IBHRE CEPS Exam Study Set — 2026/2027
IBHRE CERTIFIED ELECTROPHYSIOLOGY SPECIALIST (CEPS) EXAM STUDY SET
2026/2027 | 200 Questions | Exam Prep
International Board of Heart Rhythm Examiners
Instructions: Select the best answer for each question. SATA items require selecting all correct responses.
Ordered items require placing steps in the correct sequence. Answers and rationales follow each question.
SECTION I: EP FUNDAMENTALS: CARDIAC ANATOMY & PHYSIOLOGY
1. The sinoatrial (SA) node is located in which anatomic structure of the heart?
A. Interatrial septum near the os of the coronary sinus
B. Upper portion of the crista terminalis at the SVC-RA junction
C. Subendocardial layer of the interventricular septum
D. Right atrial appendage along the pectinate muscles
Correct Answer: B. Upper portion of the crista terminalis at the SVC-RA junction
Rationale: The SA node is the primary pacemaker of the heart, located in the superior aspect of the crista
terminalis at the junction of the superior vena cava and the right atrium. It is a crescent-shaped structure
approximately 10–20 mm long. The SA node is richly innervated by both sympathetic and
parasympathetic fibers. The interatrial septum near the coronary sinus (A) is near the AV node. The
subendocardial interventricular septum (C) contains the His bundle and bundle branches. The right atrial
appendage (D) contains pectinate muscles but is not the SA node location.
2. Which cardiac structure serves as the primary electrical connection between the atria and
ventricles?
A. Eustachian ridge
B. Fossa ovalis
C. Triangle of Koch
D. Ligament of Marshall
Correct Answer: C. Triangle of Koch
Rationale: The triangle of Koch is an important anatomic landmark on the right atrial septum bounded
by the tendon of Todaro, the septal leaflet of the tricuspid valve, and the os of the coronary sinus. The AV
node resides within this triangle and is the sole normal electrical connection between the atria and
ventricles. The Eustachian ridge (A) separates the SVC from the RA appendage. The fossa ovalis (B) is a
remnant of the foramen ovale. The ligament of Marshall (D) is a vestigial fold on the lateral left atrium.
3. The coronary sinus receives venous drainage from which of the following cardiac veins?
A. Anterior cardiac veins only
B. Great, middle, and small cardiac veins
C. Thebesian veins exclusively
D. Pulmonary veins
Correct Answer: B. Great, middle, and small cardiac veins
Rationale: The coronary sinus is the major venous drainage system of the heart, located in the posterior
atrioventricular groove. It collects blood from the great cardiac vein (anterior interventricular groove),
middle cardiac vein (posterior interventricular groove), small cardiac vein (right marginal area), and the
posterior vein of the left ventricle. The anterior cardiac veins (A) drain directly into the right atrium. The
Thebesian veins (C) are small venous channels draining directly into cardiac chambers. The pulmonary
veins (D) carry oxygenated blood from the lungs to the left atrium.
4. Stimulation of the right vagus nerve primarily affects which cardiac structure?
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, IBHRE CEPS Exam Study Set — 2026/2027
A. SA node — decreases automaticity
B. AV node — decreases automaticity
C. Ventricular myocardium — decreases contractility
D. His-Purkinje system — slows conduction
Correct Answer: A. SA node — decreases automaticity
Rationale: Right vagal stimulation primarily affects the SA node, decreasing its rate of depolarization
(negative chronotropic effect). Left vagal stimulation predominantly affects the AV node, prolonging AV
conduction (negative dromotropic effect). The vagus nerve has minimal direct effect on the ventricular
myocardium (C) or the His-Purkinje system (D) because parasympathetic innervation is sparse in the
ventricles. This differential innervation is important in EP studies for understanding autonomic effects on
arrhythmogenesis.
5. During Phase 0 of the ventricular myocyte action potential, which ion channel is primarily
responsible for rapid depolarization?
A. L-type calcium channels
B. T-type calcium channels
C. Fast sodium channels
D. Inward rectifier potassium channels
Correct Answer: C. Fast sodium channels
Rationale: Phase 0 of the ventricular myocyte action potential is caused by rapid influx of sodium ions
through fast voltage-gated Na+ channels (INa), producing a rapid upstroke to approximately +20 mV.
