Effects of chronotropic incompetence and beta-blocker use on the exercise treadmill test in men

Objective Our purpose was to assess the diagnostic characteristics of the e xercise test in patients who foil to reach conventional target heart rates and in patients on P-blockers. Background Exercise test results are often considered "inadequate" or "nond iagnostic" in patients taking beta -blockers and in patients who do not ach ieve 85% of their age-predicted maximal heart rate. Methods The results of exercise tests and coronary angiography performed to evaluate chest pain in 1282 male patients without a prior history of myoca rdial infarction, coronary revascularization, diagnostic Q wave on the base line electrocardiogram, or previous cardiac catheterization were analyzed w ith respect to beta -blocker exposure and Failure to reach 85% age-predicte d maximal heart rate. Sensitivity, specificity, and predictive accuracy of exercise testing, as well as area under the curve for the receiver operatin g characteristic plots were calculated For these subgroups with use of coro nary angiography as the reference. The angiographic criterion for significa nt coronary artery disease was 50% narrowing or greater in one or more majo r coronary arteries. Results The population was divided into 4 exclusive groups on the basis of whether they reached their target heart rates and whether they were receivi ng beta -blockers. Sixty to 40 percent of this clinical population failed t o reach target heart rate, of which 24% (n = 303) were receiving beta -bloc kers and 40% (n = 518) were not. The group of patients who reached target h eart rate and were not taking beta -blockers was taken as the reference gro up (n = 409). The group of patients supposedly beta -blocked but who reache d the target heart rate (n = 52) had hemodynamic and test characteristics s imilar to those of the reference group and most likely were not taking thei r beta -blockers or were not adequately dosed. The prevalence of angiograph ic coronary disease was significantly higher in the 2 groups failing to rea ch target heart rate, both in the presence and absence of beta -blockers, c ompared with the reference group (68% and 64%, respectively, vs 49%, P < .0 1). Although the areas under the curve of the receiver operating characteri stic curves for ST depression of the groups Failing to reach target heart r ate were not significantly different from the reference group, the predicti ve accuracy and sensitivity were significantly lower For 1 mm of ST depress ion in the beta -blocked group who did not reach target heart rate (predict ive accuracy of 56% vs 67%, sensitivity of 44% vs 58%, P < .01). The only w ay to maintain sensitivity with the standard exercise test in the beta -blo cker group who failed to reach target heart rate was to use a treadmill sco re or 0.5-mm Si depression as the criteria for abnormal. Conclusion Sensitivity and predictive accuracy of standard ST criteria for exercise-induced ST depression are significantly decreased in male patients who are taking beta -blockers and do not reach target heart rate. In those who foil to reach target heart rate and are not beta -blocked, sensitivity and predictive accuracy are maintained.