Defibrillators Don’t Deliver in Dialysis

Patients undergoing dialysis have a high mortality rate, a large proportion of which has been attributed to sudden cardiac death (SCD). 1 This elevated risk is likely attributable to a confluence of arrhythmic triggers including electrolyte and fluid shifts, myocardial ischemia, and dialysis-induced hemodynamic stress superimposed on a vulnerable cardiac substrate of left ventricular hypertrophy, fibrosis, and autonomic dysregulation to name but a few of the many contributing factors. 1 Although the risk of SCD is higher in patients undergoing dialysis than in those with congestive heart failure, the former have been excluded or nominally enrolled in all previous trials of implantable defibrillators (ICDs) because competing risks were expected to lessen the benefit of the device. 1 The decision to exclude these patients may have been prescient, because cohort studies that evaluated the role of ICDs in patients undergoing dialysis have almost uniformly found no improvement in survival and high complication rates regardless of implant indication. 2,3However, because these studies by definition evaluated patients undergoing dialysis with contemporaneous indications for device implantation, no data existed on the utility of primary prevention ICDs in a dialysis population with a preserved left ventricular ejection fraction where the competing risk of death from nonarrhythmic cardiovascular causes is expected to be lower. 2It is in this context that the ICD2 trial (A Prospective Randomized Controlled Trial to Evaluate the Prevention of Sudden Cardiac Death Using Implantable Cardioverter Defibrillators in Dialysis Patients) provides important insights into this poorly understood yet growing population of patients.In this issue of Circulation, Jukema et al 4 present the first-ever randomized controlled trial of ICDs in patients undergoing dialysis.Patients on chronic hemo-or peritoneal dialysis with a left ventricular ejection fraction ≥35% were randomly assigned to receive a transvenous ICD or no device therapy and followed for a median of 6.8 years.After enrolling 188 of the planned 200 patients over a 10year period, the trial was terminated for futility.The cumulative death rate was just >50% and similar in both groups, whereas the incidence of the primary end point of SCD was 9.7% in the ICD group and 7.9% in the control despite 13.8% of the ICD recipients receiving appropriate therapy for ventricular tachyarrhythmias (ventricular tachycardia/ventricular fibrillation [VT/VF]).As has been seen with other device studies in this population, the complication rates were high and dominated by infection and lead failure.First and foremost, the authors are to be commended for the design and execution of a critically important study in a patient population too frequently ignored in cardiovascular trials.The fact that it took >10 years to enroll 188 patients is a testament to both the perseverance of the authors and the challenges of enrolling patients who are undergoing dialysis in such trials.The