Patients who are hospitalized because of chest pain and suspected acute myocardial infarction, but in whom the diagnosis is ruled out, are at high risk for subsequent cardiac events (cardiac death or nonfatal acute myocardial infarction). Risk stratification was done for 158 such patients who underwent exercise thallium-201 scintigraphy at the time of discharge.
Thirty-eight patients (24%) were women, and all patients were followed for 7 years. The diagnostic sensitivity, specificity, and predictive value of thallium scintigraphy for the identification of patients having subsequent cardiac events during follow-up was calculated.
A cardiac event occurred in 41 patients during the follow-up period. Presence of both transient and permanent defects and abnormal ST-segment responses during thallium scintigraphy were significantly associated with an impaired prognosis (P< 0.0001). The highest sensitivity (85%) was achieved by the combination of transient defect with or without persistent defect and with or without abnormal ST-segment response. The highest specificity was provided by a transient defect (90%), and the predictive value of a positive test result was 60%. Seventeen of 29 patients with a transient defect had a cardiac event during follow-up. Patients with normal test results had excellent prognoses; 93% of 82 patients were free of cardiac events during follow-up.
Exercise thallium-201 scintigraphy is suitable for long-term risk stratification in patients with chest pain and suspected but unconfirmed myocardial infarction, because high- and very low-risk subsets can be identified at the time of discharge.