Mixed angina pectoris.

Patients who present with episodes of angina caused both by an increase in oxygen demand and by transient impairment of supply have a mixed form of angina. Distinctive clinical features allow the classification of patients in everyday practice. At one end of the spectrum are patients who have angina only and always when they exercise beyond an essentially fixed level; their angina is fairly predictable and has been termed secondary angina. At the other end of the spectrum are patients who have a normal exercise tolerance but have angina at rest or during activities usually well tolerated that must be caused by a transient impairment of coronary blood flow; their angina is typically unpredictable and has been termed primary angina. We adopted the term primary to emphasize the possible existence of multiple causes of impairment of coronary flow, which together are to be contrasted with the traditional prevailing concept of angina being secondary to excessive increase in demand. In between these ends of the spectrum are most of the patients with angina pectoris encountered in clinical practice: they have a rather predictable ceiling of exercise that they cannot exceed without developing angina, but they also have a variable proportion of unpredictable anginal attacks that occur spontaneously or at levels of activity that are usually well tolerated. We introduced the concept of mixed forms of angina when we became aware that the same patient could experience angina both as a result of an excessive increase in myocardial demand, i.e., secondary angina, and as a result of the transient impairment of coronary blood flow supply, i.e., primary angina.