function?

Generating the P wave
Initiating spontaneous depolarization
Limiting ventricular rate during rapid atrial arrhythmias (Correct answer)
Conducting impulses faster to the ventricles

Correct answer: Limiting ventricular rate during rapid atrial arrhythmias

The AV node's inherent delay and refractory period act as a gatekeeper, preventing excessively rapid atrial rates from being conducted to the ventricles at dangerous speeds.

Question 14: A CRAT observes an ECG tracing with a thick, uniform, and fuzzy baseline. The interference is regular and consistent across all leads. Which of the following is the most likely cause of this artifact?

Patient shivering
Loose limb electrode
AC (60-cycle) interference (Correct answer)
Patient respiration

Correct answer: AC (60-cycle) interference

AC (60-cycle) interference presents as a thick, uniform, fuzzy baseline caused by electrical noise from nearby equipment or improper grounding. Patient shivering causes somatic tremor, which is more erratic and jagged. A loose electrode typically causes a wandering baseline or intermittent signal loss, and patient respiration causes a slow, undulating wandering baseline.

Question 15: Standard ECG paper runs at which speed?

50 mm/sec
10 mm/sec
25 mm/sec (Correct answer)
100 mm/sec

Correct answer: 25 mm/sec

Standard ECG paper speed is 25 mm/second, making each small box (1 mm) equal to 40 ms and each large box (5 mm) equal to 200 ms.

Question 16: A reentrant arrhythmia requires which three conditions to be established and maintained?

Two SA nodes and an accessory pathway
A closed circuit pathway, unidirectional block in one limb, and slow conduction in the other limb allowing recovery (Correct answer)
Three P waves for each QRS complex
Complete AV block and ventricular escape rhythm

Correct answer: A closed circuit pathway, unidirectional block in one limb, and slow conduction in the other limb allowing recovery

Reentry requires an anatomical or functional circuit with two pathways, unidirectional block in one pathway (impulse cannot go forward but can conduct backward), and slow enough conduction in the alternate pathway that the blocked pathway recovers and can be re-excited.

Question 17: In a patient with Wolff-Parkinson-White syndrome who develops atrial fibrillation, which ECG feature poses the greatest danger?

Rapid conduction over the accessory pathway causing very fast ventricular rates (Correct answer)
Complete heart block
ST segment depression
Prolonged PR interval

Correct answer: Rapid conduction over the accessory pathway causing very fast ventricular rates

In WPW with atrial fibrillation, the accessory pathway bypasses the AV node rate-limiting function, allowing extremely rapid ventricular rates up to 300 bpm that can degenerate into ventricular fibrillation.

Question 18: In the chain of survival, early defibrillation for VF is critical because VF survival decreases by approximately how much for each minute without defibrillation?

7-10% per minute (Correct answer)
50% per minute
15-20% per minute
1-2% per minute

Correct answer: 7-10% per minute

Without defibrillation, survival rates for VF decrease 7-10% for every minute that passes, making rapid defibrillation the most critical intervention after cardiac arrest.

Question 19: A patient in atrial flutter with 2:1 conduction is most likely to show a ventricular rate near which value?

200 bpm
300 bpm
75 bpm
150 bpm (Correct answer)

Correct answer: 150 bpm

With typical atrial flutter at 300 bpm and 2:1 AV conduction, the ventricular rate is 300 divided by 2, equaling 150 bpm.

Question 20: A patient's ECG strip shows a narrow complex tachycardia at a regular rate of 150 bpm. The baseline has a characteristic "saw-tooth" appearance, which is most prominent in leads II, III, and aVF. No clear P waves are discernible. What is the most likely atrial arrhythmia?

Multifocal Atrial Tachycardia
Sinus Tachycardia
Atrial Fibrillation
Atrial Flutter (Correct answer)

Correct answer: Atrial Flutter

Atrial Flutter is characterized by a rapid, regular atrial rate (around 250-350 bpm) that creates a 'saw-tooth' pattern of flutter waves. [1, 9, 25] A 2:1 AV block is very common, resulting in a regular ventricular rate of approximately 150 bpm. [7, 25] Atrial Fibrillation is irregularly irregular with no discernible P waves, Sinus Tachycardia has normal P waves preceding each QRS, and Multifocal Atrial Tachycardia is irregular with at least three different P wave morphologies. [4, 19, 27]

Question 21: New-onset LBBB in a patient presenting with chest pain should be managed as which of the following until proven otherwise?

A sign of stable coronary artery disease
An artifact requiring lead repositioning
A STEMI equivalent requiring emergent reperfusion evaluation (Correct answer)
A benign finding requiring no urgent intervention

Correct answer: A STEMI equivalent requiring emergent reperfusion evaluation

New or presumably new LBBB with chest pain is treated as a STEMI equivalent per ACC/AHA guidelines because it may conceal ST elevation and indicate an acute coronary occlusion.

Question 22: A CRAT at a central monitoring station observes a patient's rhythm abruptly change to a chaotic, disorganized pattern with no identifiable QRS complexes. What is the technician's IMMEDIATE priority?

Check the patient's medical record for a Do-Not-Resuscitate (DNR) order.
Continue to observe the rhythm for 30 seconds to confirm it is not a temporary artifact.
Activate the emergency response system (e.g., call a 'code blue') and notify the nurse. (Correct answer)
Troubleshoot the electrodes to rule out a loose lead.

Correct answer: Activate the emergency response system (e.g., call a 'code blue') and notify the nurse.

The rhythm described is ventricular fibrillation, which is a lethal arrhythmia requiring immediate intervention. The technician's first and most critical responsibility is to activate the emergency response system to bring immediate medical help to the patient's bedside. Delaying this action to check records or troubleshoot equipment could be fatal.

Question 23: In a rhythm strip, you observe regular P waves at 75 bpm and regular wide QRS complexes at 35 bpm with no consistent PR relationship. Which rhythm is present?

Third-degree (complete) AV block with ventricular escape rhythm (Correct answer)
Atrial flutter with variable block
Accelerated idioventricular rhythm
Mobitz type II second-degree AV block

Correct answer: Third-degree (complete) AV block with ventricular escape rhythm

Regular P waves and regular wide QRS at a slow independent rate with no consistent PR interval is the hallmark of complete heart block with a ventricular escape rhythm.

Question 24: Which of the following cardiac arrest rhythms is considered "non-shockable" and is characterized by a total absence of discernible electrical activity on the ECG?

Asystole (Correct answer)
Ventricular Fibrillation
Torsades de Pointes
Pulseless Ventricular Tachycardia

Correct answer: Asystole

Asystole, often called "flatline," is the cessation of all electrical activity in the heart. [4, 7, 10] It is a non-shockable rhythm because there is no electrical chaos to reset; the goal of treatment is to restart electrical activity through high-quality CPR and medications like epinephrine. Ventricular Fibrillation and Pulseless Ventricular Tachycardia are shockable rhythms.

Question 25: Which feature best differentiates a junctional rhythm from a sinus rhythm with first-degree AV block?

PR interval length alone
Heart rate
P wave morphology and axis — junctional P waves are inverted in inferior leads while sinus P waves are upright (Correct answer)
QRS duration

Correct answer: P wave morphology and axis — junctional P waves are inverted in inferior leads while sinus P waves are upright

The key differentiator is P wave direction: sinus rhythm produces upright P waves in II, III, aVF regardless of PR length, while junctional rhythms produce inverted or absent P waves in inferior leads.

Question 26: A patient on anticoagulation therapy develops a new atrial fibrillation. Why is anticoagulation particularly important in this setting?

Anticoagulation improves cardiac output in atrial fibrillation
Anticoagulation prevents atrial fibrillation from recurring
Atrial fibrillation promotes thrombus formation in the left atrial appendage, creating risk of embolic stroke (Correct answer)
Anticoagulation controls the ventricular rate in atrial fibrillation

Correct answer: Atrial fibrillation promotes thrombus formation in the left atrial appendage, creating risk of embolic stroke

In atrial fibrillation, the left atrial appendage loses effective contractile function and blood pools, predisposing to thrombus formation that can embolize to the cerebral circulation, causing stroke.

