DC Dysrhythmia Equipment & Technology 2 — Questions and Answers
Question 1: What type of pacemaker fires only when the heart's intrinsic rate falls below a programmed set rate?
- Fixed-rate (asynchronous) pacemaker
- Demand (synchronous) pacemaker (Correct answer)
- Biventricular pacemaker
- Epicardial pacemaker
Correct answer: Demand (synchronous) pacemaker
A demand pacemaker continuously senses the patient's intrinsic rhythm and fires only when the rate falls below the programmed lower rate limit, preventing competition with native beats.
Question 2: In the NASPE/BPEG pacemaker nomenclature code, what does the first letter represent?
- Rate response capability
- Chamber(s) sensed
- Chamber(s) paced (Correct answer)
- Programming features
Correct answer: Chamber(s) paced
The first letter of the NBG pacemaker code designates the chamber(s) paced: A (atrium), V (ventricle), D (dual — both), or O (none).
Question 3: What ECG finding is characteristic of a functioning ventricular pacemaker spike?
- Narrow QRS complex preceded by a pacemaker spike
- Wide QRS complex preceded by a pacemaker spike (Correct answer)
- Delta wave with a short PR interval
- Prolonged PR interval with normal QRS width
Correct answer: Wide QRS complex preceded by a pacemaker spike
Ventricular pacing produces a pacemaker spike followed by a wide QRS because ventricular activation travels via slow cell-to-cell conduction rather than the His-Purkinje system.
Question 4: What is pacemaker failure to capture?
- The pacemaker fails to sense intrinsic cardiac activity
- A pacemaker spike is present but does not produce myocardial depolarization (Correct answer)
- The pacemaker fires at an incorrect rate
- The pacemaker fails to inhibit when intrinsic activity occurs
Correct answer: A pacemaker spike is present but does not produce myocardial depolarization
Failure to capture occurs when a pacemaker spike is visible on ECG but is not followed by a P wave or QRS complex, indicating the stimulus is insufficient to depolarize the myocardium.
Question 5: Which condition most commonly causes pacemaker failure to sense?
- Low battery voltage
- Lead dislodgement or fracture (Correct answer)
- Electromagnetic interference
- Increased pacing threshold
Correct answer: Lead dislodgement or fracture
Lead dislodgement or fracture is the most common cause of sensing failure because it disrupts the electrical connection between the myocardium and the pulse generator.
Question 6: What is the function of rate modulation (R) in modern pacemakers?
- Prevents pacemaker-mediated tachycardia
- Adjusts pacing rate based on physiologic demand such as physical activity (Correct answer)
- Reduces battery drain during periods of rest
- Synchronizes atrial and ventricular pacing timing
Correct answer: Adjusts pacing rate based on physiologic demand such as physical activity
Rate modulation uses physiologic sensors (motion, minute ventilation) to automatically increase the pacing rate during physical activity, mimicking the normal chronotropic response.
DC Dysrhythmia Equipment & Technology 2
What type of pacemaker fires only when the heart's intrinsic rate falls below a programmed set rate?