Multicenter Automatic Defibrillator Implantation Trial and MADIT II are implantable cardioverter defibrillator (or ICD) trials which investigate whether prophylactic ICD therapy in moderately high-risk coronary patients (in addition to conventional therapy) would significantly reduce death compared with patients treated with conventional therapy alone.

The MADIT II trial started in 1997 and ended in 2001 where the safety committee stopped the study because the benefits were already statistically significant.

The study included patients with a prior myocardial infarction

Myocardial infarction

Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...

 and an ejection fraction

Ejection fraction

In cardiovascular physiology, ejection fraction is the fraction of Blood pumped out of the Right Ventricle of the heart to the Pulmonary Circulation and Left Ventricle of the heart to the Systemic Circulation with each Heart beat or Cardiac cycle...

less than or equal to 30%.

The results were a reduction in mortality of 31% compared to patients receiving conventional therapy alone.