Question 27: A technician notices a slow, undulating, up-and-down drift of the isoelectric line on a patient's ECG strip. This type of artifact is best described as:

Wandering baseline (Correct answer)
60-cycle interference
AC interference
Somatic tremor

Correct answer: Wandering baseline

A wandering baseline is a low-frequency artifact characterized by the slow drift of the isoelectric line. It is most commonly caused by patient breathing, body movement, or poor electrode-to-skin contact, which alters the electrical impedance at the electrode site.

Question 28: In high-degree AV block with a 4:1 conduction ratio, what is the ventricular rate if the atrial rate is 80 bpm?

20 bpm (Correct answer)
80 bpm
10 bpm
40 bpm

Correct answer: 20 bpm

With a 4:1 AV conduction ratio and an atrial rate of 80 bpm, only 1 in 4 P waves conducts, giving a ventricular rate of 80 divided by 4 = 20 bpm.

Question 29: The ST segment on the ECG represents:

Atrial depolarization
Ventricular filling time
The period between ventricular depolarization and repolarization (Correct answer)
AV node conduction delay

Correct answer: The period between ventricular depolarization and repolarization

The ST segment represents the early phase of ventricular repolarization and is evaluated for elevation or depression suggesting ischemia or injury.

Question 30: Which action by the monitor technician is most appropriate when observing a new sustained run of wide complex tachycardia at 200 bpm in a monitored patient?

Call pharmacy to obtain adenosine
Silence the alarm and wait to see if the rhythm self-terminates
Independently increase the patient's IV fluids
Immediately notify the bedside nurse and document the rhythm strip with date and time (Correct answer)

Correct answer: Immediately notify the bedside nurse and document the rhythm strip with date and time

The monitor technician's critical role is immediate notification of clinical staff and accurate documentation — clinical interventions are the responsibility of licensed nurses and physicians.

Question 31: To ensure electrical safety and prevent microshock to an electrically susceptible patient during ECG monitoring, which of the following is a critical safety feature of the equipment?

Ensuring the lead wires are less than three feet long
A properly functioning three-prong, grounded plug (Correct answer)
Plugging the monitor into a multi-outlet power strip
Using a two-prong plug to avoid ground interference

Correct answer: A properly functioning three-prong, grounded plug

A three-prong, grounded plug is a fundamental safety mechanism in medical equipment. The third prong provides a safe path for stray electrical current to flow to the ground, preventing it from passing through the patient, which could cause a dangerous microshock or macroshock. Using adapters or two-prong plugs eliminates this crucial safety feature.

Question 32: Which of the following ECG characteristics is the hallmark of a normally functioning ventricular-paced rhythm?

A pacing spike following every T wave.
A wide, bizarre QRS complex preceded by a pacing spike. (Correct answer)
The absence of pacing spikes when the intrinsic rate is high.
A narrow QRS complex preceded by a pacing spike.

Correct answer: A wide, bizarre QRS complex preceded by a pacing spike.

When a pacemaker stimulates the ventricle directly (typically the right ventricle), the electrical impulse spreads through the ventricular muscle in an abnormal, slower pathway, rather than the rapid His-Purkinje system. This results in a wide QRS complex (>0.12 seconds), similar in appearance to a bundle branch block or a PVC. [2, 12, 16]

Question 33: A CRAT is alerted to a patient who is unresponsive and has no palpable pulse. The cardiac monitor, however, displays an organized, narrow-complex rhythm at a rate of 70 bpm. This clinical situation is best described as:

Pulseless Electrical Activity (PEA) (Correct answer)
Ventricular Fibrillation
Asystole
Normal Sinus Rhythm

Correct answer: Pulseless Electrical Activity (PEA)

Pulseless Electrical Activity (PEA) is a life-threatening condition defined by the presence of an organized or semi-organized electrical rhythm on the ECG monitor in a patient who lacks a palpable pulse. [2, 9] The heart's electrical system is functioning, but it is not generating mechanical contractions sufficient to produce a pulse and circulate blood.

Question 34: Which cells in the heart have the property of automaticity, meaning they can spontaneously depolarize?

Pacemaker cells in the SA node, AV node, and His-Purkinje system (Correct answer)
Only SA node cells
Ventricular muscle cells only
All cardiac muscle cells equally

Correct answer: Pacemaker cells in the SA node, AV node, and His-Purkinje system

Automaticity — the ability to spontaneously depolarize — is possessed by pacemaker cells throughout the conduction system, with the SA node having the highest rate.

Question 35: Documentation of rhythm strips in clinical monitoring should include which essential elements?

Only the patient name and date
Heart rate and QRS duration only
Only the rhythm interpretation
Patient name/ID, date and time, lead(s) monitored, rhythm interpretation, clinical context, and documenting clinician's identification (Correct answer)

Correct answer: Patient name/ID, date and time, lead(s) monitored, rhythm interpretation, clinical context, and documenting clinician's identification

Complete rhythm strip documentation requires patient identification, precise date and time, lead being monitored, rhythm interpretation, any relevant clinical context (symptoms, interventions), and identification of the person documenting.

Question 36: Which respiratory pattern produces the most pronounced sinus arrhythmia?

Mechanical ventilation at high PEEP
Breath-holding at end expiration
Slow, deep breathing (Correct answer)
Rapid shallow breathing

Correct answer: Slow, deep breathing

Slow, deep breathing produces the most pronounced sinus arrhythmia because larger tidal volumes create greater changes in intrathoracic pressure and more significant vagal modulation with each respiratory cycle.

Question 37: Which characteristic of the QRS complex in complete heart block provides a clue about the location of the escape pacemaker?

Narrow QRS indicates ventricular origin
Wide QRS always indicates atrial origin
Narrow QRS suggests a junctional escape; wide QRS suggests a ventricular escape (Correct answer)
QRS width is unrelated to escape pacemaker location

Correct answer: Narrow QRS suggests a junctional escape; wide QRS suggests a ventricular escape

Junctional escape pacemakers activate the ventricles via the normal His-Purkinje system, producing narrow QRS complexes, while ventricular escape foci cause wide, aberrant QRS complexes.

Question 38: A rhythm strip shows regular QRS complexes intermixed with artifact spikes from a patient's implanted pacemaker. How can you best distinguish paced beats from artifact?

Paced beats are followed by a wide QRS complex after each pacemaker spike (Correct answer)
Pacemaker spikes occur randomly with no relationship to QRS complexes
Artifact spikes are always followed by a QRS complex
Paced beats produce narrow QRS complexes

Correct answer: Paced beats are followed by a wide QRS complex after each pacemaker spike

True pacemaker spikes are immediately followed by a ventricular depolarization (wide QRS), while artifact spikes from external sources have no consistent relationship to cardiac complexes.

Question 39: Sustained monomorphic ventricular tachycardia with a pulse is initially managed with which approach?

IV adenosine as first-line agent
Synchronized cardioversion if unstable, or IV antiarrhythmics (amiodarone or procainamide) if stable (Correct answer)
Immediate unsynchronized defibrillation regardless of hemodynamics
Observation only

Correct answer: Synchronized cardioversion if unstable, or IV antiarrhythmics (amiodarone or procainamide) if stable

Stable monomorphic VT with a pulse may be treated pharmacologically (amiodarone, procainamide) while unstable VT (hypotension, altered consciousness, chest pain) requires immediate synchronized cardioversion.

Question 40: Which clinical condition is most commonly associated with junctional escape rhythm as a primary rhythm?

