First of all, cardiac arrest and heart attack are not the same thing- although a heart attack can cause a cardiac arrest if blood supply is not restored to the heart quick enough and/or major blood/oxygen supply is cut off. Heart attacks simply mean that there has been a prolonged reduction in oxygen supply to part of the heart muscle- as a result of a blockage. Tissue/cell death then occurs as a result of this and the area is said to be infarcted. MIs generally occur in older people who have coronary artery disease where there is significant narrowing of the arteries. Fatty plaques build up in the arteries over time, platelets aggregate to form thrombi and blockage of the artery can then occur. In younger people a heart attack can be caused by a clot that is the result of trauma or injury to the chest area or some young people can have high cholesterol and CAD. Cardiac arrest simply means that the heart has stopped pumping blood around the body due to a disturbance in heart rhythm, most commonly ventricular fibrillation. Many different things can cause this. A blockage in the artery, as I mentioned above can cause this, but unconfirmed reports are suggesting he died of an overdose of prescription drugs which can cause both respiratory and cardiac arrest.