Effects of Muscle Electrical Stimulation on Peak VO₂ in Cardiac Transplant Patients

Peak oxygen consumption (peak VO₂) has become a critical component in the evaluation of heart transplant recipients (HTR). In these patients, peak VO₂ remains low after cardiac transplantation mainly because of persisting peripheral limitations in the working muscles. Muscular electrical stimulation, on the other hand, has been shown to enhance the oxidative capacity of healthy muscle. It was the purpose of our investigation to study the effects of ES on the peak VO₂ of HTR. Fourteen (11 males and 3 females) HTR (age: 57 ± 7 yr, mean ± SD; height: 163 ± 7 cm, weight: 70.5 ± 8.6 kg) were selected as subjects and each of them was randomly assigned to one of two groups: (a) group EXP (n = 7), receiving electrical stimulation on both quadriceps muscles during a period of 8 weeks, and (b) group CONT (n = 7), not receiving electrical stimulation. Before (PRE) and after (POST) the aforementioned 8-week period, respectively, all the subjects performed a cardiopulmonary exercise test (ramp protocol) on a cycle ergometer for peak VO₂ determination. PRE values of peak VO₂ were similar in both groups (17.1 ± 2.0 vs 16.9 ± 3.8 ml x kg^-1 x min^-1 in EXP and CONT, respectively). However, peak values of VO₂ significantly increased in EXP (p < 0.05) after the period of electrical stimulation (POST peak VO₂: 18.7 ± 2.0 mix kg^-1), whereas no change was observed in CONT (POST peak VO₂: 16.2 ± 3.2 ml x kg^-1 x min^-1). In conclusion, electrical stimulation could therefore be used to improve the functional capacity of HTR. and might be included in the rehabilitation programs of this population group.

Key words

Peak oxygen consumption - cardiac transplantation - electrical stimulation