Relias Dysrhythmia Basic A Test — 2026/2027 — Complete Questions and Correct Answers AHA Guidelines for Cardiac Monitoring
RELIAS DYSRHYTHMIA BASIC A TEST
2026/2027 — COMPLETE QUESTIONS AND CORRECT ANSWERS WITH EXPLANATIONS
Aligned with Relias Dysrhythmia Testing Standards, AHA Guidelines for Cardiac Monitoring, and Basic Electrocardiogram
Interpretation Competencies (2026/2027 Edition).
Volume: 100 questions (4-option MCQ, single best answer) | Cognitive mix: 25% recall · 50% application · 25% analysis (rhythm strip
interpretation) | Style: ~75% scenario-based (strip interpretation, patient presentation), ~25% direct knowledge
Special inclusions: 25 rhythm strip identification scenarios · 10 ACLS clinical management questions · 10 'distinguish similar rhythms' questions
| Sections: 8 dysrhythmia competency areas | Format: Question stem + A–D options + Correct Answer + 2–3 sentence Relias/AHA rationale.
Section 1: Cardiac Anatomy & Electrophysiology
Q1.
Which structure normally serves as the primary pacemaker of the heart, initiating electrical impulses at an intrinsic rate of 60–100
beats per minute?
A. Atrioventricular (AV) node
B. Sinoatrial (SA) node *[CORRECT]*
C. Bundle of His
D. Purkinje fibers
Correct Answer: B
The SA node, located in the upper right atrium near the entry of the superior vena cava, is the heart's dominant pacemaker with an intrinsic
firing rate of 60-100 bpm. The AV node (A) fires at 40-60 bpm and serves as a backup pacemaker. The Bundle of His (C) and Purkinje fibers
(D) fire at 20-40 bpm as escape pacemakers. The SA node's faster rate normally suppresses all lower pacemakers (overdrive suppression).
Damage to the SA node allows escape rhythms to emerge.
Q2.
During phase 0 of a cardiac myocyte action potential, which event is responsible for the rapid depolarization?
A. Efflux of potassium ions
B. Influx of sodium ions through fast sodium channels *[CORRECT]*
C. Influx of calcium ions through slow calcium channels
D. Efflux of chloride ions
Correct Answer: B
Phase 0 (rapid depolarization) in ventricular myocytes and Purkinje fibers is caused by rapid influx of sodium (Na+) through fast voltage-gated
sodium channels. This creates the sharp upstroke of the action potential. Calcium influx through slow channels (C) characterizes phase 0 of SA
and AV nodal cells (slow-response action potentials) — this is why calcium channel blockers slow AV conduction. Potassium efflux (A) occurs
during phases 1 and 3 (repolarization). Phase 0 is the target of class I antiarrhythmics (sodium channel blockers).
Q3.
In a cardiac action potential, which phase represents the plateau phase and is mediated by balanced calcium influx and potassium
efflux?
A. Phase 0
B. Phase 1
C. Phase 2 *[CORRECT]*
D. Phase 3
Correct Answer: C
Phase 2 (plateau phase) is the distinctive feature of cardiac muscle — a prolonged plateau caused by slow calcium (Ca2+) influx through
L-type channels balanced by potassium (K+) efflux. This plateau gives cardiac muscle its long refractory period, preventing tetanic contraction.
Phase 0 (A) is rapid depolarization (Na+ influx). Phase 1 (B) is initial repolarization (transient K+ efflux). Phase 3 (D) is rapid repolarization
(K+ efflux). Calcium channel blockers (class IV antiarrhythmics) target phase 2 of nodal cells.
Q4.
Which refractory period prevents a cardiac myocyte from responding to ANY stimulus, regardless of strength?
A. Relative refractory period
B. Effective (absolute) refractory period *[CORRECT]*
C. Supernormal period
D. Ectopic period
Correct Answer: B
The effective refractory period (ERP), corresponding to phases 0-2 of the action potential, prevents any new depolarization regardless of
stimulus strength — protecting the heart from tetany. The relative refractory period (A), during phase 3, allows a strong stimulus to provoke a
premature beat (the 'vulnerable period' — R-on-T phenomenon). The supernormal period (C) is a brief window near the end of repolarization
with heightened excitability. ERP is fundamental to preventing fatal arrhythmias.
