Implantable Cardiac Monitors in High-Risk Post-Infarction Patients With Cardiac Autonomic Dysfunction
Condition: Myocardial Infarction; Autonomic Nervous System Diseases
MeSH terms: Nervous System Diseases; Autonomic Nervous System Diseases; Primary Dysautonomias; Myocardial Infarction; Infarction
Study type: Interventional

Summary: 
      The majority of deaths after myocardial infarction occurs in patients with preserved left
      ventricular ejection fraction (>35%) for whom no prophylactic strategies exist. Periodic
      Repolarization Dynamics (PRD) and Deceleration Capacity (DC) of heart rate are autonomic risk
      markers that identify a new high risk group of patients with LVEF 35-50% who have the same
      poor prognosis as patients with LVEF ≤35%.

      In SMART-MI, post-infarction patients with LVEF 35-50% and abnormal PRD and/or DC will be
      randomly assigned to biomonitoring-guided therapy or conventional follow-up.
    

Detailed description: 
      Sudden cardiac death (SCD) is the most common single cause of death in the industrialized
      world. Patients after myocardial infarction (MI) are at increased risk of SCD. Current
      guidelines recommend prophylactic ICD-implantation in post-MI patients with reduced left
      ventricular ejection fraction (LVEF ≤35%). However, the majority of arrhythmic deaths after
      MI occurs in patients with LVEF >35% in whom no specific prophylactic strategies exist,
      indicating an important unmet medical need.

      There is a large body of evidence that presence of cardiac autonomic dysfunction after MI is
      associated with an increased susceptibility to malignant brady- and tachyarrhythmias
      eventually culminating in SCD. Periodic repolarization dynamics (PRD) and heart rate
      deceleration capacity (DC) are clinically validated autonomic risk markers that provide
      strong and independent prognostic information in post-MI patients with LVEF >35%. PRD and DC
      reflect different facets of autonomic function and can therefore be used in combination to
      predict risk. Previous studies demonstrated that combined assessment of PRD and DC identifies
      a new high-risk group among post-MI patients with moderately reduced LVEF (36-50%). This new
      high-risk group has similar characteristics with respect to prognosis and patient numbers as
      the established high-risk group identified by LVEF ≤35%.

      However, the exact mechanisms leading to death in this new high-risk group need to be
      investigated in order to develop specific preventive strategies. As known from studies with
      implantable cardiac monitors (ICM) in post-MI patients with LVEF ≤40% eventual death is often
      preceded by primarily asymptomatic serious arrhythmic events. These data suggest a potential
      time frame for pre-emptive interventions in case of arrhythmic events, which could improve
      outcome.

      Therefore, SMART-MI will assess the occurrence and prognostic implications of serious
      arrhythmic events in this newly identified high-risk group by remote monitoring with ICM.
      Survivors of acute MI (<40 days) and LVEF 36-50% undergo autonomic testing for presence of
      abnormal PRD and/or DC. Those with autonomic dysfunction will be randomly assigned to
      ICM-implantation or conventional follow-up. Superiority of ICMs in detection of predefined
      serious arrhythmic events will be tested based on a time-to-event analysis. A central ICM
      core lab will be implemented allowing for a response to arrhythmias within 48h. The effect of
      remote monitoring on clinical outcomes will be tested as secondary endpoints. The study will
      provide the rationale for a future guideline-relevant study testing prophylactic therapies in
      this newly identified high-risk group.
    

Intervention name(s): Medtronic Reveal LINQ implantable cardiac monitor
Intervention type(s): Device
Intervention description(s): The implantable cardiac monitor is implanted under the skin in the region of the thorax. It continuously monitors the heart's electrical activity for up to three years. Predefined arrhythmias are daily transmitted to a central core lab. In case of arrhythmias, specific guideline-based treatment is initiated within 48h.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Diagnostic
Keywords: Myocardial infarction; Autonomic nervous system; Risk stratification; Implantable cardiac monitor; Sudden cardiac death; ECG