The Optimal Timing of Primary Prevention Implantable Cardioverter-Defibrillator Referral in the Rapidly Changing Medical Landscape.

Abstract

The use of implantable cardioverter-defibrillators (ICDs) significantly reduces the risk of mortality in patients with heart failure with reduced ejection fraction (HFrEF). Current guidelines, which are based on seminal clinical trials published nearly 2 decades ago, recommend that patients be on optimal medical therapy for HF for a minimum of 3 months prior to referral for prophylactic ICD. This waiting period allows for left ventricular reverse remodeling and improvement in HF symptoms, which may render primary prevention ICD implantation unnecessary. However, medical therapy for HFrEF has significantly evolved since the publication of these landmark trials. Given the plethora of medical therapy options now available for HFrEF, it is appropriate to reassess the duration of this waiting period. In the present review, we examine the landmark randomized trials in primary prevention of sudden cardiac death in patients with HFrEF, we summarize the novel medical therapies (sacubitril-valsartan, SGLT2 inhibitors, ivabradine, vericiguat and omecamtiv mecarbil) that have emerged since the publication of these trials, discuss the optimal timing of ICD referral, and review subtypes of non-ischemic cardiomyopathy where timing of ICD insertion is guided by alternative criteria. With the steps now needed to optimize medical therapy for HFrEF, both in terms of classes of drugs and doses of each agent, it can easily take up to 6 months to achieve optimization. Following that, waiting periods of 3 months (for ischemic cardiomyopathy) and 6 months (for non-ischemic cardiomyopathy) may be required to allow adequate reverse remodeling before re-evaluating for ICD implantation.