CRAT — Certified Rhythm Analysis Technician — Questions and Answers

Question 1: A regular rhythm with a narrow QRS complex with no notes P wave and rates between 40-6- bpm is known as:

Junctional escape rhythm (Correct answer)
Accelerated junctional rhythm
Premature ventricular contraction
Idioventricular escape rhythm

Correct answer: Junctional escape rhythm

Explanation: A junctional escape rhythm is characterized by a regular rhythm, narrow QRS complexes, and rates typically between 40 to 60 bpm. In this rhythm, the electrical impulses originate from the atrioventricular junction (AV node or His-Purkinje system) as a backup pacemaker when the normal pacemaker fails to function.

Question 2: AV dissociation that is NOT due to complete heart block can occur in which situation?

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

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

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

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

Right ventricular outflow tract, producing a right bundle branch block pattern
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)

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 5: Which coronary artery most commonly supplies the SA node?

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

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 6: Left bundle branch block (LBBB) on ECG is confirmed by which set of findings?

QRS duration ≥ 120 ms with RSR' pattern in V1 and wide S waves in I and V6
QRS duration ≥ 120 ms, broad notched R in lateral leads (I, aVL, V5-V6), and rS pattern in V1 (Correct answer)
Wide QRS with absent R wave in all leads
Short QRS with delta waves

Correct answer: QRS duration ≥ 120 ms, broad notched R in lateral leads (I, aVL, V5-V6), and rS pattern in V1

LBBB produces QRS ≥ 120 ms, a broad, notched or slurred R wave in lateral leads (I, aVL, V5, V6), and a deep rS or QS pattern in V1 — the opposite pattern from RBBB.

Question 7: In a junctional rhythm, P waves appear inverted in the inferior leads (II, III, aVF) because of which mechanism?

P waves originate from the right atrium
The PR interval is prolonged
Atria do not depolarize at all in junctional rhythm
Retrograde atrial activation from the AV junction travels superiorly, opposite to normal sinus direction (Correct answer)

Correct answer: Retrograde atrial activation from the AV junction travels superiorly, opposite to normal sinus direction

Junctional impulses activate the atria in a retrograde (bottom-up) direction, causing the electrical wavefront to travel toward the base of the heart — opposite to normal sinus direction — producing inverted P waves in inferior leads.

Question 8: 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 9: Which characteristic of the QRS complex in complete heart block provides a clue about the location of the escape pacemaker?

Wide QRS always indicates atrial origin
Narrow QRS suggests a junctional escape; wide QRS suggests a ventricular escape (Correct answer)
Narrow QRS indicates ventricular origin
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 10: In the autonomic nervous system, vagal (parasympathetic) stimulation affects the heart primarily through which neurotransmitter and receptor?

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

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 11: Which of these is a method that can be used to calculate the ventricular rate of a cardiac rhythm when the R-R is regular?

Multiply the number of large boxes between 2 R waves by 300
Divide the number of large boxes between 2 R waves into 300 (Correct answer)
Add the number of large boxes between 2 R waves to 300
Subtract the number of large boxes between 2 R waves from 300

Correct answer: Divide the number of large boxes between 2 R waves into 300

Explanation: To calculate the ventricular rate when the R-R intervals are regular, divide 300 by the number of large boxes between two consecutive R waves on the ECG strip. This method provides an estimate of the heart rate in beats per minute (bpm).

Question 12: Left anterior fascicular block (LAFB) is characterized by which QRS axis on a 12-lead ECG?

Left axis deviation (−45° to −90°) (Correct answer)
Extreme right axis deviation (+180° to −90°)
Normal axis (0° to +90°)
Right axis deviation (+90° to +180°)

Correct answer: Left axis deviation (−45° to −90°)

LAFB produces marked left axis deviation (typically −45° to −90°) because the depolarization wave must travel inferiorly via the posterior fascicle before activating the anterior wall superiorly.

Question 13: Hyperthyroidism most commonly affects sinus rhythm by causing which finding?

Ventricular tachycardia
Third-degree AV block
Sinus tachycardia or atrial fibrillation (Correct answer)
Sinus bradycardia

Correct answer: Sinus tachycardia or atrial fibrillation

Excess thyroid hormone increases adrenergic sensitivity and cardiac automaticity, most commonly producing sinus tachycardia and, in severe cases, atrial fibrillation.

Question 14: Wandering atrial pacemaker differs from multifocal atrial tachycardia primarily by which criterion?

QRS is wider in wandering atrial pacemaker
Heart rate is less than 100 bpm in wandering atrial pacemaker (Correct answer)
PR interval is constant in wandering atrial pacemaker
P wave morphology is fixed in wandering atrial pacemaker

Correct answer: Heart rate is less than 100 bpm in wandering atrial pacemaker

Wandering atrial pacemaker has three or more P wave morphologies and an irregular rhythm but a rate less than 100 bpm, while MAT is defined by a rate of 100 bpm or greater.

Question 15: A CRAT is analyzing a rhythm strip and observes complete AV dissociation. The atrial rate (P-P interval) is regular at 100 bpm, and the ventricular rate (R-R interval) is regular at 42 bpm. There is no consistent relationship between the P waves and the QRS complexes. What is this rhythm?

