MAYO ECG Exam
2026/2027 Insider Test Bank
Complete Q&A & Verified A+ Solutions | 150 Questions
Key Domains Covered
• Cardiac Anatomy & Electrophysiology (Conduction System, Action Potentials)
• Normal ECG Components (P wave, QRS complex, T wave, U wave, Intervals)
• Sinus Rhythms (Normal, Bradycardia, Tachycardia, Arrhythmia)
• Atrial Dysrhythmias (PAC, Atrial Fibrillation, Atrial Flutter, SVT)
• Junctional Dysrhythmias
• Ventricular Dysrhythmias (PVC, VTach, VFib, Torsades)
• Heart Blocks (1st, 2nd, Type I/II, 3rd Degree)
• Ischemia & Infarction Patterns (ST Elevation, Depression, T Wave Inversion, Q Waves)
• Electrolyte & Drug Effects on ECG
• Pacemaker & 12-Lead ECG Interpretation
,Introduction
This structured MAYO ECG Exam Test Bank for 2026/2027 provides a comprehensive set of 150 exam-
style questions with complete Q&A and verified solutions. It is designed to prepare healthcare
professionals (nurses, physicians, technicians) for Mayo Clinic ECG interpretation competency exams,
emphasizing rhythm identification, ischemia/infarction recognition, conduction abnormalities, and
clinical application of ECG findings to patient care.
All correct answers appear in bold cyan blue, accompanied by rationales explaining rhythm identification
based on rate, regularity, P wave morphology, PR interval, and QRS duration; ECG criteria for ischemia
or infarction; appropriate clinical interventions; recognition of electrolyte or drug-induced changes; and
why alternative interpretations or interventions would lead to incorrect treatment or delayed care.
,MAYO ECG Comprehensive Test Bank (150 Questions)
1. The sinoatrial (SA) node is located in which area of the heart?
A. Right atrium near the superior vena cava B. Left atrium near the pulmonary vein
C. Interventricular septum D. Base of the left ventricle
Correct Answer: A
Rationale: The SA node is located in the superior aspect of the right atrium near the opening of the superior vena
cava. It is the primary pacemaker of the heart, generating impulses at 60-100 bpm. Its location at this strategic
point allows rapid depolarization of both atria through internodal pathways.
2. Which ion is most responsible for the rapid depolarization phase (Phase 0) of the cardiac action
potential in ventricular myocytes?
A. Calcium (Ca2+) B. Potassium (K+)
C. Sodium (Na+) D. Chloride (Cl-)
Correct Answer: C
Rationale: Phase 0 of the ventricular action potential is caused by rapid influx of sodium ions (Na+) through fast
voltage-gated sodium channels. This rapid depolarization drives the membrane potential from approximately -90
mV to +20 mV. In contrast, SA node cells rely on calcium influx for Phase 0, which accounts for the slower upstroke
in pacemaker cells.
3. What is the normal resting membrane potential of a ventricular myocyte?
A. -70 mV B. -90 mV
C. +20 mV D. 0 mV
Correct Answer: B
Rationale: The normal resting membrane potential of a ventricular myocyte is approximately -90 mV. This negative
potential is maintained primarily by the Na+/K+ ATPase pump, which extrudes 3 sodium ions for every 2 potassium
ions imported, and by the selective permeability of the cell membrane to potassium during diastole.
4. Which phase of the cardiac action potential corresponds to the ST segment on the ECG?
A. Phase 0 B. Phase 1
C. Phase 2 (Plateau) D. Phase 3
Correct Answer: C
Rationale: Phase 2 (the plateau phase) corresponds to the ST segment on the ECG. During this phase, calcium
influx through L-type calcium channels balances potassium efflux, creating a sustained depolarization that prolongs
the action potential. This plateau is essential for coordinating cardiac contraction and is unique to cardiac
myocytes.
