To compare the efficiency of two programs of exercise-based rehabilitation that are different for heart rate (HR) training in patients with coronary artery disease: heart rate (HR) according to Karvonen formula (HR training =70% (max HR -rest HR) +rest HR) or HR recorded at the gas exchange ventilatory threshold (VT). TYPE: Controlled randomised clinical trial.
Cardiovascular rehabilitation unit.
Twenty-four male patients (54 +/-9.5 years old) with coronary artery disease were allocated at random to one of the two groups: KHR group (n =13) according to Karvonen formula (n =11), and VTHR group according to VT determined by exertion test (n =13). The exercised-based program was similar for all the patients, differing only in HR training (five daily sessions a week for four weeks). Assessment tests were performed at D1 and D28 and included: - an exercise test with measure of HR and double product (HR x blood pressure) at rest, submaximal and maximal intensity, with measure of oxygen consumption and gas exchanges at rest and at maximum exercise; - specific functional tests based on daily life activities; - dyspnea assessment at maximal intensity; - quality of life measurement by SF36. It was taken notice of the drugs taken by the patients, specially betablockers.
At inclusion, the two groups were not different for parametric (age, body mass index) and non parametric values (medical or surgical treatment, comorbidity). Even though HR training was significantly different (p <10(-6)), at the end of the program there was a significant increase of power and oxygen consumption at VT (+42.6%, p <10(-6); +18.6%, p <10(-5)) and at maximal intensity (+18.7 %, p <10(-6); 14.2 %, p <10(-5)), but differences between the two groups were not significant; double product was significantly lower at rest (-13.9 %, p <10(-5)) and at submaximal exertion (-10.6 %, p < 10(-3)). Yet, the two groups differed in HR, and HR increased in VTHR group and decreased in KHR, the difference being significant at VT (p =0.05), at submaximal (p =0.037) and maximal exercise (p = 0.05). Dyspnea at maximal intensity was higher in VTHR but SF36 values were not different.
These results confirm the efficiency of cardiac training program according to Karvonen formula as to ventilatory threshold. However, there is a negative chronotropic effect of cardiac training according to Karvonen formula with a higher intensity, which corresponds to a less cardiac work for a same activity.