Independent contribution of myocardial perfusion defects to exercise capacity and heart rate recovery for prediction of all-cause mortality in patients with known or suspected coronary heart disease

OBJECTIVES The goal of this study was to determine the value of thallium201 single photon emission computed tomography (SPECT) imaging for prediction of all-cause mortality when considered along with functional capacity and heart rate recovery. BACKGROUND Myocardial perfusion defects identified by thallium201 SPECT imaging are predictive of cardiac events. Functional capacity and heart rate recovery are exercise measures that also have prognostic implications. METHODS We followed 7,163 consecutive adults referred for symptom-limited exercise thallium SPECT (mean age 60 ± 10, 25% women) for 6.7 years. Using information theory, we identified a probable best model relating nuclear findings to outcome to calculate a prognostic nuclear score. RESULTS There were 855 deaths. Intermediate- and high-risk prognostic nuclear scores were noted in 28% and 10% of patients. Compared with those with low-risk scans, patients with an intermediate-risk score were at increased risk for death (14% vs. 9%, hazard ratio: 1.67, 95% confidence interval [CI]: 1.44 to 1.95, p < 0.0001), while those with high-risk scores were at greater risk (24%, hazard ratio: 2.98, 95% CI: 2.49 to 3.56, p < 0.0001). In multivariable analyses that adjusted for clinical characteristics, functional capacity and heart rate recovery, an intermediate-risk nuclear score remained predictive of death (adjusted hazard ratio: 1.50, 95% CI: 1.28 to 1.76, p < 0.0001), as did a high-risk score (adjusted hazard ratio: 2.76, 95% CI: 2.13 to 2.56, p < 0.0001). Impaired functional capacity and decreased heart rate recovery provided additional prognostic information. CONCLUSIONS Myocardial perfusion defects detected by thallium SPECT imaging are independently predictive of long-term all-cause death, even after accounting for exercise capacity, heart rate recovery and other potential confounders.