Final answer:
Angina pectoris is chest pain caused by insufficient oxygen to the heart muscle due to partial blockage of coronary arteries by plaque.
Step-by-step explanation:
When a patient is diagnosed with angina pectoris, it is important to explain that this condition is characterized by chest pain or discomfort that occurs when the heart muscle doesn't receive adequate amounts of oxygen. This lack of oxygen, or ischemia is often due to partial blockage of the coronary arteries by the buildup of plaque a condition known as atherosclerosis.
Angina pectoris may present as stable or unstable angina and it serves as a symptom of underlying coronary heart disease, which can increase the risk of more serious events like a heart attack. The accurate explanation for angina pectoris in the context of the question provided would be: D. the heart muscle isn't getting enough oxygen.