ACC/AHA 2002 Guideline Update for Exercise Testing: Summary Article : A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1997 Exercise Testing Guidelines)

Both attenuated heart rate recovery following exercise and the Duke treadmill exercise score have been demonstrated to be independent predictors of mortality, but their prognostic value relative to each other has not been studied. To assess the associations among abnormal heart rate recovery, treadmill exercise score, and death in patients referred specifically for exercise electrocardiography. Prospective cohort study conducted in an academic medical center between September 1990 and December 1997, with a median follow-up of 5.2 years. A total of 9454 consecutive patients (mean [SD] age, 53 [11] years; 78% male) who underwent symptom-limited exercise electrocardiographic testing. Exclusion criteria included age younger than 30 years, history of heart failure or valvular disease, pacemaker implantation, and uninterpretable electrocardiograms. All-cause mortality, as predicted by abnormal heart rate 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). 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 univariate 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 intermediate- 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 adjusting for age, sex, standard cardiovascular risk factors, medication use, and other potential confounders, abnormal heart rate recovery remained predictive of death (among the 8549 patients not taking beta-blockers, adjusted HR, 2.13; 95% CI, 1.63-2.78; P<.001), as did intermediate- or high-risk treadmill exercise score (adjusted HR, 1. 49; 95% CI, 1.15-1.92; P =.002). There was no interaction between these 2 predictors. In this cohort of patients referred specifically for exercise electrocardiography, both abnormal heart rate recovery and treadmill exercise score were independent predictors of mortality. Heart rate recovery appears to provide additional prognostic information to the established treadmill exercise score and should be considered for routine incorporation into exercise test interpretation. JAMA. 2000;284:1392-1398.

Chronotropic incompetence, an attenuated heart rate response to exercise, is a predictor of all-cause mortality in healthy populations. This association may be independent of exercise-induced myocardial perfusion defects. To examine the prognostic significance of chronotropic incompetence in a low-risk cohort of patients referred for treadmill stress testing with thallium imaging. Prospective cohort study conducted between September 1990 and December 1993. Tertiary care academic medical center. Consecutive patients (1877 men and 1076 women; mean age, 58 years) who were not taking beta-blockers and who were referred for symptom-limited treadmill thallium testing. Association of chronotropic incompetence, defined as either failure to achieve 85% of the age-predicted maximum heart rate or a low chronotropic index, a heart rate response measure that accounts for effects of age, resting heart rate, and physical fitness, with all-cause mortality during 2 years of follow-up. Three hundred sixteen patients (11%) failed to reach 85% of the age-adjusted maximum heart rate, 762 (26%) had a low chronotropic index, and 612 (21%) had thallium perfusion defects. Ninety-one patients died during the follow-up period. After adjustment for age, sex, thallium perfusion defects, and other confounders, failure to reach 85% of the age-predicted maximum heart rate was associated with increased risk of death (adjusted relative risk [RR], 1.84; 95% confidence interval [CI], 1.13-3.00; P=.01), as was a low chronotropic index (adjusted RR, 2.19; 95% CI, 1.43-3.44; P<.001). Among patients with known or suspected coronary disease, chronotropic incompetence is independently predictive of all-cause mortality, even after considering thallium perfusion defects. Incorporation of chronotropic response into the routine interpretation of stress thallium studies may improve the prognostic power of this test.

We tested the hypothesis that an emergency department-based protocol for rapidly ruling out myocardial ischemia would reduce hospital time and expense but maintain diagnostic accuracy. Patients with a missed diagnosis of myocardial infarction have a high mortality rate; however, providing routine hospital care to low risk patients may not be time- or cost-effective. One hundred low risk patients were entered into the study and randomized either to an emergency department-based rapid rule-out protocol (n = 50) or to routine hospital care (n = 50). Patients receiving routine care were managed by their attending physicians. The rapid protocol included serum enzyme testing at 0, 3, 6 and 9h, serial electrocardiograms with continuous ST segment monitoring and, if results were negative, a predischarge graded exercise test. Study patients were also compared with 160 historical control subjects. Myocardial infarction or unstable angina occurred in 6% of patients within 30 days; no diagnoses were missed. By intention to treat analysis (n = 50 in each group), the hospital stay was shorter and charges were lower with the rapid protocol than with routine care (p = 0.001). Among patients in whom ischemia was ruled out, those assigned to the rapid protocol had a shorter hospital stay (median 11.9 vs. 22.8 h, p = 0.0001) and lower initial ($893 vs $1,349, p = 0.0001) and 30-day ($898 vs. $1,522, p = 0.0001) hospital charges than did patients given routine care. In historical control subjects, the hospital stay was longer (median 34.5 h, p = 0.001 vs. either group) and charges greater (median $2,063, p = 0.001, vs rapid protocol, p = 0.02, vs. routine care group). In low risk patients who present to the emergency department with chest pain, the rapid protocol ruled out myocardial infarction and unstable angina more quickly and cost-effectively than did routine hospital care.