Heart rate recovery and treadmill exercise score as predictors of mortality in patients referred for exercise ECG

Context Both attenuated heart rate recovery following exercise and the Duke tread mill exercise score have been demonstrated to be independent predict ors of mortality, belt their prognostic value relative to each other has no t been studied. Objective To assess the associations among abnormal heart rate recovery, tr eadmill exercise score, and death in patients referred specifically for exe rcise electrocardiography. Design and Setting Prospective cohort study conducted in an academic medica l center between September 1990 and December 1997, with a median follow-up of 5.2 years. Patients A total of 9454 consecutive patients (mean [SD] age, 53 [11] years ; 78% male) who underwent symptom-limited exercise electrocardiographic tes ting. Exclusion criteria included age younger than 30 years, history of hea rt failure or valvular disease, pacemaker implantation, and uninterpretable electrocardiograms. Main Outcome Measures All-cause mortality, as predicted by abnormal heart r ate recovery, defined as failure of heart rate to decrease by more than 12/ min during the first minute after peak exercise, and by treadmill exercise score, defined as (exercise time) - (5 x maximum ST-segment deviation) - (4 x treadmill angina index). Results Three hundred twelve deaths occurred in the cohort. Abnormal heart rate recovery and intermediate- or high-risk treadmill exercise score were present in 20% (n =1852) and 21% (n =1996) of patients. respectively. in un ivariate analyses, death was predicted by both abnormal heart rate recovery (8% vs 2% in patients with normal heart rate recovery; hazard ratio [HR], 4.16; 95% confidence interval [CI], 3.33-5.19; chi(2)=158; P<.001) and inte rmediate- or high-risk treadmill exercise score (8% vs 2% in patients with low-risk scores; HR, 4.28; 95% CI, 3.43-5.35; chi(2)=164; P<.001). After ad justing for age, sex, standard cardiovascular risk factors, medication use, and other potential confounders, abnormal heart rate recovery remained pre dictive of death (among the 8549 patients not taking p-blockers, adjusted H R, 2.13; 95% CI, 1.63-2.78; P<.001), as did intermediate- or high-risk trea dmill exercise score (adjusted HR, 1.49, 95% CI, 2.15-1.92; P=.002). There was no interaction between these 2 predictors. Conclusions in this cohort of patients referred specifically for exercise e lectrocardiography, both abnormal heart rate recovery and treadmill exercis e score were independent predictors of mortality. Heart rate recovery appea rs to provide additional prognostic information to the established treadmil l exercise score and should be considered for routine incorporation into ex ercise test interpretation.