​Coronary artery disease (CAD) is the most common type of heart disease. A heart attack is usually the instance when a person discovers that he or she has coronary artery disease as the disease can develop slowly and without symptoms over decades.

Coronary artery disease (CAD) occurs when the arteries that supply blood to the heart become hardened and narrowed. The narrowing and hardening of the arteries is due to build-up of fatty deposits called plaque on the arteries' inner walls. Reducing blood flow to the heart which can cause chest pains (or angina). Such chest pains/tightness may present itself when a person is engaged in physical strenous activity such as brisk walking, running or when climbing stairs. However, with rest, these chest pains disappear.

When a complete blockage of the arteries occurs, it is called a heart attack. A person experiencing a heart attack will feel a sudden severe chest pain, breathing difficulties, sweating and persistent chest pain. 

To discover coronary artery disease at an early stage, exercise tests can be used to determine if there is a lack of oxygen supply to the heart.