The original use of the AICD for primary prevention of arrhythmic collapse (other than in patients with channelopathy) was in patients post MI with reduced ejection fraction as validated in the MADIT and MADIT II studies. The indications were expanded to patients with dilated cardiomyopathy of all causes after SCD-HeFT. In SCD-HeFT about half the patients had ischemic DCM and about half non-ischemic. But up to now no one had done this same study on a population composed purely of patients with non-ischemic DCM. That was the subject of this study recently published in NEJM. From the article:
The benefit of an implantable cardioverter–defibrillator (ICD) in patients with symptomatic systolic heart failure caused by coronary artery disease has been well documented. However, the evidence for a benefit of prophylactic ICDs in patients with systolic heart failure that is not due to coronary artery disease has been based primarily on subgroup analyses. The management of heart failure has improved since the landmark ICD trials, and many patients now receive cardiac resynchronization therapy (CRT).Methods
In a randomized, controlled trial, 556 patients with symptomatic systolic heart failure (left ventricular ejection fraction, less than or equal to 35%) not caused by coronary artery disease were assigned to receive an ICD, and 560 patients were assigned to receive usual clinical care (control group). In both groups, 58% of the patients received CRT. The primary outcome of the trial was death from any cause. The secondary outcomes were sudden cardiac death and cardiovascular death.Results
After a median follow-up period of 67.6 months, the primary outcome had occurred in 120 patients (21.6%) in the ICD group and in 131 patients (23.4%) in the control group (hazard ratio, 0.87; 95% confidence interval [CI], 0.68 to 1.12; P=0.28). Sudden cardiac death occurred in 24 patients (4.3%) in the ICD group and in 46 patients (8.2%) in the control group (hazard ratio, 0.50; 95% CI, 0.31 to 0.82; P=0.005). Device infection occurred in 27 patients (4.9%) in the ICD group and in 20 patients (3.6%) in the control group (P=0.29).Conclusions
In this trial, prophylactic ICD implantation in patients with symptomatic systolic heart failure not caused by coronary artery disease was not associated with a significantly lower long-term rate of death from any cause than was usual clinical care. (Funded by Medtronic and others; DANISH ClinicalTrials.gov number, NCT00542945.)
But things are not as a superficial reading of the conclusion might indicate. First, if you had a device you were only half as likely to drop dead suddenly (NNT 25). Moreover, although it did not reach statistical significance the point estimate for all cause mortality in the device group was lower.
What are the implications for practice? First, before you exclude a patient with DCM from device therapy you would want to rule out coronary disease. We usually do that anyway but the guidelines give us some wiggle room. Second, for those in whom CAD is ruled out we will have to rethink device recommendations on each individual case. It can be expected, and considered appropriate, that individual clinician judgment and patient preferences will drive decision making and some degree of practice variation.