IBHRE - International Board of Heart Rhythm Examiners Device Troubleshooting and Programming Questions and Answers — Questions and Answers
Question 1: A patient with a dual-chamber pacemaker for sick sinus syndrome has a device check. The rhythm strip shows ventricular pacing spikes occurring 40ms after the peak of native, conducted QRS complexes. This observation is most consistent with which device issue?
- Crosstalk
- Ventricular undersensing (Correct answer)
- T-wave oversensing
- Loss of capture
Correct answer: Ventricular undersensing
The device is firing shortly after a native QRS, which means it failed to 'see' the intrinsic ventricular event. This is the definition of undersensing. To correct this, the ventricular sensitivity needs to be made more sensitive by decreasing the mV value (e.g., from 4.0 mV to 2.0 mV). Crosstalk involves inappropriate inhibition of ventricular output due to oversensing the atrial pacing stimulus. T-wave oversensing would involve sensing the T-wave and potentially inhibiting the next needed pace. Loss of capture means pacing spikes are not followed by a QRS.
Question 2: A patient with a new CRT-D device for heart failure is seen for follow-up. Device interrogation reveals a biventricular pacing percentage of only 82%. The event log shows that most of the non-paced beats are due to intrinsic ventricular conduction following a sensed atrial event. Which programming adjustment is most likely to increase the biventricular pacing percentage?
- Increasing the lower rate limit to 80 bpm
- Activating a ventricular sense response feature
- Lengthening the post-ventricular atrial refractory period (PVARP)
- Shortening the sensed atrioventricular (AV) delay (Correct answer)
Correct answer: Shortening the sensed atrioventricular (AV) delay
To maximize biventricular pacing, the device must deliver its pacing stimulus before the patient's own conduction system depolarizes the ventricles. If intrinsic conduction is occurring, it means the programmed AV delay is too long. Shortening the sensed AV delay will allow the device to pace the ventricles sooner after a sensed P-wave, 'winning the race' against the intrinsic conduction and thereby increasing the percentage of biventricular pacing. While other features exist, shortening the AV delay is the most direct and fundamental adjustment for this specific problem.
Question 3: An active patient with an ICD for primary prevention receives an inappropriate shock. The stored intracardiac electrogram (EGM) shows a stable sinus rhythm, but the ventricular sensing channel is obscured by high-frequency, non-physiologic signals that are counted in the tachyarrhythmia zone, leading to therapy. What is the most likely cause of these signals?
- Atrial fibrillation with rapid ventricular response
- T-wave oversensing
- Lead noise from a conductor fracture or insulation breach (Correct answer)
- Pacemaker-mediated tachycardia
Correct answer: Lead noise from a conductor fracture or insulation breach
High-frequency, non-physiologic signals ('noise') on the ventricular EGM are a classic sign of a lead integrity issue, such as a conductor wire fracture or an insulation breach. This noise can be misinterpreted by the device as ventricular fibrillation, leading to inappropriate shocks. T-wave oversensing would appear as double-counting of each QRS-T complex. Atrial fibrillation would show a physiologic, though irregular, ventricular rhythm. PMT is a paced rhythm and would not appear as high-frequency noise.
Question 4: A routine interrogation of a VVI pacemaker reveals intermittent pacing spikes that are not followed by a QRS complex. A threshold test is performed and shows the ventricular capture threshold is 3.5V @ 0.4ms. The device is currently programmed to an output of 2.5V @ 0.4ms. What is the most appropriate immediate programming change?
- Increase the ventricular output to 4.5V @ 0.4ms (Correct answer)
- Increase the ventricular sensitivity by lowering the mV value
- Decrease the lower rate limit by 10 ppm
- Change the pacing mode to VVO
Correct answer: Increase the ventricular output to 4.5V @ 0.4ms
The issue is loss of capture, where the programmed pacing output is insufficient to depolarize the myocardium. The threshold test confirms this, as the required energy (3.5V) is higher than the delivered energy (2.5V). The immediate solution is to increase the pacing output to a value that provides an adequate safety margin above the measured threshold. An output of 4.5V provides a 1.0V safety margin. Changing sensitivity, rate, or mode does not address the failure to capture.
Question 5: A patient with a dual-chamber pacemaker presents with a rapid, regular paced rhythm at the device's programmed upper tracking rate. The intracardiac EGM confirms a repeating sequence of a ventricular paced event followed by a retrograde atrial sensed event, which then triggers the next ventricular paced event. Which dedicated device feature is designed to automatically terminate this rhythm?
- Rate Smoothing
- Ventricular Sense Response
- PMT Intervention Algorithm (Correct answer)
- Mode Switching
Correct answer: PMT Intervention Algorithm
This scenario describes a classic Pacemaker-Mediated Tachycardia (PMT), also known as an endless-loop tachycardia. Modern pacemakers have specific algorithms, often called 'PMT Intervention' or similar names, that automatically detect this pattern and terminate it. A common method is for the device to extend the post-ventricular atrial refractory period (PVARP) for one cycle, which makes the atrial channel blind to the retrograde P-wave, breaking the loop. Mode switching is for atrial tachyarrhythmias, and the other options do not specifically address the PMT mechanism.
Question 6: Which of the following rate-response sensors functions by delivering subthreshold electrical pulses and measuring the changes in electrical resistance across the chest cavity to estimate respiratory effort?
- Accelerometer
- QT Interval Sensor
- Peak Endocardial Acceleration (PEA)
- Minute Ventilation Sensor (Correct answer)
Correct answer: Minute Ventilation Sensor
A minute ventilation (MV) sensor measures changes in transthoracic impedance. As a patient breathes, the amount of air in the lungs changes, which alters the electrical impedance of the chest. The sensor delivers small electrical pulses and measures this changing impedance to estimate the patient's respiratory rate and tidal volume, which correlates with metabolic demand. An accelerometer is a motion sensor that detects physical activity. A QT interval sensor and PEA sensor measure cardiac-related parameters.
IBHRE - International Board of Heart Rhythm Examiners Device Troubleshooting and Programming Questions and Answers
A patient with a dual-chamber pacemaker for sick sinus syndrome has a device check.
The rhythm strip shows ventricular pacing spikes occurring 40ms after the peak of native, conducted QRS complexes.
This observation is most consistent with which device issue?