Page 1 Dysrhythmia Interpretation Certification Preparation Relias Basic A Review
,Relias Dysrhythmia Basic A Test — 2026/2027 — Complete Questions and Correct Answers AHA Guidelines for Cardiac Monitoring
Q5.
The PR interval on the EKG represents the time required for electrical impulse conduction from the:
A. SA node to the AV node
B. Atria to the ventricles through the AV node and Bundle of His *[CORRECT]*
C. Bundle of His to the Purkinje fibers
D. SA node to the ventricular myocardium
Correct Answer: B
The PR interval (normal 0.12-0.20 sec) measures conduction from atrial depolarization through the AV node, Bundle of His, and bundle
branches to the start of ventricular depolarization. It is measured from the beginning of the P wave to the beginning of the QRS complex.
Prolongation indicates delayed AV conduction (first-degree AV block). The QRS represents ventricular depolarization, the QT interval total
ventricular depolarization + repolarization. SA to AV node (A) is incomplete; bundle to Purkinje (C) is the QRS.
Q6.
Which statement correctly describes the normal electrical conduction sequence of the heart?
A. AV node → SA node → Bundle of His → Purkinje fibers
B. SA node → AV node → Bundle of His → bundle branches → Purkinje fibers *[CORRECT]*
C. Bundle of His → SA node → AV node → Purkinje fibers
D. Purkinje fibers → bundle branches → AV node → SA node
Correct Answer: B
Normal conduction sequence: SA node (initiates impulse) → intra-atrial and internodal pathways → AV node (delay of ~0.10 sec allowing
atrial kick) → Bundle of His → right and left bundle branches → Purkinje fibers (rapid spread through ventricles). This sequence ensures
coordinated atrial then ventricular contraction. Any disruption produces conduction abnormalities (AV blocks, bundle branch blocks). The AV
node delay allows ventricular filling during atrial systole.
Q7.
Why is the AV nodal delay (~0.10 seconds) physiologically important?
A. It allows the ventricles to fully depolarize before contracting
B. It allows the atria to complete contraction and empty into the ventricles before ventricular contraction begins
*[CORRECT]*
C. It prevents SA node firing
D. It allows time for the QRS to form
Correct Answer: B
The AV nodal delay (approximately 0.10 seconds) ensures atrial systole completes before ventricular systole begins, allowing optimal ventricular
filling (the 'atrial kick' contributes 15-30% of ventricular filling). This delay synchronizes the cardiac cycle. Loss of atrial kick (e.g., atrial
fibrillation) reduces cardiac output by 15-30%, which is clinically significant in patients with diastolic dysfunction (stiff ventricles). The delay is
mediated by slow calcium channel conduction in the AV node.
Q8.
The ST segment on the EKG represents which electrophysiological event?
A. Atrial depolarization
B. Ventricular depolarization
C. Ventricular repolarization (plateau phase — all cells depolarized equally) *[CORRECT]*
D. Atrial repolarization
Correct Answer: C
The ST segment corresponds to the plateau phase (phase 2) of the ventricular action potential, when all ventricular myocytes are uniformly
depolarized — there is no net electrical difference, so the segment is normally isoelectric (flat at baseline). ST elevation or depression indicates
ischemia, injury, infarction, or electrolyte abnormality. P wave = atrial depolarization; QRS = ventricular depolarization; T wave = ventricular
repolarization. Atrial repolarization is hidden within the QRS.
Q9.
Which property of cardiac cells allows them to initiate an electrical impulse spontaneously without external stimulation?
A. Excitability
B. Conductivity
C. Contractility
D. Automaticity *[CORRECT]*
Correct Answer: D
Automaticity is the ability of cardiac pacemaker cells to spontaneously generate electrical impulses. The SA node has the highest automaticity
(60-100 bpm), followed by the AV node (40-60 bpm) and Purkinje fibers (20-40 bpm). Excitability (A) is the ability to respond to a stimulus.
Conductivity (B) is the ability to transmit impulses. Contractility (C) is the ability to contract in response to a stimulus. Loss of automaticity in the
SA node allows escape rhythms from lower pacemaker sites.
