It is widely held that angina pectoris results from a mismatch between restricted coronary artery blood flow and an increased myocardial work load. The very converse is also true, namely, typical angina may be experienced by patients with angiographically intact coronary arteries. If the pro-vocative factor is due to inadequate oxygen delivery in relation to the cardiac work load, it is difficult to reconcile the striking divergence between the effort required to induce pain on different occasions.
Clinicians well recognize the stereotypic pattern in the occurrence of angina.
A patient may be able to exert strenuously indoors without any discomfort although limited while walking outdoors with ambient temperatures similar in both settings. Modest activity on first arising in the morning is more likely to precipitate angina than greater exertion later in the day. The threshold for pain is lower with the onset of activity than during its continuance. Customary work, although arduous, usually does not induce angina. At times, seemingly innocuous stimuli, minor psychologic stresses or miniscule efforts can set off anginal episodes.