Q.1 What is the primary purpose of a defibrillator?
To regulate heart rate during normal rhythm
To deliver a therapeutic shock to terminate ventricular fibrillation
To monitor blood pressure continuously
To provide long‑term pacing support
Explanation - Defibrillators deliver a high‑energy electric shock that depolarizes the entire myocardium, allowing the natural pacemaker to re‑establish a normal rhythm.
Correct answer is: To deliver a therapeutic shock to terminate ventricular fibrillation
Q.2 Which component of a pacemaker determines the timing interval between two consecutive paced beats?
Pulse generator
Lead insulation
Rate‑responsive sensor
Battery
Explanation - The rate‑responsive sensor detects physiological activity (e.g., motion) and adjusts the pacing interval, effectively setting the heart rate.
Correct answer is: Rate‑responsive sensor
Q.3 In a typical external defibrillator, the energy delivered is measured in:
Volts
Amperes
Joules
Watts
Explanation - Defibrillation energy is expressed in joules (J), which represents the amount of electrical work done on the heart.
Correct answer is: Joules
Q.4 Which waveform is most commonly used by modern automated external defibrillators (AEDs) for ventricular fibrillation?
Monophasic rectangular
Biphasic truncated exponential
Sinusoidal AC
Tri‑phase square
Explanation - Biphasic truncated exponential waveforms are more efficient, requiring lower energy to achieve successful defibrillation compared with monophasic waveforms.
Correct answer is: Biphasic truncated exponential
Q.5 What is the typical battery voltage of an implanted cardiac pacemaker?
1.2 V
3.6 V
9 V
12 V
Explanation - Most modern pacemakers use lithium‑iodine batteries that provide a nominal voltage of about 3.6 V.
Correct answer is: 3.6 V
Q.6 Which mode of pacemaker operation is represented by the code 'VVI'?
Ventricular pacing, ventricular sensing, inhibited response
Ventricular pacing, ventricular sensing, triggered response
Dual‑chamber pacing, dual‑chamber sensing, inhibited response
Atrial pacing, atrial sensing, triggered response
Explanation - In the VVI mode, the device paces the ventricle, senses ventricular activity, and inhibits pacing when intrinsic activity is detected.
Correct answer is: Ventricular pacing, ventricular sensing, inhibited response
Q.7 What is the purpose of the 'lead' in a pacemaker system?
To store electrical energy
To connect the pulse generator to the heart muscle
To monitor blood oxygen levels
To provide a wireless communication link
Explanation - Leads are insulated wires that transmit pacing impulses from the generator to the myocardium and also sense intrinsic cardiac activity.
Correct answer is: To connect the pulse generator to the heart muscle
Q.8 Which of the following is a major safety feature of an external defibrillator?
Automatic impedance measurement before shock delivery
Continuous delivery of low‑level current during charging
Battery removal during shock
Manual calculation of shock energy by the operator
Explanation - Modern defibrillators automatically measure chest impedance to adjust the delivered energy, ensuring effective and safe shock delivery.
Correct answer is: Automatic impedance measurement before shock delivery
Q.9 Which type of pacemaker is designed to treat patients with both bradycardia and tachycardia?
Single‑chamber pacemaker
Dual‑chamber pacemaker
Implantable cardioverter‑defibrillator (ICD)
Rate‑responsive pacemaker
Explanation - An ICD can deliver pacing for bradycardia and also provide anti‑tachycardia therapy (shock or pacing) for life‑threatening fast rhythms.
Correct answer is: Implantable cardioverter‑defibrillator (ICD)
Q.10 What is the typical maximum energy output of a biphasic external defibrillator used in hospitals?
50 J
100 J
200 J
360 J
Explanation - Biphasic external defibrillators commonly provide up to 200 J, which is sufficient for most adult defibrillation needs.
Correct answer is: 200 J
Q.11 During pacemaker implantation, which anatomical structure is most commonly used for the right ventricular lead placement?
Right atrial appendage
Left ventricular apex
Right ventricular apex
Coronary sinus
Explanation - The right ventricular apex provides a stable site with good contact for pacing and is the conventional location for lead fixation.
Correct answer is: Right ventricular apex
Q.12 What does the term 'refractory period' refer to in the context of defibrillation?
The time needed to recharge the capacitor
The period after a shock during which the heart cannot be re‑stimulated
The interval between successive pacemaker spikes
The delay before the AED analyzes the rhythm
Explanation - After a defibrillation shock, myocardial cells enter a refractory period during which they are temporarily unresponsive to further electrical stimuli.
Correct answer is: The period after a shock during which the heart cannot be re‑stimulated
Q.13 Which of the following best describes the function of a 'rate‑responsive' pacemaker?
It paces at a fixed rate irrespective of patient activity.
It adjusts pacing rate based on sensed physiological parameters such as motion or respiration.
It delivers high‑energy shocks to terminate arrhythmias.
It only senses intrinsic cardiac activity without pacing.
Explanation - Rate‑responsive pacemakers contain sensors (e.g., accelerometer, minute ventilation) that modulate the pacing rate according to the patient’s activity level.
Correct answer is: It adjusts pacing rate based on sensed physiological parameters such as motion or respiration.
Q.14 Which component of a defibrillator stores the high‑voltage energy needed for the shock?
Battery pack
Capacitor bank
Inductor coil
Resistor network
Explanation - Capacitors are charged to high voltage and then rapidly discharged through the patient to deliver the therapeutic shock.
Correct answer is: Capacitor bank
Q.15 In a dual‑chamber pacemaker, what is the main advantage of 'AV synchrony'?
Lower battery consumption
Coordinated atrial and ventricular contraction
Higher shock energy delivery
Simpler surgical implantation
Explanation - AV synchrony ensures that atrial contraction precedes ventricular contraction, optimizing cardiac output and mimicking natural physiology.
Correct answer is: Coordinated atrial and ventricular contraction
Q.16 Which of the following is NOT a typical indication for implanting a pacemaker?
Second‑degree AV block type I
Sinus node dysfunction
Ventricular tachycardia
Third‑degree AV block
Explanation - Ventricular tachycardia is usually treated with an ICD or antiarrhythmic drugs, not a standard pacemaker.
Correct answer is: Ventricular tachycardia
Q.17 What is the typical lifespan of a pacemaker battery before replacement is required?
1–2 years
3–5 years
7–10 years
15–20 years
Explanation - Modern lithium‑iodine batteries can reliably power a pacemaker for about 7–10 years, depending on usage and programmed settings.