Ventricular hypertrophy
Sick sinus syndrome with sinus arrest (Correct answer)
Bundle branch block
Atrial fibrillation

Correct answer: Sick sinus syndrome with sinus arrest

Sick sinus syndrome, in which the SA node fails to generate adequate impulses, allows the junctional escape pacemaker to take over as the primary rhythm.

Question 41: The conduction system terminates with the:

Atrioventricular Junction
Sinoatrial Node
None of the above
Purkinje Network (Correct answer)

Correct answer: Purkinje Network

Explanation: The conduction system of the heart terminates with the Purkinje network, which consists of specialized fibers responsible for rapidly conducting the electrical impulses to the myocardium, triggering ventricular contraction.

Question 42: Which coronary artery most commonly supplies the SA node?

Left circumflex artery
Left main coronary artery
Left anterior descending artery (LAD)
Right coronary artery (RCA) (Correct answer)

Correct answer: Right coronary artery (RCA)

In approximately 60% of individuals, the SA node is perfused by the right coronary artery, which is why inferior MI (RCA territory) often causes sinus bradycardia or AV block.

Question 43: The combination of right bundle branch block (RBBB) and left anterior fascicular block (LAFB) is called:

Bifascicular block (Correct answer)
Trifascicular block
Complete heart block
Hemiblock

Correct answer: Bifascicular block

Bifascicular block refers to simultaneous blockage of two of the three fascicles; RBBB + LAFB is the most common combination, involving two-thirds of the trifascicular conduction system.

Question 44: A patient's ECG shows a completely flat line in lead II only, while other leads record normally. The most likely cause is which of the following?

Electrode misplacement on both limbs
Asystole
Disconnected or failed lead II electrode (Correct answer)
Pacemaker failure

Correct answer: Disconnected or failed lead II electrode

A flat line in one lead only, while other leads continue to show cardiac activity, indicates a technical failure specific to that lead — most likely a disconnected electrode.

Question 45: In a normal sinus rhythm, the sinus node fires at a rate of:

101-150 per minute
151-180 per minute
61-100 per minute (Correct answer)
40-60 per minute

Correct answer: 61-100 per minute

Explanation: In a normal sinus rhythm, the sinus node fires at a rate of 60 to 100 times per minute, which represents the normal range for heart rate in adults.

Question 46: Depolarization of cardiac muscle cells occurs primarily due to rapid influx of which ion?

Calcium (Ca2+)
Chloride (Cl-)
Potassium (K+)
Sodium (Na+) (Correct answer)

Correct answer: Sodium (Na+)

Phase 0 of the cardiac action potential in non-pacemaker cells is characterized by rapid sodium influx through fast sodium channels, causing the steep upstroke of depolarization.

Question 47: When a patient with a pacemaker is receiving electrocautery during surgery, which pacemaker problem can occur?

Loss of pacing lead insulation
Oversensing of electrocautery current causing pacemaker inhibition (Correct answer)
Permanent pacemaker reprogramming to a faster rate
Immediate battery depletion

Correct answer: Oversensing of electrocautery current causing pacemaker inhibition

Electrosurgical (Bovie) current can be sensed by the pacemaker as cardiac activity (oversensing), inhibiting pacing output — dangerous in pacemaker-dependent patients who may develop bradycardia or asystole.

Question 48: Which of the following ECG findings is the defining characteristic of Second-Degree AV Block, Mobitz I (Wenckebach)?

A constant PR interval with intermittently dropped QRS complexes.
A fixed 2:1 ratio of P waves to QRS complexes.
Progressive lengthening of the PR interval until a QRS complex is dropped. (Correct answer)
Complete dissociation of P waves and QRS complexes.

Correct answer: Progressive lengthening of the PR interval until a QRS complex is dropped.

The hallmark of Second-Degree AV Block, Mobitz I (Wenckebach) is the progressive prolongation of the PR interval over several beats, culminating in a P wave that is not followed by a QRS complex (a dropped beat). [2, 6, 18] After the dropped beat, the cycle typically repeats.

Question 49: Which ECG parameter should be verified first when the paper tracing appears abnormally large or small for all waveforms?

Paper speed setting
Filter settings
Lead selection
Calibration/gain setting (should show 10 mm/mV deflection) (Correct answer)

Correct answer: Calibration/gain setting (should show 10 mm/mV deflection)

Standard ECG calibration is 10 mm per millivolt. If all waveforms are too large or too small, the gain (calibration) setting has been changed from the standard.

Question 50: During ventricular depolarization, which ECG component is produced?

U wave
P wave
QRS complex (Correct answer)
T wave

Correct answer: QRS complex

The QRS complex represents ventricular depolarization — the electrical activation that spreads through the ventricular myocardium triggering contraction.

Question 51: When performing a 12-lead ECG, the RL (right leg) electrode serves primarily which purpose?

Records the aVF lead signal
Provides the negative reference for limb leads
Electrical ground/reference to reduce common-mode noise (Correct answer)
Positive electrode for lead III

Correct answer: Electrical ground/reference to reduce common-mode noise

The right leg electrode serves as the ground electrode, providing a common reference point that helps the ECG machine cancel out common-mode electrical noise affecting all leads equally.

Question 52: Wolff-Parkinson-White (WPW) syndrome produces which classic triad of ECG findings?

Short PR, inverted P waves, and narrow QRS
Long PR interval, narrow QRS, and peaked T waves
Short PR interval (< 120 ms), delta wave (slurred QRS upstroke), and wide QRS complex (Correct answer)
Delta waves only with normal PR interval

Correct answer: Short PR interval (< 120 ms), delta wave (slurred QRS upstroke), and wide QRS complex

WPW is characterized by a short PR interval (accessory pathway bypasses AV nodal delay), delta wave (early pre-excitation of the ventricle producing slurred QRS onset), and widened QRS (fusion of pre-excited and normally conducted ventricular activation).

Question 53: All of the following are potential P wave presentations in a junctional rhythm EXCEPT:

Upright and uniform before each QRS with a PR interval of 0.16 seconds (Correct answer)
Inverted, appearing immediately after the QRS complex
Inverted, appearing immediately before the QRS complex
Absent, buried within the QRS complex

Correct answer: Upright and uniform before each QRS with a PR interval of 0.16 seconds

An upright, uniform P wave with a normal PR interval (0.12-0.20 seconds) is the hallmark of a sinus rhythm, originating from the SA node. In a junctional rhythm, the P wave, if visible, results from retrograde atrial activation and will be inverted in the inferior leads and may appear before, during (hidden), or after the QRS complex.

Question 54: A technician is analyzing a rhythm strip and notes a run of three or more consecutive wide-complex beats at a rate of 140 bpm. The rhythm is regular. This finding is best classified as:

Accelerated Idioventricular Rhythm (AIVR)
A run of multifocal PVCs
Supraventricular Tachycardia with Aberrancy
Ventricular Tachycardia (VT) (Correct answer)

Correct answer: Ventricular Tachycardia (VT)

Ventricular Tachycardia (VT) is defined as a rhythm with three or more consecutive beats of ventricular origin at a rate greater than 100 bpm. AIVR has a rate of 41-100 bpm, and while SVT with aberrancy has a wide QRS, the description points directly to the definition of VT.

Question 55: If a dual chamber pacemaker ventricular lead senses a non-cardiac signal, what is MOST LIKELY to occur?

Atrial under sensing
Failure to capture ventricle
Failure to ventricular pace (Correct answer)
Inappropriate atrial pacing

Correct answer: Failure to ventricular pace

Explanation: If a dual chamber pacemaker's ventricular lead senses a non-cardiac signal, it may incorrectly interpret it as a heartbeat, leading to a failure to deliver the appropriate pacing stimulus to the ventricle. This can result in a failure to ventricular pace, meaning the ventricle does not receive the necessary pacing impulse, potentially leading to symptoms related to bradycardia or other rhythm disturbances.

