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IBHRE CERTIFICATION EXAM STUDY GUIDE EXAM 2026
QUESTIONS LATEST 2026 – 2027 VERSION SOLVED
QUESTIONS & ANSWERS
IBHRE Certification Exam Study Guide
Questions with Rationales
1. The sinoatrial (SA) node, the heart's primary pacemaker, is located in which of
the following structures?
• A) Left atrium near the pulmonary veins
• B) Superior aspect of the right atrium near the opening of the superior vena cava
• C) Interatrial septum near the coronary sinus
• D) Base of the right ventricle
Answer: B - The SA node is located at the junction of the superior vena cava and the
right atrium . The AV node is located in the interatrial septum near the coronary sinus,
and the His-Purkinje system extends through the ventricles .
2. During which phase of the ventricular action potential does rapid depolarization
occur due to sodium influx?
• A) Phase 0
• B) Phase 1
• C) Phase 2
• D) Phase 3
Answer: A - Phase 0 is the rapid depolarization phase caused by fast inward sodium
current through voltage-gated sodium channels. Phase 1 is early rapid repolarization,
Phase 2 is the plateau (calcium influx), and Phase 3 is rapid repolarization (potassium
efflux) .
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3. Which ionic current is primarily responsible for the plateau phase (Phase 2) of
the ventricular action potential?
• A) Rapid inward sodium current
• B) Rapid outward potassium current
• C) Slow inward calcium current
• D) Sodium-calcium exchange current
Answer: C - The plateau phase (Phase 2) is maintained by a balance between slow
inward calcium current through L-type calcium channels and outward potassium
current. The calcium influx is the dominant inward current that sustains depolarization
during the plateau .
4. The effective refractory period (ERP) of the AV node at a normal heart rate is
approximately:
• A) 50-100 ms
• B) 200-300 ms
• C) 400-500 ms
• D) 600-700 ms
Answer: B - The AV node ERP is approximately 200-300 ms at normal heart rates. This
relatively long refractory period protects the ventricles from rapid atrial rates . The atrial
ERP is shorter (150-250 ms), and ventricular ERP is approximately 200-300 ms as well.
5. Sympathetic stimulation of the heart primarily affects which phase of the SA
node action potential?
• A) Phase 0: Increases the rate of depolarization
• B) Phase 2: Prolongs the plateau phase
• C) Phase 3: Slows repolarization
• D) Phase 4: Increases the slope of pacemaker depolarization
Answer: D - Sympathetic stimulation releases norepinephrine, which acts on beta-1
adrenergic receptors to increase the slope of phase 4 (pacemaker potential) in SA node
cells. This accelerates the rate of diastolic depolarization, increasing heart rate .
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6. Which coronary artery supplies the SA node in approximately 60% of the
population?
• A) Left circumflex artery
• B) Posterior descending artery
• C) Left anterior descending artery
• D) Right coronary artery
Answer: D - The right coronary artery (RCA) supplies the SA node in approximately 60%
of individuals (right-dominant circulation). In about 40%, the left circumflex artery
supplies the SA node .
7. The AV node is supplied by which coronary artery in most patients?
• A) Left anterior descending artery
• B) Right coronary artery
• C) Left circumflex artery
• D) Both B and C depending on dominance
Answer: D - The AV node is supplied by the right coronary artery in right-dominant
circulation and by the left circumflex artery in left-dominant circulation. Understanding
coronary anatomy is essential for recognizing ischemic causes of conduction
abnormalities.
8. Which phase of the action potential is most prolonged by Class III antiarrhythmic
drugs?
• A) Phase 0
• B) Phase 1
• C) Phase 2
• D) Phase 3
Answer: D - Class III antiarrhythmic drugs (e.g., amiodarone, sotalol) prolong Phase 3
(repolarization) by blocking potassium channels, resulting in prolonged refractoriness
and QT interval.
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9. The His bundle penetrates the fibrous body at which structure?
• A) The tricuspid annulus
• B) The central fibrous body
• C) The membranous septum
• D) The coronary sinus
Answer: B - The His bundle penetrates the central fibrous body (the trigone) and
courses along the membranous septum before dividing into the left and right bundle
branches.
10. Which of the following statements about Phase 4 of the action potential is
correct?
• A) It is present only in ventricular myocytes
• B) It represents the resting membrane potential in automatic cells
• C) It is the rapid repolarization phase
• D) It occurs only during tachycardia
Answer: B - Phase 4 represents the resting membrane potential or diastolic
depolarization in automatic cells (SA node, AV node, His-Purkinje). It is the phase where
automaticity occurs in pacemaker cells.
11. The primary neurotransmitter released by parasympathetic stimulation of the
heart is:
• A) Norepinephrine
• B) Epinephrine
• C) Acetylcholine
• D) Dopamine
Answer: C - Parasympathetic stimulation releases acetylcholine, which acts on
muscarinic receptors to decrease heart rate. Norepinephrine is released by
sympathetic stimulation.
