Dipyridamole Stress Echocardiography

Abstract

Dipyridamole was the first, and probably still is, the most widely used pharmacological stress agent in cardiac imaging [1, 2]; it is safe, easily accessible, and — at least in most countries (with the notable exception of the United States) inexpensive. Its main cardiac imaging applications stem from two fundamental properties, which are the two imaging sides of the same pathophysiological coin of coronary arteriolar vasodilation: the hyperemic effect and the pro-ischemic effect [3]. The hyperemic effect is the conceptual basis for myocardial perfusion imaging, usually with radionuclide scintigraphy; the ischemic effect is the requisite for functional imaging, usually with 2-D echocardiography (Fig.1). The two entities — hyperemic stress and ischemic stress -are tightly linked and can be considered as two different aspects of the same phenomenon, which requires endogenous adenosine accumulation as the common biochemical pathway (Table 1). The predominance of the hyperemic over the ischemic manifestation will depend on the dose of dipyridamole (determining the amount of adenosine accumulation) and on the underlying coronary anatomy. With relatively low intravenous dipyridamole doses, in the presence of absent to moderate coronary artery disease, the hyperemic effect will prevail. With relatively high doses, in the presence of moderate to severe coronary artery disease, the ischemic effect will dominate. Some dipyridamole stress manifestations are better understood within the hyperemic conceptual framework while others within the ischemic framework.