MI (Myocardial infarction) is defined as a heart attack that is produced when a clot has developed in a coronary vessel, blocking the flow of blood to the heart; a cutoff of blood to the heart muscle, causing damage to the heart MI is also referred to as a heart attack. Myocardial infarction is also known as Angina pectoris or Cardiac arrest. Chest pain is a common symptom. .