IBHRE CCDS TEST FINAL EXAM ACTUAL EXAM 2
VERSIONS (VERSION A AND B) COMPLETE ACCURATE
EXAM QUESTIONS WITH DETAILED VERIFIED ANSWERS
(100% CORRECT ANSWERS) / ALREADY GRADED A+
1|Page
,IBHRE CCDS TEST FINAL EXAM
2026/2027 Examination
Total Questions: 200
Instructions:
• Answer all questions.
• Select the single best answer.
• Each question has four answer choices: A, B, C, and D.
• Select only ONE answer for each question.
SECTION 1: Fundamentals of Electrophysiology, Electronics, and Pharmacology
Questions 1–25
Q1. Which formula correctly represents Ohm's Law as applied to pacing systems?
A. V = I² × R
B. V = I × R
C. V = I / R
D. V = R / I
Correct Answer: B. V = I × R
Rationale: Ohm's Law states that voltage (V) equals current (I) multiplied by resistance or
impedance (R). This fundamental relationship is essential for calculating pacing parameters such as
current drain and battery longevity. Choice A represents power (P = I²R), not voltage. Choices C and
D invert the relationship incorrectly. In pacing, impedance is calculated as voltage divided by current,
confirming V = I × R .
Q2. A pacing lead delivers a 5-volt pulse with a current of 10 milliamperes. What is the
impedance of the lead system?
A. 50 ohms
B. 200 ohms
C. 500 ohms
D. 2,000 ohms
Correct Answer: C. 500 ohms
Rationale: Using Ohm's Law rearranged as R = V / I, impedance equals voltage divided by
current. Converting 10 milliamperes to 0.01 amperes: R = 5 V / 0.01 A = 500 ohms. This calculation is
routinely performed during device interrogation to assess lead integrity. A sudden increase in
impedance may indicate conductor fracture, while a decrease may suggest insulation breach.
2|Page
, Q3. Which ion movement primarily occurs during phase 0 of the action potential in ventricular
contractile tissue?
A. Calcium influx
B. Potassium efflux
C. Sodium influx
D. Chloride influx
Correct Answer: C. Sodium influx
Rationale: In ventricular myocytes and Purkinje fibers, phase 0 depolarization is mediated by
rapid sodium influx through fast sodium channels. This produces the rapid upstroke characteristic of
these tissues. In contrast, nodal tissue (SA and AV nodes) depends primarily on calcium influx for
phase 0, which is why nodal tissue conducts more slowly and is less negative at rest .
Q4. What is the rheobase of a strength-duration curve?
A. The pulse width at which threshold is twice the minimum voltage
B. The minimum voltage required to capture at an infinitely long pulse duration
C. The maximum voltage that can be delivered without tissue damage
D. The pulse duration required for capture at 2 volts
Correct Answer: B. The minimum voltage required to capture at an infinitely long pulse duration
Rationale: Rheobase represents the horizontal asymptote of the strength-duration curve—the
minimum voltage or current required for capture as pulse duration approaches infinity. In clinical
practice, thresholds are measured at finite pulse widths (typically 0.4–0.5 ms), so rheobase is a
theoretical construct. Chronaxie, by contrast, is the pulse width at which threshold equals twice the
rheobase .
Q5. Which battery chemistry is most commonly used in modern pacemakers due to its high
energy density and predictable depletion characteristics?
A. Nickel-cadmium
B. Lithium-iodine
C. Alkaline-manganese
D. Silver-zinc
Correct Answer: B. Lithium-iodine
Rationale: Lithium-iodine batteries have been the standard for pacemakers because of their high
energy density, low self-discharge rate, and predictable voltage decline that allows elective
replacement indicator (ERI) timing. They do not require reformation and have excellent longevity.
ICDs typically use lithium-silver vanadium oxide batteries, which can deliver higher peak currents for
defibrillation .
3|Page
, Q6. A patient with a dual-chamber pacemaker programmed to DDD mode at 60–120 ppm has an
intrinsic atrial rate of 80 bpm and a paced ventricular rate of 80 bpm. What is the most likely
explanation for the paced ventricular complexes?