Sinus Arrhythmia with a junctional escape rhythm
Atrial Fibrillation with a slow ventricular response
Third-Degree AV Block (Correct answer)
Second-Degree AV Block, Mobitz II with 2:1 conduction

Correct answer: Third-Degree AV Block

Third-Degree (Complete) AV Block is defined by the complete absence of conduction between the atria and ventricles. [4, 13] This results in AV dissociation, where the atria and ventricles beat independently of each other, each controlled by its own pacemaker. [15, 16] The ECG shows regular P-P intervals and regular R-R intervals, but the two are not related.

Question 16: What does the TP segment of the ECG represent?

Atrial repolarization
Ventricular systole
AV node refractory period
The true isoelectric baseline during diastole (Correct answer)

Correct answer: The true isoelectric baseline during diastole

The TP segment, occurring between the end of the T wave and the start of the next P wave, represents the true isoelectric baseline during diastole.

Question 17: 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
Left bundle branch block (Correct answer)
Right bundle branch block
Ventricular tachycardia

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 18: Current of microampere levels that may cause cardiac fibrillation when applied directly to the heart through invasive catheters is called what?

Microshock (Correct answer)
Cardioversion
Defibrillation
Macroshock

Correct answer: Microshock

Microshock refers to small electrical currents (as low as 10-100 microamperes) that can trigger ventricular fibrillation when applied directly to the heart via invasive lines or cardiac catheters, bypassing normal skin resistance.

Question 19: The MOST effective ECG analysis requires the following sequence of steps:

Regularity, rate, P wave, PR interval, and QRS complex (Correct answer)
Rate, P wave, PR interval, QRS complex, regularity
P wave, PR interval, QRS complex, regularity, and rate
PR interval, P wave, regularity, rate, and QRS complex

Correct answer: Regularity, rate, P wave, PR interval, and QRS complex

Explanation: Regularly assessing the regularity of the rhythm, followed by determining the rate, and then evaluating the P wave, PR interval, and QRS complex can be an effective sequence for ECG analysis. This approach allows for a systematic evaluation of both rhythm and conduction abnormalities, ensuring comprehensive interpretation.

Question 20: A QRS complex measuring 0.14 seconds is considered:

Absent
Wide or abnormal (Correct answer)
Normal
Slightly prolonged

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 21: A technician at a central monitoring station observes a patient's rhythm abruptly change to coarse Ventricular Fibrillation. What is the most critical and immediate action for the technician to take?

Adjust the ECG gain to confirm the rhythm's morphology.
Activate the facility's emergency response system (e.g., call a "Code Blue"). (Correct answer)
Print a strip of the rhythm for the patient's chart.
Telephone the patient's nurse to ask them to check on the patient.

Correct answer: Activate the facility's emergency response system (e.g., call a "Code Blue").

Ventricular Fibrillation is a lethal arrhythmia requiring immediate defibrillation. [27, 28, 31] The CRAT's primary responsibility is to recognize the rhythm and immediately activate the emergency response system to bring the resuscitation team and defibrillator to the patient's bedside as quickly as possible.

Question 22: An accelerated junctional rhythm differs from a junctional escape rhythm primarily in which way?

Accelerated junctional rhythm has wide QRS complexes
Accelerated junctional rhythm has a rate of 60-100 bpm, faster than normal junctional escape (Correct answer)
Accelerated junctional rhythm never has P waves
Accelerated junctional rhythm is slower than escape rhythm

Correct answer: Accelerated junctional rhythm has a rate of 60-100 bpm, faster than normal junctional escape

Accelerated junctional rhythm occurs when the junctional pacemaker fires faster than its intrinsic 40-60 bpm escape rate, at 60-100 bpm, usurping the sinus node.

Question 23: 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?

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

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 24: Pacemaker undersensing is identified by which ECG pattern?

Pacemaker spikes firing at inappropriate times during or after intrinsic cardiac beats (Correct answer)
Pacemaker spikes exactly timed to the R wave
Pacemaker spikes only during tachycardia
Complete absence of pacemaker spikes

Correct answer: Pacemaker spikes firing at inappropriate times during or after intrinsic cardiac beats

Undersensing means the pacemaker fails to detect intrinsic cardiac activity, causing it to fire at its programmed interval even when the heart has already depolarized spontaneously.

Question 25: Which layer of the heart is responsible for the electrical-to-mechanical coupling that produces contraction?

Pericardium
Epicardium
Endocardium
Myocardium (Correct answer)

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

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

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 27: Which of the following correctly describes the function of the Purkinje fibers?

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

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 28: What is the primary purpose of the 'synchronized' mode during cardioversion?

To synchronize with the patient's breathing
To increase the energy delivered
To allow repeated shocks automatically
To prevent shock delivery during the vulnerable T wave period (Correct answer)

Correct answer: To prevent shock delivery during the vulnerable T wave period

Synchronization ensures the shock is delivered on the R wave rather than the T wave, preventing the R-on-T phenomenon that could trigger ventricular fibrillation.

Question 29: 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?

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

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 30: While monitoring a patient, the CRAT suddenly observes a flat line on Lead II, while Leads I and III appear normal. What is the MOST appropriate first step?

Replace the telemetry transmitter battery.
Check the electrodes and lead wires for the right arm and left leg. (Correct answer)
Initiate a code blue.
Check the patient's pulse and responsiveness.

Correct answer: Check the electrodes and lead wires for the right arm and left leg.

