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© 2000 European Society of Cardiology
Exercise training in heart failure: time to go beyond surrogate endpoints
Central Hospital in Rogaland, Cardiology Division 4011 Stavanger, Norway
* Tel.: +47-51518000; fax: +47-51519921. E-mail address: trout{at}online.no
Although there is intense focus on the pharmacological approach to therapy in heart failure, it has been difficult to generate clinical interest in exercise training as a potential treatment. This is not due to a lack of evidence of efficacy. The literature provides ample evidence of a positive effect on exercise capacity and symptoms in diverse populations [1]. However, the available studies are small, single-centre efforts that have focused on obtaining mechanistic information explaining the salutary effects of exercise training [2]. Perhaps the most useful data were presented by the European Heart Failure Training Group, which reviewed the progress of 134 stable, heart failure patients in randomised, controlled trials of physical training [3].
There is strong evidence that much of the reduced functional capacity and exercise intolerance associated with CHF represents a peripheral myopathy resulting from chronic deconditioning [4]. The suggested mechanisms explaining improvement following training are multifactorial. Improvements in regional blood flow, capillary density, muscle bioenergetics, autonomic tone and neurohumoral status have been documented.
Part of the problem in initiating training programs is clearly economic in that no one profits commercially from offering exercise training to patients with heart failure. A team of cardiac rehabilitation therapists must be trained and funded. Adequate facilities are required and long-term therapy is necessary. Most state or private healthcare agencies will not refund these expenditures. Convincing documentation of efficacy is needed in order to persuade clinicians and administrators of the value of this therapeutic option.
Design problems that are inherent to the evaluation of an open intervention have made it difficult to initiate a large multicentre study evaluating the effect of long-term exercise training on morbidity and mortality. It is impossible to perform a double-blinded study and crossover designs have substantial sequence effects. There is no consensus regarding the most efficacious frequency, duration or type of exercise intervention. Although most trials have evaluated exercise capacity as the endpoint, studies include maximal, submaximal and endurance protocols with no uniform methodology. Similarly, the most appropriate methods and endpoints to assess efficacy are debated as well as which population of heart failure patients should be targeted. Furthermore, it is difficult to isolate the effects of exercise alone in that patients are usually exposed to multiple interventions and compliance cannot be assessed accurately. There is considerable publication bias and obviously, this is not a data set that easily lends itself to meta-analyses.
The target population usually consists of symptomatic patients who often have important co-morbid conditions such as pulmonary, peripheral vascular or orthopaedic diseases that may limit exercise. Present thinking is considerably more liberal regarding contraindications and most experienced centres will only exclude patients who have concomitant diseases that preclude sufficient exertion during training sessions. It is important to target the patients most likely to profit from training since the cost of treatment is substantial. Patients must first be identified, evaluated and motivated by clinicians. Although few trials have included sufficient numbers of women, a recent publication specifically addressed this issue and demonstrated substantial improvement [5]. The trials that have evaluated the participants’ quality of life have consistently demonstrated improvement [6]. Clearly, clinical research is needed to identify the population most likely to respond favourably in order to permit efficient resource utilisation.
Progress in this field requires a major collaborative effort. A sufficient number of patients must be evaluated in order to assess the effect on morbidity and mortality in a heterogeneous population of patients with symptomatic heart failure. There is adequate experience and expertise now available to move forward and perform a large, international, multicentre trial. The Clinical Trials Group at the Royal Brompton Hospital in London, has taken an initiative and collected an experienced group willing to collaborate in such a trial. A protocol is now available that represents the collective input from these investigators. EXIST (Exercise Intervention in Stable Heart Failure Trial) is being led by Andrew Coats and Marcus Flather. The target population is 2000 symptomatic patients randomised to training or usual care. Survival and morbidity endpoints will be recorded. The trial is currently recruiting centres and applying for funding.
Physicians responsible for the care of patients with heart failure have the opportunity to take the lead. Participation in collaborative, clinical research trials appropriately designed to define the role of this potentially efficacious intervention is the next step. If the training effect is limited to symptomatic improvement, then only symptomatic patients should be targeted. The evidence to date would suggest that the greatest benefit would be observed in deconditioned, well-motivated patients with symptomatic heart failure. If improvement in morbidity and mortality can be demonstrated in a wider spectrum of heart failure patients, then clearly a larger population should be offered an opportunity to participate in a training program. In this case, it’s the patients that will profit.K. DicksteinCentral Hospital in Rogaland,Cardiology Division,4011 Stavanger,Norway
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- Piepoli M., Flather M., Coats A.J.S. Overview of studies of exercise training in chronic heart failure. The need for a prospective randomised European trial. Eur Heart J (1998) 16:830–841.
- McKelvie R., Teo K., McCartney N., Humen D., Montague T., Yusuf S. Effects of exercise training in patients with congestive heart failure: a critical review. J Am Coll Cardiol (1995) 25:789–796.[Abstract]
- European Heart Failure Training Group. Experience from controlled trials of physical training in chronic heart failure. Protocol and patient factors in effectiveness in the improvement in exercise tolerance. Eur Heart J (1988) 19:446–475.
- Opasich C., Ambrosino N., Felicetti G., et al. Heart failure related myopathy: clinical and pathophysiological insights. Eur Heart J (1999) 20:1191–1200.
[Abstract/Free Full Text] - Tyni-Lenne R., Gordon A., Europe E., Jansson E., Sylven C. Exercise-based rehabilitation improves skeletal muscle capacity, exercise tolerance and quality of life in both men and women with chronic heart failure. J Card Failure (1998) 4:9–17.[Medline]
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[Abstract/Free Full Text]
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  L TAVAZZI and P GIANNUZZI Physical training as a therapeutic measure in chronic heart failure: time for recommendations Heart, July 1, 2001; 86(1): 7 - 11. [Full Text] [PDF]
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