A. Normal DDD tracking of sinus rhythm
B. Ventricular undersensing
C. Atrial undersensing
D. Pacemaker-mediated tachycardia
Correct Answer: B. Ventricular undersensing
Rationale: In DDD mode with an intrinsic atrial rate of 80 bpm, the device should track the P
waves and inhibit ventricular pacing if intrinsic conduction is present. Paced ventricular complexes at
the same rate as the intrinsic atrial rate suggest the device is not sensing intrinsic ventricular
depolarizations and is therefore pacing inappropriately. Ventricular undersensing should be
suspected and evaluated by examining the intracardiac electrogram .
Q7. Which lead insulation material is specifically designed to reduce fibroblast ingrowth and
facilitate lead extraction?
A. Silicone
B. 80A polyurethane
C. ePTFE (expanded polytetrafluoroethylene)
D. 55D polyurethane
Correct Answer: C. ePTFE (expanded polytetrafluoroethylene)
Rationale: ePTFE is used in lead insulation specifically because its microporous structure reduces
fibroblast ingrowth and tissue adhesion, making lead extraction easier if required. Silicone is flexible
but more prone to fibrotic encapsulation. Polyurethane (both 80A and 55D) has been associated
with environmental stress cracking and metal ion oxidation, though newer formulations have
improved .
Q8. Which of the following best describes the Wedensky effect in cardiac pacing?
A. The ability of a subthreshold stimulus to capture when delivered during the relative refractory
period
B. The phenomenon where a suprathreshold stimulus fails to capture due to tissue refractoriness
C. The increased excitability of tissue following a subthreshold conditioning stimulus
D. The gradual decline in capture threshold over time after lead implantation
Correct Answer: C. The increased excitability of tissue following a subthreshold conditioning
stimulus
Rationale: The Wedensky effect describes how a subthreshold stimulus can facilitate subsequent
capture by a second stimulus that would otherwise be subthreshold, due to partial depolarization
that brings the membrane closer to threshold. This principle is relevant to understanding pacing
threshold behavior and the strength-duration relationship .
4|Page
VERSIONS (VERSION A AND B) COMPLETE ACCURATE
EXAM QUESTIONS WITH DETAILED VERIFIED ANSWERS
(100% CORRECT ANSWERS) / ALREADY GRADED A+
1|Page
,IBHRE CCDS TEST FINAL EXAM
2026/2027 Examination
Total Questions: 200
Instructions:
• Answer all questions.
• Select the single best answer.
• Each question has four answer choices: A, B, C, and D.
• Select only ONE answer for each question.
SECTION 1: Fundamentals of Electrophysiology, Electronics, and Pharmacology
Questions 1–25
Q1. Which formula correctly represents Ohm's Law as applied to pacing systems?
A. V = I² × R
B. V = I × R
C. V = I / R
D. V = R / I
Correct Answer: B. V = I × R
Rationale: Ohm's Law states that voltage (V) equals current (I) multiplied by resistance or
impedance (R). This fundamental relationship is essential for calculating pacing parameters such as
current drain and battery longevity. Choice A represents power (P = I²R), not voltage. Choices C and
D invert the relationship incorrectly. In pacing, impedance is calculated as voltage divided by current,
confirming V = I × R .
Q2. A pacing lead delivers a 5-volt pulse with a current of 10 milliamperes. What is the
impedance of the lead system?
A. 50 ohms
B. 200 ohms
C. 500 ohms
D. 2,000 ohms
Correct Answer: C. 500 ohms
Rationale: Using Ohm's Law rearranged as R = V / I, impedance equals voltage divided by
current. Converting 10 milliamperes to 0.01 amperes: R = 5 V / 0.01 A = 500 ohms. This calculation is
routinely performed during device interrogation to assess lead integrity. A sudden increase in
impedance may indicate conductor fracture, while a decrease may suggest insulation breach.
2|Page
, Q3. Which ion movement primarily occurs during phase 0 of the action potential in ventricular
contractile tissue?
