What are the complication of myocardial infarction?

Several possible: There are a range of possible complications. The heart is a muscle, and can be weakened by a heart attack and lead to heart failure. The heart has a conduction system which can be damaged and can lead to arrhythmias and cardiac arrest. Many people die from their heart attack, while others have one and don't realize it. Unfortunately about 1/2 of the time the first sign of heart disease is death.

Numerous: Sudden death, irregular heartbeats ventricular fibrillation. Heart failure ruptured valve chordae or muscle ruptured heart ventricular aneurysm most are diagnosable, and treatable these days.