A flat line in a single lead, especially when other leads show a rhythm, indicates a technical problem, not a clinical emergency. Lead II is recorded between the right arm (RA) and left leg (LL) electrodes. Therefore, the first step should be to check the connection of these specific electrodes and their associated wires. Checking the patient is always important, but in the context of an isolated lead failure, the technical issue should be addressed first.

Question 31: Atropine is administered in cardiac emergencies primarily to treat:

Symptomatic bradycardia (Correct answer)
Ventricular tachycardia
Premature ventricular contractions
Atrial flutter

Correct answer: Symptomatic bradycardia

Atropine blocks vagal (parasympathetic) tone to increase heart rate and is the first-line drug for symptomatic bradycardia per ACLS guidelines.

Question 32: During which phase of the cardiac cycle do the ventricles contract, forcing blood into the aorta and pulmonary artery?

Diastole
Isovolumetric relaxation
Systole (Correct answer)
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 33: In right bundle branch block, a wide, slurred S wave is characteristically seen in which leads?

V3 and V4
V1 and V2
I, aVL, V5, and V6 (Correct answer)
II, III, and aVF

Correct answer: I, aVL, V5, and V6

The terminal slurred S wave in leads I, aVL, V5, and V6 represents the delayed right ventricular depolarization force traveling away from these left-sided lateral leads in RBBB.

Question 34: 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 35: What is the intrinsic pacemaker rate of the atrioventricular (AV) junction?

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

Correct answer: 40-60 bpm

The AV junction, which includes the AV node and the bundle of His, has an intrinsic pacemaker rate of 40-60 beats per minute. It serves as a secondary pacemaker, taking over if the primary pacemaker, the SA node (60-100 bpm), fails.

Question 36: In a normal sinus rhythm, the sinus node fires at a rate of:

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

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 37: What does the ST segment on the ECG represent?

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

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

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

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

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

Correct answer: Ventricular repolarization

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

Question 40: 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?

Dextrocardia
Reversal of the left arm and right arm electrodes (Correct answer)
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 41: Which heart valve is responsible for preventing the backflow of oxygenated blood from the left ventricle into the left atrium?

Mitral valve (Correct answer)
Pulmonary valve
Tricuspid valve
Aortic 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 42: What is the intrinsic firing rate of the AV node if it serves as the escape pacemaker?

60-100 bpm
100-150 bpm
40-60 bpm (Correct answer)
20-40 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 43: 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
Sinus Arrhythmia (Correct answer)
Normal Sinus Rhythm
Sinus Bradycardia

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 44: 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)
1 P wave
4 P waves
2 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 45: New-onset LBBB in a patient presenting with chest pain should be managed as which of the following until proven otherwise?

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

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 46: A rhythm strip shows an upright P wave before every QRS complex, a regular R-R interval, a ventricular rate of 72 bpm, a PR interval of 0.16 seconds, and a QRS duration of 0.08 seconds. How would this rhythm be interpreted?

Sinus Tachycardia
Normal Sinus Rhythm (Correct answer)
Sinus Arrhythmia
Sinus Bradycardia

Correct answer: Normal Sinus Rhythm

This rhythm meets all the criteria for Normal Sinus Rhythm: a heart rate between 60-100 bpm, a regular rhythm, a P wave preceding every QRS complex, a constant PR interval between 0.12-0.20 seconds, and a QRS duration less than 0.12 seconds.

Question 47: The refractory period of the AV node serves which primary function?

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

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

A fixed 2:1 ratio of P waves to QRS complexes.
A constant PR interval with intermittently dropped 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: In first-degree AV block, which ECG finding is diagnostic?

PR interval less than 120 ms
PR interval greater than 200 ms with every P wave conducted (Correct answer)
Complete dissociation between P waves and QRS complexes
Dropped QRS complexes with progressive PR lengthening

Correct answer: PR interval greater than 200 ms with every P wave conducted

First-degree AV block is defined by a PR interval exceeding 200 ms (one large box) with every P wave successfully conducting to the ventricles.

Question 50: Which factor most significantly affects the quality of ECG signal transmission in telemetry monitoring?

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

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

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

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

0.40 seconds
0.20 seconds (Correct answer)
0.04 seconds
0.10 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 53: Synchronized cardioversion is indicated for which of the following rhythms?

Ventricular fibrillation
Unstable supraventricular tachycardia with a pulse (Correct answer)
Asystole
Pulseless electrical activity

Correct answer: Unstable supraventricular tachycardia with a pulse

Synchronized cardioversion delivers a shock timed to the R wave and is used for unstable tachyarrhythmias with a pulse, avoiding accidental delivery during the T wave.

Question 54: On the ECG, which measurement defines a normal PR interval?

80-120 ms
120-200 ms (Correct answer)
200-240 ms
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 55: Ensuring that the electrocardiograph is properly grounded reduces the risk of:

Paper speed acceleration
Electrical shock
60-cycle electrical interference (Correct answer)
Faulty interpretation of results

Correct answer: 60-cycle electrical interference

Explanation: If the electrocardiograph is not properly grounded, it can pick up interference from the electrical system, including the 60-cycle electrical interference, which can distort the ECG signal and lead to inaccurate interpretations.

Question 56: Which respiratory pattern produces the most pronounced sinus arrhythmia?

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

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

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

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 58: Idioventricular rhythm (ventricular escape rhythm) is expected to fire at which rate range?

