Defibrillation testing of the implantable cardioverter defibrillator: when, how, and by whom?

Abstract

The implantable cardioverter-defibrillator (ICD) has become an integral part of treatment for a variety of patients with symptomatic, or at risk for, ventricular tachyarrhythmias. The ICD's effectiveness is attributed to its ability to promptly detect and terminate ventricular tachycardia (VT) and fibrillation (VF). The clinical trials that established the positive role of ICD therapy were based on patients who underwent some form of defibrillation testing at the time of implantation. Therefore, since its advent, intraoperative defibrillation testing of the ICD to assure reliable detection and termination of VT/VF has been a standard practice. But because of advances in defibrillator and lead technology, which now facilitates successful device implantation (i.e., low defibrillation energy requirement to allow for an adequate programmed safety margin) in the majority of patients, the necessity of defibrillation testing has been called into attention. Despite substantial progress, it is not altogether clear whether a wholesale abandonment of intraoperative ICD testing is appropriate at this point. We review pertinent data regarding pros and cons of ICD testing and offer a suggestion as to when, how, and who should test ICDs.

Figure 1

From top to bottom: atrial electrograms, ventricular electrograms, and marker channel. AS and VS indicates, respectively, atrial sensing and ventricular sensing. Shows an episode of induced ventricular fibrillation (dotted arrow) followed by a single successful 11 J shock (arrow) delivered by a 31 J output device.

Figure 2

From top to bottom: atrial electrograms, ventricular electrograms, and marker channel. The tracing is continuous (top to bottom panel). Shows an episode of induced ventricular fibrillation (dotted arrow) followed by a failed 15 J shock (arrow), followed by a second successful 25 J shock (open arrow) delivered by a 35 J output device. AS and VS indicates, respectively, atrial and ventricular sensing.

Figure 3

A suggested approach to intraoperative ICD testing. See text for details.