CRAT — Certified Rhythm Analysis Technician — Questions and Answers

Question 1: Paroxysmal supraventricular tachycardia (PSVT) most commonly has which ventricular rate range?

100-120 bpm
250-350 bpm
150-250 bpm (Correct answer)
60-100 bpm

Correct answer: 150-250 bpm

PSVT characteristically presents with a sudden-onset, regular tachycardia at 150-250 bpm with narrow QRS complexes unless aberrant conduction is present.

Question 2: 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 3: Ventricular flutter is best described by which ECG appearance?

Regular narrow complex tachycardia at 200 bpm
Regular sinusoidal wide complex tachycardia at 200-300 bpm with no discernible QRS-T separation (Correct answer)
Irregular wide complex tachycardia
Completely chaotic electrical activity

Correct answer: Regular sinusoidal wide complex tachycardia at 200-300 bpm with no discernible QRS-T separation

Ventricular flutter appears as a regular, sinusoidal (smooth, continuous wave) wide complex tachycardia at 200-300 bpm where QRS complexes and T waves merge into continuous undulation without distinct separation.

Question 4: The morphology of a PVC can provide information about where in the ventricle the ectopic focus is located. A PVC with LBBB morphology (negative QRS in V1) suggests the focus is located where?

SA node
Left ventricle
AV node
Right ventricle (Correct answer)

Correct answer: Right ventricle

A PVC with LBBB morphology indicates the focus is in the right ventricle — the right ventricle activates first (making V1 negative as depolarization moves away), and the left ventricle activates later, similar to left bundle branch block pattern.

Question 5: Which of the following rhythms may be characterized by regular P-P and regular R-R intervals occurring at different rates?

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

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 6: A patient with a DDD pacemaker has an underlying sinus bradycardia. The ECG shows a pacing spike immediately followed by a P wave, which is then followed by a second pacing spike and a wide QRS complex. This pattern repeats consistently. What is the correct interpretation?

Failure to sense the atrium
Atrial pacing with intact AV conduction
Ventricular pacing only
AV sequential pacing (Correct answer)

Correct answer: AV sequential pacing

This pattern represents normal AV sequential pacing in a dual-chamber (DDD) pacemaker. The first spike paces the atrium because the intrinsic rate is too slow. The pacemaker then waits for a programmed AV delay. If an intrinsic QRS does not appear within that time, the pacemaker delivers a second stimulus to pace the ventricle. This ensures both atrial and ventricular contraction are synchronized. [2, 11, 13]

Question 7: To be classified as a sinus rhythm, which of the following criteria regarding the PR interval must be met?

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

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 8: Sinus tachycardia is most appropriately managed by which approach?

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

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

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

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 10: 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?

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

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

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

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

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

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 13: Which of the following ECG findings is essential for the diagnosis of Multifocal Atrial Tachycardia (MAT)?

A ventricular rate less than 100 bpm
A regularly irregular rhythm
At least three different P wave morphologies in the same lead (Correct answer)
The absence of an isoelectric baseline

Correct answer: At least three different P wave morphologies in the same lead

The defining criteria for Multifocal Atrial Tachycardia (MAT) are a heart rate greater than 100 bpm, an irregular rhythm, and the presence of at least three distinct P-wave morphologies in the same lead. [3, 27, 28] A rate less than 100 bpm with these P wave characteristics would be a Wandering Atrial Pacemaker. [28, 29] While the rhythm is irregular, it is not 'regularly irregular', and it does have an isoelectric baseline between P waves. [3]

Question 14: All of the following are potential P wave presentations in a junctional rhythm EXCEPT:

Inverted, appearing immediately after the QRS complex
Upright and uniform before each QRS with a PR interval of 0.16 seconds (Correct answer)
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 15: 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?

Divide the number of large boxes between 2 R waves into 300 (Correct answer)
Multiply the number of large boxes between 2 R waves by 300
Subtract the number of large boxes between 2 R waves from 300
Add the number of large boxes between 2 R waves to 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 16: 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?