These channels activate at -70 mV and inactivate within milliseconds. L-type calcium channels (A) are
responsible for Phase 2 (plateau) and are dominant in Phase 0 of slow-response cells (SA and AV nodal
cells). T-type calcium channels (B) contribute to SA node pacemaker depolarization. Inward rectifier
potassium channels (D) are responsible for Phase 3 repolarization (IK1) and maintaining resting
membrane potential.
6. Select all that apply. Which of the following are characteristics of slow-response action
potentials found in the SA and AV nodes? [Select All That Apply]
A. Dependence on calcium influx for Phase 0 depolarization
B. More negative resting membrane potential (-90 mV)
C. Slower upstroke velocity (dV/dt) compared to fast-response cells
D. Presence of significant phase 4 spontaneous depolarization
E. Absence of a plateau phase (Phase 2)
Correct Answer: A. Dependence on calcium influx for Phase 0 depolarization, C. Slower
upstroke velocity (dV/dt) compared to fast-response cells, D. Presence of significant phase 4
spontaneous depolarization
Rationale: Slow-response cells in the SA and AV nodes depend on calcium influx through L-type calcium
channels for Phase 0 (A), resulting in a slower upstroke velocity (C) and reduced conduction velocity
compared to fast-response cells. SA node cells exhibit spontaneous Phase 4 depolarization (D) due to the
funny current (If), allowing automaticity. Slow-response cells have a less negative resting potential
(approximately -60 mV, not -90 mV) (B is incorrect). Both slow and fast cells have a plateau phase (E is
incorrect), though it is less prominent in nodal cells.
7. The effective refractory period (ERP) of the atrial myocardium coincides primarily with
which phase(s) of the action potential?
A. Phase 0 only
B. Phases 1 and 2
C. Phases 0, 1, 2, and part of Phase 3
D. Phase 4 only
Correct Answer: C. Phases 0, 1, 2, and part of Phase 3
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, IBHRE CEPS Exam Study Set — 2026/2027
Rationale: The effective refractory period is the interval during which a cell cannot be re-excited
regardless of stimulus strength. In atrial and ventricular myocytes, the ERP extends from the onset of
Phase 0 (depolarization) through most of Phase 3 (repolarization), ending when approximately 80–90% of
repolarization is complete. During this period, most sodium channels remain inactivated. The relative
refractory period (RRP) follows the ERP during late Phase 3, when a stronger-than-normal stimulus can
produce depolarization, but conduction is slow and the action potential amplitude is reduced.
8. Which ion channel is primarily responsible for Phase 4 spontaneous depolarization
(pacemaker potential) in the SA node?
A. Rapid delayed rectifier potassium current (IKr)
B. Hyperpolarization-activated cyclic nucleotide-gated channel (If/funny current)
C. Transient outward potassium current (Ito)
D. Sodium-calcium exchanger (NCX) current
Correct Answer: B. Hyperpolarization-activated cyclic nucleotide-gated channel (If/funny
current)
Rationale: The funny current (If) is carried by hyperpolarization-activated cyclic nucleotide-gated (HCN)
channels that are activated at membrane potentials of approximately -60 mV and contribute to slow
diastolic depolarization in SA node pacemaker cells. If is a nonselective cation current carrying both Na+
and K+ ions. While IKr (A) contributes to repolarization and the decay of IKr during Phase 4 also aids
depolarization, If is the primary pacemaker current. Ito (C) is responsible for Phase 1 (early repolarization)
in ventricular cells. The NCX current (D) plays a secondary role in late Phase 4 depolarization.
9. On a 12-lead ECG, the PR interval primarily represents conduction through which
structures?
A. SA node to atrial myocardium
B. Atrial myocardium, AV node, His bundle, and bundle branches
C. His-Purkinje system to ventricular myocardium
D. Ventricular depolarization and repolarization
Correct Answer: B. Atrial myocardium, AV node, His bundle, and bundle branches
Rationale: The PR interval (normal 120–200 ms) represents the time from the onset of atrial
depolarization to the onset of ventricular depolarization. It includes conduction through the atrial
myocardium, AV node (which accounts for the majority of the PR interval, approximately 50–100 ms), His
bundle, bundle branches, and proximal Purkinje fibers. Prolongation of the PR interval (>200 ms) indicates
first-degree AV block, most commonly due to delayed AV nodal conduction. The SA node to atrial
myocardium (A) is not directly measurable on surface ECG. The QRS complex (C) represents His-Purkinje
to ventricular activation.