A. Calcium influx
B. Potassium efflux
C. Sodium influx
D. Chloride influx
Correct Answer: C. Sodium influx
Rationale: In ventricular myocytes and Purkinje fibers, phase 0 depolarization is mediated by
rapid sodium influx through fast sodium channels. This produces the rapid upstroke characteristic of
these tissues. In contrast, nodal tissue (SA and AV nodes) depends primarily on calcium influx for
phase 0, which is why nodal tissue conducts more slowly and is less negative at rest .
Q4. What is the rheobase of a strength-duration curve?
A. The pulse width at which threshold is twice the minimum voltage
B. The minimum voltage required to capture at an infinitely long pulse duration
C. The maximum voltage that can be delivered without tissue damage
D. The pulse duration required for capture at 2 volts
Correct Answer: B. The minimum voltage required to capture at an infinitely long pulse duration
Rationale: Rheobase represents the horizontal asymptote of the strength-duration curve—the
minimum voltage or current required for capture as pulse duration approaches infinity. In clinical
practice, thresholds are measured at finite pulse widths (typically 0.4–0.5 ms), so rheobase is a
theoretical construct. Chronaxie, by contrast, is the pulse width at which threshold equals twice the
rheobase .
Q5. Which battery chemistry is most commonly used in modern pacemakers due to its high
energy density and predictable depletion characteristics?
A. Nickel-cadmium
B. Lithium-iodine
C. Alkaline-manganese
D. Silver-zinc
Correct Answer: B. Lithium-iodine
Rationale: Lithium-iodine batteries have been the standard for pacemakers because of their high
energy density, low self-discharge rate, and predictable voltage decline that allows elective
replacement indicator (ERI) timing. They do not require reformation and have excellent longevity.
ICDs typically use lithium-silver vanadium oxide batteries, which can deliver higher peak currents for
defibrillation .
3|Page
, Q6. A patient with a dual-chamber pacemaker programmed to DDD mode at 60–120 ppm has an
intrinsic atrial rate of 80 bpm and a paced ventricular rate of 80 bpm. What is the most likely
explanation for the paced ventricular complexes?
A. Normal DDD tracking of sinus rhythm
B. Ventricular undersensing
C. Atrial undersensing
D. Pacemaker-mediated tachycardia
Correct Answer: B. Ventricular undersensing
Rationale: In DDD mode with an intrinsic atrial rate of 80 bpm, the device should track the P
waves and inhibit ventricular pacing if intrinsic conduction is present. Paced ventricular complexes at
the same rate as the intrinsic atrial rate suggest the device is not sensing intrinsic ventricular
depolarizations and is therefore pacing inappropriately. Ventricular undersensing should be
suspected and evaluated by examining the intracardiac electrogram .
Q7. Which lead insulation material is specifically designed to reduce fibroblast ingrowth and
facilitate lead extraction?
A. Silicone
B. 80A polyurethane
C. ePTFE (expanded polytetrafluoroethylene)
D. 55D polyurethane
Correct Answer: C. ePTFE (expanded polytetrafluoroethylene)
Rationale: ePTFE is used in lead insulation specifically because its microporous structure reduces
fibroblast ingrowth and tissue adhesion, making lead extraction easier if required. Silicone is flexible
but more prone to fibrotic encapsulation. Polyurethane (both 80A and 55D) has been associated
with environmental stress cracking and metal ion oxidation, though newer formulations have
improved .
Q8. Which of the following best describes the Wedensky effect in cardiac pacing?
A. The ability of a subthreshold stimulus to capture when delivered during the relative refractory
period
B. The phenomenon where a suprathreshold stimulus fails to capture due to tissue refractoriness
C. The increased excitability of tissue following a subthreshold conditioning stimulus
D. The gradual decline in capture threshold over time after lead implantation
Correct Answer: C. The increased excitability of tissue following a subthreshold conditioning
stimulus
Rationale: The Wedensky effect describes how a subthreshold stimulus can facilitate subsequent
capture by a second stimulus that would otherwise be subthreshold, due to partial depolarization
that brings the membrane closer to threshold. This principle is relevant to understanding pacing
threshold behavior and the strength-duration relationship .
4|Page
