Almost all the heart attacks are sudden in onset and the cause is a rupture of the growing blockages. The blockages are usually covered by a thin membrane called Intimal membrane, which also keep the deposits intact. This elastic membrane gets more and more stretched as more and more fatty deposits occur. But if the fatty deposits continue below this permeable membrane, one day the time will come, when the membrane cannot stretch further and breaks off. This leads to the formation of a clot or thrombus inside the tube, closing the lumen completely. This completes the process of heart attack. The area of the myocardium (heart muscles) which gets the blood through the closed artery, dies - in the event of no blood supply.

Heart attack, often occurs after a heavy meal full of fat, after sudden anger or excessive sorrow or grief or excessive stress. Heart attacks occur more frequently in the early mornings. Heart attacks also occur during the process of Angiography and Angioplasty when the catheter or balloon is inflated and completely blocks the lumen of the coronary artery or breaks off the blockage by mechanical means.