Letter by Kumar and Kounis Regarding Article, “Coronary Artery Spasm: A 2009 Update”

We read the elegant update on coronary artery spasm by Stern et al 1 with great interest.It is true that the mechanism and precipitating factors of coronary artery spasm are not well understood.Table 2 in the article comprehensibly highlights various possible pathophysiological factors involved in coronary artery spasm such as increased vasomotor tone, smooth muscle contraction, vagal withdrawal, sympathetic activity, endothelial dysfunction, and role of nitric oxide and phospholipase C.However, the role of intracoronary mast cell activation, which induces the release of vasospastic agents, also merits inclusion in this list. 2,3arious inflammatory mediators such as histamine, neutral proteases, arachidonic acid products, platelet-activating factor, and a variety of cytokines and chemokines released during the allergic reactions are powerful coronary vasospastic agents.These agents constitute the pathophysiological basis of Kounis syndrome, 3 which is characterized by the concurrence of acute coronary events with allergic or hypersensitivity reactions.In an editorial, Braunwald 4 noted that vasospastic angina can be induced by "allergic reactions with mediators such as histamine or leukotrienes acting on coronary vascular smooth muscle."Vasospasm associated with cardiac interventions is a wellrecognized phenomenon.The role of allergic reaction to various medications given during intervention, including aspirin, lansoprazole, and angiotensin-converting inhibitors, is increasingly being recognized as the cause of vasospasm.Even local hypersensitivity reaction to stents and endovascular devices is a matter of concern.