Faut-il rééduquer les coronariens au seuil ventilatoire ?

Abstract

PURPOSE: 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. SETTING: Cardiovascular rehabilitation unit. METHOD: 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 × 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. RESULTS: 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. DISCUSSION AND CONCLUSION: 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.