Pathophysiological basis for noninvasive functional evaluation of coronary stenosis.

A number of tests are used for the noninvasive detection of coronary stenosis, which results from the combination of different stimuli (exercise, pacing, dobutamine, dipyridamole, etc.) and different signals and methodologies (ECG, echocardiography, scintigraphy). In this article, the theoretical assumptions for and the methodological limitations of the functional evaluation of the degree of coronary stenosis are considered within the framework of pathophysiology. In particular, the issues of dilating coronary circulation by either increasing myocardial O2 demand or infusing dipyridamole and of assessing coronary reserve by either flow- or ischemia-related techniques are examined. In addition, the hypotheses of a physiological blood steal during exercise, a decrement of exercise ischemic threshold secondary to additional pharmacological vasodilation, and coronary vasospasm in Prinzmetal's angina patients, following the sequence dipyridamole-aminophylline, are discussed on the basis of preliminary studies.