Dipyridamole echocardiography test in patients with normal or near normal coronary arteries

We read with great interest the paper by Sicari et al.1 dealing with the prognostic value of dipyridamole echocardiography test in patients with chest pain syndrome and angiographically normal or near normal coronary arteries and the accompanying editorial by Marwick.2 This study, based in a large cohort with long-term follow-up, shows that dipyridamole echocardiography can identify a subgroup with a less benign prognosis. Intravenous dipyridamole is a potent coronary vasodilator that has been extensively investigated over the past several years in the non-invasive assessment of patients with suspected coronary artery disease. On the other hand, the ability of dipyridamole to provoke coronary artery spasm in patients with variant angina and angiographically normal coronary arteries is less well known. Although the mechanisms of dipyridamole-induced coronary artery spasm remain unclear, this ‘false-positive’ test response in patients with normal coronary arteries can be induced by dipyridamole3,4 or by aminophylline.5,6 Aminophylline is a dipyridamole antidote, routinely infused at the end of the test, which produces an abrupt withdrawal of coronary artery vasodilatation which may trigger coronary artery spasms in patients with variant angina. Fujita et al.7 found a sensitivity of 69% (11 of 16) for dipyridamole echocardiography in patients with coronary artery spasm and normal or nearly normal coronary arteries. Sicari et al.1 and Marwick2 do not mention the ability of dipyridamole echocardiography to provoke coronary artery spasm in patients with normal or near normal coronary arteries and variant angina. However, it is conceivable that the prognostic value of this test could be due, in part, to the detection of patients with spontaneous coronary artery spasm.