Page 2 Dysrhythmia Interpretation Certification Preparation Relias Basic A Review
, Relias Dysrhythmia Basic A Test — 2026/2027 — Complete Questions and Correct Answers AHA Guidelines for Cardiac Monitoring
Q10.
In a cardiac action potential, which phase is responsible for spontaneous diastolic depolarization in pacemaker cells (SA and AV
nodes)?
A. Phase 0
B. Phase 2
C. Phase 3
D. Phase 4 *[CORRECT]*
Correct Answer: D
Phase 4 (resting membrane potential) in pacemaker cells shows spontaneous slow diastolic depolarization due to slow Na+ influx ('funny
current' or If). When threshold is reached, an action potential fires. This is the basis of automaticity. In non-pacemaker cells (ventricular
myocytes), phase 4 is flat (stable resting membrane potential). Phase 4 slope determines heart rate — increased sympathetic tone
(catecholamines) steepens the slope and increases rate; parasympathetic tone (vagal) flattens it and slows rate.
Q11.
Which cranial nerve provides parasympathetic innervation to the SA and AV nodes, slowing heart rate?
A. Cranial nerve V (trigeminal)
B. Cranial nerve X (vagus) *[CORRECT]*
C. Cranial nerve VII (facial)
D. Cranial nerve IX (glossopharyngeal)
Correct Answer: B
The vagus nerve (CN X) provides parasympathetic innervation to the heart via the AV plexus, releasing acetylcholine at SA and AV nodal tissue
— slowing SA node firing rate and prolonging AV node conduction time. This is why vagal maneuvers (carotid sinus massage, Valsalva)
terminate SVT. Excess vagal tone causes sinus bradycardia, sinus pauses, and AV blocks. Sympathetic innervation (T1-T4) increases rate and
contractility through norepinephrine at beta-1 receptors.
Q12.
The QRS complex on a normal EKG represents which electrophysiological event?
A. Atrial depolarization
B. Ventricular depolarization *[CORRECT]*
C. Ventricular repolarization
D. Atrial repolarization
Correct Answer: B
The QRS complex represents ventricular depolarization — the rapid spread of the electrical impulse through the bundle branches and Purkinje
fibers to depolarize the ventricular myocardium. Normal QRS duration is <0.12 sec (3 small boxes). Wide QRS (>0.12 sec) indicates abnormal
ventricular activation (bundle branch block, ventricular rhythm, hyperkalemia, or sodium channel blocker toxicity). Atrial depolarization is the P
wave; ventricular repolarization is the T wave. The Q wave is the first negative deflection after the P wave.
Q13.
Which electrolyte imbalance most commonly prolongs the QT interval and predisposes to Torsades de Pointes?
A. Hypernatremia
B. Hyponatremia
C. Hypokalemia *[CORRECT]*
D. Hyperchloremia
Correct Answer: C
Hypokalemia, hypomagnesemia, and hypocalcemia all prolong the QT interval by altering action potential repolarization. Prolonged QT
predisposes to early afterdepolarizations (EADs) and Torsades de Pointes (polymorphic VT). Other QT-prolonging factors: medications (class
IA, class III antiarrhythmics; certain antibiotics, antipsychotics, methadone), congenital long QT syndrome. QTc >500 ms significantly increases
risk. Treatment: correct electrolytes, stop offending drugs, IV magnesium sulfate. Sodium (A, B) and chloride (D) abnormalities do not prolong
QT.
Q14.
The T wave on the EKG represents:
A. Atrial repolarization
B. Ventricular repolarization *[CORRECT]*
C. Atrial depolarization
D. Ventricular depolarization
Correct Answer: B
The T wave represents ventricular repolarization (recovery of ventricular myocardium to resting state). Normal T waves are asymmetric and
upright in most leads. Peaked T waves suggest hyperkalemia or early MI (hyperacute T waves). Inverted T waves suggest ischemia, ventricular
hypertrophy, or bundle branch block. Tall, peaked, symmetrical T waves in multiple leads with shortened QT suggest hyperkalemia. T wave
changes must be interpreted in clinical context.