60-100 bpm
40-60 bpm
Less than 20 bpm
20-40 bpm (Correct answer)

Correct answer: 20-40 bpm

Ventricular escape pacemakers in the Purkinje fibers have the lowest intrinsic automaticity rate of 20-40 bpm, emerging when all higher pacemakers (SA node and AV junction) fail.

Question 59: A rhythm analysis technician observes an ECG strip where the PR interval is consistently 0.26 seconds for every beat. The rhythm is regular, with an atrial and ventricular rate of 68 bpm. Each P wave is followed by a QRS complex. What is the correct interpretation?

Normal Sinus Rhythm
Second-Degree AV Block, Mobitz I
Sinus Bradycardia
First-Degree AV Block (Correct answer)

Correct answer: First-Degree AV Block

First-Degree AV Block is characterized by a prolonged but constant PR interval greater than 0.20 seconds. [9, 11] In this rhythm, every P wave is conducted to the ventricles, resulting in a 1:1 relationship between P waves and QRS complexes. [1] The rate is within the normal sinus range, and the PR interval of 0.26 seconds is the key diagnostic feature.

Question 60: Depolarization of cardiac muscle cells occurs primarily due to rapid influx of which ion?

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

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 61: Pacemaker oversensing causes which problem?

Inappropriate inhibition of pacing pulses due to sensing signals that are not cardiac in origin (Correct answer)
Pacing at a rate faster than programmed
Failure to sense intrinsic cardiac activity
Pacing spikes that do not produce QRS complexes

Correct answer: Inappropriate inhibition of pacing pulses due to sensing signals that are not cardiac in origin

Oversensing occurs when the pacemaker incorrectly interprets non-cardiac signals (muscle potentials, electromagnetic interference) as intrinsic cardiac activity, inhibiting appropriate pacing and causing bradycardia.

Question 62: Which chest electrode position is placed at the fourth intercostal space to the right of the sternum?

V3
V4
V2
V1 (Correct answer)

Correct answer: V1

V1 is placed at the fourth intercostal space just to the right of the sternal border, providing the key reference lead for P wave morphology and bundle branch block analysis.

Question 63: Triggered activity as a mechanism of arrhythmia is caused by which electrophysiological phenomenon?

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

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 64: Which electrolyte imbalance is most likely to cause refractory ventricular arrhythmias resistant to standard treatment?

Hypophosphatemia
Hypomagnesemia (Correct answer)
Hypernatremia
Hyperchloremia

Correct answer: Hypomagnesemia

Hypomagnesemia is a common cause of refractory ventricular arrhythmias, and IV magnesium replacement is essential before antiarrhythmic therapy can be effective.

Question 65: What is the significance of a junctional escape rhythm appearing at a rate slower than 40 bpm?

It is normal and expected
It confirms atropine has been given
It indicates the rhythm is actually ventricular in origin
It may indicate junctional suppression, possibly due to enhanced vagal tone, medication effect, or junctional disease (Correct answer)

Correct answer: It may indicate junctional suppression, possibly due to enhanced vagal tone, medication effect, or junctional disease

A junctional rhythm below 40 bpm suggests the junctional pacemaker itself is suppressed, raising concern for medications (beta-blockers, digoxin), hyperkalemia, or intrinsic junctional disease.

Question 66: Digoxin toxicity can cause which ECG changes?

Peaked T waves and wide QRS
Prolonged QT with U waves
Scooped ST depression and bradyarrhythmias (Correct answer)
ST elevation in anterior leads

Correct answer: Scooped ST depression and bradyarrhythmias

Digoxin toxicity classically causes scooped or 'Salvador Dali mustache' ST depression, bradyarrhythmias, and various AV blocks.

Question 67: Wolff-Parkinson-White (WPW) syndrome produces which classic triad of ECG findings?

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

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

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

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 69: When analyzing a rhythm strip for atrial fibrillation, which characteristic is the most definitive indicator of this arrhythmia?

A rapid heart rate exceeding 150 bpm
A narrow QRS complex (<0.12s)
An irregularly irregular R-R interval with no discernible P waves (Correct answer)
The presence of coarse fibrillatory waves

Correct answer: An irregularly irregular R-R interval with no discernible P waves

The hallmark of Atrial Fibrillation is the combination of an irregularly irregular rhythm (varying R-R intervals) and the absence of clear, discernible P waves, which are replaced by a chaotic or fibrillating baseline. [4, 8, 18] While the rate is often rapid, it can be controlled, and fibrillatory waves are not always visible. [4] A narrow QRS is typical but can be wide with aberrant conduction, so it is not the most definitive feature. [4]

Question 70: 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 71: Pacemaker-mediated tachycardia (PMT) can occur in dual-chamber pacemakers due to which mechanism?

Undersensing of ventricular complexes
Battery depletion causes rapid pacing
Retrograde P waves are sensed by the atrial channel, triggering ventricular pacing, creating a reentrant loop (Correct answer)
The pacemaker spontaneously increases its own rate

Correct answer: Retrograde P waves are sensed by the atrial channel, triggering ventricular pacing, creating a reentrant loop

PMT occurs in DDD pacemakers when a premature ventricular beat conducts retrogradely to the atria; the resulting retrograde P wave is sensed by the atrial channel, which then triggers ventricular pacing, which again conducts retrogradely — creating a pacemaker-dependent reentrant loop.

