CBSE Class 10 Answered
The heart muscle requires a constant supply of oxygen-rich blood to nourish it, which is done by the coronary arteries. In case of coronary artery disease, those arteries become narrow and blood cannot flow properly through it. In addition plaques of different sizes build up within the artery. When the plaque' ruptures, platelets come to the area, and blood clots form around the plaque. If a blood clot totally blocks the artery, the heart muscle becomes starved for oxygen. Within a short time, death of heart muscle cells occurs, causing permanent damage. This is called a myocardial infarction (MI), or heart attack. While it is unusual, a heart attack can also be caused by a spasm of a coronary artery.