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Coronary spasm is defined as a condition in which a relatively large coronary artery running on the surface of the heart transiently exhibits abnormal contraction. If a coronary artery is completely or nearly completely occluded by spasm, transmural ischemia occurs in the region perfused by the artery, which in turn causes anginal attacks with ST elevation on the ECG. If a coronary artery is partially occluded or diffusely narrowed by spasm, or if it is completely occluded by spasm but sufficient collateral flow has developed distally, nontransmural ischemia occurs, causing anginal attacks with ST depression on the ECG. These pathological conditions are collectively termed vasospastic angina (also termed coronary spastic angina), as a type of angina caused by coronary spasm. Variant angina, characterized by ST elevation during anginal attacks, is another type of vasospastic angina. Coronary spasm has been shown to play key roles in the onset of not only variant angina but also rest angina, effort angina, acute myocardial infarction, and other related conditions. 1 The mechanism of involvement of coronary spasm in the onset of acute coronary syndrome is now being elucidated. 2-4In drawing up the present guidelines, cases of vasospastic angina were categorized into three classes as described below. Please note that no evidence levels are established for the guidelines, since no large-scale clinical studies of this condition have been performed. Classification of Recommendations

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