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

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 17: 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 18: 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: 100 bpm, Low: 60 bpm
High: 90 bpm, Low: 70 bpm
High: 150 bpm, Low: 40 bpm
High: 120 bpm, Low: 50 bpm (Correct answer)

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 19: 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:

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

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

Initiating spontaneous depolarization
Limiting ventricular rate during rapid atrial arrhythmias (Correct answer)
Generating the P wave
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 21: Which cells in the heart have the property of automaticity, meaning they can spontaneously depolarize?

Ventricular muscle cells only
Pacemaker cells in the SA node, AV node, and His-Purkinje system (Correct answer)
Only SA node cells
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 22: During which phase of the cardiac cycle do the ventricles contract, forcing blood into the aorta and pulmonary artery?

Systole (Correct answer)
Diastole
Isovolumetric relaxation
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 23: The large box method for estimating heart rate from a regular rhythm divides 300 by the number of large boxes between consecutive R waves. If there are 4 large boxes between R waves, what is the approximate heart rate?

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

Correct answer: 75 bpm

Using the 300 method: 300 divided by 4 large boxes between R waves equals 75 bpm.

Question 24: 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)
Sinus Tachycardia
Accelerated Junctional Rhythm
Atrial Fibrillation

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

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

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 26: Procainamide's primary antiarrhythmic mechanism is:

Blocking beta-adrenergic receptors
Blocking calcium channels in the SA node
Blocking fast sodium channels to slow conduction (Correct answer)
Blocking potassium channels only

Correct answer: Blocking fast sodium channels to slow conduction

Procainamide is a Class IA sodium channel blocker that slows intraventricular conduction and prolongs the refractory period.

Question 27: Which cardiac chamber contains MOST of the muscle mass of the heart?

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

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 28: 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
Disconnected or failed lead II electrode (Correct answer)
Pacemaker failure
Electrode misplacement on both limbs

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 29: A patient's ECG shows wide complex tachycardia at 180 bpm. Which feature most strongly supports a ventricular rather than supraventricular origin?

Rate of 180 bpm
Regular R-R intervals
QRS duration of 120-140 ms
AV dissociation with P waves marching independently through QRS complexes (Correct answer)

Correct answer: AV dissociation with P waves marching independently through QRS complexes

AV dissociation — independent P wave and QRS activity with no relationship between them — is the most specific ECG finding confirming ventricular tachycardia.

Question 30: Idioventricular rhythm (ventricular escape rhythm) is expected to fire at which rate range?

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

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 31: 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?

Atrial Fibrillation
Atrial Flutter
Sinus Tachycardia
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 32: A patient has a normal narrow QRS at 70 bpm but develops LBBB morphology when the rate increases to 110 bpm. This phenomenon is called:

Rate-dependent (tachycardia-dependent) LBBB (Correct answer)
Wolff-Parkinson-White syndrome
Intermittent LBBB
Brugada pattern

Correct answer: Rate-dependent (tachycardia-dependent) LBBB

Rate-dependent (phase 3) LBBB occurs when an increased heart rate causes the cycle length to fall within the refractory period of the left bundle branch, producing block only at faster rates.

Question 33: In patients with frequent PVCs, which marker is most predictive of adverse outcomes (increased risk of sudden cardiac death)?

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

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 34: An EKG caliper measurement of peak-to-peak flutter waves reveals five small boxes. What is the atrial rate of for this rhythm?

150 BPM
120 BPM
300 BPM (Correct answer)
60 BPM

Correct answer: 300 BPM

Explanation: Each small box represents 0.04 seconds, and since there are five small boxes between the flutter waves, the total time for five small boxes is 0.20 seconds. To convert this to beats per minute (BPM), you invert the time interval (1/0.20) which equals 5, then multiply by 60 to convert seconds to minutes, resulting in 300 beats per minute (BPM).

Question 35: Depolarization of cardiac muscle cells occurs primarily due to rapid influx of which ion?

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

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 36: A corrected QT (QTc) interval greater than 500 ms is clinically significant because it:

Signals atrial fibrillation
Indicates a normal variant
Indicates a first-degree AV block
Increases the risk of Torsades de Pointes (Correct answer)

Correct answer: Increases the risk of Torsades de Pointes

A prolonged QTc >500 ms significantly increases the risk of Torsades de Pointes, a potentially fatal ventricular arrhythmia.

