A wearable cardioverterdefibrillator did not reduce arrhythmic death in MI with reduced ejection fraction

Abstract

Question In patients who have a myocardial infarction (MI) and a reduced ejection fraction (EF), does using a wearable cardioverterdefibrillator (WCD) shortly after MI reduce risk for arrhythmic death? Methods Design Randomized controlled trial (RCT) (Vest Prevention of Early Sudden Death Trial [VEST]). ClinicalTrials.gov NCT01446965. Allocation Unclear allocation concealment.* Blinding Blinded* (outcome adjudicators). Follow-up period Mean 84 days. Setting 108 clinical centers in the USA, Poland, Germany, and Hungary. Patients 2348 adults 18 years of age (mean age 61 y, 73% men) who were hospitalized with acute MI, had an EF 35% (assessed 8 h after the MI if no revascularization or if the patient had percutaneous coronary intervention, or 48 h if the patient had coronary artery bypass grafting), and were within 7 days of discharge. Exclusion criteria included current implantable cardioverterdefibrillator (ICD) or unipolar pacemaker, clinically important valve disease, long-term hemodialysis, indication for an ICD, chest circumference that would not accommodate the WCD, or discharge to a nursing facility with expected stay >7 days. Intervention WCD plus guideline-directed (usual) care (n =1554) or usual care alone (n =794) (2:1 allocation). Patients in the WCD group were fitted with the Zoll LifeVest WCD, trained in its use, and instructed to wear the device for 3 months except while bathing. Outcomes Arrhythmic death (sudden death or nonsudden death due to ventricular tachyarrhythmia) at 90 days. Secondary outcomes included all-cause mortality and adverse events. Due to slow recruitment and lower-than-expected WCD wear time, the original primary outcome of all-cause mortality at 60 days was changed to arrhythmic death at 90 days and the sample size was changed to 2300 patients, which provided 70% power to detect a between-group difference. Patient follow-up 97% (intention-to-treat analysis). Main results The main efficacy results are in the Table. 1.4% of patients in the WCD group received 1 appropriate shock, and 0.6% received 1 inappropriate shock. 12 of the 48 patients in the WCD group who died were wearing the device at the time. Patients in the WCD group were more likely to report rashes (15.3% vs 7.1%, P <0.001) and less likely to report shortness of breath (39% vs 45%, P =0.004) than were patients in the usual-care group. Conclusion In patients who have a myocardial infarction and a reduced ejection fraction, using a wearable cardioverterdefibrillator shortly after MI did not reduce risk for arrhythmic death. Wearable cardioverterdefibrillator (WCD) plus usual care vs usual care alone in patients who have a myocardial infarction and a reduced ejection fraction Outcomes Event rates At a mean 84 d WCD + usual care Usual care alone RRR (95% CI) Arrhythmic death 1.6% 2.4% 33% (21 to 63) All-cause mortality 3.1% 4.9% 36% (0 to 58) Abbreviations defined in Glossary. RRR and CI calculated from usual-care event rates and relative risks in article. Secondary outcome analyzed with prioritized correction accounting for correlation (P =0.05). Commentary In the VEST study, a WCD did not reduce arrhythmic death at 90 days. The trial was probably underpowered to detect a difference in the primary endpoint, which was changed during the trial from all-cause mortality at 60 days due to low enrollment. Statistical power calculations assumed 70% adherence to WCDactual adherence was 41% at 90 days. Additionally, arrhythmic deaths were difficult to adjudicate. 5% of deaths were indeterminate and not included as arrhythmic deaths in the primary analysis, and 5 of 9 patients wearing the device were initially adjudicated as having arrhythmic death but this was disproved later. Most deaths in the WCD group occurred in patients not wearing the WCD. On-treatment analysis showed lower rates of arrhythmic death in those wearing vs not wearing the WCD, but this difference was not statistically significant when corrected for multiple endpoints (0.37 vs 0.86/100 person-mo, rate ratio 0.43, CI 0.21 to 0.91, Bonferroni corrected P =0.32). Results of VEST are consistent with 2 RCTs that showed that ICDs implanted early after an MI in patients with reduced EF had no overall mortality benefit; reductions in sudden death were offset by increases in nonsudden death (1, 2). Only 56% of early sudden cardiac deaths are arrhythmic, and not all ventricular arrhythmias are aborted with defibrillation (3). In VEST, 4 of 9 patients wearing the device at the time of death were appropriately defibrillated but died from recurrent ventricular arrhythmia or agonal rhythms. In patients with acute MI and reduced EF, VEST provides no evidence that a WCD reduces arrhythmic death at 90 days.