Correct answer is: 7–10 years
Q.18 Which term describes the process of charging a defibrillator’s capacitor to the preset energy level?
Cycling
Charging
Arming
Discharging
Explanation - The device charges the capacitor to a specific voltage that corresponds to the selected joule setting before a shock can be delivered.
Correct answer is: Charging
Q.19 What safety precaution must be taken before delivering a shock with an external defibrillator?
Ensure the patient is lying on a metal table.
Remove all metal jewelry from the patient.
Place the pads directly on the patient's clothing.
Press the 'defibrillate' button without analyzing rhythm.
Explanation - Metal objects can conduct current and cause burns or unintended shocks; they should be removed before defibrillation.
Correct answer is: Remove all metal jewelry from the patient.
Q.20 In an ICD, which therapy is delivered first when a ventricular tachyarrhythmia is detected?
High‑energy shock
Anti‑tachycardia pacing (ATP)
Defibrillation with biphasic waveform
External manual cardioversion
Explanation - ICDs often attempt ATP, which uses rapid pacing bursts to interrupt re‑entrant circuits before delivering a high‑energy shock.
Correct answer is: Anti‑tachycardia pacing (ATP)
Q.21 What does the acronym 'AED' stand for?
Automatic Electrical Defibrillator
Automated Emergency Device
Automated External Defibrillator
Advanced Electrocardiogram Detector
Explanation - AEDs are portable devices designed to automatically assess heart rhythm and deliver a shock if a shockable rhythm is detected.
Correct answer is: Automated External Defibrillator
Q.22 Which of the following is the most common cause of pacemaker malfunction?
Battery depletion
Lead fracture or insulation breach
Excessive heart rate
High ambient temperature
Explanation - Lead integrity is critical; fractures or insulation failures can cause loss of pacing or inappropriate sensing.
Correct answer is: Lead fracture or insulation breach
Q.23 What is the primary function of the 'sense' circuit in a pacemaker?
To deliver electrical shocks
To detect intrinsic cardiac activity
To recharge the battery
To monitor blood pressure
Explanation - The sense circuit monitors the heart's natural electrical signals to decide whether pacing is needed.
Correct answer is: To detect intrinsic cardiac activity
Q.24 Which of the following is a contraindication for using a defibrillator on a patient?
Patient is in atrial fibrillation
Patient is pregnant
Patient has a metallic implant in the chest
Patient is unconscious
Explanation - Metal implants can conduct current and increase the risk of burns; alternative shock placement or techniques are required.
Correct answer is: Patient has a metallic implant in the chest
Q.25 What does the term 'impedance' refer to in defibrillation?
Resistance of the defibrillator circuitry
The voltage level of the shock
The opposition to current flow through the patient's thorax
The frequency of the delivered waveform
Explanation - Chest impedance influences how much voltage is needed to deliver the desired energy to the heart.
Correct answer is: The opposition to current flow through the patient's thorax
Q.26 Which sensor type is commonly used in rate‑responsive pacemakers to detect patient activity?
Temperature sensor
Accelerometer
pH sensor
Light sensor
Explanation - Accelerometers detect motion, allowing the pacemaker to increase heart rate during physical activity.
Correct answer is: Accelerometer
Q.27 What is the typical duration of a defibrillation pulse delivered by an AED?
1–5 ms
5–15 ms
15–30 ms
30–60 ms
Explanation - AEDs usually deliver a brief pulse lasting between 5 and 15 milliseconds to achieve effective defibrillation while minimizing tissue damage.
Correct answer is: 5–15 ms
Q.28 Which pacing mode provides atrial pacing, ventricular pacing, and atrial sensing with a triggered response?
DDD
VVI
AAI
DVI
Explanation - DDD mode senses both chambers and can pace either atrium or ventricle, delivering a trigger when intrinsic activity is absent.
Correct answer is: DDD
Q.29 In an ICD, what does the term 'over‑drive pacing' refer to?
Delivering a shock at a higher voltage than programmed
Rapid pacing at a rate faster than the tachycardia to terminate it
Increasing the battery voltage during charging
Synchronizing pacing with the respiratory cycle
Explanation - Over‑drive pacing (a form of ATP) attempts to halt a tachyarrhythmia by pacing the heart faster than the arrhythmic circuit.
Correct answer is: Rapid pacing at a rate faster than the tachycardia to terminate it
Q.30 Which of the following best describes a 'biphasic' defibrillation waveform?
A single polarity shock followed by a pause
Two consecutive shocks of opposite polarity
A sinusoidal AC current
A high‑frequency pulsed waveform
Explanation - Biphasic waveforms deliver a positive phase followed immediately by a negative phase, improving defibrillation efficacy.
Correct answer is: Two consecutive shocks of opposite polarity
Q.31 What is the purpose of a 'safety lockout' interval in an AED?
To prevent repeated shocks within a short period
To allow the battery to recharge
To give time for ECG recording
To synchronize with the pacemaker
Explanation - Safety lockout ensures that the device does not deliver another shock until the heart rhythm has been reassessed, reducing the risk of unnecessary shocks.
Correct answer is: To prevent repeated shocks within a short period
Q.32 Which of the following is the most common site for placing a left ventricular lead in cardiac resynchronization therapy (CRT)?
Right atrial appendage
Coronary sinus
Left ventricular apex
Right ventricular outflow tract
Explanation - The coronary sinus provides access to the lateral or posterior veins of the left ventricle, the preferred location for CRT leads.
Correct answer is: Coronary sinus
Q.33 Which clinical condition is an absolute indication for an implantable cardioverter‑defibrillator (ICD)?
First‑degree AV block
History of sustained ventricular tachycardia
Atrial flutter
Sinus bradycardia
Explanation - Patients with prior sustained VT are at high risk for sudden cardiac death, warranting ICD implantation.
Correct answer is: History of sustained ventricular tachycardia
Q.34 What is the function of the 'refractory period' setting in a pacemaker?
To define the minimum interval between sensed events and pacing output
To set the maximum battery life
To control the amplitude of the pacing pulse
To adjust the voltage of a defibrillation shock
Explanation - The refractory period prevents the pacemaker from interpreting its own pacing output as intrinsic activity.
Correct answer is: To define the minimum interval between sensed events and pacing output
Q.35 Which type of energy conversion is used in the charging circuit of a modern defibrillator?
Mechanical to electrical
Chemical to mechanical
Electrical to chemical
Electrical to electrical (DC‑DC conversion)
Explanation - Defibrillators use DC‑DC converters to step up battery voltage to the high voltage needed for capacitor charging.
