Identifying high-risk post-infarction patients by autonomic testing - Below the tip of the iceberg

Abstract

Despite major advances in medical therapies late mortality after myocardial infarction (MI) is still high. A substantial proportion of post-MI patients die from sudden cardiac death. Prophylactic implantable-cardioverter defibrillator (ICD) therapy has been established for post-MI patients with reduced left ventricular ejection fraction (LVEF ≤35%). However, most patients who die after MI have an LVEF >35%. For this large group of patients, no specific prophylactic strategies exist. There is strong evidence that measures of cardiac autonomic dysfunction after MI provide important prognostic information in post-MI patients with preserved LVEF. Combinations of autonomic markers can identify high-risk patients after MI with LVEF >35% whose prognosis is equally worse than that of patients with LVEF ≤35%. The ongoing REFINE-ICD (NCT00673842) and SMART-MI trials (NCT02594488) test different preventive strategies in high-risk post-MI patients with cardiac autonomic dysfunction and LVEF 36-50%. While REFINE-ICD follows the traditional concept of ICD-implantation, SMART-MI uses implantable cardiac monitors with remote monitoring capabilities to sensitively detect asymptomatic, but prognostically relevant arrhythmias that could trigger specific diagnostic and therapeutic interventions.

Keywords: Cardiac autonomic function; ECG; Heart rate variability; Implantable defibrillator myocardial infarction; Sudden cardiac death.