Low-voltage shock impedance measurements: A false sense of security.

BACKGROUND: Implantable cardioverter defibrillators use low-voltage shock impedance measurements to monitor the lead integrity. However, previous case reports suggest that low-voltage shock impedance measurements may fail to detect insulation breaches that can cause life-threatening electrical short circuits. METHODS AND RESULTS: We report six cases of insulation breaches in transvenous defibrillation leads that were not obvious during standard interrogations and testing of the lead beforehand. In two cases, an electrical short circuit during commanded shock delivery for internal electrical cardioversion resulted in a total damage of the ICD generator. In one of these cases, commanded shock delivery induced ventricular fibrillation, which required external defibrillation. In two cases, a shock due to ventricular tachycardia was aborted as the shock impedance was less than 20 Ω. However, in both cases the tiny residual shock energy terminated the ventricular tachycardia. In contrast, in one case the residual energy of the aborted shock did not end ventricular fibrillation induced at defibrillator threshold testing. In one case, the ICD indicated an error code for a short circuit condition detected during an adequate shock delivery. CONCLUSIONS: This case series illustrates that low-voltage shock impedance measurements can fail to detect insulation breaches. These data suggest that in patients without a contraindication, traditional defibrillator threshold testing or high voltage synchronized shock at the time of device replacement should be considered.

Pacemaker-mediated arrhythmias.

Pacemakers can be directly involved in initiating or sustaining different forms of arrhythmia. These can cause symptoms such as dyspnea, palpitations, and decompensated heart failure. Early detection of these arrhythmias and optimal pacemaker programming is pivotal. The aim of this review article is to summarize the different types of pacemaker-mediated arrhythmias, their predisposing factors, and mechanisms of prevention or termination.

Long-term pacemaker dependency and impact of pacing on mortality following transcatheter aortic valve replacement with the LOTUS valve.

OBJECTIVES: To determine permanent pacemaker (PPM) dependency following transcatheter aortic valve replacement (TAVR) with the Lotus™ valve system (Boston Scientific), and the impact of PPM implantation on long-term morbidity and mortality. BACKGROUND: Conduction abnormalities are among the most common complications following TAVR. Limited studies have assessed pacing dependency following TAVR. METHODS: Consecutive patients (n = 166) with severe aortic stenosis who underwent TAVR with the Lotus valve system were prospectively recruited from a single-center. PPMs were implanted according to standard clinical criteria. Patients were followed in-hospital and at 1, 3, 6, and 12 months to determine pacemaker dependency and clinical outcomes. RESULTS: Fourteen patients with a pre-existing PPM (8%) were excluded with the remaining 152 patients aged 83.6 ± 5.6 years and 46% male. PPMs were implanted 3.8 ± 4 days post-TAVR in 38/152 patients (25%). Indication for PPM was complete heart block in 29 (76%) of patients. At 30-day and one-year follow up, 57% and 38% of patients were pacemaker dependent, respectively. The mean ventricular pacing percentage decreased in the first three months after PPM implantation and remained relatively stable after that. CONCLUSION: Only 38% of Lotus recipients who require a PPM following TAVR with the Lotus valve remain pacing dependent at one year.

Loss of cardiac resynchronization therapy in a patient with a biventricular implantable cardioverter-defibrillator.

Here, we discuss the case of a man with a history of ischemic cardiomyopathy and cardiac resynchronization therapy defibrillator implantation, who presented to emergency department with decompensated heart failure due to the loss of resynchronization therapy. The reason for the malfunction was left ventricle upper rate interval lock-in due to inappropriate programming of the device.

Aborted sudden cardiac death in a patient with implantable loop recorder.

We discuss a 46-year-old man with history of hypertension and inferior wall myocardial infarction and mild left ventricular dysfunction who presented with aborted sudden cardiac death due to episodes of ventricular tachyarrhythmia detected by a Reveal-LINQ which had been implanted one year prior to presentation.