5. The atrioventricular (AV) node is located in which anatomical region?
, A. Left atrium B. Interatrial septum near the coronary sinus
C. Right ventricular outflow tract D. Aortic root
Correct Answer: B
Rationale: The AV node is located in the inferior portion of the interatrial septum, near the opening of the coronary
sinus and the tricuspid valve. It serves as the critical electrical gateway between the atria and ventricles,
introducing a physiologic delay (PR interval) that allows ventricular filling before contraction. The AV node's slow
conduction velocity also protects the ventricles from excessively rapid atrial rates.
6. What is the primary function of the Bundle of His?
A. Initiate the cardiac impulse B. Delay atrioventricular conduction
C. Rapidly conduct impulses from the AV node D. Repolarize the ventricles
to the bundle branches
Correct Answer: C
Rationale: The Bundle of His (atrioventricular bundle) rapidly conducts electrical impulses from the AV node
through the interventricular septum to the right and left bundle branches. It is the only electrical connection
between the atria and ventricles. Its fast conduction velocity ensures synchronized ventricular depolarization.
7. The Purkinje fibers distribute electrical impulses to which cardiac structure?
A. The atria B. The SA node
C. The ventricular endocardium D. The pericardium
Correct Answer: C
Rationale: Purkinje fibers are specialized conducting fibers that distribute electrical impulses from the bundle
branches to the ventricular endocardium. They enable rapid and synchronized depolarization of the ventricular
myocardium from endocardium to epicardium, producing efficient ventricular contraction. Purkinje fibers can also
serve as latent pacemakers at a rate of 20-40 bpm.
8. What is the intrinsic firing rate of the SA node?
A. 20-40 bpm B. 40-60 bpm
C. 60-100 bpm D. 100-150 bpm
Correct Answer: C
Rationale: The SA node has an intrinsic firing rate of 60-100 beats per minute, making it the dominant pacemaker
under normal conditions. The AV node fires at 40-60 bpm, and Purkinje fibers at 20-40 bpm. This hierarchical rate
difference ensures that the fastest pacemaker (SA node) overrides slower latent pacemakers, a principle known as
overdrive suppression.
9. Which coronary artery supplies blood to the SA node in most individuals?
A. Left anterior descending artery (LAD) B. Right coronary artery (RCA)
C. Circumflex artery D. Posterior descending artery
2026/2027 Insider Test Bank
Complete Q&A & Verified A+ Solutions | 150 Questions
Key Domains Covered
• Cardiac Anatomy & Electrophysiology (Conduction System, Action Potentials)
• Normal ECG Components (P wave, QRS complex, T wave, U wave, Intervals)
• Sinus Rhythms (Normal, Bradycardia, Tachycardia, Arrhythmia)
• Atrial Dysrhythmias (PAC, Atrial Fibrillation, Atrial Flutter, SVT)
• Junctional Dysrhythmias
• Ventricular Dysrhythmias (PVC, VTach, VFib, Torsades)
• Heart Blocks (1st, 2nd, Type I/II, 3rd Degree)
• Ischemia & Infarction Patterns (ST Elevation, Depression, T Wave Inversion, Q Waves)
• Electrolyte & Drug Effects on ECG
• Pacemaker & 12-Lead ECG Interpretation
,Introduction
This structured MAYO ECG Exam Test Bank for 2026/2027 provides a comprehensive set of 150 exam-
style questions with complete Q&A and verified solutions. It is designed to prepare healthcare
professionals (nurses, physicians, technicians) for Mayo Clinic ECG interpretation competency exams,
emphasizing rhythm identification, ischemia/infarction recognition, conduction abnormalities, and
clinical application of ECG findings to patient care.
All correct answers appear in bold cyan blue, accompanied by rationales explaining rhythm identification
based on rate, regularity, P wave morphology, PR interval, and QRS duration; ECG criteria for ischemia
or infarction; appropriate clinical interventions; recognition of electrolyte or drug-induced changes; and
why alternative interpretations or interventions would lead to incorrect treatment or delayed care.
,MAYO ECG Comprehensive Test Bank (150 Questions)
1. The sinoatrial (SA) node is located in which area of the heart?
A. Right atrium near the superior vena cava B. Left atrium near the pulmonary vein
C. Interventricular septum D. Base of the left ventricle
Correct Answer: A
Rationale: The SA node is located in the superior aspect of the right atrium near the opening of the superior vena
cava. It is the primary pacemaker of the heart, generating impulses at 60-100 bpm. Its location at this strategic
point allows rapid depolarization of both atria through internodal pathways.