Correct answer is: Electrical to electrical (DC‑DC conversion)
Q.36 In a pacemaker system, the term 'capture' refers to:
Successful detection of intrinsic cardiac activity
The ability of a pacing stimulus to depolarize the myocardium
Battery voltage exceeding 4 V
The storage of energy in the capacitor
Explanation - Capture is confirmed when a paced spike is followed by a depolarization (P‑wave or QRS) on the ECG.
Correct answer is: The ability of a pacing stimulus to depolarize the myocardium
Q.37 What is the typical frequency range of the biphasic waveform used in modern AEDs?
0.5–2 Hz
30–100 Hz
150–250 Hz
500–1000 Hz
Explanation - Biphasic truncated exponential waveforms generally have a dominant frequency between 150 and 250 Hz, balancing efficacy and tissue safety.
Correct answer is: 150–250 Hz
Q.38 Which of the following is the most common failure mode of an external defibrillator’s pads?
Overheating
Loss of adhesion leading to high impedance
Battery leakage
Signal interference with Wi‑Fi
Explanation - If the pads do not adhere well, the interface impedance rises, reducing delivered energy and compromising shock effectiveness.
Correct answer is: Loss of adhesion leading to high impedance
Q.39 What does the 'V' in the pacemaker mode code 'VDD' signify?
Ventricular pacing
Variable rate
Voltage‑controlled pacing
Vagal stimulation
Explanation - The first letter indicates the chamber paced; 'V' stands for ventricular pacing.
Correct answer is: Ventricular pacing
Q.40 Which of the following statements about the 'defibrillation threshold' (DFT) is correct?
DFT is the minimum battery voltage required for device operation.
DFT is the lowest energy that reliably terminates VF in a particular patient.
DFT is the maximum safe shock energy for all patients.
DFT is the time interval between consecutive shocks.
Explanation - DFT testing determines the minimum effective energy for successful defibrillation, allowing device programming to a safe margin.
Correct answer is: DFT is the lowest energy that reliably terminates VF in a particular patient.
Q.41 Which lead configuration is used for left‑sided ventricular pacing in a biventricular pacemaker?
Single-coil lead placed in the right ventricle
Quadripolar lead placed via the coronary sinus
Unipolar lead in the atrial appendage
Dual‑coil lead in the left atrium
Explanation - Quadripolar leads allow multiple pacing vectors within the coronary sinus for optimal left ventricular capture.
Correct answer is: Quadripolar lead placed via the coronary sinus
Q.42 During a pacemaker interrogation, a sudden increase in sensed amplitude may indicate:
Battery depletion
Lead dislodgement
Myocardial infarction
Electromagnetic interference
Explanation - Dislodged leads may pick up larger, non‑cardiac signals, leading to higher sensed amplitudes.
Correct answer is: Lead dislodgement
Q.43 What is the typical charging time for a 200 J biphasic shock in a modern AED?
1–2 seconds
3–5 seconds
8–10 seconds
15–20 seconds
Explanation - Modern AEDs are designed to charge quickly; a 200 J biphasic shock usually takes about 3 to 5 seconds.
Correct answer is: 3–5 seconds
Q.44 Which component of a pacemaker is primarily responsible for delivering the pacing pulse?
Sense amplifier
Pulse generator output stage
Battery management unit
Telemetry antenna
Explanation - The output stage switches the battery voltage to create the high‑voltage, short‑duration pulse sent to the heart via the lead.
Correct answer is: Pulse generator output stage
Q.45 Which of the following best explains why biphasic shocks are preferred over monophasic shocks?
Biphasic shocks require less energy to achieve defibrillation.
Biphasic shocks are easier to generate with simple circuitry.
Monophasic shocks cause less myocardial damage.
Monophasic shocks have a longer duration.
Explanation - Biphasic waveforms are more efficient; they achieve the same success rate with lower energy, reducing myocardial injury.
Correct answer is: Biphasic shocks require less energy to achieve defibrillation.
Q.46 In pacemaker terminology, what does the term 'hysteresis' refer to?
A delay before the device powers on
A programmed lower rate limit that allows the heart to drop below the set rate before pacing resumes
The time taken for the capacitor to charge
The maximum voltage the device can deliver
Explanation - Hysteresis permits the intrinsic heart rate to fall below the set lower limit before pacing, providing more physiologic pacing.
Correct answer is: A programmed lower rate limit that allows the heart to drop below the set rate before pacing resumes
Q.47 Which of the following is a typical indication for a 'single‑chamber' ventricular pacemaker?
Atrioventricular (AV) block with intact sinus node
Atrial flutter with normal AV conduction
Third‑degree AV block with atrial arrhythmia
Sick sinus syndrome with normal AV node
Explanation - When the atrial rhythm is reliable but ventricular conduction fails, a single‑chamber VVI pacemaker can maintain ventricular rhythm.
Correct answer is: Atrioventricular (AV) block with intact sinus node
Q.48 What is the purpose of a 'magnet' applied over a pacemaker during a medical procedure?
To permanently disable the device
To temporarily switch the device to an asynchronous pacing mode
To increase the battery voltage
To initiate an automatic defibrillation shock
Explanation - A magnet forces many pacemakers into a fixed asynchronous mode (e.g., DOO) to prevent inhibition from external electrical noise.
Correct answer is: To temporarily switch the device to an asynchronous pacing mode
Q.49 Which ECG change indicates successful capture after a pacemaker spike?
A flat line after the spike
A P‑wave following the spike
A QRS complex following the spike
An inverted T‑wave after the spike
Explanation - Ventricular capture is confirmed when the pacing spike is followed by a QRS complex on the ECG.
Correct answer is: A QRS complex following the spike
Q.50 In an ICD, what does 'VT zone' refer to?
The range of heart rates classified as ventricular tachycardia for therapy delivery
The physical location of the device in the chest
The battery voltage range for device operation
The frequency band used for telemetry
Explanation - ICDs are programmed with zones (e.g., VT, VF) defining heart rate thresholds that trigger appropriate therapies.
Correct answer is: The range of heart rates classified as ventricular tachycardia for therapy delivery
Q.51 Which of the following best describes the function of the 'telemetry' system in a pacemaker?
It provides wireless communication for programming and data retrieval.
It monitors blood glucose levels.
It delivers high‑energy shocks.
It charges the device battery.
Explanation - Telemetry allows clinicians to interrogate the device, adjust settings, and download diagnostic data without surgery.