Question 72: In third-degree (complete) heart block, how do atria and ventricles relate to each other?

P waves conduct to ventricles after a very long PR interval
Ventricular rate equals atrial rate
They beat completely independently at their own intrinsic rates (Correct answer)
P waves and QRS complexes maintain a fixed but abnormal ratio

Correct answer: They beat completely independently at their own intrinsic rates

In complete heart block, no atrial impulses are conducted to the ventricles, so each chamber maintains its own independent pacemaker and rate.

Question 73: A CRAT is setting up a telemetry monitor for a stable adult patient with a baseline sinus rhythm of 80 bpm. To minimize non-actionable alarms while ensuring safety, which of the following heart rate alarm settings is most appropriate?

High: 120 bpm, Low: 50 bpm (Correct answer)
High: 90 bpm, Low: 70 bpm
High: 150 bpm, Low: 40 bpm
High: 100 bpm, Low: 60 bpm

Correct answer: High: 120 bpm, Low: 50 bpm

Standard practice for stable adult patients is to set alarm parameters that are wide enough to avoid alarm fatigue from normal variations but narrow enough to detect significant changes. A high limit of 120 bpm and a low limit of 50 bpm is a widely accepted and safe range for a patient with a baseline of 80 bpm. The other ranges are either too narrow, leading to excessive alarms, or too wide, potentially missing a clinically significant event.

Question 74: A patient with bifascicular block (RBBB + LAFB) also has a prolonged PR interval. This pattern is clinically significant because it suggests:

An accessory pathway as in WPW syndrome
Accelerated AV nodal conduction
Increased vagal tone causing benign bradycardia
Disease in all three fascicles with risk of progressing to complete AV block (Correct answer)

Correct answer: Disease in all three fascicles with risk of progressing to complete AV block

Bifascicular block with a prolonged PR interval (trifascicular block pattern) indicates disease affecting all three conduction fascicles and carries significant risk of progression to complete third-degree AV block.

Question 75: The RACE protocol in rapid rhythm assessment stands for which systematic approach?

Regularity, Amplitude, Conduction, Evaluation
Rate, Axis, Complexes, ECG interpretation
Rate, Atrial activity, Conduction (PR interval), Everything else (QRS, ST, QT) (Correct answer)
Rhythm, Arrhythmia, Cardiac output, Electrophysiology

Correct answer: Rate, Atrial activity, Conduction (PR interval), Everything else (QRS, ST, QT)

The RACE mnemonic guides systematic ECG rhythm interpretation by evaluating Rate, Atrial activity (P waves), Conduction (PR interval), and Everything else including QRS and ST changes.

Question 76: 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?

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

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 77: The QT interval is measured from:

End of QRS to start of T wave
Start of QRS to peak of T wave
Start of Q wave to end of T wave (Correct answer)
Start of P wave to end of T wave

Correct answer: Start of Q wave to end of T wave

The QT interval is measured from the beginning of the QRS complex to the end of the T wave and represents total ventricular depolarization and repolarization.

Question 78: The QTc (corrected QT) is used to adjust for heart rate. Using Bazett's formula, QTc is prolonged when it exceeds which threshold in adults?

PR interval × heart rate
360 ms
440-450 ms (with upper limits: 450 ms in men, 460 ms in women) (Correct answer)
500 ms in all patients

Correct answer: 440-450 ms (with upper limits: 450 ms in men, 460 ms in women)

QTc greater than 440-450 ms in men or 460-470 ms in women is generally considered prolonged, with QTc > 500 ms carrying the highest risk for torsades de pointes.

Question 79: On an EKG, the depolarization of the atria, which leads to their contraction, is represented by which waveform?

U wave
P wave (Correct answer)
QRS complex
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 80: The immediate treatment for pulseless ventricular tachycardia is which intervention?

IV adenosine
Synchronized cardioversion
IV amiodarone bolus only
Unsynchronized defibrillation (cardioversion) (Correct answer)

Correct answer: Unsynchronized defibrillation (cardioversion)

Pulseless VT is treated identically to VF with immediate unsynchronized defibrillation, as it represents a cardiac arrest requiring immediate restoration of organized rhythm.

Question 81: The NBG (NASPE/BPEG) pacemaker code uses letters to describe pacemaker function. In a VVI pacemaker, what does the second 'V' indicate?

The ventricle is the paced chamber
The device is rate-responsive
The mode is inhibited
The ventricle is the sensed chamber (Correct answer)

Correct answer: The ventricle is the sensed chamber

In the NBG code, the first letter indicates the paced chamber, the second letter indicates the sensed chamber. In VVI, the second V means the ventricle is the sensed chamber.

Question 82: 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 Atrial Contraction (PAC) (Correct answer)
Premature Junctional Contraction (PJC)
Premature Ventricular Contraction (PVC)

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 83: A rhythm strip shows P wave morphology varying in at least three different shapes with an irregular rate above 100 bpm. What arrhythmia is present?

Wandering atrial pacemaker
Multifocal atrial tachycardia (Correct answer)
Atrial fibrillation
Atrial flutter with variable block

Correct answer: Multifocal atrial tachycardia

Multifocal atrial tachycardia (MAT) is defined by three or more distinct P wave morphologies, an irregular rhythm, and a rate greater than 100 bpm.