Question 37: 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?

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

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

0.12–0.20 seconds (Correct answer)
0.22–0.30 seconds
0.06–0.10 seconds
0.30–0.40 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 39: 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?

Initiate a code blue.
Replace the telemetry transmitter battery.
Check the electrodes and lead wires for the right arm and left leg. (Correct answer)
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 40: Which calculation method uses the number of large squares between two R waves to estimate heart rate?

60 divided by R-R interval in seconds
600 divided by number of large squares
1500 divided by number of small squares
300 divided by number of large squares (Correct answer)

Correct answer: 300 divided by number of large squares

The '300 rule' divides 300 by the number of large squares between two consecutive R waves to estimate heart rate quickly.

Question 41: In standard calibration ECG graph paper, a deflection of the tracing upward or downward by one large box (outlined by thick, dark lines) from the baseline represents:

1.0 volt
0.25 millivolt
0.5 millivolt (Correct answer)
1.0 millivolt

Correct answer: 0.5 millivolt

Explanation: In standard calibration ECG graph paper, each large box represents 0.5 millivolts (mV) of electrical activity. So, a deflection of the tracing upward or downward by one large box from the baseline represents a change of 0.5 millivolts in electrical potential.

Question 42: Sixty-cycle (60 Hz) interference on an ECG most likely results from which cause?

Incorrect lead placement
Loose electrode gel
Patient movement
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 43: 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?

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

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 44: When documenting a rhythm requiring intervention, a CRAT should record:

The rhythm identification, time of onset, patient symptoms, interventions, and patient response (Correct answer)
Only the time the arrhythmia resolved
Just the medication given
Only the heart rate and blood pressure

Correct answer: The rhythm identification, time of onset, patient symptoms, interventions, and patient response

Complete documentation includes rhythm identification, onset time, patient symptoms, all interventions performed, and the patient's response to treatment.

Question 45: Sinus arrhythmia is best described as which pattern?

Irregular R-R intervals that vary with respiration, with all other sinus rhythm criteria intact (Correct answer)
Irregular rhythm due to multiple P wave morphologies
Irregular rhythm with absent P waves
Regular rhythm with variable PR intervals

Correct answer: Irregular R-R intervals that vary with respiration, with all other sinus rhythm criteria intact

Sinus arrhythmia is a normal variant where heart rate increases with inspiration and decreases with expiration, producing slight R-R interval variation while maintaining normal sinus P waves and PR intervals.

Question 46: Current of microampere levels that may cause cardiac fibrillation when applied directly to the heart through invasive catheters is called what?

Defibrillation
Cardioversion
Macroshock
Microshock (Correct answer)

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

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

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 48: 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)
AC interference
60-cycle 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 49: When analyzing a rhythm strip for atrial fibrillation, which characteristic is the most definitive indicator of this arrhythmia?

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

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 50: 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?

Loose limb electrode
Patient respiration
AC (60-cycle) interference (Correct answer)
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 51: Adenosine is the drug of choice for terminating which arrhythmia?

Paroxysmal supraventricular tachycardia (PSVT) (Correct answer)
Ventricular fibrillation
Torsades de Pointes
Atrial fibrillation

Correct answer: Paroxysmal supraventricular tachycardia (PSVT)

Adenosine transiently blocks AV node conduction and is the first-line drug for terminating PSVT by interrupting re-entry circuits involving the AV node.

Question 52: 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
75 bpm (Correct answer)
50 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 53: The left bundle branch divides into how many main fascicles?

Two (Correct answer)
Three
One
Four

Correct answer: Two

The left bundle branch divides into two main fascicles: the left anterior fascicle and the left posterior fascicle, each of which can be independently blocked.

Question 54: Which waveform represents ventricular repolarization on an ECG strip?

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

Correct answer: T wave

Explanation: The T wave on an ECG represents ventricular repolarization, which is the phase of the cardiac cycle when the ventricles reset their electrical state in preparation for the next contraction.

Question 55: When defibrillating a patient, which safety precaution is most critical immediately before delivering the shock?

