Prognostic value of dipyridamole thallium imaging after acute myocardial infarction in older patients

OBJECTIVE: To assess the utility of intravenous dipyridamole thallium testi ng for predicting major cardiac events following acute myocardial infarctio n in older patients. DESIGN: Prospective cohort study with a median follow-up of 18 months. SETTING: A university teaching hospital. PARTICIPANTS: 73 patients aged 65 years and older with enzymatically confir med acute myocardial infarction (mean age 75 years, 56% male, 71% white). MEASUREMENTS: All patients underwent a detailed clinical assessment, an ech ocardiogram, and an intravenous dipyridamole thallium stress test before ho spital discharge. The study endpoint was death or nonfatal reinfarction dur ing the follow-up period. RESULTS: Overall, 24 patients (33%) died or developed recurrent myocardial infarction during follow-up. Among 44 patients with a reversible thallium d efect, 19 (43%) reached the study endpoint, compared with only five of 29 p atients (17%) without reversible ischemia (P = .04). On multivariate analys is, independent prognostic variables included non-use of aspirin at hospita l discharge (P = .002), decreased left ventricular systolic function (P = . 009), non-use of a betablocker at hospital discharge (P = .013), and revers ible ischemia on thallium scintigraphy (P = .025). The relative risks for d eath or reinfarction associated with non-use of aspirin, non-use of a beta- blocker, left ventricular dysfunction, and reversible ischemia were 2.65, 2 .39, 2.01, and 2.51, respectively. Patients with three or four of these ris k: factors had an 83% probability of death or reinfarction, compared with 4 1% in patients with two risk factors and 6% in patients with one or no risk factor (P < .001). CONCLUSION: Intravenous dipyridamole thallium imaging provides independent prognostic information in older patients with acute myocardial infarction. Moreover, the combination of clinical, echocardiographic, and dapyridamole thallium variables effectively stratifies older postinfarction patients int o high-, intermediate-, and low-risk categories for death or recurrent myoc ardial infarction.