Question 84: A CRAT observes a straight, flat line on a patient's cardiac monitor. The patient was previously in sinus rhythm. What is the technician's most appropriate initial action?

Increase the monitor's alarm volume.
Quickly check for loose leads or patient disconnection. (Correct answer)
Immediately document the rhythm as asystole.
Wait for 60 seconds to see if the rhythm changes.

Correct answer: Quickly check for loose leads or patient disconnection.

While a flat line can represent true asystole, it is frequently caused by technical issues such as lead disconnection, incorrect lead selection, or low signal gain. [20, 21, 26] Before activating an emergency response, the technician must perform a rapid check of the equipment to rule out technical error. This is a crucial step in preventing false alarms.

Question 85: The Sgarbossa criteria are used to identify acute MI in the presence of which ECG pattern?

Wolff-Parkinson-White pattern
Left bundle branch block (Correct answer)
Right bundle branch block
Complete AV block

Correct answer: Left bundle branch block

Sgarbossa criteria help identify acute MI in the setting of LBBB because LBBB causes secondary ST-T changes that can mask ischemic ST changes.

Question 86: What is the minimum number of consecutive ventricular beats at 100 bpm or greater required to define ventricular tachycardia?

Two consecutive beats
Five or more consecutive beats
Ten 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 87: What does a delta wave at the onset of the QRS complex suggest?

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

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

AV node → SA node → bundle branches → ventricles
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

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 89: Which cardiac chamber contains MOST of the muscle mass of the heart?

Left atrium
Right atrium
Right ventricle
Left ventricle (Correct answer)

Correct answer: Left ventricle

Explanation: The left ventricle contains the most muscle mass of the heart because it is responsible for pumping oxygenated blood throughout the entire body, requiring significant muscular force.

Question 90: A CRAT identifies a sustained, wide-complex tachycardia at a rate of 170 bpm on a patient's monitor. To help the clinical team determine the urgency of intervention, which associated patient finding is the most critical to report?

The patient's code status.
The patient's diet order (NPO status).
The patient's last dose of cardiac medication.
The patient's blood pressure and level of consciousness. (Correct answer)

Correct answer: The patient's blood pressure and level of consciousness.

The immediate management of Ventricular Tachycardia depends entirely on whether the patient is hemodynamically stable or unstable. [12, 14, 18] Key indicators of instability include hypotension (low blood pressure), altered mental status (confusion, loss of consciousness), signs of shock, and acute chest pain. This information dictates whether the patient requires immediate electrical cardioversion versus medical management.

Question 91: Which cells in the heart have the property of automaticity, meaning they can spontaneously depolarize?

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

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 92: The axis of the heart on a 12-lead ECG is considered to have left axis deviation when it falls within which range?

0 to +90 degrees
-90 to -180 degrees exclusively
+90 to +180 degrees
-30 degrees to -90 degrees (or beyond -30 to -180 degrees depending on criteria) (Correct answer)

Correct answer: -30 degrees to -90 degrees (or beyond -30 to -180 degrees depending on criteria)

Left axis deviation (LAD) is defined as a frontal plane QRS axis more negative than -30 degrees, producing a predominantly positive QRS in lead I and negative QRS in lead aVF.

Question 93: In a junctional escape rhythm, the QRS complex is typically narrow because of which reason?

The impulse originates in the ventricles
The impulse reaches the ventricles via the normal His-Purkinje conduction system (Correct answer)
The impulse bypasses the AV node entirely
Ventricular muscle activates simultaneously from multiple foci

Correct answer: The impulse reaches the ventricles via the normal His-Purkinje conduction system

Since junctional impulses travel through the normal bundle of His, bundle branches, and Purkinje fibers to activate the ventricles, the QRS duration is narrow — less than 120 ms — identical to sinus conducted beats.

Question 94: Normal sinus rhythm requires which set of criteria?

Rate 60-100 bpm with no P waves
Regular P waves upright in II and inverted in aVR, constant PR 120-200 ms, rate 60-100 bpm, narrow QRS (Correct answer)
PR interval greater than 200 ms, rate 60-100 bpm
P waves inverted in II, 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 95: During continuous cardiac monitoring, an alarm is triggered for a critical low heart rate. What should the monitor technician do first?

Adjust the alarm threshold upward
Assume it is a false alarm due to artifact
Silence the alarm and continue monitoring
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 96: Which of the following best describes the P wave in AVNRT?

P waves are often buried within or immediately after the QRS complex (Correct answer)
P waves are clearly visible before each QRS with a normal PR interval
P waves are sawtooth in appearance
P waves are absent with chaotic baseline

Correct answer: P waves are often buried within or immediately after the QRS complex

In AVNRT, retrograde P waves are typically buried within or occur just after the QRS due to near-simultaneous atrial and ventricular depolarization, appearing as pseudo-r in V1 or pseudo-S in inferior leads.

Question 97: PVCs occurring in pairs (two consecutive PVCs) are referred to as which term?

Trigeminy
Salvos
Bigeminy
Couplets (Correct answer)

Correct answer: Couplets

Two consecutive PVCs are called a couplet. Three or more consecutive PVCs constitute a run of ventricular tachycardia.

Question 98: Which of the following AV block types is most likely to require immediate pacemaker implantation?

Mobitz type II second-degree AV block (Correct answer)
First-degree AV block
Mobitz type I second-degree AV block
Fascicular block without AV block

Correct answer: Mobitz type II second-degree AV block

Mobitz type II carries high risk of sudden progression to complete heart block and usually requires permanent pacemaker implantation.

