CORRESPONDENCE: LETTER TO THE EDITOR
Questions in Cardiac Resynchronization Therapy: Metabolic Implications
Tim Karhausen*,
Martin Stockburger, MD,
Wolfram Doehner, MD, PhD and
Stefan D. Anker, MD, PhD
* Applied Cachexia Research, Department of Cardiology, Charite Medical School, Humboldt University Berlin, Augustenburger Platz 1, 13353 Berlin, Germany (Email: tim.karhausen{at}charite.de).
With great interest we read the study by Bax et al. (1) relating to unresolved questions of cardiac resynchronization therapy (CRT). Many different trials have shown the beneficial effects of CRT using a variety of quantitative assessments such as the 6-min walk test, peak oxygenconsumption (VO2), New York Heart Association (NYHA) functional class, quality-of-life measures, or mortality as primary end points. Among the exercise test variables, ventilatory efficiency (VE/VCO2) slope is increasingly recognized as at least as good and possibly an even better prognostic indicator than peak VO2 (2). Does CRT improve VE/VCO2 slope? So far only one uncontrolled study has addressed this question, and after 1 to 3 months no improvement was seen. A large body of evidence shows that chronic heart failure (CHF) affects skeletal muscle functional capacity and metabolic status (like increased insulin resistance [3]), which in turn contribute to patient symptoms. Information on changes of these parameters with CRT would be relevant in order to shed more light on the mechanisms of CRT-related improvement of symptomatic status. In CHF patients a lower body mass index and a decrease in body weight are associated with worse outcome (4). Treatments that are clearly beneficial in CHF have also been shown to prevent weight loss (angiotensin-converting enzyme inhibitors and beta-blockers [4]) or even increased body fat mass (beta-blockers) (5). Until today there are no data on changes in body weight or body composition following CRT. We agree with Bax et al. (1) that much more research remains to be done regarding CRT. We believe that metabolic pathways should be an important focus of these investigations. This will promote our understanding of the pathophysiology of CHF and of the response to CRT and may help to better guide patient selection for cardiac resynchronization therapy.
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1. Bax JJ, Abraham T, Barold SS, et al. Cardiac resynchronization therapypart 2—issues during and after device implantation and unresolved questions. J Am Coll Cardiol 2005;46:2168-2182.[Abstract/Free Full Text]2. Ponikowski P, Francis DP, Piepoli MF, et al. Enhanced ventilatory response to exercise in patients with chronic heart failure and preserved exercise tolerancemarker of abnormal cardiorespiratory reflex control and predictor of poor prognosis. Circulation 2001;103:967-972.[Abstract/Free Full Text] 3. Doehner W, Rauchhaus M, Ponikowski P, et al. Impaired insulin sensitivity as an independent risk factor for mortality in patients with stable chronic heart failure J Am Coll Cardiol 2005;46:1019-1026.[Abstract/Free Full Text] 4. Anker SD, Negassa A, Coats AJ, et al. Prognostic importance of weight loss in chronic heart failure and the effect of treatment with angiotensin-converting-enzyme inhibitorsan observational study. Lancet 2003;361:1077-1083.[CrossRef][Web of Science][Medline] 5. Lainscak M, Keber I, Anker SD. Body composition changes in patients with systolic heart failure treated with beta blockersa pilot study. Int J Cardiol 2006;106:319-322.[CrossRef][Web of Science][Medline]
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