Verify the patient is unconscious
Ensure all personnel are clear of the patient and bed before discharging (Correct answer)
Set the defibrillator to synchronized mode
Apply conductive gel to the patient's chest before paddles

Correct answer: Ensure all personnel are clear of the patient and bed before discharging

Clearing all personnel from the patient and bed is the most critical safety step — delivering the shock while anyone is in contact risks severe electrical injury to bystanders.

Question 56: Synchronized cardioversion is indicated for which of the following rhythms?

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

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 57: Which condition must be excluded BEFORE diagnosing left posterior fascicular block (LPFB)?

Right ventricular hypertrophy and lateral wall MI must be ruled out (Correct answer)
QRS duration must exceed 0.12 seconds
The patient must have a documented history of hypertension
ST elevation must be present in inferior leads

Correct answer: Right ventricular hypertrophy and lateral wall MI must be ruled out

LPFB is a diagnosis of exclusion because right ventricular hypertrophy, lateral MI, and pulmonary disease can all cause right axis deviation that mimics LPFB's ECG pattern.

Question 58: 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
P waves and QRS complexes maintain a fixed but abnormal ratio
They beat completely independently at their own intrinsic rates (Correct answer)

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

Placing electrodes over hairy areas without preparation
Using cold water to clean the skin
Cleaning and lightly abrading the skin to remove oils and dead cells before electrode placement (Correct answer)
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 60: The NBG (NASPE/BPEG) pacemaker code uses letters to describe pacemaker function. In a VVI pacemaker, what does the second 'V' indicate?

The device is rate-responsive
The ventricle is the paced chamber
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 61: In the chain of survival, early defibrillation for VF is critical because VF survival decreases by approximately how much for each minute without defibrillation?

1-2% per minute
50% per minute
7-10% per minute (Correct answer)
15-20% 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 62: 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?

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

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

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

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 64: Which ECG finding is the classic sign of acute ST-elevation myocardial infarction (STEMI)?

ST segment elevation greater than 1 mm in two or more contiguous leads (Correct answer)
T wave inversion in all leads
New left bundle branch block only
ST depression greater than 0.5 mm in multiple leads

Correct answer: ST segment elevation greater than 1 mm in two or more contiguous leads

STEMI requires ST elevation greater than 1 mm (2 mm in V2-V3) in two or more anatomically contiguous leads, representing a current of injury from transmural myocardial ischemia.

Question 65: What is pacemaker syndrome?

Electromagnetic interference inhibiting pacing
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
Battery depletion causing pacemaker failure

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 66: A CRAT observes a regular rhythm on a patient's monitor with a rate of 75 bpm. The QRS complexes are 0.06 seconds wide. There are inverted P waves in lead II just before each QRS complex, with a PR interval of 0.10 seconds. What is the correct interpretation of this rhythm?

Junctional Tachycardia
Junctional Escape Rhythm
Accelerated Junctional Rhythm (Correct answer)
Sinus Rhythm with PACs

Correct answer: Accelerated Junctional Rhythm

This rhythm is an Accelerated Junctional Rhythm. The rate of 61-100 bpm is faster than the intrinsic rate of the AV junction but slower than tachycardia. The presence of inverted P waves with a short PR interval confirms the junctional origin. Junctional Escape Rhythm is slower (40-60 bpm), and Junctional Tachycardia is faster (>100 bpm).

Question 67: Which of the following is the defining characteristic of Sinus Arrhythmia?

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

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 68: Which respiratory pattern produces the most pronounced sinus arrhythmia?

Mechanical ventilation at high PEEP
Rapid shallow breathing
Slow, deep breathing (Correct answer)
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 69: What is the intrinsic firing rate of the AV node if it serves as the escape pacemaker?

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

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 70: Ventricular fibrillation on an ECG is best described by which appearance?

Regular wide complex tachycardia at 150-250 bpm
Fine regular oscillations at 300 bpm
Absent all electrical activity
Chaotic, irregular waveforms with no discernible QRS complexes (Correct answer)

Correct answer: Chaotic, irregular waveforms with no discernible QRS complexes

Ventricular fibrillation produces completely chaotic, irregular electrical activity with no organized QRS complexes — the ventricles quiver rather than contract effectively.