Question 99: Which medication should be avoided in patients with Wolff-Parkinson-White (WPW) syndrome presenting with atrial fibrillation?

AV nodal blocking agents (e.g., adenosine, verapamil) (Correct answer)
Procainamide
Amiodarone
Magnesium sulfate

Correct answer: AV nodal blocking agents (e.g., adenosine, verapamil)

AV nodal blocking agents are contraindicated in WPW with AF because they can enhance conduction through the accessory pathway, potentially causing ventricular fibrillation.

Question 100: 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?

Troubleshoot the electrodes to rule out a loose lead.
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)

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 101: A patient's ECG shows a regular, narrow-complex rhythm at a rate of 120 bpm. No P waves are visible before, during, or after the QRS complexes. This rhythm is best described as:

Junctional Tachycardia (Correct answer)
Accelerated Junctional Rhythm
Atrial Fibrillation
Sinus Tachycardia

Correct answer: Junctional Tachycardia

This rhythm is Junctional Tachycardia. The rate is greater than 100 bpm, the QRS is narrow, and there are no visible P waves, which are characteristic findings. The AV junction has overridden the SA node due to enhanced automaticity, firing at a rate above 100 bpm.

Question 102: Improper placement of the V4 electrode (placed too high, at the 4th ICS instead of 5th) would most likely affect which finding?

Limb lead voltage amplitude
QT interval duration
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 103: Which ECG finding is expected during the absolute refractory period of the cardiac cycle?

Any stimulus can produce fibrillation
No cardiac stimulus can produce a new action potential — corresponds to the QRS complex through early T wave (Correct answer)
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 104: A characteristic of a third-degree AVB is:

An aberrant neuro pathway in the right atrium
The conduction of the atrial impulse failing to reach the ventricle (Correct answer)
An aberrant pathway in the left atrium
The automaticity of the ventricle exceeding that of the atria

Correct answer: The conduction of the atrial impulse failing to reach the ventricle

Explanation: In third-degree atrioventricular block (AVB), also known as complete heart block, the atrial electrical impulses fail to conduct to the ventricles. This results in an independent rhythm between the atria and ventricles, leading to the characteristic dissociation between P waves and QRS complexes on an ECG.

Question 105: When performing a 12-lead ECG, the RL (right leg) electrode serves primarily which purpose?

Electrical ground/reference to reduce common-mode noise (Correct answer)
Records the aVF lead signal
Provides the negative reference for limb leads
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 106: In the 6-second strip method for calculating heart rate, you count the number of QRS complexes and:

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

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

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

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 108: Which of the following correctly describes an INCOMPLETE right bundle branch block?

QRS <0.10 sec with right axis deviation
QRS ≥0.12 sec with rSR' in V1
QRS ≥0.12 sec without rSR' pattern
QRS 0.10–0.11 sec with rSR' in V1 (Correct answer)

Correct answer: QRS 0.10–0.11 sec with rSR' in V1

Incomplete RBBB shows the characteristic rSR' morphology in V1 but with a QRS duration between 0.10 and 0.11 seconds, indicating partial rather than complete conduction delay.

Question 109: Atrial flutter is best described as a rapid atrial depolarization of:

A single reentry focus (Correct answer)
A ventricular focus
Multiple foci
A sinus node focus

Correct answer: A single reentry focus

Explanation: Atrial flutter is characterized by a rapid, regular atrial depolarization originating from a single reentrant circuit within the atria. This single reentry focus leads to the characteristic sawtooth pattern on an ECG.

Question 110: Why should the defibrillator be kept readily accessible near monitored patients in the cardiac care unit?

It improves ECG signal quality
It is required for blood pressure monitoring
It is used routinely for pacemaker programming
Life-threatening arrhythmias such as VF or pulseless VT can occur without warning and require immediate defibrillation (Correct answer)

Correct answer: Life-threatening arrhythmias such as VF or pulseless VT can occur without warning and require immediate defibrillation

Immediate defibrillation within the first minutes of VF is the most critical determinant of survival, so defibrillators must be immediately available in monitored care settings.

Question 111: Accelerated idioventricular rhythm (AIVR) most commonly occurs in which clinical setting?

Hyperkalemia
Reperfusion after myocardial infarction (Correct answer)
Digoxin toxicity
Complete heart block

Correct answer: Reperfusion after myocardial infarction

AIVR is a classic reperfusion arrhythmia seen within hours of restoring coronary flow after MI (thrombolytics or PCI), generally considered benign and self-limiting.

Question 112: 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?

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

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 113: Which interval is most commonly used to assess AV conduction time?

ST segment duration
RR interval
QT interval
PR interval (Correct answer)

Correct answer: PR interval

The PR interval reflects the time for impulse conduction from the SA node through the atria and AV node to the ventricles.

Question 114: Which clinical condition most commonly causes unifocal PVCs in hospitalized patients without structural heart disease?

Structural valve disease
Complete heart block
Electrolyte disturbances (hypokalemia, hypomagnesemia) (Correct answer)
Congenital long QT syndrome

Correct answer: Electrolyte disturbances (hypokalemia, hypomagnesemia)

Electrolyte abnormalities — particularly hypokalemia and hypomagnesemia — are among the most common reversible causes of PVCs in hospitalized patients, as they alter membrane potential stability.

