Is it beneficial to add electromyostimulation to conventional exercise training in heart failure?

Classically, electromyostimulation (EMS) is largely used to treat muscle atrophy due to muscle disuse either in healthy individuals or patients with neuromuscular disorders.1 Also in sports science EMS is considered an alternative approach in enhancing maximal strength, power and sprint ability.2 Besides all these applications electrical stimulation of lower limb muscles is also considered as an alternative approach of exercise training in patients with chronic heart failure (CHF). In recent years conventional exercise training programmes have come to be considered as a cornerstone in the management of patients with cardiovascular diseases, and numerous studies documented a clear benefit with respect to exercise capacity and quality of life (QOL; reviewed in Lewinter3 and Pandey4). Unfortunately, not all patients are willing to actively participate or are able to attend exercise training programmes. In addition, the absence of a beneficial effect of exercise training on exercise capacity has strong prognostic value for adverse cardiac events, independent of classical risk factors.5 Therefore alternative approaches are warranted. As mentioned above, EMS may be one alternative for the non-responders of exercise training or to patients who are not able to perform exercise. Already in the late 1980s Dirk Pette and colleagues could document in animal experiments that chronic low-frequency stimulation of rabbit fast-twitch muscle induces progressive increases in slow myosin light chain mRNAs followed by an increase in the slow myosin heavy chain mRNA.6 In clinical applications EMS uses skin electrodes to produce a controlled and comfortable muscle contraction. Being a passive form of ‘muscle training’, EMS can be easily performed to exercise leg muscles while seated even by otherwise handicapped individuals precluded from being physically active. So far several studies have been performed analysing the effect of EMS in comparison with conventional exercise training or with sedentary patients. In a recently published meta-analysis,7 Gomes Neto and coworkers included 13 studies comparing EMS versus conventional aerobic exercise (AET; six studies) or EMS versus no exercise (seven studies). When comparing with inactive individuals a clear benefit of EMS with respect to VO2peak, six minute walk test (6MWT) and QOL was evident. This clear benefit of EMS was absent when EMS was compared with conventional AET. Change in VO2peak was even greater in AET, whereas no difference was seen for 6MWT and QOL between the two intervention strategies. This is in line with a recently published Cochrane analysis,8 evaluating the effect of electrical stimulation for muscle weakness in adults with advanced disease, such as chronic obstructive pulmonary disease, chronic respiratory disease, CHF and thoracic cancer. The authors concluded that EMS may be an effective treatment for muscle weakness in adults with progressive disease and could be considered as an exercise treatment for use within rehabilitation programmes. Nevertheless we have to keep in mind that even the authors of this Cochrane analysis ranked the quality of the evidence for an improvement in muscle strength, endurance and mass and overall exercise performance as moderate to low. This low confidence is based on the variability of the results seen in the clinical studies, which is due to a great variability in stimulation frequencies, stimulation duration and the muscle being stimulated. Unfortunately, so far no study is available comparing different methods of application. Another so far not completely answered question is whether EMS on top of an exercise training programme generates an additive effect with respect to exercise capacity, muscle mass and QOL. In the current issue of the European Journal of Preventive Cardiology Marie Christine Iliou and colleagues present a study in which they analysed effects of combined exercise training and EMS in CHF patients.9 In a multicentre randomized prospective study 91 CHF patients (New York Heart Association (NYHA) II/III) were randomized either into an exercise training (20 training sessions, 30–60 min during a period of 4–8 weeks at a heart rate obtained at the first ventilator threshold) or an exercise + EMS (around 20 low frequency quadricipital EMS) group. A significant improvement in VO2peak by 10–14% and an improvement in QOL was observed, but with no difference between the two groups independent of age. This result, obtained in a multicentre study, clearly documented that EMS on top of exercise training does not show any additional improvement in exercise capacity and QOL in CHF patients. A side aspect reported in the multicentre study is that muscle damage (based on creatine kinase measurements) was observed in the conventional exercise group but was absent in the exercise + EMS group. Is the result reported by Iliou unexpected or in line with the current literature and what is the take home message? Screening the current literature, a recent study in healthy male individuals (VO2peak 55 ± 5 ml min−1 kg−1) documented that exercise training (cycling) or exercise training + superimposed EMS led to an increase in VO2peak without any significance between the groups.10 With respect to CHF patients the study published by Soska and colleagues11 randomized 71 patients (NYHA II/III, left ventricular ejection fraction ∼32%) into three groups: aerobic training, EMS, aerobic training + EMS. Also in this study, no significant difference was found after 12 weeks of intervention between the groups. Therefore, it is reasonable to conclude that the addition of EMS on top of aerobic training does not result in additional benefits when compared with aerobic training or EMS alone. Does this mean that EMS is of no value in treating CHF patients? This question can clearly be answered with no, since several studies, as outlined above, clearly documented a positive effect of EMS on exercise capacity and QOL when compared with controls. Therefore, EMS may be a valuable tool to treat CHF patients who do not qualify for (comorbidities, or advanced or end-stage heart failure) or comply with conventional exercise training programmes. EMS may also be seen as a bridge to conventional training in the case of the physical status of the patient being too poor to start with conventional training. The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. The author(s) received no financial support for the research, authorship, and/or publication of this article.