10. During an EP study, intracardiac recordings from the His bundle catheter show an AH
interval of 280 ms. The QRS complex is narrow. Which of the following is the MOST likely
interpretation?
A. First-degree AV block (intra-Hisian delay)
B. Prolonged AV nodal conduction time
C. Interventricular conduction delay
D. Accelerated junctional rhythm
Correct Answer: B. Prolonged AV nodal conduction time
Rationale: The AH interval (normally 50–120 ms) measures conduction time from the low right atrium
through the AV node to the His bundle. An AH interval of 280 ms indicates prolonged AV nodal conduction,
consistent with first-degree AV block at the level of the AV node. This is the most common site of first-
degree AV block. Intra-Hisian delay (A) would prolong the HV interval, not the AH interval.
Interventricular conduction delay (C) would widen the QRS complex. Accelerated junctional rhythm (D)
would show a short or absent AH interval as the His bundle fires before the atrium.
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, IBHRE CEPS Exam Study Set — 2026/2027
11. The normal HV interval measured during an EP study is approximately which range?
A. 20–40 ms
B. 35–55 ms
C. 55–75 ms
D. 80–120 ms
Correct Answer: B. 35–55 ms
Rationale: The HV interval (normally 35–55 ms) represents conduction from the His bundle through the
right bundle branch and Purkinje network to ventricular myocardium. Prolongation of the HV interval
(>55 ms) indicates His-Purkinje disease, which carries prognostic significance and may warrant
permanent pacemaker implantation. An HV interval >70 ms or the presence of infra-Hisian second-degree
AV block during pacing is a Class I indication for pacemaker implantation. Values of 20–40 ms (A) are
unusually short, and values of 55–75 ms (C) represent mild prolongation.
12. Which autonomic nervous system effect increases heart rate and AV nodal conduction
velocity?
A. Increased parasympathetic tone via the vagus nerve
B. Increased sympathetic tone via beta-1 adrenergic stimulation
C. Decreased acetylcholine release from the vagus nerve only
D. Alpha-2 adrenergic receptor activation
Correct Answer: B. Increased sympathetic tone via beta-1 adrenergic stimulation
Rationale: Sympathetic stimulation via beta-1 adrenergic receptors increases heart rate (positive
chronotropic effect), AV nodal conduction velocity (positive dromotropic effect), and myocardial
contractility (positive inotropic effect). Norepinephrine released from sympathetic nerve endings and
circulating epinephrine activate adenylate cyclase, increasing cAMP levels, which enhances calcium
channel currents (ICa,L) and the funny current (If). Vagal stimulation (A, C) has the opposite effect. Alpha-
2 receptors (D) are primarily presynaptic and modulate norepinephrine release.
13. The crista terminalis is an important anatomic structure in the right atrium that serves as
which of the following?
A. The site of AV node location
B. A boundary between the sinus venosus and the trabeculated right atrium
C. The primary attachment of the tricuspid valve
D. The pathway for the left bundle branch
Correct Answer: B. A boundary between the sinus venosus and the trabeculated right atrium
Rationale: The crista terminalis is a vertical muscular ridge on the posterolateral wall of the right atrium
that separates the smooth-walled sinus venosus (derived from the embryonic sinus venosus, receiving the
SVC, IVC, and coronary sinus) from the trabeculated (rough) portion of the right atrium (derived from the
primitive atrium). The crista terminalis is an important site for atrial tachycardias and can produce
double potentials on EP mapping. The AV node (A) is located in the triangle of Koch. The tricuspid valve (C)
attaches to the tricuspid annulus. The left bundle branch (D) courses along the left side of the
interventricular septum.
14. Which ECG lead placement is MOST sensitive for detecting right ventricular infarction?
A. Lead V1
B. Lead V4R
C. Lead aVF
D. Lead V5
Correct Answer: B. Lead V4R
Rationale: Lead V4R (right-sided chest lead placed in the 5th intercostal space at the right midclavicular
line) is the most sensitive lead for detecting right ventricular infarction, which occurs in approximately 30–
4
IBHRE CERTIFIED ELECTROPHYSIOLOGY SPECIALIST (CEPS) EXAM STUDY SET
2026/2027 | 200 Questions | Exam Prep
International Board of Heart Rhythm Examiners
Instructions: Select the best answer for each question. SATA items require selecting all correct responses.