Question 115: Pulseless electrical activity (PEA) is defined by which combination of findings?

Organized ECG rhythm with no detectable pulse (Correct answer)
Ventricular fibrillation without a pulse
Regular ECG rhythm with a strong palpable pulse
No ECG activity and no pulse

Correct answer: Organized ECG rhythm with no detectable pulse

PEA is the presence of organized electrical activity on the ECG (excluding VT/VF) with no palpable pulse — the heart generates electrical signals but fails to produce effective mechanical contraction.

Question 116: In a 12-lead ECG, which leads are considered the inferior leads?

II, III, and aVF (Correct answer)
V1, V2, and V3
I, aVL, and V5-V6
aVR, V1, and V2

Correct answer: II, III, and aVF

Leads II, III, and aVF view the inferior wall of the left ventricle (supplied by the right coronary artery) and are called the inferior leads.

Question 117: Which calcium channel blocker is primarily used to control ventricular rate in atrial fibrillation?

Nimodipine
Nifedipine
Amlodipine
Diltiazem (Correct answer)

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 118: Left posterior fascicular block (LPFB) produces which axis deviation, and in which leads are small Q waves characteristically seen?

Left axis deviation; Q waves in V5 and V6
Right axis deviation; Q waves in V1 and V2
Left axis deviation; Q waves in I and aVL
Right axis deviation; Q waves in II, III, and aVF (Correct answer)

Correct answer: Right axis deviation; Q waves in II, III, and aVF

LPFB causes right axis deviation with small Q waves in II, III, and aVF because activation travels initially anteriorly via the anterior fascicle then shifts inferiorly, producing inferior Q waves.

Question 119: In atrial fibrillation, which ECG finding is most characteristic?

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

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 120: The cardiac action potential plateau phase (Phase 2) is maintained primarily by which ion current?

Chloride influx
Slow inward calcium current (ICa-L) (Correct answer)
Rapid sodium influx
Rapid potassium efflux

Correct answer: Slow inward calcium current (ICa-L)

Phase 2 of the ventricular action potential is sustained by the slow inward L-type calcium current, which balances potassium efflux and maintains the membrane potential near zero for an extended period.

Question 121: Which of the following ECG findings is the most definitive characteristic of a rhythm originating from the AV junction?

An inverted or absent P wave with a short PR interval if visible (Correct answer)
A regularly irregular R-R interval
A wide QRS complex (>0.12 seconds)
A heart rate greater than 100 bpm

Correct answer: An inverted or absent P wave with a short PR interval if visible

Rhythms originating in the AV junction cause retrograde (backward) depolarization of the atria. This results in P waves that are inverted in leads II, III, and aVF, or are absent because they are buried within the QRS complex. If a P wave precedes the QRS, the PR interval is short (<0.12 seconds) because the impulse has less distance to travel to the ventricles.

Question 122: On a standard ECG recorded at 25 mm/sec, each large box (5 mm) represents what duration of time?

40 ms (0.04 seconds)
100 ms (0.10 seconds)
200 ms (0.20 seconds) (Correct answer)
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 123: In high-degree AV block with a 4:1 conduction ratio, what is the ventricular rate if the atrial rate is 80 bpm?

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

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

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

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

75 bpm (Correct answer)
50 bpm
150 bpm
100 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 126: A CRAT notices a patient in sustained stable monomorphic VT. After confirming the patient is stable, the next appropriate intervention is:

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

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 127: A patient's ECG shows a P wave in every beat, upright in lead II, with a constant PR interval of 220 ms and a rate of 72 bpm. What is the correct interpretation?

Normal sinus rhythm with first-degree AV block (Correct answer)
Junctional rhythm
Sinus bradycardia with first-degree AV block
Normal sinus rhythm without any abnormality

Correct answer: Normal sinus rhythm with first-degree AV block

Rate is 72 bpm (normal sinus range), P waves are upright in II (sinus origin), and PR interval is 220 ms — above the 200 ms upper limit — indicating first-degree AV block superimposed on otherwise normal sinus rhythm.

Question 128: Hospital alarm fatigue is a significant patient safety concern because it most commonly leads to which outcome?

Clinicians becoming desensitized and ignoring alarms, potentially missing critical events (Correct answer)
Reduced accuracy of ECG interpretation
Alarms becoming louder over time
Patients developing anxiety about their monitoring

Correct answer: Clinicians becoming desensitized and ignoring alarms, potentially missing critical events

Alarm fatigue occurs when excessive nuisance alarms cause clinicians to become habituated, muting alarms or delaying response, which has led to preventable patient deaths when true critical alarms are ignored.

Question 129: 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:

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

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 130: To get an accurate measurement of the QRS complex, measure from:

The end of the Q wave to the end of the S wave
Before the Q wave to after the end of the S wave
The beginning of the Q wave to the end of the S wave (Correct answer)
The middle of the Q wave to the middle of the S wave

Correct answer: The beginning of the Q wave to the end of the S wave

Explanation: To measure the duration of the QRS complex accurately, it's typically measured from the beginning of the Q wave to the end of the S wave, representing the total time for ventricular depolarization. This method provides a consistent and reliable measurement of the QRS complex duration.

Question 131: During ventricular depolarization, which ECG component is produced?

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

Correct answer: QRS complex

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

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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