Arrhythmia Detection After MI

Overview

Patients post acute myocardial infarction (AMI) have a high risk of mortality but the use of an implantable defibrillator in the early aftermath of an AMI has not been shown to improve patients' survival. The VEST trial recently demonstrated an improved overall survival in post AMI patients with the use of a wearable defibrillator. The same improvement was not demonstrated for the risk of sudden cardiac death. Monitoring patients after AMI using an implantable cardiac monitor (ICM) may document findings that can impact patient management and eventually improve their outcomes. We are therefore conducting the AID MI trial to examine the impact of ICM on patient management in the post AMI setting.

Patients who have ventricular tachycardia or fibrillation at least 48 hours after an acute myocardial infarction (AMI) have a higher risk of sudden cardiac death. Current guidelines recommend that for primary prevention of sudden cardiac death, patients with left ventricular ejection fraction (LVEF) ≤ 35% should wait at least 40 days post-AMI or 90 days post revascularization prior to receiving an implantable cardioverter defibrillator (ICD). This period of time potentially leaves a vulnerable population without protection from sudden cardiac death (SCD). The landmark MADIT I and MADIT II trials demonstrated that ICD therapy was associated with significantly improved survival in patients with ischemic cardiomyopathy at any interval of time. The DINAMIT study demonstrated that ICD placement less than 40 days after AMI had a reduction in arrhythmic mortality at the cost of an increase in non-arrhythmic mortality. Results from these and other studies suggest that the risk of SCD after AMI may be time-dependent and that patients at increased risk for SCD are also at increased risk for death from other causes. Thus, there is a need for additional studies to identify subsets of patients with arrhythmias that may benefit from other therapeutic interventions such as ablations, anti-arrhythmic medications, implantable cardiac devices, or other therapies. The CARISMA study was the first study to document the incidence of cardiac arrhythmias in post-AMI patients with left ventricular dysfunction (LVEF≤40%) using an implantable loop recorder. Results showed high incidences of arrhythmias such as new-onset AF (27.6%) and high-degree AV block (9.8%). Subsequent studies showed that these arrhythmias were associated with increased risk of major cardiovascular events such as heart failure, ventricular tachyarrhythmias, stroke, reinfarction, or cardiac death. It has been shown that utilizing remote monitoring as part of clinical care in patients with cardiac implantable electronic devices is associated with improved all-cause survival; the magnitude of survival increases with the degree of adherence to remote monitoring and the timeliness to enroll and activate in remote monitoring shortly after device implantation. These studies suggest the need for further investigation and evaluation of acute and long-term cardiac monitoring in post-AMI patients, in an effort to identify patients at greatest risk, inform clinical decision making and potentially reduce the risk of all-cause mortality. In addition, the ability to remotely monitor patients may minimize the time to diagnosis and enable early intervention in this patient population.