Question 56: In the autonomic nervous system, vagal (parasympathetic) stimulation affects the heart primarily through which neurotransmitter and receptor?

Dopamine acting on D1 receptors
Acetylcholine acting on M2 muscarinic receptors in the SA and AV nodes (Correct answer)
Norepinephrine acting on beta-1 receptors
Epinephrine acting on alpha-1 receptors

Correct answer: Acetylcholine acting on M2 muscarinic receptors in the SA and AV nodes

Parasympathetic (vagal) fibers release acetylcholine, which binds M2 muscarinic receptors on SA and AV nodal cells, slowing the heart rate and prolonging AV nodal conduction via potassium channel activation.

Question 57: Which Class I antiarrhythmic is commonly used for ventricular arrhythmias, especially in the acute setting of myocardial infarction?

Digoxin
Diltiazem
Verapamil
Lidocaine (Correct answer)

Correct answer: Lidocaine

Lidocaine is a Class IB sodium channel blocker used for ventricular arrhythmias, particularly in the context of acute myocardial infarction.

Question 58: A pacemaker spike followed by a wide, abnormal QRS complex indicates what type of pacing?

Atrial pacing with successful capture
Failure to capture
Ventricular pacing with successful capture (Correct answer)
Oversensing

Correct answer: Ventricular pacing with successful capture

A pacemaker spike immediately followed by a wide QRS complex confirms ventricular pacing with successful capture — the pacemaker stimulus has successfully depolarized the ventricular myocardium.

Question 59: Which calcium channel blocker is primarily used to control ventricular rate in atrial fibrillation?

Amlodipine
Diltiazem (Correct answer)
Nifedipine
Nimodipine

Correct answer: Diltiazem

Diltiazem (a non-dihydropyridine calcium channel blocker) slows AV nodal conduction and is commonly used for rate control in atrial fibrillation.

Question 60: A rhythm analysis technician observes a wide, bizarre QRS complex measuring 0.14 seconds on a patient's EKG. The beat occurs earlier than the next expected sinus beat, is not preceded by a P wave, and is followed by a pause. What is this single beat best described as?

Premature Atrial Contraction (PAC)
Aberrantly Conducted Supraventricular Beat
Premature Junctional Contraction (PJC)
Premature Ventricular Contraction (PVC) (Correct answer)

Correct answer: Premature Ventricular Contraction (PVC)

This describes a Premature Ventricular Contraction (PVC). The key features are its premature nature, a wide QRS complex (≥0.12 seconds) due to its ventricular origin, the absence of a preceding P wave, and a subsequent compensatory pause.

Question 61: AV dissociation that is NOT due to complete heart block can occur in which situation?

Atrial flutter with 2:1 block
Normal sinus rhythm
First-degree AV block
Accelerated junctional rhythm that exceeds the sinus rate (Correct answer)

Correct answer: Accelerated junctional rhythm that exceeds the sinus rate

AV dissociation without complete block occurs when a lower pacemaker (junctional or ventricular) accelerates to exceed the sinus rate, causing the two chambers to beat independently without true block.

Question 62: Which of the following rhythms may be characterized by regular P-P and regular R-R intervals occurring at different rates?

First-degree heart block
Wenckebach
Atrial fibrillation
Complete heart block (Correct answer)

Correct answer: Complete heart block

Explanation: In a complete heart block, there is a dissociation between the atrial and ventricular rates, resulting in regular P-P intervals (atrial rate) and regular R-R intervals (ventricular rate), but occurring at different rates due to the interruption in the electrical conduction between the atria and ventricles.

Question 63: A patient's intrinsic heart rate is 50 bpm. Their pacemaker is programmed with a lower rate limit of 60 bpm, but no pacing spikes are visible on the ECG strip. This observation is most consistent with which pacemaker issue?

Failure to pace (failure to fire) (Correct answer)
Undersensing
Failure to capture
Pacemaker-mediated tachycardia

Correct answer: Failure to pace (failure to fire)

Failure to pace, also called failure to fire or output failure, is the inability of the pacemaker to deliver a stimulus when it is needed. [1, 7] In this scenario, since the patient's heart rate has fallen below the programmed lower limit, the pacemaker should be firing, but the absence of pacing spikes indicates it is not delivering any output. [4, 7]

Question 64: Right bundle branch block (RBBB) produces which classic ECG pattern?

Broad notched R in lateral leads with QS in V1
RSR' (rabbit ears) pattern in V1 and wide S waves in leads I, aVL, and V6 (Correct answer)
Peaked T waves and widened QRS
Delta waves and short PR interval

Correct answer: RSR' (rabbit ears) pattern in V1 and wide S waves in leads I, aVL, and V6

RBBB produces the classic RSR' (M-shaped or rabbit ears) pattern in V1-V2 and wide, slurred S waves in I, aVL, V5-V6 due to delayed right ventricular activation.

Question 65: Which ion primarily responsible for Phase 3 (rapid repolarization) of the ventricular action potential?

Potassium efflux through IKr and IKs channels (Correct answer)
Calcium influx
Chloride efflux
Sodium influx

Correct answer: Potassium efflux through IKr and IKs channels

Phase 3 rapid repolarization is driven by potassium efflux through the delayed rectifier potassium channels (IKr and IKs), restoring the negative resting membrane potential.

Question 66: On the ECG, which measurement defines a normal PR interval?

80-120 ms
200-240 ms
120-200 ms (Correct answer)
60-100 ms

Correct answer: 120-200 ms

The normal PR interval ranges from 120 to 200 ms (3 to 5 small boxes on standard ECG paper), representing atrial depolarization and AV nodal conduction time.

Question 67: Normal sinus rhythm requires which set of criteria?

Regular P waves upright in II and inverted in aVR, constant PR 120-200 ms, rate 60-100 bpm, narrow QRS (Correct answer)
Rate 60-100 bpm with no P waves
P waves inverted in II, rate 60-100 bpm
PR interval greater than 200 ms, rate 60-100 bpm

Correct answer: Regular P waves upright in II and inverted in aVR, constant PR 120-200 ms, rate 60-100 bpm, narrow QRS

Normal sinus rhythm requires an SA node origin (upright P in II, inverted in aVR), normal PR interval (120-200 ms), heart rate 60-100 bpm, and narrow QRS complexes.

Question 68: Which factor most significantly affects the quality of ECG signal transmission in telemetry monitoring?

Distance from the transmitter to the receiver and physical barriers between them (Correct answer)
The brand of ECG machine
The time of day monitoring occurs
The patient's heart rate

Correct answer: Distance from the transmitter to the receiver and physical barriers between them

Telemetry signal quality degrades with increasing distance from the receiver and when the patient moves behind walls, into elevators, or into areas with thick concrete or metal barriers that attenuate the radio frequency signal.

Question 69: A patient is experiencing a blockage in the right coronary artery (RCA). Which of the following structures is most likely to be affected?

Left ventricle and interventricular septum
SA node and right ventricle (Correct answer)
Anterior wall of the left ventricle
Left atrium and circumflex artery

Correct answer: SA node and right ventricle

The right coronary artery (RCA) supplies blood to the right atrium, right ventricle, and, in most individuals, the sinoatrial (SA) node and the atrioventricular (AV) node. A blockage in the RCA can therefore impact the heart's primary pacemaker and the right-sided chambers.

Question 70: Sixty-cycle (60 Hz) interference on an ECG most likely results from which cause?

Loose electrode gel
Incorrect lead placement
Nearby electrical equipment or poor electrode grounding (Correct answer)
Patient movement

Correct answer: Nearby electrical equipment or poor electrode grounding

60 Hz artifact appears as a thick, fuzzy baseline caused by electromagnetic interference from AC power sources including nearby electrical equipment or inadequate grounding.

Question 71: Sinus tachycardia is most appropriately managed by which approach?