Ordered items require placing steps in the correct sequence. Answers and rationales follow each question.
SECTION I: EP FUNDAMENTALS: CARDIAC ANATOMY & PHYSIOLOGY
1. The sinoatrial (SA) node is located in which anatomic structure of the heart?
A. Interatrial septum near the os of the coronary sinus
B. Upper portion of the crista terminalis at the SVC-RA junction
C. Subendocardial layer of the interventricular septum
D. Right atrial appendage along the pectinate muscles
Correct Answer: B. Upper portion of the crista terminalis at the SVC-RA junction
Rationale: The SA node is the primary pacemaker of the heart, located in the superior aspect of the crista
terminalis at the junction of the superior vena cava and the right atrium. It is a crescent-shaped structure
approximately 10–20 mm long. The SA node is richly innervated by both sympathetic and
parasympathetic fibers. The interatrial septum near the coronary sinus (A) is near the AV node. The
subendocardial interventricular septum (C) contains the His bundle and bundle branches. The right atrial
appendage (D) contains pectinate muscles but is not the SA node location.
2. Which cardiac structure serves as the primary electrical connection between the atria and
ventricles?
A. Eustachian ridge
B. Fossa ovalis
C. Triangle of Koch
D. Ligament of Marshall
Correct Answer: C. Triangle of Koch
Rationale: The triangle of Koch is an important anatomic landmark on the right atrial septum bounded
by the tendon of Todaro, the septal leaflet of the tricuspid valve, and the os of the coronary sinus. The AV
node resides within this triangle and is the sole normal electrical connection between the atria and
ventricles. The Eustachian ridge (A) separates the SVC from the RA appendage. The fossa ovalis (B) is a
remnant of the foramen ovale. The ligament of Marshall (D) is a vestigial fold on the lateral left atrium.
3. The coronary sinus receives venous drainage from which of the following cardiac veins?
A. Anterior cardiac veins only
B. Great, middle, and small cardiac veins
C. Thebesian veins exclusively
D. Pulmonary veins
Correct Answer: B. Great, middle, and small cardiac veins
Rationale: The coronary sinus is the major venous drainage system of the heart, located in the posterior
atrioventricular groove. It collects blood from the great cardiac vein (anterior interventricular groove),
middle cardiac vein (posterior interventricular groove), small cardiac vein (right marginal area), and the
posterior vein of the left ventricle. The anterior cardiac veins (A) drain directly into the right atrium. The
Thebesian veins (C) are small venous channels draining directly into cardiac chambers. The pulmonary
veins (D) carry oxygenated blood from the lungs to the left atrium.
4. Stimulation of the right vagus nerve primarily affects which cardiac structure?
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, IBHRE CEPS Exam Study Set — 2026/2027
A. SA node — decreases automaticity
B. AV node — decreases automaticity
C. Ventricular myocardium — decreases contractility
D. His-Purkinje system — slows conduction
Correct Answer: A. SA node — decreases automaticity
Rationale: Right vagal stimulation primarily affects the SA node, decreasing its rate of depolarization
(negative chronotropic effect). Left vagal stimulation predominantly affects the AV node, prolonging AV
conduction (negative dromotropic effect). The vagus nerve has minimal direct effect on the ventricular
myocardium (C) or the His-Purkinje system (D) because parasympathetic innervation is sparse in the
ventricles. This differential innervation is important in EP studies for understanding autonomic effects on
arrhythmogenesis.
5. During Phase 0 of the ventricular myocyte action potential, which ion channel is primarily
responsible for rapid depolarization?
A. L-type calcium channels
B. T-type calcium channels
C. Fast sodium channels
D. Inward rectifier potassium channels
Correct Answer: C. Fast sodium channels
Rationale: Phase 0 of the ventricular myocyte action potential is caused by rapid influx of sodium ions
through fast voltage-gated Na+ channels (INa), producing a rapid upstroke to approximately +20 mV.
