A heart attack is caused by a clot that blocks the flow of blood through a coronary artery. The coronary arteries become narrowed by a process known as atherosclerosis, which is also called hardening of the arteries. Once the arteries become narrowed, a clot can completely block the artery. The clot interrupts the blood flow and the supply of oxygen to part of the heart muscle.

The process of atherosclerosis includes:

• The inner wall of the artery becomes damaged by:
• Changes in blood flow
• Infection
• Smoking
• Diabetes
• High blood pressure
• As the wall or the artery attempts to repair itself, cholesterol builds up on the inside surface of the artery, forming a plaque.
• Plaques narrow the inside of the arteries, which reduces blood flow. This can lead to blood clot formation inside the vessel.

Examples:

• Atherosclerosis
• Blood clot formation within a vessel