Acute Coronary Syndromes Without Obstructive Coronary Atherosclerosis

The large prevalence at autopsy studies, as well as at coronary angiography, of obstructive coronary atherosclerosis in patients presenting cardiac ischemic pain led to the dominant concept, in the past century, that flow-limiting coronary artery stenoses were the only cause of ischemic heart disease (IHD).1 This notion was then supported by the observation that revascularization procedures improved symptoms and outcomes in several patient subsets. This also led to the paradigm that an ischemic cardiac origin of chest pain had to be excluded when significant coronary artery stenoses were not detected at angiography. Few research groups only, including ours, noticed, however, that obstructive coronary atherosclerosis did not explain all cases of IHD, and proved that dynamic changes in epicardial coronary artery tone and abnormalities of coronary microcirculation were responsible for IHD in a sizeable proportion of patients, even in the absence of significant coronary atherosclerosis.2,3 This view, initially considered with skepticism, has progressively been accepted by the scientific community. In particular, variant angina and primary stable microvascular angina, caused by epicardial spasm and coronary microvascular dysfunction respectively, have now been included in international guidelines.4Article see p 285In more recent years, particular interest has been raised by the causes and mechanisms of acute coronary syndromes (ACSs) that cannot be explained by the presence of obstructive coronary atherosclerosis. ACSs are usually caused by coronary thrombus formation at the site of a complicated atherosclerotic plaque. Accordingly, antithrombotic drugs and invasive strategies have substantially improved the clinical outcomes of these patients. Yet, several studies of patients with ACSs, in particular those presenting without persisting ST-segment– elevation (NSTE-ACS), have consistently shown that a sizeable proportion do not present obstructive stenoses nor coronary thrombosis is able to account for the occurrence of acute myocardial ischemia. The lack of obstructive atherosclerosis …