How to Manage a High Defibrillation Threshold in ICD Patients: and Does it Really Matter?

Abstract

In the 30 years since its introduction, implantable cardioverter defibrillator (ICD) hardware and programming has evolved greatly. Coupled with a better understanding of how patient factors and anti-arrhythmic drug therapy affect ICD function, these changes have resulted in a modern ICD system which is highly effective at terminating ventricular arrhythmias. This has led to a marked decrease in the conduct of intraoperative defibrillation testing. Still, clinicians are faced with patients who have had unsuccessful intraoperative defibrillation testing or who have experienced one or more failed clinical shocks for ventricular arrhythmias. Thus, clinicians caring for ICD patients must understand the expected performance of modern ICD systems, understand the issues with intraoperative defibrillation testing, and have a strategy for dealing with patients when their ICD has failed to terminate a clinical or induced ventricular arrhythmia. This review will focus on the clinical approach to such patients, including trouble-shooting and system revision.

Traumatic Tension Pneumothorax as a Cause of ICD Failure: A Case Report and Review of the Literature

“…Pneumothorax has long been recognized as a reversible cause of serious ventricular arrhythmia [22] and increased defibrillation thresholds [20, 23, 24]. ICDs are being implanted with increasing frequency given primary and secondary prevention indications [25].…”

Is Defibrillation Testing Necessary for Implantable Transvenous Defibrillators?

“…3 Thus, any potential benefit of DT would only be realized by those patients whose ICD fails to terminate VF at the time of intraoperative testing. However, recent registries and clinical trials show that in 90% to 95% of cases, the initial ICD configuration successfully terminates VF 9-13 and when measured, the defibrillation threshold is far below the maximum output of modern devices (Table 1).…”

“…There is only limited high-quality data to show that interventions to improve defibrillation efficacy actually work. 3 Data to support the use of azygous or coronary sinus coils are limited to case reports and small series, [25][26][27] and a recent study of programmable shock waveform failed to show a reduction in defibrillation threshold using tilt-based programming. 28 There is a reasonably large (n=177) series demonstrating that the addition of a subcutaneous lead can reduce defibrillation threshold by ≈10 J, 11 although this study cannot determine whether acute improvements in intraoperative defibrillation threshold improve the success of defibrillation for clinical arrhythmias.…”

“…However, the ICD evolved over time, with the introduction of transvenous systems, biphasic waveforms, and active cans, which made failure to sense and treat VF much less common. 2,3 Modern ICDs are also capable of delivering energies >40 J, thus many have started to question the rationale for DT in the modern era.…”

Routine DFT testing in patients undergoing ICD implantation does not improve mortality: A systematic review and meta‐analysis

“…Nevertheless, recent evolution of implant techniques and technology has made deviations from this clinical practice more common. Newer ICDs are much more efficient than in the past, with higher energy devices providing improved safety margin, possessing biphasic shock delivery, active cans, and improved leads . DFT testing is not free of inherent complications as well, with one registry reporting death, hemodynamic compromise, emergent intubation, prolonged CPR, strokes, and precipitation of heart failure during and after the procedure .…”