Role of adenosine thallium-201 tomography for defining long-term risk in patients after acute myocardial infarction.

ABSTRACT

OBJECTIVES: This study prospectively evaluated whether early assessment with adenosine thallium-201 tomography could better refine risk stratification on the basis of absolute extent of myocardial ischemia in postinfarction patients in clinically stable condition. BACKGROUND: Postinfarction patients are at increased risk for subsequent cardiac events. However, identifying high risk patients among those with residual myocardial ischemia is suboptimal. METHODS: All 146 patients enrolled underwent assessment of left ventricular function and had adenosine tomography performed early (mean [+/- SD] 5 +/- 3 days) after infarction. Excluded from analysis were 51 patients with revascularization after scintigraphy and 3 lost to follow-up. Statistical risk models were therefore generated from the remaining 92 patients. RESULTS: Cardiac events occurred in 30 (33%) of 92 patients over 15.7 +/- 4.9 months. Univariate predictors of all events were quantified perfusion defect size (p < 0.0001), absolute extent of left ventricular ischemia (p < 0.000001) and ejection fraction (p < 0.0001). Risk was best predicted by Cox analysis on the basis of 1) absolute extent of ischemia and ejection fraction (chi-square 24.6); 2) percent infarct zone ischemia and ejection fraction (chi-square 24.4); or 3) total perfusion defect size and percent infarct zone ischemia (chi-square 18.9). The variables that predicted all cardiac events were equally powerful at predicting only death and nonfatal reinfarction. Death was best predicted by total perfusion defect size. CONCLUSIONS: Risk analysis of individual patients early after infarction is feasible on the basis of the quantified extent of scintigraphic ischemia and severity of left ventricular dysfunction.