Identifying and treating the underlying cause (fever, pain, hypovolemia, anxiety, hyperthyroidism) (Correct answer)
Immediate cardioversion
Adenosine administration
IV beta-blockers as first-line treatment always

Correct answer: Identifying and treating the underlying cause (fever, pain, hypovolemia, anxiety, hyperthyroidism)

Sinus tachycardia is almost always a secondary, compensatory response — the appropriate treatment is to identify and address the underlying physiological cause, not to suppress the tachycardia directly.

Question 72: Which atrial arrhythmia is characterized by a sawtooth pattern at a rate of 250-350 bpm on the ECG?

Atrial tachycardia
Atrial fibrillation
Atrial flutter (Correct answer)
Multifocal atrial tachycardia

Correct answer: Atrial flutter

Atrial flutter produces the classic sawtooth flutter waves (F waves) at 250-350 bpm, best visible in leads II, III, aVF, and V1.

Question 73: An ECG strip shows an extremely slow, irregular rhythm with wide, bizarrely shaped QRS complexes at a rate of less than 20 bpm. No discernible P waves are present. This rhythm is characteristic of:

Third-Degree AV Block
Agonal Rhythm (Correct answer)
Complete Sinus Arrest
Idioventricular Rhythm

Correct answer: Agonal Rhythm

An agonal rhythm, often called a "dying heart," is a terminal arrhythmia characterized by a very slow (often <20 bpm), irregular rate with wide and misshapen QRS complexes. [1, 3, 17] It represents the last electrical discharges from the ventricles and is a sign of impending or current cardiac arrest.

Question 74: Which medication is a common pharmacological cause of AV block?

Atropine
Epinephrine
Digoxin (Correct answer)
Dopamine

Correct answer: Digoxin

Digoxin enhances vagal tone and slows AV nodal conduction, and toxicity can cause all degrees of AV block including complete heart block.

Question 75: Which lead position is used for most right ventricular apical pacing, and what ECG pattern does it produce?

Left ventricular free wall, producing a narrow QRS
Coronary sinus, producing a narrow QRS complex
Right ventricular apex, producing a left bundle branch block (LBBB) pattern with left axis deviation (Correct answer)
Right ventricular outflow tract, producing a right bundle branch block pattern

Correct answer: Right ventricular apex, producing a left bundle branch block (LBBB) pattern with left axis deviation

Traditional RV apical pacing activates the left ventricle last (via slow myocardial spread), producing an LBBB morphology in V1 with left axis deviation — the expected ECG appearance of successful right ventricular pacing.

Question 76: What minimum QRS duration is required to diagnose a complete bundle branch block?

≥0.10 seconds
≥0.14 seconds
≥0.08 seconds
≥0.12 seconds (Correct answer)

Correct answer: ≥0.12 seconds

A complete bundle branch block requires a QRS duration of ≥0.12 seconds (3 small squares at standard paper speed) on the ECG.

Question 77: Improper placement of the V4 electrode (placed too high, at the 4th ICS instead of 5th) would most likely affect which finding?

QT interval duration
Limb lead voltage amplitude
R wave progression and ST segment changes in the precordial leads (Correct answer)
PR interval measurements

Correct answer: R wave progression and ST segment changes in the precordial leads

Misplacing V4 alters the precordial R wave progression pattern and may falsely suggest poor R wave progression or anterior ischemia, since each lead records a different spatial perspective of the heart.

Question 78: Which of the following is the defining characteristic of Sinus Arrhythmia?

A progressively lengthening PR interval
An irregular rhythm that varies with respiration (Correct answer)
A heart rate consistently above 100 bpm
The absence of P waves

Correct answer: An irregular rhythm that varies with respiration

Sinus Arrhythmia is a variant of sinus rhythm where the R-R interval varies, often in relation to the respiratory cycle. The heart rate typically increases with inspiration and decreases with expiration, resulting in an irregular rhythm.

Question 79: A rhythm analysis technician is reviewing a 6-second strip that shows a regular rhythm with a heart rate of 50 bpm. P waves are not discernible, and the QRS complexes are narrow, measuring 0.08 seconds. Which rhythm should the technician identify?

Idioventricular Rhythm
Sinus Bradycardia
Third-Degree AV Block
Junctional Rhythm (Correct answer)

Correct answer: Junctional Rhythm

This rhythm is identified as a Junctional Rhythm (or Junctional Escape Rhythm) because the heart rate is between 40-60 bpm, which is the intrinsic rate of the AV junction. The absence of P waves and the presence of a narrow QRS complex are classic indicators that the impulse is originating from the AV junction and traveling down the normal ventricular conduction pathway.

Question 80: A patient is admitted with palpitations. The ECG shows a regular, narrow-complex tachycardia at 130 bpm. There is a P wave before each QRS, but the P wave morphology is different from the patient's baseline sinus rhythm ECG, being inverted in lead III. The PR interval is constant. What is the most likely diagnosis?

Sinus Tachycardia
Atrial Fibrillation
Atrial Flutter
Atrial Tachycardia (Correct answer)

Correct answer: Atrial Tachycardia

Atrial Tachycardia originates from a single ectopic focus in the atria, resulting in a regular rhythm with abnormal P waves that have a consistent morphology, different from the sinus P waves. [2, 16] Sinus Tachycardia would have normal P wave morphology for that patient. [19] Atrial Fibrillation is irregular and lacks P waves, and Atrial Flutter has a characteristic saw-tooth baseline. [4, 9]

Question 81: A patient's rhythm strip shows a regular rhythm at 55 bpm with upright P waves in lead II and a PR interval of 160 ms. How should this rhythm be classified?

Normal sinus rhythm
First-degree AV block with sinus bradycardia
Junctional rhythm
Sinus bradycardia (Correct answer)

Correct answer: Sinus bradycardia

Upright P waves in II, constant normal PR interval (160 ms is within 120-200 ms), and rate below 60 bpm with regular rhythm meets criteria for sinus bradycardia specifically.

Question 82: In atrial fibrillation, which ECG finding is most characteristic?

Regularly irregular rhythm with delta waves
Irregularly irregular rhythm with absent distinct P waves (Correct answer)
Regular rhythm with sawtooth flutter waves
Regular rhythm with prolonged PR interval

Correct answer: Irregularly irregular rhythm with absent distinct P waves

Atrial fibrillation produces an irregularly irregular ventricular rhythm and replaces distinct P waves with chaotic fibrillatory f waves at 350-600 bpm.

Question 83: A technician reviews a rhythm strip showing an atrial rate of 75 bpm and a ventricular rate of 38 bpm. The P-P interval is regular, and the R-R interval is regular. P waves can be seen marching through the QRS complexes, with some appearing just before, some buried within, and some after the QRS. This describes:

Second-Degree AV Block, Mobitz I
Second-Degree AV Block, Mobitz II
First-Degree AV Block
Third-Degree AV Block (Correct answer)

Correct answer: Third-Degree AV Block

This scenario describes the classic features of Third-Degree (Complete) AV Block. There is complete AV dissociation, meaning the atrial impulses (P waves) have no relationship to the ventricular responses (QRS complexes). [13, 15] The atria and ventricles beat at their own regular, independent rates, with the atrial rate being faster than the ventricular escape rate. [4, 28]

Question 84: Which of the following correctly describes the function of the Purkinje fibers?

To initiate the heartbeat as the primary pacemaker.
To rapidly transmit electrical impulses to the ventricular myocardium, causing coordinated contraction. (Correct answer)
To supply oxygenated blood directly to the heart muscle.
To delay the electrical impulse between the atria and ventricles.

Correct answer: To rapidly transmit electrical impulses to the ventricular myocardium, causing coordinated contraction.

The Purkinje fibers are a network of specialized cells that rapidly conduct the electrical impulse from the bundle branches to the ventricular muscle cells. This rapid transmission ensures a coordinated and efficient contraction of the ventricles.

Question 85: What does a delta wave at the onset of the QRS complex suggest?

