Cardiac syndrome X: mystery continues.

Cardiac syndrome X (CSX) continues to be a mystery for clinicians who see patients with symptoms suggestive of obstructive coronary disease but who in fact lack evidence of coronary obstruction. Mysterious, this syndrome also stands out by the fact that it appears to preferentially affect women. In this supplement issue of the Canadian Journal of Cardiology (CJC) focused on persistent cardiac pain, CSX rightly deserves discussion by Arthur et al., alongside other outstanding topics in cardiology, such as mechanisms of cardiac pain (Rosen), classification of nonrevascularizable patients (Jolicoeur et al.), refractory angina management (McGillion et al.), and the continued problem, impact, and management of stable angina (Parker). While Arthur et al. provide a comprehensive coverage of the current state of our knowledge of CSX, we, in this editorial, would like to emphasize some of the points raised regarding CSX in the hope of helping to demystify this syndrome and provide a useful roadmap for the future. The American Heart Association has estimated that over 9 million people in the United States suffer from angina pectoris, which significantly impacts quality of life, ability to work, and costs to society. Within this group of people, a large number suffer a condition called CSX. The first description of patients with angina pectoris and normal coronary arteries appeared in 1967 and was followed by more reports. Arbogast and Bourassa described 10 patients with a definite electrocardiogram ischemic pattern during atrial pacing, typical or atypical angina pectoris, and normal or near normal coronary arteriograms, and labelled them as group X. In 1973, describing this patient group, Kemp first used the name syndrome X. Ingrained in its definition almost half a century ago, the mystery of this syndrome still continues to challenge our understanding of its mechanisms and hence few avenues for treatment have been proposed. CSX is a condition that causes angina or angina-like chest pain with exertion. It is characterized by an ST-segment depression on treadmill exercise testing, but normal coronary arteriography, with no spontaneous or inducible epicardial coronary artery spasm on ergonovine or acetylcholine provocation