Correct answer is: It provides wireless communication for programming and data retrieval.
Q.52 What is the typical pulse width (duration) of a pacing stimulus delivered by a modern pacemaker?
0.05–0.2 ms
0.3–0.5 ms
0.8–1.2 ms
2–3 ms
Explanation - Most pacemakers use a pulse width between 0.3 and 0.5 ms to achieve capture while minimizing battery drain.
Correct answer is: 0.3–0.5 ms
Q.53 Which of the following is the most common cause of inappropriate shocks in ICD patients?
Lead fracture
Battery depletion
Electromagnetic interference from external devices
Atrial fibrillation misinterpreted as ventricular tachycardia
Explanation - ICDs may mistake rapid atrial rhythms for ventricular tachyarrhythmias, leading to inappropriate shocks.
Correct answer is: Atrial fibrillation misinterpreted as ventricular tachycardia
Q.54 Which of the following statements about 'automatic' versus 'manual' defibrillation is correct?
Automatic defibrillation requires the operator to select shock energy manually.
Manual defibrillation involves the device analyzing rhythm and deciding to shock without user input.
Automatic defibrillation devices can assess rhythm and advise the operator before delivering a shock.
Manual defibrillation devices cannot deliver biphasic shocks.
Explanation - AEDs automatically analyze the ECG and prompt the user to press the shock button only when a shockable rhythm is detected.
Correct answer is: Automatic defibrillation devices can assess rhythm and advise the operator before delivering a shock.
Q.55 In a pacemaker, the term 'output voltage' refers to:
The voltage measured across the battery terminals
The voltage of the pacing pulse delivered to the heart
The voltage used for telemetry communication
The voltage required to charge the internal capacitor
Explanation - Output voltage is the amplitude of the pacing pulse; typical values are 2–5 V for ventricular pacing.
Correct answer is: The voltage of the pacing pulse delivered to the heart
Q.56 Which physiological parameter is NOT commonly used by rate‑responsive pacemakers for sensor input?
Respiratory rate
Body temperature
Physical activity (accelerometer)
Minute ventilation
Explanation - Temperature is not a reliable indicator of metabolic demand; the other three are common sensor modalities.
Correct answer is: Body temperature
Q.57 What is the primary advantage of a 'quadripolar' left‑ventricular lead over a 'bipolar' lead in CRT?
Lower manufacturing cost
Multiple pacing vectors that improve lead placement flexibility and reduce phrenic nerve capture
Higher impedance
Simpler surgical implantation
Explanation - Quadripolar leads provide four electrodes, enabling selection of optimal pacing configurations and reducing side‑effects.
Correct answer is: Multiple pacing vectors that improve lead placement flexibility and reduce phrenic nerve capture
Q.58 Which of the following best describes the term 'shockable rhythm'?
Any rhythm slower than 40 bpm
Ventricular fibrillation or pulseless ventricular tachycardia
Atrial fibrillation with rapid ventricular response
Normal sinus rhythm
Explanation - Only VF and pulseless VT are considered shockable; other rhythms require different interventions.
Correct answer is: Ventricular fibrillation or pulseless ventricular tachycardia
Q.59 During implantation, which imaging modality is most commonly used to guide lead placement?
Magnetic resonance imaging (MRI)
Computed tomography (CT)
Fluoroscopy
Ultrasound
Explanation - Fluoroscopic X‑ray provides real‑time visualization of leads and catheters during the procedure.
Correct answer is: Fluoroscopy
Q.60 What is the typical energy range (in joules) delivered by an implantable cardioverter‑defibrillator (ICD) for a ventricular shock?
0.5–2 J
5–15 J
10–40 J
50–100 J
Explanation - Implantable ICDs deliver shocks in the 10–40 J range, sufficient to terminate ventricular arrhythmias while conserving battery life.
Correct answer is: 10–40 J
Q.61 Which of the following is NOT a standard pacing mode abbreviation?
DDD
AAI
VVI
PPP
Explanation - Standard mode codes use three letters (e.g., DDD, AAI, VVI). 'PPP' is not a recognized pacing mode.
Correct answer is: PPP
Q.62 What does the term 'chronaxie' describe in cardiac electrophysiology?
The time between two consecutive ventricular beats
The minimum duration of an electric pulse at twice the rheobase needed to stimulate tissue
The refractory period of the atrioventricular node
The latency of the pacemaker response
Explanation - Chronaxie is a measure of tissue excitability used to design pacing and defibrillation pulses.
Correct answer is: The minimum duration of an electric pulse at twice the rheobase needed to stimulate tissue
Q.63 Which of the following best describes 'pacing capture threshold'?
The maximum voltage the device can output
The lowest stimulus amplitude that consistently results in myocardial depolarization
The time interval between two paced beats
The battery voltage at which pacing stops
Explanation - Capture threshold testing determines the minimal output needed for reliable pacing, influencing programming and battery longevity.
Correct answer is: The lowest stimulus amplitude that consistently results in myocardial depolarization
Q.64 In the context of defibrillation, what does 'post‑shock rhythm analysis' accomplish?
It measures the battery voltage after shock delivery.
It determines whether a subsequent shock is required.
It calibrates the impedance sensor.
It recharges the capacitor.
Explanation - After each shock, the device reassesses the cardiac rhythm to decide if another shock or other therapy is needed.
Correct answer is: It determines whether a subsequent shock is required.
Q.65 Which component of a pacemaker system is most vulnerable to electromagnetic interference (EMI) from external sources?
Battery
Lead insulation
Sense amplifier
Telemetry antenna
Explanation - The sense amplifier detects low‑amplitude cardiac signals and can be affected by external electromagnetic fields, leading to oversensing or undersensing.
Correct answer is: Sense amplifier
Q.66 What is the purpose of a 'rechargeable' ICD battery, when used?
To allow indefinite device life without surgical replacement
To provide higher voltage output for shocks
To enable the patient to charge the device via a transcutaneous system
To reduce the size of the pulse generator
Explanation - Some newer ICDs use rechargeable lithium‑ion batteries that can be recharged through the skin using inductive coupling, extending device life.
Correct answer is: To enable the patient to charge the device via a transcutaneous system
Q.67 Which of the following best explains why 'leadless' pacemakers are gaining popularity?
They provide dual‑chamber pacing without leads.
They eliminate lead‑related complications such as fracture or infection.
They can deliver high‑energy shocks like an ICD.
They are powered by external wireless energy.
