In a client with atherosclerosis, what is the most likely cause of angina?

Angina pectoris is primarily caused by an inadequate supply of oxygen to the heart muscle (myocardium) relative to its demand. In individuals with atherosclerosis, the coronary arteries become narrowed due to the buildup of plaques, which can significantly reduce blood flow. This reduction in blood flow leads to decreased oxygenation of the myocardium, especially during times of increased myocardial oxygen demand such as during physical exertion or emotional stress.

When the heart's demand for oxygen exceeds the ability of the narrowed coronary arteries to supply that oxygen, angina occurs. This condition manifests as chest pain or discomfort. Therefore, the most likely cause of angina in a client with atherosclerosis is indeed decreased oxygenation to the myocardium.

Other options, such as reduction of plaque, increased blood flow, and hypoxia of peripheral tissues, do not directly relate to the most common mechanism of angina in this context. Reduced plaque could theoretically improve blood flow and oxygenation, while increased blood flow would alleviate the symptoms of angina rather than cause them. Hypoxia of peripheral tissues is more related to systemic conditions rather than localized myocardial oxygen deprivation, which is the key trigger for angina in patients with coronary artery disease.