These channels activate at -70 mV and inactivate within milliseconds. L-type calcium channels (A) are
responsible for Phase 2 (plateau) and are dominant in Phase 0 of slow-response cells (SA and AV nodal
cells). T-type calcium channels (B) contribute to SA node pacemaker depolarization. Inward rectifier
potassium channels (D) are responsible for Phase 3 repolarization (IK1) and maintaining resting
membrane potential.
6. Select all that apply. Which of the following are characteristics of slow-response action
potentials found in the SA and AV nodes? [Select All That Apply]
A. Dependence on calcium influx for Phase 0 depolarization
B. More negative resting membrane potential (-90 mV)
C. Slower upstroke velocity (dV/dt) compared to fast-response cells
D. Presence of significant phase 4 spontaneous depolarization
E. Absence of a plateau phase (Phase 2)
Correct Answer: A. Dependence on calcium influx for Phase 0 depolarization, C. Slower
upstroke velocity (dV/dt) compared to fast-response cells, D. Presence of significant phase 4
spontaneous depolarization
Rationale: Slow-response cells in the SA and AV nodes depend on calcium influx through L-type calcium
channels for Phase 0 (A), resulting in a slower upstroke velocity (C) and reduced conduction velocity
compared to fast-response cells. SA node cells exhibit spontaneous Phase 4 depolarization (D) due to the
funny current (If), allowing automaticity. Slow-response cells have a less negative resting potential
(approximately -60 mV, not -90 mV) (B is incorrect). Both slow and fast cells have a plateau phase (E is
incorrect), though it is less prominent in nodal cells.
7. The effective refractory period (ERP) of the atrial myocardium coincides primarily with
which phase(s) of the action potential?
A. Phase 0 only
B. Phases 1 and 2
C. Phases 0, 1, 2, and part of Phase 3
D. Phase 4 only
Correct Answer: C. Phases 0, 1, 2, and part of Phase 3
2
, IBHRE CEPS Exam Study Set — 2026/2027
Rationale: The effective refractory period is the interval during which a cell cannot be re-excited
regardless of stimulus strength. In atrial and ventricular myocytes, the ERP extends from the onset of
Phase 0 (depolarization) through most of Phase 3 (repolarization), ending when approximately 80–90% of
repolarization is complete. During this period, most sodium channels remain inactivated. The relative
refractory period (RRP) follows the ERP during late Phase 3, when a stronger-than-normal stimulus can
produce depolarization, but conduction is slow and the action potential amplitude is reduced.
8. Which ion channel is primarily responsible for Phase 4 spontaneous depolarization
(pacemaker potential) in the SA node?
A. Rapid delayed rectifier potassium current (IKr)
B. Hyperpolarization-activated cyclic nucleotide-gated channel (If/funny current)
C. Transient outward potassium current (Ito)
D. Sodium-calcium exchanger (NCX) current
Correct Answer: B. Hyperpolarization-activated cyclic nucleotide-gated channel (If/funny
current)
Rationale: The funny current (If) is carried by hyperpolarization-activated cyclic nucleotide-gated (HCN)
channels that are activated at membrane potentials of approximately -60 mV and contribute to slow
diastolic depolarization in SA node pacemaker cells. If is a nonselective cation current carrying both Na+
and K+ ions. While IKr (A) contributes to repolarization and the decay of IKr during Phase 4 also aids
depolarization, If is the primary pacemaker current. Ito (C) is responsible for Phase 1 (early repolarization)
in ventricular cells. The NCX current (D) plays a secondary role in late Phase 4 depolarization.
9. On a 12-lead ECG, the PR interval primarily represents conduction through which
structures?
A. SA node to atrial myocardium
B. Atrial myocardium, AV node, His bundle, and bundle branches
C. His-Purkinje system to ventricular myocardium
D. Ventricular depolarization and repolarization
Correct Answer: B. Atrial myocardium, AV node, His bundle, and bundle branches
Rationale: The PR interval (normal 120–200 ms) represents the time from the onset of atrial
depolarization to the onset of ventricular depolarization. It includes conduction through the atrial
myocardium, AV node (which accounts for the majority of the PR interval, approximately 50–100 ms), His
bundle, bundle branches, and proximal Purkinje fibers. Prolongation of the PR interval (>200 ms) indicates
first-degree AV block, most commonly due to delayed AV nodal conduction. The SA node to atrial
myocardium (A) is not directly measurable on surface ECG. The QRS complex (C) represents His-Purkinje
to ventricular activation.