Explanation - Leadless pacemakers are self‑contained devices implanted directly in the right ventricle, reducing the risk of lead failures.
Correct answer is: They eliminate lead‑related complications such as fracture or infection.
Q.68 Which term refers to the programmed maximum heart rate a pacemaker will allow in a rate‑responsive mode?
Upper rate limit (URL)
Lower rate limit (LRL)
Maximum sensor threshold
Chronotropic limit
Explanation - The URL caps the pacing rate to prevent excessively high heart rates despite sensor input.
Correct answer is: Upper rate limit (URL)
Q.69 What is the most common cause of 'oversensing' in a pacemaker?
Battery depletion
Myopotential (muscle) signals
Lead fracture
High pacing output
Explanation - Muscle activity near the lead can be detected as cardiac events, causing the pacemaker to withhold pacing (oversensing).
Correct answer is: Myopotential (muscle) signals
Q.70 Which of the following best describes the term 'defibrillation pad polarity'?
The order in which pads are placed on the chest
The electrical charge (positive or negative) assigned to each pad during shock delivery
The color coding of the pads
The manufacturer’s model number
Explanation - Polarity determines which pad is the anode and which is the cathode for the biphasic waveform.
Correct answer is: The electrical charge (positive or negative) assigned to each pad during shock delivery
Q.71 In an ICD, which therapy is used to treat a fast ventricular tachycardia that is hemodynamically stable?
High‑energy shock
Anti‑tachycardia pacing (ATP)
External cardioversion
Pharmacologic therapy only
Explanation - ATP can terminate stable VT by delivering paced beats faster than the VT cycle length, often avoiding the need for a shock.
Correct answer is: Anti‑tachycardia pacing (ATP)
Q.72 What is the typical duration of a biphasic shock pulse delivered by an AED?
1–5 ms
5–15 ms
20–30 ms
50–100 ms
Explanation - AED biphasic shocks are brief, usually lasting between 5 and 15 milliseconds, to achieve effective defibrillation while minimizing tissue injury.
Correct answer is: 5–15 ms
Q.73 Which of the following statements about 'lead extraction' is true?
It can be performed without any specialized tools.
It is generally a simple outpatient procedure.
It carries risk of vascular injury and requires specialized equipment.
It is only necessary when the battery is depleted.
Explanation - Lead extraction is a complex procedure that may involve laser sheaths or mechanical tools and has potential complications such as vessel damage.
Correct answer is: It carries risk of vascular injury and requires specialized equipment.
Q.74 Which of the following is the most appropriate first‑step management after delivering a successful shock with an AED?
Immediately start chest compressions
Check the patient’s pulse before any further action
Apply a second set of AED pads
Turn off the AED
Explanation - After a shock, the patient should be reassessed and if no pulse is present, high‑quality chest compressions should be resumed immediately.
Correct answer is: Immediately start chest compressions
Q.75 Which term describes the use of a pacemaker to treat heart failure by synchronizing ventricular contractions?
Cardiac resynchronization therapy (CRT)
Implantable cardioverter‑defibrillation (ICD)
Automatic external defibrillation (AED)
Ventricular assist device (VAD)
Explanation - CRT uses biventricular pacing to improve coordination between the left and right ventricles, benefitting patients with heart failure.
Correct answer is: Cardiac resynchronization therapy (CRT)
Q.76 What is the typical frequency of the alternating current (AC) component in a biphasic truncated exponential waveform?
10–30 Hz
50–60 Hz
150–250 Hz
500–1000 Hz
Explanation - The dominant frequency of biphasic waveforms used in defibrillation is generally in the 150–250 Hz range.
Correct answer is: 150–250 Hz
Q.77 Which of the following is a standard safety recommendation for by‑standers when an AED is in use?
Stand on the patient’s chest to improve conductivity.
Hold the patient’s hands to prevent movement.
Ensure no one touches the patient during charging and shock delivery.
Apply the AED pads directly over a pacemaker generator.
Explanation - Touching the patient can divert current and pose a risk of shock to by‑standers; the patient must be alone during shock delivery.
Correct answer is: Ensure no one touches the patient during charging and shock delivery.
Q.78 What is the primary function of the 'refractory period' in an ICD’s detection algorithm?
To prevent the device from delivering multiple shocks for the same arrhythmia
To allow the battery to recharge
To synchronize the shock with the QRS complex
To increase the shock amplitude
Explanation - After a therapy is delivered, a refractory period disables further detections temporarily to avoid unnecessary multiple shocks.
Correct answer is: To prevent the device from delivering multiple shocks for the same arrhythmia
Q.79 Which component in a defibrillator converts stored electrical energy into the high‑voltage shock waveform?
Transformer
Inverter
Switching circuit (e.g., MOSFETs)
Capacitor bank
Explanation - High‑speed switching devices discharge the capacitor bank and shape the waveform (monophasic or biphasic) delivered to the patient.
Correct answer is: Switching circuit (e.g., MOSFETs)
Q.80 What is the main advantage of using a 'dual‑coil' ICD lead over a single‑coil lead?
Reduced cost
Lower impedance and better defibrillation efficacy
Simpler implantation technique
Compatibility with all pacemaker models
Explanation - Dual‑coil leads provide a broader shock vector, improving defibrillation success and lowering required energy.
Correct answer is: Lower impedance and better defibrillation efficacy
Q.81 Which of the following best characterizes the term 'bypass tract' in the context of cardiac electrophysiology?
A surgically created conduit for blood flow
An abnormal electrical pathway that can cause tachyarrhythmias
A special type of pacemaker lead
The route used for ICD lead implantation
Explanation - Bypass tracts, such as accessory pathways in Wolff‑Parkinson‑White syndrome, allow impulses to circumvent the AV node.
Correct answer is: An abnormal electrical pathway that can cause tachyarrhythmias
Q.82 What is the standard recommended energy for the first shock delivered by an AED in an adult?
50 J
120 J
200 J
360 J
Explanation - Current guidelines advise a first shock of 200 J biphasic for adult patients using most AEDs.
Correct answer is: 200 J
Q.83 Which of the following is NOT a typical function of a modern cardiac implantable device's telemetry system?
Wireless programming of device parameters
Real‑time transmission of intracardiac electrograms
Delivery of high‑energy therapeutic shocks
Battery status monitoring
Explanation - Telemetry is used for communication and data exchange; shock delivery is performed by the device’s therapy circuit, not by telemetry.
Correct answer is: Delivery of high‑energy therapeutic shocks
Q.84 Which of the following best defines the term 'ventricular capture'?
