A65 year old male complains of pain on exertion and is diagnosed with angina pectoris. the occurrence of pain is due to: cardiac output has fallen below normal levels. the myocardial oxygen supply has fallen below demand. myocardial stretch has exceeded the upper limits. the vagus nerve is stimulated.

The myocardical oxygen supply has fallen below demand.

Explanation:

Angina is the name given to chest pain caused by decreased blood flow in the heart, which is called ischemia. The biggest cause of angina is atherosclerosis, which happens when plaque builds up inside the coronary arteries and this accumulation of fat causes the arteries to narrow or even become clogged, and the blood can't flow. Thus, the heart does not receive the necessary nutrients, such as oxygen, because of decreased blood flow, which causes chest pain.