Heartbeat is a contraction and relaxation of the heart muscles.

Heart receives oxygenated blood from lungs.

Oxygenated blood is pumped to the rest of the body by heart.

Intensity of contraction depends on nutrition and oxygen supply to heart.

A heart muscle receives blood through coronary arteries.

Narrowing or blockade of coronary artery causes decreased blood supply to heart.

Decreased blood supply results in reduced oxygen and nourishment to heart muscles.

One of the causes of decreased blood supply is narrowing or blockade by cholesterol plaques.

Plaque builds up in the artery walls.

Enlarged plaque can block artery or piece of a plaque may dislodge and pushed in to smaller arteries resulting in complete blockade of smaller artery.

Lack of blood to heart muscles result in lack of adequate oxygen and nourishment.

Heart contraction becomes weak.

Eventually heart stops or fibrillates resulting in heart attack.