VARIATiT ANGINA



In 1959 Prinzmetal described a syndrome of chest pain occurring unrelated to exertion and as­sociated with ST segment elevation recorded on the ECG . The syndrome is often associated with cardiac arrhythmias, including ventricular fibrillation and heart block, and sud­den death may occur. These episodes of angina more commonly occur between midnight and 8 a.m. Rarely, acute myocardial infarction results. Prinzmetal’s angina appears to be due to spasm in the conductance portion of the coronary arter­ies, resulting in decreased oxygen delivery to the myocardium. Patients may have concomitant fixed obstructive lesions and therefore also ex­perience angina with exertion. The classic elec­trocardiographic pattern of coronary spasm is lo­calized ST elevation, although ST depression alone or T wave changes may occur. Coronary an­giography during Prinzmetal’s angina may reveal spasm at the site of a severe coronary athero­sclerotic lesion, a mild atherosclerotic lesion, or a normal coronary artery. Patients with no or mild fixed coronary obstruction tend to have a more benign course than those with severe obstruc­tions. The cause of coronary spasm is unknown. Provocative testing with ergonovine, an ergot al­kaloid with alpha-adrenergic and serotoninergic effects, is a relatively sensitive and specific test for coronary artery spasm. Vessels prone to spasm appear to be supersensitive to its vasoconstrictive properties. When administered in incremental doses to a total of 0.05 to 0.4 mg intravenously, coronary artery spasm, chest pain, and ST ele­vation are provoked in susceptible individuals. Prolonged spasm with significant ischemia and serious arrhythmias is a potential hazard. Nitro­glycerin may be injected directly into the coro­nary vasculature to quickly reverse the spasm if it is severe. Ergonovine testing generally is safe, especially if performed in the catheterization lab, but probably should not be done in patients who have flowrestricting coronary obstructions, and the drug should be administered in extremely low starting doses.

In patients with Prinzmetal’s angina beta block­ade may be detrimental by allowing unopposed alpha-adrenergic vasoconstriction. Calcium chan­nel blockers are very effective in treating vaso­spastic angina, and their effects may be additive to that of nitrates, since the mechanism of action is different. Coronary artery bypass surgery is not helpful in patients with vasospasm and normal or nearly normal coronary arteries but may be useful in patients who have fixed significant stenoses.