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IBHRE CCDS /INTERNATIONAL BOARD OF
HEART RHYTHM EXAMINERS FINAL EXAM
MCQS/GLOBUS 201 FINAL Newest Exam
Preparation With Complete Questions And Correct
Answers With Rationales Already Graded A+ Brand
New Version!!
QUESTION 1
Which component of the cardiac conduction system is primarily
responsible for initiating each normal heartbeat?
A) Atrioventricular (AV) node
B) Bundle of His
C) Purkinje fibers
D) Sinoatrial (SA) node
Answer: D
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Explanation: The sinoatrial (SA) node is the natural pacemaker of the
heart. It generates spontaneous depolarizations at a rate of 60-100
beats per minute, setting the fundamental rhythm for the entire cardiac
conduction system. The AV node serves to delay conduction between
the atria and ventricles, the Bundle of His transmits impulses from the
AV node to the bundle branches, and Purkinje fibers distribute the
electrical signal throughout the ventricular myocardium. None of these
structures possess the intrinsic automaticity or the dominant pacemaker
function of the SA node.
QUESTION 2
During a ventricular action potential, the rapid upstroke (phase 0) is
mainly caused by influx of which ion?
A) Na⁺
B) Ca²⁺
C) K⁺
D) Cl⁻
Answer: A
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Explanation: The rapid upstroke of the ventricular action potential
(phase 0) is produced by the opening of fast voltage-gated sodium
channels, allowing a rapid influx of Na⁺ ions into the cell. This produces
the steep depolarization characteristic of phase 0. Calcium influx is
primarily responsible for the plateau phase (phase 2), while potassium
efflux mediates repolarization phases (phases 1 and 3). Chloride ions
play a relatively minor role in cardiac action potential physiology.
QUESTION 3
In Ohm's Law, if a pacemaker lead measures a voltage of 4 V and a
current of 2 mA, what is the resistance of the circuit?
A) 0.5 Ω
B) 2 kΩ
C) 4 Ω
D) 8 Ω
Answer: B
Explanation: Ohm's Law states that Resistance (R) = Voltage (V) /
Current (I). Substituting the given values: R = 4 V / 0.002 A = 2000 Ω = 2
kΩ. Understanding Ohm's Law is fundamental to pacemaker
technology, as it governs the relationship between voltage, current, and
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resistance in pacing circuits. Clinically, lead impedance is a critical
parameter monitored during follow-up, as significant deviations may
indicate lead fracture, insulation breach, or other complications.
QUESTION 4
Chronaxie is defined as the minimum duration required to stimulate
cardiac tissue when the stimulus voltage is set at:
A) Rheobase
B) Twice the rheobase
C) Half the rheobase
D) Ten times the rheobase
Answer: B
Explanation: Chronaxie is the pulse width required to achieve capture
when the stimulus voltage is set at twice the rheobase. The rheobase is
the minimum voltage that can excite tissue at an infinitely long pulse
duration. Chronaxie is a standard electrophysiologic parameter that,
along with rheobase, characterizes the strength-duration relationship
for cardiac tissue stimulation. Understanding this relationship is
essential for programming pacemaker outputs to ensure reliable
capture while maximizing device longevity.
IBHRE CCDS /INTERNATIONAL BOARD OF
HEART RHYTHM EXAMINERS FINAL EXAM
MCQS/GLOBUS 201 FINAL Newest Exam
Preparation With Complete Questions And Correct
Answers With Rationales Already Graded A+ Brand
New Version!!
QUESTION 1
Which component of the cardiac conduction system is primarily
responsible for initiating each normal heartbeat?
A) Atrioventricular (AV) node
B) Bundle of His
C) Purkinje fibers
D) Sinoatrial (SA) node
Answer: D
,2|Page
Explanation: The sinoatrial (SA) node is the natural pacemaker of the
heart. It generates spontaneous depolarizations at a rate of 60-100
beats per minute, setting the fundamental rhythm for the entire cardiac
conduction system. The AV node serves to delay conduction between
the atria and ventricles, the Bundle of His transmits impulses from the
AV node to the bundle branches, and Purkinje fibers distribute the
electrical signal throughout the ventricular myocardium. None of these
structures possess the intrinsic automaticity or the dominant pacemaker
function of the SA node.
QUESTION 2
During a ventricular action potential, the rapid upstroke (phase 0) is
mainly caused by influx of which ion?
A) Na⁺
B) Ca²⁺
C) K⁺
D) Cl⁻
Answer: A
,3|Page
Explanation: The rapid upstroke of the ventricular action potential
(phase 0) is produced by the opening of fast voltage-gated sodium
channels, allowing a rapid influx of Na⁺ ions into the cell. This produces
the steep depolarization characteristic of phase 0. Calcium influx is
primarily responsible for the plateau phase (phase 2), while potassium
efflux mediates repolarization phases (phases 1 and 3). Chloride ions
play a relatively minor role in cardiac action potential physiology.
QUESTION 3
In Ohm's Law, if a pacemaker lead measures a voltage of 4 V and a
current of 2 mA, what is the resistance of the circuit?
A) 0.5 Ω
B) 2 kΩ
C) 4 Ω
D) 8 Ω
Answer: B
Explanation: Ohm's Law states that Resistance (R) = Voltage (V) /
Current (I). Substituting the given values: R = 4 V / 0.002 A = 2000 Ω = 2
kΩ. Understanding Ohm's Law is fundamental to pacemaker
technology, as it governs the relationship between voltage, current, and
, 4|Page
resistance in pacing circuits. Clinically, lead impedance is a critical
parameter monitored during follow-up, as significant deviations may
indicate lead fracture, insulation breach, or other complications.
QUESTION 4
Chronaxie is defined as the minimum duration required to stimulate
cardiac tissue when the stimulus voltage is set at:
A) Rheobase
B) Twice the rheobase
C) Half the rheobase
D) Ten times the rheobase
Answer: B
Explanation: Chronaxie is the pulse width required to achieve capture
when the stimulus voltage is set at twice the rheobase. The rheobase is
the minimum voltage that can excite tissue at an infinitely long pulse
duration. Chronaxie is a standard electrophysiologic parameter that,
along with rheobase, characterizes the strength-duration relationship
for cardiac tissue stimulation. Understanding this relationship is
essential for programming pacemaker outputs to ensure reliable
capture while maximizing device longevity.
