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

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 increase d cardiovascular risk and mortality. However, the relative importance of these variables as predictors of all-cause mortality is not well es tablished. Methods. Analyses were based on 3,400 consecutive adults un dergoing symptom-limited exercise Tl-201 SPECT testing at the Clevelan d Clinic Foundation between September 1990 and December 1993; none had previous invasive procedures, heart failure or valve disease. Estimat ed functional capacity, classified by age and gender, and thallium per fusion defects, expressed as a stress extent thallium score on a 12 se gment scale, were analyzed to determine their relative prognostic impo rtance during 2 years of follow-up. Results. Of 3,400 patients, 108 (3 .2%) died during follow-up; 32 deaths were identified as cardiac relat ed. On univariable analysis, estimated functional capacity was a stron g predictor of death, with 62 (57%) deaths occurring in patients achie ving <6 metabolic equivalents (METs) (log rank chi-square 86, p < 0.00 01). On multivariable analysis, the strongest independent predictors o f all cause mortality were fair or poor functional capacity (adjusted relative risk [RR] 3.96, 95% confidence interval [CI] 2.36 to 6.64, ch i-square 27, p < 0.0001) and age (adjusted RR for 10 years 2.25, 95% C I 1.80 to 2.80, chi-square 27, p < 0.0001). The presence of SPECT thal lium perfusion defects was a less powerful predictor of death (for eac h 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 b oth 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). Con clusions. In this clinically low risk group, estimated functional capa city was a strong and ovenwhelmingly important independent predictor o f 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. (C) 1997 by the Am erican College of Cardiology.