Question 71: In the normal cardiac conduction sequence, what is the correct order of activation?

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

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 72: A patient post-cardiac surgery develops a regular narrow-complex tachycardia at 110 bpm with inverted P waves in lead II occurring just after each QRS. Which rhythm is most likely?

AVNRT
Sinus tachycardia
Atrial flutter with 2:1 block
Junctional tachycardia (Correct answer)

Correct answer: Junctional tachycardia

Regular narrow-complex tachycardia at 110 bpm with retrograde P waves (inverted in II) immediately after QRS in a post-cardiac surgery patient is consistent with junctional tachycardia due to enhanced automaticity.

Question 73: Which waveform on the ECG represents ventricular repolarization?

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

Correct answer: T wave

The T wave represents ventricular repolarization — the recovery phase of the ventricles after contraction.

Question 74: Which layer of the heart is responsible for the electrical-to-mechanical coupling that produces contraction?

Endocardium
Myocardium (Correct answer)
Pericardium
Epicardium

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 75: 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 76: The immediate treatment for pulseless ventricular tachycardia is which intervention?

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

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 77: Automaticity in pacemaker cells is generated by which mechanism?

Passive potassium influx
Spontaneous slow diastolic depolarization (Phase 4) driven by the If funny current (Correct answer)
Rapid sodium channel opening during rest
Calcium pump activity

Correct answer: Spontaneous slow diastolic depolarization (Phase 4) driven by the If funny current

Pacemaker cell automaticity results from Phase 4 spontaneous diastolic depolarization — a slow inward current (If, the funny current) that progressively depolarizes the cell toward threshold during diastole.

Question 78: 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 79: 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 80: What cardiac rhythm is shown in this presenting rhythm strip from a trans telephonic pacemaker check?

Sinus rhythm
Paced ventricular rhythm
Atrial fibrillation
Paced atrial rhythm (Correct answer)

Correct answer: Paced atrial rhythm

Explanation: In a paced atrial rhythm, regular spikes are seen representing the pacing of the atria by the pacemaker. This is characterized by consistent atrial pacing spikes followed by atrial depolarization.

Question 81: In a junctional rhythm, P waves appear inverted in the inferior leads (II, III, aVF) because of which mechanism?

The PR interval is prolonged
P waves originate from the right atrium
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 82: A patient on anticoagulation therapy develops a new atrial fibrillation. Why is anticoagulation particularly important in this setting?

Atrial fibrillation promotes thrombus formation in the left atrial appendage, creating risk of embolic stroke (Correct answer)
Anticoagulation prevents atrial fibrillation from recurring
Anticoagulation controls the ventricular rate in atrial fibrillation
Anticoagulation improves cardiac output 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 83: Which atrial arrhythmia is characterized by a sawtooth pattern at a rate of 250-350 bpm on the ECG?

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

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 84: Sinus node dysfunction presenting with alternating bradycardia and tachycardia (typically AFib with rapid ventricular response alternating with sinus pauses) is called what syndrome?

Brugada syndrome
Sick sinus syndrome (bradycardia-tachycardia syndrome) (Correct answer)
Wolff-Parkinson-White syndrome
Long QT syndrome

Correct answer: Sick sinus syndrome (bradycardia-tachycardia syndrome)

Bradycardia-tachycardia syndrome is a subset of sick sinus syndrome where atrial tachyarrhythmias (often AFib) alternate with periods of profound sinus bradycardia or sinus pauses.

Question 85: Why should the defibrillator be kept readily accessible near monitored patients in the cardiac care unit?

It is required for blood pressure monitoring
It improves ECG signal quality
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 86: Which of the following correctly describes the function of the Purkinje fibers?

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

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 87: 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)
Constant PR interval with every other P wave blocked
Complete AV dissociation

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.

Question 88: Which heart valve is responsible for preventing the backflow of oxygenated blood from the left ventricle into the left atrium?

