This study will assess whether an implantable defibrillator will increase the likelihood of survival in patients who have had a heart attack, have abnormal test results from a 24 hour heart monitor, and who have low normal heart function.

The REFINE ICD trial will assess whether prophylactic ICD therapy, guided by non-invasive risk assessment tools, reduces mortality in MI survivors with better-preserved LV function.

Site investigators are responsible for screening. Subjects must meet all inclusion criteria. Subjects with any exclusion criteria will be excluded.

Initial inclusion criteria (eligibility for Holter screening).

• 18 - 80 years old at time of consent

• History of MI ≥ 2 months prior to screening based on ESC/ACCF/AHA/WHF criteria (both STEMI and NSTEMI subjects are eligible)

• Appropriate post-MI management including revascularization where indicated

• No contra-indication for transvenous ICD placement (e.g., mechanical tricuspid valve, known vascular access problems, active sepsis, etc.)

• LVEF 36% - 50% measured at least 40 days after a confirmed MI ≥ 3 months after coronary angioplasty or coronary bypass surgery and within the following time windows:

  • LVEF ≤ 7 months of screening visit if index MI was ≤ 1 year of enrolment
  • LVEF ≤ 13 months of screening visit if index MI was > 1 & < 3 years of enrolment
  • LVEF ≤ 25 months of screening visit if index MI was ≥ 3 years of enrolment

• Proven, necessary or appropriate medications (e.g. beta-blocker, ACE inhibitor / ARB, statin, and anti-platelet)

• In normal sinus rhythm (ECG documented) ≤ 8 weeks prior to the screening Holter

• Written informed consent

• Able and willing to complete the screening Holter, including the six-minute hall walk

Additional inclusion criterion (eligibility for randomization).

• Abnormal HRT & TWA (core lab interpretation) on Holter performed at least 2 months after the index MI and the specified time after coronary revascularization
• In normal sinus rhythm (ECG documented) within 8 weeks prior to the screening Holter
• In normal sinus rhythm for ≥ 18 hours of the 24 hr screening Holter as determined by the study Holter Core Lab

Exclusion criteria (randomization or registry).

• Use of antiarrhythmic drugs
• Clinical indication for permanent pacemaker or a cardiac resynchronization device
• Clinical indication for an ICD or cardiac resynchronization ICD
• Prior implantation of a pacemaker, ICD, or Cardiac Resynchronization device
• Any condition, in the investigator's judgment, that would limit life expectancy to < 12 months
• Chronic renal failure (hemodialysis or peritoneal dialysis)
• Active ischemia that is amenable to revascularization if not previously revascularized
• Participation in another trial that may interfere with the REFINE ICD results.
• Pregnancy
• Inability to comply with the follow-up schedule

uncertain