Pre-excitation syndrome (e.g., WPW) (Correct answer)
Hyperkalemia
Left ventricular hypertrophy
Right bundle branch block

Correct answer: Pre-excitation syndrome (e.g., WPW)

A delta wave — a slurred upstroke at the start of the QRS — indicates pre-excitation of the ventricles via an accessory pathway, as seen in Wolff-Parkinson-White syndrome.

Question 86: While reviewing a 12-lead ECG, a technician observes that the P wave and QRS complex are inverted in Lead I and upright in lead aVR. The R-wave progression in the precordial leads is normal. What is the most likely cause of these findings?

Reversal of the left arm and right arm electrodes (Correct answer)
Dextrocardia
Posterior myocardial infarction
Reversal of the right arm and left leg electrodes

Correct answer: Reversal of the left arm and right arm electrodes

The classic presentation for the reversal of the left arm and right arm electrodes is an inverted P wave and QRS complex in Lead I and an upright P wave and QRS complex in lead aVR. This is because Lead I's polarity is reversed (viewing from a positive right arm to a negative left arm). Dextrocardia would show this pattern in limb leads but would also show reversed R-wave progression in the chest leads.

Question 87: In the normal cardiac conduction sequence, what is the correct order of activation?

Bundle branches → AV node → SA node → atria
SA node → atria → AV node → bundle of His → bundle branches → Purkinje fibers → ventricles (Correct answer)
SA node → AV node → atria → ventricles
AV node → SA node → bundle branches → ventricles

Correct answer: SA node → atria → AV node → bundle of His → bundle branches → Purkinje fibers → ventricles

Normal conduction proceeds from the SA node through the atria, pauses at the AV node, then travels via the His-Purkinje system to activate the ventricles.

Question 88: The first negative deflection noted in the QRS complex is which wave?

R wave
T wave
Q wave (Correct answer)
S wave

Correct answer: Q wave

Explanation: The first negative deflection noted in the QRS complex is the Q wave. It represents the initial depolarization of the interventricular septum.

Question 89: A patient's ECG monitor suddenly displays a thick, fuzzy baseline with erratic, high-frequency spikes, obscuring the QRS complexes. The patient is awake and shivering. What is the most likely cause of this artifact and the technician's most appropriate initial action?

60-cycle interference; unplug nearby electrical devices.
Muscle artifact; provide the patient with a warm blanket. (Correct answer)
Wandering baseline; re-prep the skin and change the electrodes.
Ventricular fibrillation; immediately activate a code blue.

Correct answer: Muscle artifact; provide the patient with a warm blanket.

The ECG pattern described is characteristic of muscle artifact (somatic tremor), which is often caused by shivering. The most appropriate initial action is to address the root cause of the shivering by providing a warm blanket to make the patient more comfortable and obtain a clear tracing. While other options address different types of artifact or arrhythmias, they do not fit the described scenario.

Question 90: An isoelectric baseline on the ECG refers to:

Prolonged asystole
Pacemaker spike artifact
The normal baseline between waveforms with no electrical activity (Correct answer)
A flat line indicating cardiac arrest

Correct answer: The normal baseline between waveforms with no electrical activity

The isoelectric line is the flat baseline between ECG waveforms, representing zero electrical potential and used as the reference point for ST segment analysis.

Question 91: A CRAT notices on a patient's monitor that the pacemaker intermittently stops firing, causing long pauses, especially when the patient moves their arm or coughs. The technician suspects the pacemaker is incorrectly identifying muscle artifact as cardiac signals. This malfunction is known as:

Oversensing (Correct answer)
Crosstalk
Undersensing
Failure to capture

Correct answer: Oversensing

Oversensing is when the pacemaker incorrectly interprets non-cardiac electrical signals (like skeletal muscle artifact, T-waves, or EMI) as intrinsic cardiac activity. This misinterpretation inhibits the pacemaker from delivering a pacing stimulus when it's actually needed, potentially leading to pauses or syncope. [1, 5, 6]

Question 92: Which ECG finding is expected during the absolute refractory period of the cardiac cycle?

No cardiac stimulus can produce a new action potential — corresponds to the QRS complex through early T wave (Correct answer)
Any stimulus can produce fibrillation
P waves are produced by atrial repolarization
The SA node is firing rapidly

Correct answer: No cardiac stimulus can produce a new action potential — corresponds to the QRS complex through early T wave

During the absolute refractory period (QRS through mid-T wave), cardiac cells are completely depolarized and cannot respond to any stimulus regardless of its strength.

Question 93: Which structure is the primary pacemaker of the heart under normal conditions?

Purkinje fibers
Atrioventricular (AV) node
Sinoatrial (SA) node (Correct answer)
Bundle of His

Correct answer: Sinoatrial (SA) node

The SA node in the right atrium is the dominant pacemaker, firing at 60-100 bpm due to its fastest intrinsic automaticity.

Question 94: On an EKG, the depolarization of the atria, which leads to their contraction, is represented by which waveform?

QRS complex
U wave
P wave (Correct answer)
T wave

Correct answer: P wave

The P wave on an electrocardiogram (EKG) represents atrial depolarization. This electrical activity originates in the SA node and spreads across the atria, causing them to contract and pump blood into the ventricles.

Question 95: A sinus pause is defined as an absence of the expected sinus beat lasting at least how long?

One cardiac cycle only
500 ms
Two or more seconds (or twice the preceding R-R interval) (Correct answer)
0.5 seconds

Correct answer: Two or more seconds (or twice the preceding R-R interval)

A sinus pause is defined as an unexpected absence of a P wave lasting at least 2 seconds (or more than twice the preceding R-R interval), indicating a failure of the SA node to generate an impulse.

Question 96: On a standard ECG recorded at 25 mm/sec, each large box (5 mm) represents what duration of time?

200 ms (0.20 seconds) (Correct answer)
40 ms (0.04 seconds)
100 ms (0.10 seconds)
400 ms (0.40 seconds)

Correct answer: 200 ms (0.20 seconds)

At standard paper speed of 25 mm/sec, each large box (5 mm wide) represents 200 ms or 0.20 seconds; each small box (1 mm) represents 40 ms.

Question 97: The PR interval on the ECG reflects conduction through which structures?

Bundle branches and Purkinje fibers
Atria, AV node, and bundle of His (Correct answer)
SA node only
Ventricular myocardium

Correct answer: Atria, AV node, and bundle of His

The PR interval encompasses atrial depolarization (P wave) plus the conduction delay through the AV node and bundle of His before ventricular activation begins.

Question 98: A rhythm analysis technician observes a patient's EKG. The electrical impulse originates in the SA node, travels through the atria, and is then delayed at the AV node. What is the next structure the impulse will travel to in the normal conduction pathway?

Purkinje fibers
Right and left bundle branches
Ventricular myocardium
Bundle of His (Correct answer)

Correct answer: Bundle of His

Following the delay at the atrioventricular (AV) node, the electrical impulse travels to the Bundle of His. From there, it moves to the right and left bundle branches and finally to the Purkinje fibers, which causes ventricular contraction.

Question 99: In patients with frequent PVCs, which marker is most predictive of adverse outcomes (increased risk of sudden cardiac death)?

PVCs showing LBBB morphology
PVC rate exceeding 10 per hour
PVCs occurring during the day
Presence of underlying structural heart disease, particularly reduced left ventricular ejection fraction (Correct answer)

Correct answer: Presence of underlying structural heart disease, particularly reduced left ventricular ejection fraction

The most important prognostic factor for PVC-related adverse outcomes is underlying structural heart disease, particularly reduced LVEF — PVCs in structurally normal hearts carry a relatively benign prognosis.

Question 100: The P wave on the electrocardiogram represents an electrical impulse that spreads through the:

Purkinje Fibers
Bundle of His
Atria (Correct answer)
Ventricles

Correct answer: Atria

Explanation: The P wave on an electrocardiogram represents the electrical impulse spreading through the atria, signaling atrial depolarization, which initiates atrial contraction.