Aortic valve
Mitral valve (Correct answer)
Pulmonary valve
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 89: Which chest electrode position is placed at the fourth intercostal space to the right of the sternum?

V4
V2
V1 (Correct answer)
V3

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

Mobitz type II second-degree AV block (Correct answer)
Mobitz type I second-degree AV block
First-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 91: A pacemaker spike followed by a wide, abnormal QRS complex indicates what type of pacing?

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

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 92: 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 93: The MOST effective ECG analysis requires the following sequence of steps:

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

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

Hyperkalemia
Hypernatremia
Hypokalemia (Correct answer)
Hypercalcemia

Correct answer: Hypokalemia

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

Question 95: A Certified Rhythm Analysis Technician is reviewing an ECG strip and notes that the only abnormality is a heart rate of 48 beats per minute. All other parameters (P wave, PR interval, QRS complex, and regularity) are within normal limits. Which rhythm is most likely present?

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

Correct answer: Sinus Bradycardia

Sinus Bradycardia is characterized by a sinus rhythm with a rate of less than 60 beats per minute. Since all other aspects of the rhythm are normal, this is the correct interpretation.

Question 96: When a patient with a pacemaker is receiving electrocautery during surgery, which pacemaker problem can occur?

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

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 97: If a junctional rhythm shows P waves occurring immediately AFTER each QRS complex (short RP interval), what does this timing indicate?

The QRS is conducted aberrantly
AV block is present
The SA node is functioning normally
Retrograde atrial activation occurs after ventricular depolarization because the atria are activated slower than the ventricles (Correct answer)

Correct answer: Retrograde atrial activation occurs after ventricular depolarization because the atria are activated slower than the ventricles

When the AV junction activates both ventricles (antegrade via His-Purkinje) and atria (retrograde), the timing of P waves relative to QRS depends on which pathway conducts faster; slow retrograde conduction produces P waves after QRS.

Question 98: Baseline wander on an ECG is most commonly caused by which factor?

Incorrect paper speed
Patient breathing or movement causing electrode-skin interface changes (Correct answer)
Electrical interference from AC current
Low battery in the ECG machine

Correct answer: Patient breathing or movement causing electrode-skin interface changes

Baseline wander results from slow undulation of the baseline caused by patient movement, respiration, poor electrode contact, or electrode gel drying.

Question 99: In LBBB, T-wave deflections that are discordant (opposite direction) to the QRS complex are considered:

Pathological, indicating acute ischemia
A sign of hyperkalemia
Normal secondary repolarization changes (Correct answer)
Indicative of pericarditis

Correct answer: Normal secondary repolarization changes

Discordant ST-T changes are expected secondary repolarization abnormalities in LBBB resulting from the abnormal depolarization sequence and are not independently pathological.

Question 100: Magnesium sulfate is the treatment of choice for:

Torsades de Pointes (Correct answer)
First-degree AV block
Junctional escape rhythm
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 101: Digitalis toxicity is classically associated with which junctional arrhythmia pattern?

Atrial fibrillation with rapid ventricular response
Accelerated junctional rhythm with AV dissociation (Correct answer)
Sinus tachycardia
First-degree AV block without junctional escape

Correct answer: Accelerated junctional rhythm with AV dissociation

Digitalis toxicity enhances junctional automaticity (causing accelerated junctional rhythm at 60-100 bpm) while simultaneously blocking AV conduction, producing AV dissociation.

Question 102: A notched or bifid P wave (P mitrale) is associated with:

Right atrial enlargement
Ventricular hypertrophy
AV nodal delay
Left atrial enlargement (Correct answer)

Correct answer: Left atrial enlargement

A wide, notched P wave (P mitrale) indicates left atrial enlargement, often seen in mitral valve disease.

Question 103: An isoelectric baseline on the ECG refers to:

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

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 104: The R-on-T phenomenon in PVCs is dangerous because it does which of the following?

It prolongs the PR interval
It causes sinus node suppression
It produces AV block
A PVC occurring during the vulnerable period of ventricular repolarization (T wave peak) can initiate ventricular fibrillation (Correct answer)

Correct answer: A PVC occurring during the vulnerable period of ventricular repolarization (T wave peak) can initiate ventricular fibrillation

The peak of the T wave represents the vulnerable period of ventricular repolarization — when cells are partially recovered, making them susceptible to fibrillation if an electrical stimulus (PVC) falls during this window.

