Effect of Infarct Artery Patency on Prognosis After Acute Myocardial Infarction

Abstract

Background In patients with acute myocardial infarction (MI), early restoration of patency of the infarct-related artery (IRA) leads to preservation of left ventricular function and improved clinical outcome. However, there is evidence that the benefits associated with a patent IRA are out of proportion to the observed improvement in ventricular function and may result not only from salvage of ischemic myocardium but also from the opening of the IRA beyond a narrow postinfarct time window. The objectives of this study were (1) to assess the effect of IRA patency on outcome of patients after acute MI with left ventricular dysfunction while controlling for differences in left ventricular ejection fraction and the extent of coronary disease and (2) to determine the effect of angiotensin-converting enzyme (ACE) inhibitor therapy on patients with patent as well as occluded infarct arteries. Methods and Results The Survival and Ventricular Enlargement (SAVE) study consisted of 2231 patients with a documented MI and a left ventricular ejection fraction ≤40%. They were randomized to the ACE inhibitor captopril (50 mg TID) or placebo 3 to 16 days after MI and were followed for an average of 3.5 years. Left ventricular ejection fraction, measured with radionuclide left ventriculography, was repeated at the end of the follow-up period. The 946 patients in whom the patency of the IRA was established before randomization form the basis of this study. At cardiac catheterization averaging 4.2 days after infarction, 30.7% of patients had an initially occluded IRA. After revascularization, 162 of the 946 patients (17.1%) were left with an occluded IRA at the time of randomization. The 162 patients with persistently occluded IRAs and 784 with patent IRAs had similar clinical baseline characteristics, but those with occluded arteries had a slightly lower ejection fraction than the 784 patients with patent infarct arteries (30% versus 32%, P =.01). Cox proportional-hazards analyses showed that the independent predictors of all-cause mortality were hypertension (relative risk [RR] 1.94, P <.001), number of diseased coronary arteries (RR 1.68, P <.001), occluded IRA (RR 1.49, P =.039), ejection fraction (RR 1.36, P <.001), age (RR 1.10, P =.030), and use of β-adrenergic receptor blocking agents (RR 0.60, P =.007). Independent predictors of a composite end point consisting of cardiovascular mortality, morbidity, or reduction of ejection fraction of ≥9 units were occluded IRA (odds ratio [OR] 1.73, P =.002), hypertension (OR 1.71, P <.001), number of diseased vessels (OR 1.38, P <.001), ejection fraction (OR 1.18, P =.003), use of β-adrenergic receptor blocking agents (OR 0.67, P =.007), and randomization to captopril (OR 0.70, P =.009). Conclusions IRA patency within 16 days after MI predicts a favorable clinical outcome, independent of the number of obstructed coronary arteries or of left ventricular function. The beneficial effect of ACE inhibition is independent of patency status of the IRA. These findings support the need for additional, prospective clinical trials of late reperfusion in MI patients.