Page 3 Dysrhythmia Interpretation Certification Preparation Relias Basic A Review
RELIAS DYSRHYTHMIA BASIC A TEST
2026/2027 — COMPLETE QUESTIONS AND CORRECT ANSWERS WITH EXPLANATIONS
Aligned with Relias Dysrhythmia Testing Standards, AHA Guidelines for Cardiac Monitoring, and Basic Electrocardiogram
Interpretation Competencies (2026/2027 Edition).
Volume: 100 questions (4-option MCQ, single best answer) | Cognitive mix: 25% recall · 50% application · 25% analysis (rhythm strip
interpretation) | Style: ~75% scenario-based (strip interpretation, patient presentation), ~25% direct knowledge
Special inclusions: 25 rhythm strip identification scenarios · 10 ACLS clinical management questions · 10 'distinguish similar rhythms' questions
| Sections: 8 dysrhythmia competency areas | Format: Question stem + A–D options + Correct Answer + 2–3 sentence Relias/AHA rationale.
Section 1: Cardiac Anatomy & Electrophysiology
Q1.
Which structure normally serves as the primary pacemaker of the heart, initiating electrical impulses at an intrinsic rate of 60–100
beats per minute?
A. Atrioventricular (AV) node
B. Sinoatrial (SA) node *[CORRECT]*
C. Bundle of His
D. Purkinje fibers
Correct Answer: B
The SA node, located in the upper right atrium near the entry of the superior vena cava, is the heart's dominant pacemaker with an intrinsic
firing rate of 60-100 bpm. The AV node (A) fires at 40-60 bpm and serves as a backup pacemaker. The Bundle of His (C) and Purkinje fibers
(D) fire at 20-40 bpm as escape pacemakers. The SA node's faster rate normally suppresses all lower pacemakers (overdrive suppression).
Damage to the SA node allows escape rhythms to emerge.
Q2.
During phase 0 of a cardiac myocyte action potential, which event is responsible for the rapid depolarization?
A. Efflux of potassium ions
B. Influx of sodium ions through fast sodium channels *[CORRECT]*
C. Influx of calcium ions through slow calcium channels
D. Efflux of chloride ions
Correct Answer: B
Phase 0 (rapid depolarization) in ventricular myocytes and Purkinje fibers is caused by rapid influx of sodium (Na+) through fast voltage-gated
sodium channels. This creates the sharp upstroke of the action potential. Calcium influx through slow channels (C) characterizes phase 0 of SA
and AV nodal cells (slow-response action potentials) — this is why calcium channel blockers slow AV conduction. Potassium efflux (A) occurs
during phases 1 and 3 (repolarization). Phase 0 is the target of class I antiarrhythmics (sodium channel blockers).
Q3.
In a cardiac action potential, which phase represents the plateau phase and is mediated by balanced calcium influx and potassium
efflux?
A. Phase 0
B. Phase 1
C. Phase 2 *[CORRECT]*
D. Phase 3
Correct Answer: C
Phase 2 (plateau phase) is the distinctive feature of cardiac muscle — a prolonged plateau caused by slow calcium (Ca2+) influx through
L-type channels balanced by potassium (K+) efflux. This plateau gives cardiac muscle its long refractory period, preventing tetanic contraction.
Phase 0 (A) is rapid depolarization (Na+ influx). Phase 1 (B) is initial repolarization (transient K+ efflux). Phase 3 (D) is rapid repolarization
(K+ efflux). Calcium channel blockers (class IV antiarrhythmics) target phase 2 of nodal cells.
Q4.
Which refractory period prevents a cardiac myocyte from responding to ANY stimulus, regardless of strength?
A. Relative refractory period
B. Effective (absolute) refractory period *[CORRECT]*
C. Supernormal period
D. Ectopic period
Correct Answer: B
The effective refractory period (ERP), corresponding to phases 0-2 of the action potential, prevents any new depolarization regardless of
stimulus strength — protecting the heart from tetany. The relative refractory period (A), during phase 3, allows a strong stimulus to provoke a
premature beat (the 'vulnerable period' — R-on-T phenomenon). The supernormal period (C) is a brief window near the end of repolarization
with heightened excitability. ERP is fundamental to preventing fatal arrhythmias.