The detection of intrinsic ventricular activity by the pacemaker
Successful depolarization of the ventricle by a pacing stimulus
Inhibition of pacing due to sensed ventricular beats
A mechanical contraction of the ventricular wall
Explanation - Capture occurs when the pacing spike leads to a QRS complex, indicating that the stimulus has depolarized the ventricular myocardium.
Correct answer is: Successful depolarization of the ventricle by a pacing stimulus
Q.85 What is the primary reason for programming a pacemaker with a 'hysteresis' feature?
To allow the heart rate to fall below the lower rate limit before pacing resumes
To increase the amplitude of pacing pulses
To shorten the battery life intentionally
To synchronize with external devices
Explanation - Hysteresis provides a window where intrinsic beats are allowed before pacing, promoting natural rhythm when possible.
Correct answer is: To allow the heart rate to fall below the lower rate limit before pacing resumes
Q.86 Which of the following statements about the 'upper tracking limit' in a dual‑chamber pacemaker is correct?
It sets the maximum pacing rate the device will deliver in response to sensed atrial events.
It defines the minimum ventricular pacing rate.
It determines the maximum battery voltage.
It limits the duration of each pacing pulse.
Explanation - The upper tracking limit prevents the pacemaker from tracking atrial rates that are excessively fast, protecting the ventricles from tachycardia.
Correct answer is: It sets the maximum pacing rate the device will deliver in response to sensed atrial events.
Q.87 Which of the following is the most common method for verifying proper lead placement after pacemaker implantation?
Chest X‑ray
MRI scan
CT angiography
Echocardiography
Explanation - A post‑procedure chest radiograph confirms lead position and detects possible complications such as pneumothorax.
Correct answer is: Chest X‑ray
Q.88 In a modern AED, which algorithm determines whether a shock is needed?
R‑wave detection algorithm
Shock‑ability analysis based on amplitude and frequency content
Battery voltage check
User‑selected rhythm mode
Explanation - AEDs analyze the ECG waveform for characteristics of VF or VT (e.g., amplitude, frequency) to decide if a shock is indicated.
Correct answer is: Shock‑ability analysis based on amplitude and frequency content
Q.89 Which of the following best describes the function of a 'ventricular safety pacing' (VSP) feature?
Delivers a backup pacing pulse if the primary pulse fails to capture.
Inhibits pacing during high‑energy shocks.
Increases the pacing rate during exercise.
Monitors battery status.
Explanation - VSP provides a second low‑energy pulse shortly after the primary one to ensure capture when the primary pulse is insufficient.
Correct answer is: Delivers a backup pacing pulse if the primary pulse fails to capture.
Q.90 Which of the following is the most common type of battery chemistry used in modern pacemakers?
Nickel‑Cadmium (NiCd)
Alkaline
Lithium‑iodine
Lead‑acid
Explanation - Lithium‑iodine batteries provide high energy density, stable voltage, and long life suitable for implantable devices.
Correct answer is: Lithium‑iodine
Q.91 What is the main reason that 'leadless' pacemakers are implanted in the right ventricle rather than the left ventricle?
Right ventricle has lower pressure making implantation easier.
Left ventricular placement would interfere with the coronary arteries.
The right ventricle provides adequate pacing for most bradyarrhythmias and is accessible via a femoral approach.
Left ventricular pacing is contraindicated in all patients.
Explanation - Leadless devices are delivered via a catheter into the right ventricle, where they can effectively pace the heart without the need for trans‑venous leads.
Correct answer is: The right ventricle provides adequate pacing for most bradyarrhythmias and is accessible via a femoral approach.
Q.92 Which of the following best defines the term 'defibrillation shock polarity reversal'?
Switching the device on and off rapidly.
Changing the direction of current flow between the two phases of a biphasic shock.
Increasing the shock amplitude mid‑delivery.
Delivering two consecutive monophasic shocks.
Explanation - Polarity reversal is intrinsic to biphasic waveforms where the first phase is followed by a second phase of opposite polarity.
Correct answer is: Changing the direction of current flow between the two phases of a biphasic shock.
Q.93 Which of the following is NOT a typical programming parameter for a rate‑responsive pacemaker?
Sensor gain
Upper rate limit
Capture threshold
Pacing polarity
Explanation - Pacing polarity (anode/cathode configuration) is a hardware setting, not a programmable parameter of rate responsiveness.
Correct answer is: Pacing polarity
Q.94 What is the most common cause of an 'undersensing' event in a pacemaker?
Lead fracture
Excessive pacing output
Low amplitude intrinsic cardiac signals
Battery over‑voltage
Explanation - If the heart's intrinsic signals are too small, the device may fail to detect them, leading to unnecessary pacing.
Correct answer is: Low amplitude intrinsic cardiac signals
Q.95 Which of the following is true about the 'recharging' process of a rechargeable ICD battery?
It can be performed transcutaneously using inductive coupling.
It requires surgical removal of the device.
It only works when the patient is under general anesthesia.
It is done by plugging the device into a wall outlet.
Explanation - Recharging is achieved through an external coil placed over the skin, transferring energy wirelessly to the implanted battery.
Correct answer is: It can be performed transcutaneously using inductive coupling.
Q.96 Which ECG feature is most commonly used by an AED to differentiate between ventricular fibrillation and asystole?
Presence of a discernible QRS complex
Amplitude of the T‑wave
Heart rate variability
Baseline noise level
Explanation - Ventricular fibrillation shows chaotic, rapid oscillations without organized QRS complexes, whereas asystole is a flat line.
Correct answer is: Presence of a discernible QRS complex
Q.97 What does the abbreviation 'ICD' stand for in cardiac electrophysiology?
Implantable Cardioverter‑Defibrillator
Intravascular Cardiac Device
Internal Cardiac Defibrillator
Immediate Cardiac Diagnosis
Explanation - ICD is a device implanted under the skin that can detect and treat life‑threatening ventricular arrhythmias.
Correct answer is: Implantable Cardioverter‑Defibrillator
Q.98 Which of the following best explains why a pacemaker may be programmed to an 'asynchronous' mode during surgery?
To ensure the device continues pacing regardless of sensed electrical noise from surgical equipment.
To increase the battery life during the operation.
To allow the heart to beat naturally without interference.
To deliver therapeutic shocks if needed.
Explanation - Asynchronous mode (e.g., DOO) prevents the pacemaker from being inhibited by electromagnetic interference in the operating room.
Correct answer is: To ensure the device continues pacing regardless of sensed electrical noise from surgical equipment.