10. During an EP study, intracardiac recordings from the His bundle catheter show an AH
interval of 280 ms. The QRS complex is narrow. Which of the following is the MOST likely
interpretation?
A. First-degree AV block (intra-Hisian delay)
B. Prolonged AV nodal conduction time
C. Interventricular conduction delay
D. Accelerated junctional rhythm
Correct Answer: B. Prolonged AV nodal conduction time
Rationale: The AH interval (normally 50–120 ms) measures conduction time from the low right atrium
through the AV node to the His bundle. An AH interval of 280 ms indicates prolonged AV nodal conduction,
consistent with first-degree AV block at the level of the AV node. This is the most common site of first-
degree AV block. Intra-Hisian delay (A) would prolong the HV interval, not the AH interval.
Interventricular conduction delay (C) would widen the QRS complex. Accelerated junctional rhythm (D)
would show a short or absent AH interval as the His bundle fires before the atrium.
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, IBHRE CEPS Exam Study Set — 2026/2027
11. The normal HV interval measured during an EP study is approximately which range?
A. 20–40 ms
B. 35–55 ms
C. 55–75 ms
D. 80–120 ms
Correct Answer: B. 35–55 ms
Rationale: The HV interval (normally 35–55 ms) represents conduction from the His bundle through the
right bundle branch and Purkinje network to ventricular myocardium. Prolongation of the HV interval
(>55 ms) indicates His-Purkinje disease, which carries prognostic significance and may warrant
permanent pacemaker implantation. An HV interval >70 ms or the presence of infra-Hisian second-degree
AV block during pacing is a Class I indication for pacemaker implantation. Values of 20–40 ms (A) are
unusually short, and values of 55–75 ms (C) represent mild prolongation.
12. Which autonomic nervous system effect increases heart rate and AV nodal conduction
velocity?
A. Increased parasympathetic tone via the vagus nerve
B. Increased sympathetic tone via beta-1 adrenergic stimulation
C. Decreased acetylcholine release from the vagus nerve only
D. Alpha-2 adrenergic receptor activation
Correct Answer: B. Increased sympathetic tone via beta-1 adrenergic stimulation
Rationale: Sympathetic stimulation via beta-1 adrenergic receptors increases heart rate (positive
chronotropic effect), AV nodal conduction velocity (positive dromotropic effect), and myocardial
contractility (positive inotropic effect). Norepinephrine released from sympathetic nerve endings and
circulating epinephrine activate adenylate cyclase, increasing cAMP levels, which enhances calcium
channel currents (ICa,L) and the funny current (If). Vagal stimulation (A, C) has the opposite effect. Alpha-
2 receptors (D) are primarily presynaptic and modulate norepinephrine release.
13. The crista terminalis is an important anatomic structure in the right atrium that serves as
which of the following?
A. The site of AV node location
B. A boundary between the sinus venosus and the trabeculated right atrium
C. The primary attachment of the tricuspid valve
D. The pathway for the left bundle branch
Correct Answer: B. A boundary between the sinus venosus and the trabeculated right atrium
Rationale: The crista terminalis is a vertical muscular ridge on the posterolateral wall of the right atrium
that separates the smooth-walled sinus venosus (derived from the embryonic sinus venosus, receiving the
SVC, IVC, and coronary sinus) from the trabeculated (rough) portion of the right atrium (derived from the
primitive atrium). The crista terminalis is an important site for atrial tachycardias and can produce
double potentials on EP mapping. The AV node (A) is located in the triangle of Koch. The tricuspid valve (C)
attaches to the tricuspid annulus. The left bundle branch (D) courses along the left side of the
interventricular septum.
14. Which ECG lead placement is MOST sensitive for detecting right ventricular infarction?
A. Lead V1
B. Lead V4R
C. Lead aVF
D. Lead V5
Correct Answer: B. Lead V4R
Rationale: Lead V4R (right-sided chest lead placed in the 5th intercostal space at the right midclavicular
line) is the most sensitive lead for detecting right ventricular infarction, which occurs in approximately 30–
4