Page 1 Dysrhythmia Interpretation Certification Preparation Relias Basic A Review
,Relias Dysrhythmia Basic A Test — 2026/2027 — Complete Questions and Correct Answers AHA Guidelines for Cardiac Monitoring
Q5.
The PR interval on the EKG represents the time required for electrical impulse conduction from the:
A. SA node to the AV node
B. Atria to the ventricles through the AV node and Bundle of His *[CORRECT]*
C. Bundle of His to the Purkinje fibers
D. SA node to the ventricular myocardium
Correct Answer: B
The PR interval (normal 0.12-0.20 sec) measures conduction from atrial depolarization through the AV node, Bundle of His, and bundle
branches to the start of ventricular depolarization. It is measured from the beginning of the P wave to the beginning of the QRS complex.
Prolongation indicates delayed AV conduction (first-degree AV block). The QRS represents ventricular depolarization, the QT interval total
ventricular depolarization + repolarization. SA to AV node (A) is incomplete; bundle to Purkinje (C) is the QRS.
Q6.
Which statement correctly describes the normal electrical conduction sequence of the heart?
A. AV node → SA node → Bundle of His → Purkinje fibers
B. SA node → AV node → Bundle of His → bundle branches → Purkinje fibers *[CORRECT]*
C. Bundle of His → SA node → AV node → Purkinje fibers
D. Purkinje fibers → bundle branches → AV node → SA node
Correct Answer: B
Normal conduction sequence: SA node (initiates impulse) → intra-atrial and internodal pathways → AV node (delay of ~0.10 sec allowing
atrial kick) → Bundle of His → right and left bundle branches → Purkinje fibers (rapid spread through ventricles). This sequence ensures
coordinated atrial then ventricular contraction. Any disruption produces conduction abnormalities (AV blocks, bundle branch blocks). The AV
node delay allows ventricular filling during atrial systole.
Q7.
Why is the AV nodal delay (~0.10 seconds) physiologically important?
A. It allows the ventricles to fully depolarize before contracting
B. It allows the atria to complete contraction and empty into the ventricles before ventricular contraction begins
*[CORRECT]*
C. It prevents SA node firing
D. It allows time for the QRS to form
Correct Answer: B
The AV nodal delay (approximately 0.10 seconds) ensures atrial systole completes before ventricular systole begins, allowing optimal ventricular
filling (the 'atrial kick' contributes 15-30% of ventricular filling). This delay synchronizes the cardiac cycle. Loss of atrial kick (e.g., atrial
fibrillation) reduces cardiac output by 15-30%, which is clinically significant in patients with diastolic dysfunction (stiff ventricles). The delay is
mediated by slow calcium channel conduction in the AV node.
Q8.
The ST segment on the EKG represents which electrophysiological event?
A. Atrial depolarization
B. Ventricular depolarization
C. Ventricular repolarization (plateau phase — all cells depolarized equally) *[CORRECT]*
D. Atrial repolarization
Correct Answer: C
The ST segment corresponds to the plateau phase (phase 2) of the ventricular action potential, when all ventricular myocytes are uniformly
depolarized — there is no net electrical difference, so the segment is normally isoelectric (flat at baseline). ST elevation or depression indicates
ischemia, injury, infarction, or electrolyte abnormality. P wave = atrial depolarization; QRS = ventricular depolarization; T wave = ventricular
repolarization. Atrial repolarization is hidden within the QRS.
Q9.
Which property of cardiac cells allows them to initiate an electrical impulse spontaneously without external stimulation?
A. Excitability
B. Conductivity
C. Contractility
D. Automaticity *[CORRECT]*
Correct Answer: D
Automaticity is the ability of cardiac pacemaker cells to spontaneously generate electrical impulses. The SA node has the highest automaticity
(60-100 bpm), followed by the AV node (40-60 bpm) and Purkinje fibers (20-40 bpm). Excitability (A) is the ability to respond to a stimulus.
Conductivity (B) is the ability to transmit impulses. Contractility (C) is the ability to contract in response to a stimulus. Loss of automaticity in the
SA node allows escape rhythms from lower pacemaker sites.