Question 101: In a patient with a permanent pacemaker, a magnet applied over the pulse generator typically causes what pacemaker behavior?

Complete pacemaker inhibition
Rate-adaptive mode activation
Battery level testing only
Asynchronous pacing at a fixed rate (magnet rate), ignoring sensed cardiac activity (Correct answer)

Correct answer: Asynchronous pacing at a fixed rate (magnet rate), ignoring sensed cardiac activity

A magnet converts the pacemaker to asynchronous (DOO or VOO) mode, delivering pacing pulses at a fixed programmed magnet rate regardless of any sensed cardiac activity, which is useful for testing capture or overriding oversensing.

Question 102: Torsades de pointes is a form of polymorphic VT most closely associated with which ECG finding before its onset?

ST elevation
Widened QRS complex
Prolonged QT interval (Correct answer)
Shortened PR interval

Correct answer: Prolonged QT interval

Torsades de pointes typically occurs in the setting of a prolonged QT interval, which indicates prolonged ventricular repolarization and increased risk of early afterdepolarizations.

Question 103: Which of the following ECG characteristics is the most definitive feature of Ventricular Fibrillation (VF)?

A rapid, regular rhythm with wide QRS complexes.
A progressively lengthening PR interval until a QRS is dropped.
A 'saw-tooth' pattern of atrial activity.
Chaotic, disorganized electrical activity with no identifiable P, QRS, or T waves. (Correct answer)

Correct answer: Chaotic, disorganized electrical activity with no identifiable P, QRS, or T waves.

Ventricular Fibrillation is defined by its chaotic and disorganized nature. On the ECG, there are no discernible waves (P, QRS, T); instead, the baseline is wavy and chaotic, reflecting the quivering, uncoordinated contraction of the ventricles.

Question 104: In the 6-second strip method for calculating heart rate, you count the number of QRS complexes and:

Multiply by 10 (Correct answer)
Divide by 10
Multiply by 6
Divide by 6

Correct answer: Multiply by 10

In the 6-second method, counting QRS complexes in a 6-second strip and multiplying by 10 gives beats per minute.

Question 105: The T wave on the ECG represents which electrophysiological event?

AV nodal conduction
Ventricular depolarization
Ventricular repolarization (Correct answer)
Atrial repolarization

Correct answer: Ventricular repolarization

The T wave represents ventricular repolarization — the recovery phase of the ventricular cells preparing for the next depolarization.

Question 106: Atrial flutter with 4:1 AV conduction produces a ventricular rate of approximately how many bpm if the atrial rate is 300 bpm?

150 bpm
100 bpm
75 bpm (Correct answer)
50 bpm

Correct answer: 75 bpm

With an atrial flutter rate of 300 bpm and 4:1 conduction, 300 divided by 4 equals 75 bpm.

Question 107: Which underlying condition is the MOST common cause of left bundle branch block?

Electrolyte imbalance
Acute pulmonary embolism
Hypertensive heart disease or coronary artery disease (Correct answer)
Wolff-Parkinson-White syndrome

Correct answer: Hypertensive heart disease or coronary artery disease

LBBB is most commonly caused by hypertensive heart disease, coronary artery disease, or cardiomyopathy — chronic conditions that damage the left-sided conduction system.

Question 108: Beta-blockers used as antiarrhythmics belong to which Vaughan Williams class?

Class II (Correct answer)
Class IV
Class I
Class III

Correct answer: Class II

Beta-blockers are Class II antiarrhythmics that reduce heart rate and AV nodal conduction by blocking beta-adrenergic receptors.

Question 109: What is the minimum number of consecutive ventricular beats at 100 bpm or greater required to define ventricular tachycardia?

Ten or more consecutive beats
Two consecutive beats
Five or more consecutive beats
Three or more consecutive beats (Correct answer)

Correct answer: Three or more consecutive beats

Ventricular tachycardia is defined as three or more consecutive ventricular complexes (wide QRS) at a rate of 100 bpm or greater, originating from a ventricular focus.

Question 110: A CRAT observes a rhythm strip where the P-P intervals and R-R intervals vary. The overall heart rate is 70 bpm, P waves are present and uniform, the PR interval is constant at 0.18 seconds, and the QRS is narrow. This description is most consistent with:

Atrial Flutter
Normal Sinus Rhythm
Sinus Bradycardia
Sinus Arrhythmia (Correct answer)

Correct answer: Sinus Arrhythmia

The key feature described is the variation in P-P and R-R intervals, which creates an irregular rhythm. With all other parameters (rate, P wave morphology, PR interval, QRS duration) being within normal sinus limits, the correct interpretation is Sinus Arrhythmia.

Question 111: In a patient with suspected hyperkalemia, which ECG finding appears first as potassium rises from normal levels?

Flat P waves
Peaked, narrow, symmetric T waves (Correct answer)
Prolonged PR interval
Widened QRS complex

Correct answer: Peaked, narrow, symmetric T waves

The earliest ECG sign of hyperkalemia is peaked, narrow, symmetric (tent-shaped) T waves, appearing when serum potassium rises above approximately 5.5-6.0 mEq/L.

Question 112: During which phase of the cardiac cycle do the ventricles contract, forcing blood into the aorta and pulmonary artery?

Isovolumetric relaxation
Systole (Correct answer)
Diastole
Ventricular filling

Correct answer: Systole

Systole is the period of the cardiac cycle when the heart muscle contracts. Specifically, ventricular systole is when the ventricles contract, pushing blood into the major arteries. Diastole is the period of relaxation and filling.

Question 113: A prominent U wave following the T wave is most commonly associated with:

Hypercalcemia
Hypernatremia
Hyperkalemia
Hypokalemia (Correct answer)

Correct answer: Hypokalemia

A prominent U wave is classically associated with hypokalemia, and can also be seen with certain medications such as digoxin.

Question 114: To be classified as a sinus rhythm, which of the following criteria regarding the PR interval must be met?

It must be between 0.12 and 0.20 seconds. (Correct answer)
It must be greater than 0.20 seconds.
It must be less than 0.12 seconds.
It must vary with each beat.

Correct answer: It must be between 0.12 and 0.20 seconds.

A key characteristic of any sinus rhythm (Normal, Bradycardia, Tachycardia) is a consistent PR interval that falls within the normal range of 0.12 to 0.20 seconds. This interval represents the time from the start of atrial depolarization to the start of ventricular depolarization.

Question 115: On standard ECG paper, one large square represents how many seconds?

0.40 seconds
0.20 seconds (Correct answer)
0.10 seconds
0.04 seconds

Correct answer: 0.20 seconds

One large square on standard ECG paper equals 0.20 seconds (200 ms) at the standard paper speed of 25 mm/sec.

Question 116: Hyperkalemia classically produces which ECG change that can progress to ventricular fibrillation?

ST elevation in multiple leads
Progressive widening of QRS followed by sine-wave pattern (Correct answer)
Deep Q waves
Prolonged QT interval

Correct answer: Progressive widening of QRS followed by sine-wave pattern

Hyperkalemia produces sequential ECG changes: peaked T waves → PR prolongation → P wave flattening → QRS widening → sine-wave pattern → VF/asystole.

Question 117: An ECG shows a QRS of 0.14 sec with broad notched R waves in I, aVL, V5–V6 and a broad QS in V1. What is the most likely diagnosis?

Wolff-Parkinson-White syndrome
Ventricular tachycardia
Right bundle branch block
Left bundle branch block (Correct answer)

Correct answer: Left bundle branch block

Broad notched R waves in lateral leads (I, aVL, V5–V6) combined with a QS pattern in V1 and a QRS ≥0.12 seconds are the hallmark features of left bundle branch block.

