Management of Acute Non-Q-Wave Myocardial Infarction
Non-Q-wave myocardial infarction (MI) differs from Q-wave MI in 3 important respects: a smaller infarct size, possibly due to early reperfusion resulting from spontaneous thrombolysis, relief of spasm, or both; more frequent patency of the infarct-related artery; and a larger residual mass of viable but jeopardised myocardium within the perfusion zone of the infarct-related vessel. Left ventricular function is generally better unless impaired by previous MI. After the acute phase, the prognosis is worse when residual ischaemia is present, and reinfarction rates during hospitalisation and in the subsequent year of follow-up are higher. As myocardial ischaemia is potentially reversible, its presence should be actively sought in all patients with recognised non-Q-wave MI. On the basis of current knowledge and available data, the following guidelines for the management of non-Q-wave MI patients can be recommended: (1) diltiazem and aspirin should be administered to all patients as soon as the diagnosis is established, unless contraindications exist; (2) patients who develop early recurrent ischaemia on therapy (i.e. angina with associated ST-T-wave changes) should undergo prompt cardiac catheterisation and myocardial revascularisation; and (3) patients with entirely uncomplicated hospital histories who are asymptomatic should undergo exercise stress testing, preferably in conjunction with 201Tl perfusion scintigraphy, before hospital discharge. Only those patients with evidence of significant residual ischaemia need cardiac catheterisation and myocardial revascularisation.