Question 105: Which structure is the primary pacemaker of the heart under normal conditions?

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

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

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

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

Hyperchloremia
Hypomagnesemia (Correct answer)
Hypophosphatemia
Hypernatremia

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

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

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

Peaked, narrow, symmetric T waves (Correct answer)
Prolonged PR interval
Flat P waves
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 110: During ventricular depolarization, which ECG component is produced?

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

Correct answer: QRS complex

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

Question 111: The P wave on the electrocardiogram represents an electrical impulse that spreads through the:

Purkinje Fibers
Atria (Correct answer)
Ventricles
Bundle of His

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 112: Which set of criteria correctly describes left anterior fascicular block (LAFB)?

Left axis deviation, rSR' in V1, QRS ≥0.12 sec
Right axis deviation, small Q in II and III, QRS ≥0.12 sec
Left axis deviation, small Q in I and aVL, small R in II/III/aVF, QRS <0.12 sec (Correct answer)
Right axis deviation, broad S in I and V6, QRS ≥0.12 sec

Correct answer: Left axis deviation, small Q in I and aVL, small R in II/III/aVF, QRS <0.12 sec

LAFB criteria include left axis deviation (−45° to −90°), small Q waves in I and aVL, small R waves in II, III, and aVF, and a QRS duration less than 0.12 seconds.

Question 113: 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)
Third-Degree AV Block
Complete Sinus Arrest

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

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

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 115: 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:

A run of multifocal PVCs
Accelerated Idioventricular Rhythm (AIVR)
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 116: 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
-30 degrees to -90 degrees (or beyond -30 to -180 degrees depending on criteria) (Correct answer)
+90 to +180 degrees
-90 to -180 degrees exclusively

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

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

Correct answer: Class II

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

Question 118: 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 119: 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?

Sinus Bradycardia
Normal Sinus Rhythm
Second-Degree AV Block, Mobitz I
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 120: 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)
10 bpm
40 bpm
80 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 121: Which antiarrhythmic drug is classified as a Class III agent and is commonly used for atrial fibrillation and ventricular tachycardia?

Lidocaine
Metoprolol
Amiodarone (Correct answer)
Adenosine

Correct answer: Amiodarone

Amiodarone is a Class III antiarrhythmic that blocks potassium channels to prolong repolarization and is widely used for both atrial and ventricular arrhythmias.

Question 122: A monitor shows a sudden change to a flat line in one lead. What is the first action a rhythm technician should take?

Call the physician without verifying the lead
Check the patient directly and verify electrode and lead connections before calling a code (Correct answer)
Immediately call a code blue
Apply defibrillator pads

Correct answer: Check the patient directly and verify electrode and lead connections before calling a code

A flat line must be verified as a true rhythm rather than artifact by checking the patient, the electrodes, and the connections in all leads before escalating to a code response.

Question 123: Which clinical condition is most commonly associated with junctional escape rhythm as a primary rhythm?

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

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

≥0.14 seconds
≥0.08 seconds
≥0.10 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 125: 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?

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

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

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

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

Potassium efflux through IKr and IKs channels (Correct answer)
Chloride efflux
Calcium influx
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 128: A patient is experiencing a blockage in the right coronary artery (RCA). Which of the following structures is most likely to be affected?

Anterior wall of the left ventricle
SA node and right ventricle (Correct answer)
Left atrium and circumflex artery
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 129: On the ECG, which measurement defines a normal PR interval?

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

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 130: The Vaughan Williams Class IV antiarrhythmics include:

Calcium channel blockers (Correct answer)
Potassium channel blockers
Sodium channel blockers
Beta-blockers

Correct answer: Calcium channel blockers

Class IV antiarrhythmics are calcium channel blockers (e.g., diltiazem, verapamil) that slow conduction through the AV node.

Question 131: 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)
P waves inverted in II, rate 60-100 bpm
Rate 60-100 bpm with no P waves
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.

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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