Q.99 Which of the following is the most appropriate action if a patient with a pacemaker requires an MRI?
Proceed without any precautions; MRI is safe for all pacemaker patients.
Cancel the MRI and use an alternative imaging modality.
Reprogram the pacemaker to an MRI‑safe mode if the device is certified for MRI.
Turn off the pacemaker by removing the battery.
Explanation - MRI‑conditional pacemakers can be set to a safe mode that disables sensing and pacing functions during the scan to avoid malfunction.
Correct answer is: Reprogram the pacemaker to an MRI‑safe mode if the device is certified for MRI.
Q.100 In the context of defibrillation, what does the term 'energy density' refer to?
Energy per unit mass of the device
Energy delivered per unit area of the chest wall
Energy stored in the capacitor divided by battery voltage
Energy per kilogram of body weight
Explanation - Energy density influences how much of the delivered energy actually reaches the myocardium, affecting shock efficacy.
Correct answer is: Energy delivered per unit area of the chest wall
Q.101 Which of the following is a typical clinical indication for a biventricular pacemaker (CRT‑D) rather than a single‑chamber device?
First‑degree AV block
Left bundle branch block with reduced ejection fraction
Isolated sinus bradycardia
Atrial flutter
Explanation - CRT‑D improves synchrony in patients with LBBB and heart failure, enhancing cardiac output.
Correct answer is: Left bundle branch block with reduced ejection fraction
Q.102 What is the typical impedance range measured by a defibrillator before delivering a shock?
10–30 Ω
30–80 Ω
100–200 Ω
200–400 Ω
Explanation - Chest impedance for defibrillation usually falls between 30 and 80 Ω; values outside this range may indicate poor pad contact.
Correct answer is: 30–80 Ω
Q.103 Which of the following best describes the principle of 'defibrillation'?
Gradual increase of heart rate through pharmacology
Electrical reset of the heart's electrical system by delivering a high‑energy shock
Mechanical compression of the heart chambers
Cooling of the myocardium to stop arrhythmias
Explanation - Defibrillation works by depolarizing a critical mass of myocardial cells, allowing the natural pacemaker to regain control.
Correct answer is: Electrical reset of the heart's electrical system by delivering a high‑energy shock
Q.104 Which of the following best describes why a 'biphasic' waveform reduces the required shock energy compared to a 'monophasic' waveform?
It delivers two consecutive shocks, doubling the effect.
The reversal of polarity reduces the net charge needed to achieve defibrillation.
It uses higher frequency currents that are more effective.
It prolongs the duration of the shock.
Explanation - Biphasic shocks achieve the same depolarization with less total energy because the second phase cancels residual charge, improving efficiency.
Correct answer is: The reversal of polarity reduces the net charge needed to achieve defibrillation.
Q.105 What is the most common method for detecting a loss of capture during pacemaker follow‑up?
Measuring battery voltage
Observing patient’s symptoms only
Analyzing intracardiac electrograms for absence of evoked response after a pacing spike
Checking the external telemetry antenna
Explanation - Loss of capture is identified when a pacing spike is not followed by a corresponding depolarization on the ECG or intracardiac EGMs.
Correct answer is: Analyzing intracardiac electrograms for absence of evoked response after a pacing spike
Q.106 Which of the following is a typical characteristic of ventricular fibrillation on the ECG?
Regular, narrow QRS complexes at 60 bpm
Absent QRS complexes with chaotic low‑amplitude oscillations
Wide QRS complexes with a rate of 30 bpm
Flat line with no electrical activity
Explanation - VF appears as rapid, irregular, low‑amplitude waves without recognizable QRS complexes.
Correct answer is: Absent QRS complexes with chaotic low‑amplitude oscillations
Q.107 Which of the following statements about the 'refractory period' in a pacemaker is correct?
It determines the minimum interval between two consecutive pacing spikes.
It is the period during which the device ignores sensed signals after a paced beat to prevent double counting.
It sets the maximum pacing rate.
It controls battery recharging.
Explanation - The refractory period ensures that the pacemaker does not interpret its own stimulus as an intrinsic beat.
Correct answer is: It is the period during which the device ignores sensed signals after a paced beat to prevent double counting.
Q.108 Which of the following best explains why an AED includes a 'voice prompt' system?
To reduce the device's power consumption.
To guide the rescuer through the analysis and shock delivery steps, improving user performance.
To record the patient's ECG for later review.
To calibrate the device’s internal capacitor.
Explanation - Voice prompts provide step‑by‑step instructions, allowing even untrained by‑standers to use the AED effectively.
Correct answer is: To guide the rescuer through the analysis and shock delivery steps, improving user performance.
Q.109 In pacemaker terminology, what does the letter 'A' denote in the mode code 'AAI'?
Atrial pacing
Automatic mode switching
Advanced algorithm
Asynchronous pacing
Explanation - The first letter indicates the chamber that is paced; 'A' stands for atrial pacing.
Correct answer is: Atrial pacing
Q.110 Which of the following best describes the role of the 'defibrillation lead' in an ICD?
It provides a pathway for sensing intracardiac signals only.
It transmits high‑energy shocks from the device to the heart.
It measures blood pressure.
It powers the device via kinetic energy.
Explanation - The defibrillation lead carries the therapeutic shock current from the ICD to the myocardial tissue.
Correct answer is: It transmits high‑energy shocks from the device to the heart.
Q.111 Which of the following is a common feature of modern implantable pacemakers that helps reduce battery drain?
Continuous high‑energy pacing
Automatic mode switching to a lower pacing rate when intrinsic rhythm is adequate
Increasing output voltage during sleep
Never entering sleep mode
Explanation - Adaptive algorithms reduce pacing output when the patient’s own rhythm suffices, extending battery longevity.
Correct answer is: Automatic mode switching to a lower pacing rate when intrinsic rhythm is adequate
Q.112 Which of the following best defines the term 'electrical storm' in the context of ICD therapy?
A rapid succession of multiple ventricular arrhythmias requiring several shocks within a short time frame
A malfunction of the device’s battery
A severe allergic reaction to the device materials
An external electromagnetic interference event
Explanation - Electrical storm refers to frequent ICD therapies (often >3 shocks in 24 h) indicating unstable ventricular arrhythmia.
Correct answer is: A rapid succession of multiple ventricular arrhythmias requiring several shocks within a short time frame
Q.113 Which of the following is the most common placement for an atrial lead in a dual‑chamber pacemaker?
