Importance of Estimated Functional Capacity as a Predictor of All-Cause Mortality Among Patients Referred for Exercise Thallium Single-Photon Emission Computed Tomography: Report of 3,400 Patients From a Single Center

• Published in: Journal of the American College of Cardiology Vol. 30; no. 3; pp. 641 - 648
• Main Authors: Snader, Claire E, Marwick, Thomas H, Pashkow, Fredric J, Harvey, Sharon A, Thomas, James D, Lauer, Michael S
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.09.1997; Elsevier Science
• Subjects: Adult; Biological and medical sciences; Cardiovascular system; Coronary Disease - diagnosis; Coronary Disease - diagnostic imaging; Coronary Disease - physiopathology; Exercise Test; Exercise Tolerance; Female; Heart Diseases - mortality; Humans; Investigative techniques, diagnostic techniques (general aspects); Male; Medical sciences; Middle Aged; Mortality; Multivariate Analysis; Prognosis; Proportional Hazards Models; Prospective Studies; Radionuclide investigations; Space life sciences; Thallium Radioisotopes; Tomography, Emission-Computed, Single-Photon; RR; Tl-201; df; METs; OR; CI; ECG; SPECT; Radionuclide study; Human; Thallium; Prognosis; Follow up study; Mortality; Myocardium; Exercise tolerance test; Exploration; Photon; Functional capacity; Emission tomography; Non-programmatic
• ISSN: 0735-1097; 1558-3597
• DOI: 10.1016/S0735-1097(97)00217-9

Objectives. We sought to determine the relative influence of estimated functional capacity and thallium-201 (Tl-201) single-photon emission computed tomographic (SPECT) findings on prediction of short-term all-cause and cardiac-related mortality. Background. Decreased functional capacity and abnormal Tl-201 SPECT findings are predictive of increased cardiovascular risk and mortality. However, the relative importance of these variables as predictors of all-cause mortality is not well established. Methods. Analyses were based on 3,400 consecutive adults undergoing symptom-limited exercise Tl-201 SPECT testing at the Cleveland Clinic Foundation between September 1990 and December 1993; none had previous invasive procedures, heart failure or valve disease. Estimated functional capacity, classified by age and gender, and thallium perfusion defects, expressed as a stress extent thallium score on a 12-segment scale, were analyzed to determine their relative prognostic importance during 2 years of follow-up. Results. Of 3,400 patients, 108 (3.2%) died during follow-up; 32 deaths were identified as cardiac related. On univariable analysis, estimated functional capacity was a strong predictor of death, with 62 (57%) deaths occurring in patients achieving <6 metabolic equivalents (METs) (log-rank chi-square 86, p < 0.0001). On multivariable analysis, the strongest independent predictors of all-cause mortality were fair or poor functional capacity (adjusted relative risk [RR] 3.96, 95% confidence interval [CI] 2.36 to 6.64, chi-square 27, p < 0.0001) and age (adjusted RR for 10 years 2.25, 95% CI 1.80 to 2.80, chi-square 27, p < 0.0001). The presence of SPECT thallium perfusion defects was a less powerful predictor of death (for each two additional segments with defects, adjusted RR 1.21, 95% CI 1.03 to 1.43, chi-square 5, p = 0.02). Cardiac mortality was predicted by both fair or poor functional capacity (adjusted RR 4.37, 95% CI 1.59 to 12.00, chi-square 8, p = 0.004) and by stress extent thallium score (adjusted RR 1.62, 95% CI 1.25 to 2.11, chi-square 13, p = 0.0003). Conclusions. In this clinically low risk group, estimated functional capacity was a strong and overwhelmingly important independent predictor of all-cause mortality among patients undergoing exercise Tl-201 SPECT testing. The extent of myocardial perfusion defects was of comparable importance for the prediction of cardiac mortality.