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Why can coronary artery disease cause chest pain during exercise but not at rest?

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The role of coronary artery disease in heart attack — cardiovascular disease This micrograph shows a cross section of a coronary artery narrowed by an atherosclerotic plaque (purplish matter inside the artery). Most heart attacks are caused by the rupture of an atherosclerotic plaque, which triggers the formation of a clot that abruptly blocks blood flow to part of the heart muscle.

Coronary artery disease causes chest pain, known as angina pectoris, due to a disturbance in the balance between the heart muscle’s demand for oxygen and the supply provided by the coronary arteries.1

When you exercise, your heart muscle requires more oxygen-rich blood to perform the increased work. In individuals with coronary artery disease, narrowed or blocked arteries are unable to deliver this increased supply. This resulting myocardial ischemia leads to the accumulation of waste products in the heart muscle, which irritate local nerve endings and cause the sensation of pain or discomfort.12

At rest, the heart’s workload decreases, meaning its oxygen demand is lower. If the demand is reduced sufficiently, the limited blood supply provided by the diseased arteries may become adequate to meet the heart's needs, causing the symptoms to vanish.12