Outcomes for patients with anterior myocardial infarction and prior cardiac arrest in the home automated external defibrillator trial (HAT)

Background: Patients with sudden cardiac arrest occurring in the acute phase of myocardial infarction (MI-SCA) are believed to be at similar risk of death after revascularization compared with MI patients without SCA (MI-no SCA). Among patients with anterior MI, we examined whether those with MI-SCA were at greater risk of all-cause mortality or sudden cardiac death (SCD) than MI-no SCA patients.

Methods: The Home Automated External Defibrillator Trial enrolled patients with anterior MI who had not received or were candidates for an implantable cardioverter defibrillator (ICD). Our cohort included patients with a reported SCA event, in the acute phase of an MI, prior to HAT trial enrollment. Cox proportional hazards models examined the adjusted association between MI-SCA versus MI-no SCA patients and all-cause mortality and sudden cardiac death (SCD). We also determined whether the relationship between prior SCA and outcomes changed with subsequent events (syncope, revascularization, and recurrent MI) during follow-up.

Results: Of 6849 patients, 650 (9.5%) had MI-SCA before trial enrollment. Approximately 48% of patients had the MI-SCA event ≤1 year prior to enrollment; 71% of SCA events were in-hospital. MI-SCA patients were younger, more frequently white, and had higher rates of prior PCI versus MI-no SCA patients. There were no differences in adjusted all-cause mortality (hazard ratio [HR 0.95; 95% CI 0.65-1.38]) or SCD (HR 1.12; 95% CI 0.68-1.83) for MI-SCA vs. MI-no SCA. After ICD implantation, MI-SCA patients experienced higher all-cause mortality risk (HR 5.01, 95% CI 1.05-23.79) versus MI-no SCA patients; there was no mortality difference between MI-SCA and MI-no SCA patients without ICD implantation (HR 0.89, 95% CI 0.60-1.31), [interaction p = 0.035].

Conclusions: Patients with MI-SCA had similar adjusted risk of all-cause mortality and SCD compared with MI-no SCA. After ICD implantation, MI-SCA patients had higher mortality compared with MI-no SCA patients.