12. The atrioventricular (AV) node is located in which of the following regions?
IBHRE CERTIFICATION EXAM STUDY GUIDE EXAM 2026
QUESTIONS LATEST 2026 – 2027 VERSION SOLVED
QUESTIONS & ANSWERS
IBHRE Certification Exam Study Guide
Questions with Rationales
1. The sinoatrial (SA) node, the heart's primary pacemaker, is located in which of
the following structures?
• A) Left atrium near the pulmonary veins
• B) Superior aspect of the right atrium near the opening of the superior vena cava
• C) Interatrial septum near the coronary sinus
• D) Base of the right ventricle
Answer: B - The SA node is located at the junction of the superior vena cava and the
right atrium . The AV node is located in the interatrial septum near the coronary sinus,
and the His-Purkinje system extends through the ventricles .
2. During which phase of the ventricular action potential does rapid depolarization
occur due to sodium influx?
• A) Phase 0
• B) Phase 1
• C) Phase 2
• D) Phase 3
Answer: A - Phase 0 is the rapid depolarization phase caused by fast inward sodium
current through voltage-gated sodium channels. Phase 1 is early rapid repolarization,
Phase 2 is the plateau (calcium influx), and Phase 3 is rapid repolarization (potassium
efflux) .
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3. Which ionic current is primarily responsible for the plateau phase (Phase 2) of
the ventricular action potential?
• A) Rapid inward sodium current
• B) Rapid outward potassium current
• C) Slow inward calcium current
• D) Sodium-calcium exchange current
Answer: C - The plateau phase (Phase 2) is maintained by a balance between slow
inward calcium current through L-type calcium channels and outward potassium
current. The calcium influx is the dominant inward current that sustains depolarization
during the plateau .
4. The effective refractory period (ERP) of the AV node at a normal heart rate is
approximately:
• A) 50-100 ms
• B) 200-300 ms
• C) 400-500 ms
• D) 600-700 ms
Answer: B - The AV node ERP is approximately 200-300 ms at normal heart rates. This
relatively long refractory period protects the ventricles from rapid atrial rates . The atrial
ERP is shorter (150-250 ms), and ventricular ERP is approximately 200-300 ms as well.
5. Sympathetic stimulation of the heart primarily affects which phase of the SA
node action potential?
• A) Phase 0: Increases the rate of depolarization
• B) Phase 2: Prolongs the plateau phase
• C) Phase 3: Slows repolarization
• D) Phase 4: Increases the slope of pacemaker depolarization
Answer: D - Sympathetic stimulation releases norepinephrine, which acts on beta-1
adrenergic receptors to increase the slope of phase 4 (pacemaker potential) in SA node
cells. This accelerates the rate of diastolic depolarization, increasing heart rate .
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6. Which coronary artery supplies the SA node in approximately 60% of the
population?
• A) Left circumflex artery
• B) Posterior descending artery
• C) Left anterior descending artery
• D) Right coronary artery
Answer: D - The right coronary artery (RCA) supplies the SA node in approximately 60%
of individuals (right-dominant circulation). In about 40%, the left circumflex artery
supplies the SA node .
7. The AV node is supplied by which coronary artery in most patients?
• A) Left anterior descending artery
• B) Right coronary artery
• C) Left circumflex artery
• D) Both B and C depending on dominance
Answer: D - The AV node is supplied by the right coronary artery in right-dominant
circulation and by the left circumflex artery in left-dominant circulation. Understanding
coronary anatomy is essential for recognizing ischemic causes of conduction
abnormalities.
8. Which phase of the action potential is most prolonged by Class III antiarrhythmic
drugs?
• A) Phase 0
• B) Phase 1
• C) Phase 2
• D) Phase 3
Answer: D - Class III antiarrhythmic drugs (e.g., amiodarone, sotalol) prolong Phase 3
(repolarization) by blocking potassium channels, resulting in prolonged refractoriness
and QT interval.
, Page 4 of 72
9. The His bundle penetrates the fibrous body at which structure?
• A) The tricuspid annulus
• B) The central fibrous body
• C) The membranous septum
• D) The coronary sinus
Answer: B - The His bundle penetrates the central fibrous body (the trigone) and
courses along the membranous septum before dividing into the left and right bundle
branches.
10. Which of the following statements about Phase 4 of the action potential is
correct?
• A) It is present only in ventricular myocytes
• B) It represents the resting membrane potential in automatic cells
• C) It is the rapid repolarization phase
• D) It occurs only during tachycardia
Answer: B - Phase 4 represents the resting membrane potential or diastolic
depolarization in automatic cells (SA node, AV node, His-Purkinje). It is the phase where
automaticity occurs in pacemaker cells.
11. The primary neurotransmitter released by parasympathetic stimulation of the
heart is:
• A) Norepinephrine
• B) Epinephrine
• C) Acetylcholine
• D) Dopamine
Answer: C - Parasympathetic stimulation releases acetylcholine, which acts on
muscarinic receptors to decrease heart rate. Norepinephrine is released by
sympathetic stimulation.
12. The atrioventricular (AV) node is located in which of the following regions?