Right atrial appendage
Left atrial roof
Coronary sinus
Right ventricular apex
Explanation - The right atrial appendage offers stable fixation and reliable sensing for atrial leads.
Correct answer is: Right atrial appendage
Q.114 What is the principal advantage of a 'self‑adjusting' rate‑responsive pacemaker compared to a fixed‑rate device?
It eliminates the need for battery replacement.
It can automatically increase heart rate during physical activity without manual reprogramming.
It provides higher voltage shocks.
It reduces the size of the device.
Explanation - Self‑adjusting devices use sensors to modify pacing rate according to metabolic demand, improving physiological response.
Correct answer is: It can automatically increase heart rate during physical activity without manual reprogramming.
Q.115 Which of the following is NOT a typical feature of a modern AED's user interface?
Touch‑screen display
Automated rhythm analysis
Voice instructions
Manual ECG interpretation by the user
Explanation - AEDs automate ECG interpretation; users are not required to read the ECG manually.
Correct answer is: Manual ECG interpretation by the user
Q.116 During pacemaker interrogation, a clinician notices an abrupt increase in the sensed amplitude on the ventricular channel. Which of the following is the most likely cause?
Battery depletion
Lead dislodgement with closer proximity to ventricular myocardium
Increased pacing output
Software glitch
Explanation - A displaced lead may be positioned closer to the ventricular tissue, resulting in larger sensed amplitudes.
Correct answer is: Lead dislodgement with closer proximity to ventricular myocardium
Q.117 Which of the following best describes the term 're‑charging' in the context of an external defibrillator's capacitor?
The process of increasing battery voltage after a shock
The discharge of the capacitor into the patient
The period during which the capacitor stores energy before the shock is delivered
The cooling of the device after use
Explanation - Re‑charging (or charging) is the phase where the capacitor is charged to the required voltage for the upcoming shock.
Correct answer is: The period during which the capacitor stores energy before the shock is delivered
Q.118 Which of the following is the most appropriate method to test a pacemaker's capture threshold during implantation?
Increase the pacing output until an ECG QRS complex follows each pacing spike.
Measure the battery voltage directly.
Check the patient’s pulse manually.
Observe the device’s LED indicator.
Explanation - Capture threshold is determined by gradually decreasing output until capture is lost, confirming the minimal effective voltage.
Correct answer is: Increase the pacing output until an ECG QRS complex follows each pacing spike.
Q.119 Which of the following best explains why 'leadless' pacemakers have limited pacing capabilities compared to conventional systems?
They cannot be programmed remotely.
They lack the ability to sense atrial activity, limiting them to single‑chamber ventricular pacing.
They use lower battery voltage.
They are made of non‑conductive materials.
Explanation - Leadless devices are currently limited to VVI or VVI‑R modes, lacking atrial sensing/pacing due to size constraints.
Correct answer is: They lack the ability to sense atrial activity, limiting them to single‑chamber ventricular pacing.
Q.120 What is the most common reason for performing a 'defibrillation threshold' (DFT) test after ICD implantation?
To verify the battery life of the device.
To ensure the lead is positioned correctly and can deliver sufficient energy to terminate VF.
To calibrate the device’s telemetry antenna.
To program the device’s upper rate limit.
Explanation - DFT testing confirms that the implanted system can successfully defibrillate at a safety margin above the threshold.
Correct answer is: To ensure the lead is positioned correctly and can deliver sufficient energy to terminate VF.
Q.121 Which of the following statements about the 'charge‑time' of a defibrillator is correct?
Longer charge times always improve shock effectiveness.
Shorter charge times reduce the risk of patient movement before shock delivery.
Charge time is irrelevant to defibrillation success.
Charge time depends only on battery voltage.
Explanation - Rapid charging minimizes the interval during which a rescuer must keep the patient still, decreasing the chance of premature shock interruption.
Correct answer is: Shorter charge times reduce the risk of patient movement before shock delivery.
Q.122 Which of the following is a typical programming parameter for an ICD's anti‑tachycardia pacing (ATP) therapy?
Number of pacing bursts
Upper rate limit
Battery voltage
Lead impedance
Explanation - ATP settings include the number of bursts, pacing interval, and coupling interval to terminate VT.
Correct answer is: Number of pacing bursts
Q.123 Which of the following best defines the term 'chronaxie' in the context of cardiac pacing?
The minimum current required to stimulate cardiac tissue at twice the rheobase voltage.
The duration of the refractory period.
The interval between two successive paced beats.
The voltage needed to charge the capacitor.
Explanation - Chronaxie is a time constant used to characterize excitability of cardiac tissue, influencing pulse width selection.
Correct answer is: The minimum current required to stimulate cardiac tissue at twice the rheobase voltage.
Q.124 What is the main purpose of the 'low‑energy pacing' feature in some ICDs?
To provide backup pacing after a shock to prevent bradycardia.
To replace the need for high‑energy defibrillation.
To charge the device's battery during therapy.
To synchronize with external monitors.
Explanation - After a high‑energy shock, low‑energy pacing ensures the heart maintains an appropriate rhythm, avoiding pauses.
Correct answer is: To provide backup pacing after a shock to prevent bradycardia.
Q.125 Which of the following best explains why 'impedance' is measured before each defibrillation shock?
To calculate the required voltage for the selected joule setting.
To assess battery health.
To determine the patient's heart rate.
To adjust the device's telemetry frequency.
Explanation - Knowing the chest impedance allows the defibrillator to set the appropriate voltage to deliver the programmed energy.
Correct answer is: To calculate the required voltage for the selected joule setting.
Q.126 Which of the following best describes the function of a 'magnet' placed over a pacemaker during a surgical procedure?
It permanently disables the device.
It forces the pacemaker into an asynchronous mode to avoid inhibition from electrocautery.
It increases the battery voltage.
It initiates a therapeutic shock.
Explanation - A magnet temporarily changes the pacemaker to a fixed-rate mode, preventing external interference from causing pauses.
Correct answer is: It forces the pacemaker into an asynchronous mode to avoid inhibition from electrocautery.
Q.127 Which of the following best characterizes the 'refractory period' after a delivered ICD shock?
A period during which the device cannot deliver another shock, allowing myocardial recovery.
A time during which the battery recharges.
A window where the device increases pacing rate.
A duration when the device disables telemetry.
Explanation - Post‑shock refractory period prevents the ICD from delivering multiple shocks in quick succession, reducing tissue damage.
Correct answer is: A period during which the device cannot deliver another shock, allowing myocardial recovery.