2. Which ion is most responsible for the rapid depolarization phase (Phase 0) of the cardiac action
potential in ventricular myocytes?
A. Calcium (Ca2+) B. Potassium (K+)
C. Sodium (Na+) D. Chloride (Cl-)
Correct Answer: C
Rationale: Phase 0 of the ventricular action potential is caused by rapid influx of sodium ions (Na+) through fast
voltage-gated sodium channels. This rapid depolarization drives the membrane potential from approximately -90
mV to +20 mV. In contrast, SA node cells rely on calcium influx for Phase 0, which accounts for the slower upstroke
in pacemaker cells.
3. What is the normal resting membrane potential of a ventricular myocyte?
A. -70 mV B. -90 mV
C. +20 mV D. 0 mV
Correct Answer: B
Rationale: The normal resting membrane potential of a ventricular myocyte is approximately -90 mV. This negative
potential is maintained primarily by the Na+/K+ ATPase pump, which extrudes 3 sodium ions for every 2 potassium
ions imported, and by the selective permeability of the cell membrane to potassium during diastole.
4. Which phase of the cardiac action potential corresponds to the ST segment on the ECG?
A. Phase 0 B. Phase 1
C. Phase 2 (Plateau) D. Phase 3
Correct Answer: C
Rationale: Phase 2 (the plateau phase) corresponds to the ST segment on the ECG. During this phase, calcium
influx through L-type calcium channels balances potassium efflux, creating a sustained depolarization that prolongs
the action potential. This plateau is essential for coordinating cardiac contraction and is unique to cardiac
myocytes.
5. The atrioventricular (AV) node is located in which anatomical region?
, A. Left atrium B. Interatrial septum near the coronary sinus
C. Right ventricular outflow tract D. Aortic root
Correct Answer: B
Rationale: The AV node is located in the inferior portion of the interatrial septum, near the opening of the coronary
sinus and the tricuspid valve. It serves as the critical electrical gateway between the atria and ventricles,
introducing a physiologic delay (PR interval) that allows ventricular filling before contraction. The AV node's slow
conduction velocity also protects the ventricles from excessively rapid atrial rates.
6. What is the primary function of the Bundle of His?
A. Initiate the cardiac impulse B. Delay atrioventricular conduction
C. Rapidly conduct impulses from the AV node D. Repolarize the ventricles
to the bundle branches
Correct Answer: C
Rationale: The Bundle of His (atrioventricular bundle) rapidly conducts electrical impulses from the AV node
through the interventricular septum to the right and left bundle branches. It is the only electrical connection
between the atria and ventricles. Its fast conduction velocity ensures synchronized ventricular depolarization.
7. The Purkinje fibers distribute electrical impulses to which cardiac structure?
A. The atria B. The SA node
C. The ventricular endocardium D. The pericardium
Correct Answer: C
Rationale: Purkinje fibers are specialized conducting fibers that distribute electrical impulses from the bundle
branches to the ventricular endocardium. They enable rapid and synchronized depolarization of the ventricular
myocardium from endocardium to epicardium, producing efficient ventricular contraction. Purkinje fibers can also
serve as latent pacemakers at a rate of 20-40 bpm.
8. What is the intrinsic firing rate of the SA node?
A. 20-40 bpm B. 40-60 bpm
C. 60-100 bpm D. 100-150 bpm
Correct Answer: C
Rationale: The SA node has an intrinsic firing rate of 60-100 beats per minute, making it the dominant pacemaker
under normal conditions. The AV node fires at 40-60 bpm, and Purkinje fibers at 20-40 bpm. This hierarchical rate
difference ensures that the fastest pacemaker (SA node) overrides slower latent pacemakers, a principle known as
overdrive suppression.
9. Which coronary artery supplies blood to the SA node in most individuals?
A. Left anterior descending artery (LAD) B. Right coronary artery (RCA)
C. Circumflex artery D. Posterior descending artery