Question 118: Which intervention should be attempted first for a pacemaker patient presenting with failure to capture?

Increase pacing output amplitude on the programmer or apply a magnet to evaluate threshold (Correct answer)
Synchronized cardioversion
IV epinephrine infusion
Immediate surgical lead revision

Correct answer: Increase pacing output amplitude on the programmer or apply a magnet to evaluate threshold

The first step is to increase the pacing output (voltage or pulse width) via programming to overcome an elevated stimulation threshold, which may restore capture before considering invasive interventions.

Question 119: Triggered activity as a mechanism of arrhythmia is caused by which electrophysiological phenomenon?

Reentrant circuits in the AV node
Afterdepolarizations (early or delayed) that reach threshold and trigger additional action potentials (Correct answer)
Vagal suppression of pacemaker cells
Complete failure of sodium channel function

Correct answer: Afterdepolarizations (early or delayed) that reach threshold and trigger additional action potentials

Triggered activity results from afterdepolarizations — oscillations in membrane potential that occur during (early afterdepolarizations, EADs) or after (delayed afterdepolarizations, DADs) repolarization and can trigger additional action potentials.

Question 120: A technician observes a rhythm strip where the underlying sinus rhythm is interrupted by a single beat that occurs earlier than expected. This premature beat has a P wave with a different morphology from the sinus P waves, followed by a normal QRS complex. What is this single beat called?

Atrial Bigeminy
Premature Ventricular Contraction (PVC)
Premature Atrial Contraction (PAC) (Correct answer)
Premature Junctional Contraction (PJC)

Correct answer: Premature Atrial Contraction (PAC)

A Premature Atrial Contraction (PAC) is an ectopic beat originating from the atria, causing it to occur early. [5, 13] Its key features are a premature P wave with an abnormal shape compared to sinus P waves, followed by a typically normal QRS complex. [5, 24] A PJC originates in the AV junction and usually has an inverted or absent P wave. A PVC originates in the ventricles and has a wide, bizarre QRS. Atrial Bigeminy refers to a pattern where every other beat is a PAC, not the single beat itself. [5]

Question 121: What is the normal duration of the PR interval on a standard ECG?

0.12–0.20 seconds (Correct answer)
0.06–0.10 seconds
0.30–0.40 seconds
0.22–0.30 seconds

Correct answer: 0.12–0.20 seconds

The normal PR interval ranges from 0.12 to 0.20 seconds (3–5 small squares).

Question 122: Which layer of the heart is responsible for the electrical-to-mechanical coupling that produces contraction?

Epicardium
Myocardium (Correct answer)
Pericardium
Endocardium

Correct answer: Myocardium

The myocardium (middle muscular layer) is where electrical depolarization triggers calcium release and actin-myosin cross-bridge formation, producing mechanical contraction.

Question 123: Brugada syndrome is associated with which pattern on ECG?

Coved ST elevation in V1-V3 (Type 1 Brugada pattern) with right bundle branch block morphology (Correct answer)
Delta waves with short PR interval
ST depression in inferior leads
Prolonged QT with torsades

Correct answer: Coved ST elevation in V1-V3 (Type 1 Brugada pattern) with right bundle branch block morphology

Brugada syndrome is diagnosed by the Type 1 pattern: coved (downsloping) ST elevation ≥ 2 mm in V1-V3 with RBBB-like morphology, associated with risk of sudden cardiac death from polymorphic VT/VF.

Question 124: What is pacemaker syndrome?

Battery depletion causing pacemaker failure
Symptoms from loss of AV synchrony in VVI pacing, causing retrograde atrial contraction against closed mitral valve (Correct answer)
Pacemaker lead fracture causing intermittent loss of capture
Electromagnetic interference inhibiting pacing

Correct answer: Symptoms from loss of AV synchrony in VVI pacing, causing retrograde atrial contraction against closed mitral valve

Pacemaker syndrome occurs with VVI pacing when retrograde (ventriculo-atrial) conduction causes atria to contract against closed AV valves, producing low cardiac output, hypotension, and symptoms of heart failure.

Question 125: During continuous cardiac monitoring, an alarm is triggered for a critical low heart rate. What should the monitor technician do first?

Silence the alarm and continue monitoring
Adjust the alarm threshold upward
Assume it is a false alarm due to artifact
Assess the patient clinically and notify the nurse or clinician immediately (Correct answer)

Correct answer: Assess the patient clinically and notify the nurse or clinician immediately

A critical alarm must always prompt immediate patient assessment — alarms should never be silenced without clinical evaluation, as critical bradycardia may represent a life-threatening rhythm.

Question 126: A PVC that occurs during the relative refractory period is referred to as:

A couplet
BBB
R-on-T (Correct answer)
Bigeminy

Correct answer: R-on-T

Explanation: A PVC (Premature Ventricular Contraction) that occurs during the relative refractory period, where the ventricles are still in a vulnerable state, is referred to as the R-on-T phenomenon. It's called so because the PVC occurs on the peak of the T wave of the preceding beat, potentially leading to dangerous arrhythmias like ventricular tachycardia or ventricular fibrillation.

Question 127: Which feature best distinguishes atrial tachycardia from sinus tachycardia on a 12-lead ECG?

Longer QT interval
Absence of a PR interval
Abnormal P wave axis or morphology differing from sinus P waves (Correct answer)
Wider QRS complexes

Correct answer: Abnormal P wave axis or morphology differing from sinus P waves

Atrial tachycardia originates from an ectopic focus rather than the sinus node, producing P waves with an axis or morphology that differs from normal sinus P waves.

Question 128: Pacemaker failure to capture is identified by which ECG finding?

Absence of pacemaker spikes despite slow heart rate
Pacemaker spikes followed by wide QRS complexes
Pacemaker spikes occurring at twice the programmed rate
Pacemaker spikes visible without subsequent QRS complexes (Correct answer)

Correct answer: Pacemaker spikes visible without subsequent QRS complexes

Failure to capture occurs when the pacemaker fires (spike visible) but the electrical stimulus fails to depolarize the myocardium, so no QRS complex follows the spike.

Question 129: Which physiological mechanism causes increased sinus rate during exercise?

Sympathetic nervous system activation releasing norepinephrine which increases SA node automaticity (Correct answer)
Mechanical stretching of the SA node
Decreased blood pressure stimulating baroreceptors
Increased serum potassium during exercise

Correct answer: Sympathetic nervous system activation releasing norepinephrine which increases SA node automaticity

Exercise activates the sympathetic nervous system, releasing catecholamines (norepinephrine, epinephrine) that bind beta-1 adrenergic receptors on SA node cells, increasing the rate of spontaneous diastolic depolarization and thus heart rate.

Question 130: A patient has second-degree AV block with a 3:2 conduction ratio in Wenckebach pattern. How many P waves appear for every 2 QRS complexes?

3 P waves (Correct answer)
2 P waves
1 P wave
4 P waves

Correct answer: 3 P waves

A 3:2 conduction ratio means 3 P waves for every 2 conducted QRS complexes — one P wave in each cycle is blocked.

Question 131: Mobitz type I (Wenckebach) second-degree AV block is best described by which pattern?

Fixed PR interval with intermittently dropped QRS complexes
Progressive PR lengthening until a QRS is dropped, then the cycle resets (Correct answer)
Complete AV dissociation
Constant PR interval with every other P wave blocked

Correct answer: Progressive PR lengthening until a QRS is dropped, then the cycle resets

Wenckebach is characterized by progressive PR interval lengthening with each beat until one P wave is not conducted (dropped QRS), after which the cycle resets.

CRAT — Certified Rhythm Analysis Technician

The CCI CRAT exam certifies rhythm analysis technicians in ECG interpretation, arrhythmia recognition, cardiac anatomy, patient monitoring, and pacemaker analysis. Scored 0–900, pass at 650.

130

Questions

120 min

Time Limit

72%

To Pass

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