Heart rate behavior during an exercise stress test in obese patients

Background and aims: Heart rate (HR) response to exercise has not been fully described in the obese. We wanted to study the differences between obese and non-obese patients in HR behavior during an exercise stress test and to determine whether these differences influence exercise capacity. Methods and results: We studied 554 patients (318 females) who underwent a treadmill exercise test. All subjects were in sinus rhythm. Patients with ischemic heart disease, with reduced ejection fraction and patients taking drugs that interfere with FIR were excluded. The population included 231 patients with BMI < 30 kg/m(2) (group 1), 212 patients who were unfit and obese (group 2) and 111 patients who were trained obese (group 3). Resting HR was similar in the various groups. Peak FIR, FIR recovery and chronotropic index were lower in obese subjects, regardless of their fitness level. Multivariate analysis showed that HR related variables were associated with age, BMI, height, hypertension and various pharmacologic treatments, while exercise capacity was strongly dependent on HR behavior, as well. as on sex, age, BMI and diabetes. Conclusion: Obese subjects have a marked impairment of FIR behavior during exercise and in the recovery period, and the blunted increase in HR is the most important factor that influences exercise capacity. (C) 2008 Elsevier B.V. All rights reserved.