Twenty-five years of implantable defibrillator practice in the USA: Are we ready for globalization?

Abstract

As we reflect on the passage of a year and what lies ahead, few issues have occupied this discipline’s attention as the continuing and riveting saga of the implantable cardioverter-defibrillator (ICD). Progressing from an investigational curiosity to mainline clinical therapy for cardiac rhythm management has been a landmark achievement. With rapid globalization in medical advances, ICD therapy now has health care implications worldwide and has become a staple item in the health care news basket. Twenty-five years have elapsed since the initial approval of the implantable cardioverter-defibrillator for clinical use in the USA. While a quarter century of clinical experience may not qualify for the longest view of a medical therapy in the information age, there is a plethora of accumulated data and a widespread perception of a “matured” therapy. Approved for clinical use on observational clinical data, controversy dogged the early ICD years on its therapeutic value. Standards for clinical trials emerged after approval, which led to the golden age of controlled ICD clinical studies [1, 2]. The initial indications for ICD usage emerged largely from expert consensus documents, but have now been replaced by evidence-based practice guidelines, which, in significant part, are based on these trial data, and have seriously expanded ICD indications [3, 4]. Despite apparently robust clinical trial evidence, clinical usage patterns and therapeutic benefits have been repeatedly questioned [5]. When prophylactic ICD use became ubiquitous, this commentator was no exception, raising concerns of nonuniform benefit of prophylactic ICDs across target subgroups in the pages of this journal [6]. Since prophylactic device use now widely exceeds any other application, the potential risks to perceived ICD value in the Rosetta stone of clinical practice were even then recognizable [7]. A very high proportion of ICDs had not delivered therapy at replacement and, when used, often targeted ancillary tachyarrhythmias [5, 6]. In the MADIT 2 study, the annual rate of appropriate ICD interventions was a healthy 17%, but declined to a paltry 5% when indications were widened to non-ischemic heart diseases and the ejection fraction limit raised to 40% in the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) [8, 9]. The establishment of a national device registry in the United States has now bought an immense amount of clinical practice data into the fray. It has particularly highlighted discordance with clinical trial populations. At last report, over 550,000 implants (78% for prophylactic indications), provided data showing an older ICD implant population in clinical practice with a significant octogenarian component, with fewer males, more diabetics, and hypertensives and with a predominant Caucasian background [10]. Twenty-two percent did not meet current indications, but little detail exists in registry data to identify other clinical S. Saksena (*) Electrophysiology Research Foundation, 161 Washington Valley Road, Suite 201, Warren, NJ 07059, USA e-mail: EPRF@aol.com