CCI Pacemaker and Implantable Device Assessment 2 — Questions and Answers
Question 1: Which ECG finding is most consistent with pacemaker failure to capture?
- Pacing spike followed by a QRS complex
- Pacing spike not followed by a P wave or QRS complex (Correct answer)
- Absent pacing spikes with no intrinsic rhythm
- Prolonged PR interval after each pacing spike
Correct answer: Pacing spike not followed by a P wave or QRS complex
Failure to capture is identified by pacing spikes that do not produce the expected depolarization (P wave or QRS), meaning the stimulus did not excite the myocardium.
Question 2: What is the most common cause of acute pacemaker failure to capture in the early post-implant period?
- Battery depletion
- Lead dislodgement (Correct answer)
- Electromagnetic interference
- Insulation break
Correct answer: Lead dislodgement
Lead dislodgement is the most common cause of failure to capture in the early post-implant period, as leads have not yet become secured by fibrosis.
Question 3: T-wave oversensing in a VVI pacemaker most likely results in which pacemaker malfunction?
- Failure to capture
- Runaway pacemaker
- Inappropriate inhibition of pacing output (Correct answer)
- Pacemaker-mediated tachycardia
Correct answer: Inappropriate inhibition of pacing output
When the pacemaker incorrectly senses the T-wave as a QRS complex (oversensing), it is inappropriately inhibited from pacing, which can lead to pauses in a pacemaker-dependent patient.
Question 4: A pacing lead impedance measurement of 150 ohms is most consistent with which condition?
- Normal lead function
- Lead fracture (open circuit)
- Lead insulation breach (short circuit) (Correct answer)
- Battery end-of-life
Correct answer: Lead insulation breach (short circuit)
Normal pacing lead impedance is 300–1,000 ohms; impedance below 200 ohms suggests an insulation break causing a short circuit, while >2,000 ohms suggests lead fracture.
Question 5: On chest X-ray, which finding would most suggest right ventricular lead perforation?
- Lead tip at the right ventricular apex
- Bilateral pleural effusions
- Lead tip extending beyond the cardiac silhouette (Correct answer)
- Mediastinal widening
Correct answer: Lead tip extending beyond the cardiac silhouette
Lead perforation is suggested when the lead tip appears to extend outside the cardiac shadow on chest X-ray, indicating the lead has pierced the myocardial wall.
Question 6: When a magnet is applied to a permanent pacemaker, what is the primary purpose of this maneuver in clinical assessment?
- To permanently reprogram the pacing mode
- To assess battery status by inducing asynchronous pacing at a magnet rate (Correct answer)
- To increase the pacing sensitivity
- To deliver antitachycardia pacing
Correct answer: To assess battery status by inducing asynchronous pacing at a magnet rate
Magnet application causes most pacemakers to pace asynchronously at a manufacturer-specific magnet rate; a decrease in this rate from the beginning-of-life rate indicates battery depletion approaching end-of-life.
Question 7: Which pacemaker programming change is most appropriate to correct myopotential oversensing?
- Decrease the pacing output
- Increase the sensitivity (lower the mV threshold)
- Decrease the sensitivity (raise the mV threshold) (Correct answer)
- Increase the pacing rate
Correct answer: Decrease the sensitivity (raise the mV threshold)
Decreasing sensitivity (raising the sensing threshold in millivolts) makes the pacemaker less responsive to low-amplitude signals such as myopotentials, reducing inappropriate inhibition.
CCI Pacemaker and Implantable Device Assessment 2
Which ECG finding is most consistent with pacemaker failure to capture?