Page 2 Dysrhythmia Interpretation Certification Preparation Relias Basic A Review
, Relias Dysrhythmia Basic A Test — 2026/2027 — Complete Questions and Correct Answers AHA Guidelines for Cardiac Monitoring
Q10.
In a cardiac action potential, which phase is responsible for spontaneous diastolic depolarization in pacemaker cells (SA and AV
nodes)?
A. Phase 0
B. Phase 2
C. Phase 3
D. Phase 4 *[CORRECT]*
Correct Answer: D
Phase 4 (resting membrane potential) in pacemaker cells shows spontaneous slow diastolic depolarization due to slow Na+ influx ('funny
current' or If). When threshold is reached, an action potential fires. This is the basis of automaticity. In non-pacemaker cells (ventricular
myocytes), phase 4 is flat (stable resting membrane potential). Phase 4 slope determines heart rate — increased sympathetic tone
(catecholamines) steepens the slope and increases rate; parasympathetic tone (vagal) flattens it and slows rate.
Q11.
Which cranial nerve provides parasympathetic innervation to the SA and AV nodes, slowing heart rate?
A. Cranial nerve V (trigeminal)
B. Cranial nerve X (vagus) *[CORRECT]*
C. Cranial nerve VII (facial)
D. Cranial nerve IX (glossopharyngeal)
Correct Answer: B
The vagus nerve (CN X) provides parasympathetic innervation to the heart via the AV plexus, releasing acetylcholine at SA and AV nodal tissue
— slowing SA node firing rate and prolonging AV node conduction time. This is why vagal maneuvers (carotid sinus massage, Valsalva)
terminate SVT. Excess vagal tone causes sinus bradycardia, sinus pauses, and AV blocks. Sympathetic innervation (T1-T4) increases rate and
contractility through norepinephrine at beta-1 receptors.
Q12.
The QRS complex on a normal EKG represents which electrophysiological event?
A. Atrial depolarization
B. Ventricular depolarization *[CORRECT]*
C. Ventricular repolarization
D. Atrial repolarization
Correct Answer: B
The QRS complex represents ventricular depolarization — the rapid spread of the electrical impulse through the bundle branches and Purkinje
fibers to depolarize the ventricular myocardium. Normal QRS duration is <0.12 sec (3 small boxes). Wide QRS (>0.12 sec) indicates abnormal
ventricular activation (bundle branch block, ventricular rhythm, hyperkalemia, or sodium channel blocker toxicity). Atrial depolarization is the P
wave; ventricular repolarization is the T wave. The Q wave is the first negative deflection after the P wave.
Q13.
Which electrolyte imbalance most commonly prolongs the QT interval and predisposes to Torsades de Pointes?
A. Hypernatremia
B. Hyponatremia
C. Hypokalemia *[CORRECT]*
D. Hyperchloremia
Correct Answer: C
Hypokalemia, hypomagnesemia, and hypocalcemia all prolong the QT interval by altering action potential repolarization. Prolonged QT
predisposes to early afterdepolarizations (EADs) and Torsades de Pointes (polymorphic VT). Other QT-prolonging factors: medications (class
IA, class III antiarrhythmics; certain antibiotics, antipsychotics, methadone), congenital long QT syndrome. QTc >500 ms significantly increases
risk. Treatment: correct electrolytes, stop offending drugs, IV magnesium sulfate. Sodium (A, B) and chloride (D) abnormalities do not prolong
QT.
Q14.
The T wave on the EKG represents:
A. Atrial repolarization
B. Ventricular repolarization *[CORRECT]*
C. Atrial depolarization
D. Ventricular depolarization
Correct Answer: B
The T wave represents ventricular repolarization (recovery of ventricular myocardium to resting state). Normal T waves are asymmetric and
upright in most leads. Peaked T waves suggest hyperkalemia or early MI (hyperacute T waves). Inverted T waves suggest ischemia, ventricular
hypertrophy, or bundle branch block. Tall, peaked, symmetrical T waves in multiple leads with shortened QT suggest hyperkalemia. T wave
changes must be interpreted in clinical context.
Page 3 Dysrhythmia Interpretation Certification Preparation Relias Basic A Review
