Exercise technetium-99m myocardial tomography for the risk stratification of men with medically treated unstable angina pectoris

Abstract

The prognostic value of predischarge maximal exercise stress testing with technetium-99m sestamibi (MIBI) myocardial tomography was assessed in 126 consecutive men hospitalized with a diagnosis of unstable angina pectoris who were medically stabilized. None had coronary revascularization for ≤6 months after testing. Over a mean follow-up of 12 ± 7 months (range 1 to 29), 35 patients (28%) had a cardiac event—nonfatal acute myocardial infarction (n = 6), cardiac death (n = 5), or rehospitalization for unstable angina (n = 24). Any type of cardiac event occurred in 12% of patients with normal MIBI scans, compared with 39% of those with an abnormal MIBI scan (p <0.001) and 60% of those with a reversible perfusion defect (p <0.0001). Only 2% of patients with normal scans had either a nonfatal myocardial infarction or cardiac death, compared with 14% of those with abnormal MIBI scans (p <0.05) and 25% with a reversible defect (p <0.001). A fixed perfusion defect was not associated with increased cardiac risk. With use of multivariable Cox proportional-hazards modeling, the only scintigraphic variable with independent predictive value was the presence of a reversible MIBI defect, with a relative risk of 3.8 (95% confidence interval 1.6 to 8.6, p <0.05) for any cardiac event, and 19.2 (95% confidence interval 2.2 to 167.0, p <0.05) for a nonfatal myocardial infarction or cardiac death. Cardiac event-free survival was also significantly decreased in patients with a reversible perfusion defect (p <0.001). Thus, exercise stress MIBI tomography provides long-term prognostic information in patients with unstable angina who can be medically stabilized before hospital discharge. A normal MIBI scan is associated with a low risk of subsequent cardiac events, whereas a reversible perfusion defect is an independent predictor of increased cardiac risk despite continued medical therapy.