LETTER TO THE EDITOR
Reply
Cecilia Linde, MD, PhD
Karolinska Hospital, Thoracic Clinics, Box 110, Stockholm, Sweden
cecilia.linde{at}ks.se
In their letter, Moshenyat and colleagues suggest that the one-year benefits by biventricular pacing in the MUSTIC trial reflect the placebo effect by pacemaker implantation because no significant one-year improvements in objective parameters were found (1). The MUSTIC trial was designed as a randomized single-blind crossover comparison between biventricular pacing and inactive pacing (sinus rhythm) or right ventricular pacing (atrial fibrillation) assuming a 10% improvement in 6-min walk and a 10% reduction in Minnesota score by three months of active (biventricular) treatment (2). The crossover results indicate a 20% improvement in 6-min walk and a 30% improvement in quality of life. Subsequent long-term follow-up indicates that these benefits were sustained in magnitude over a one- and two-year follow-up (1,3,4). Because sample size was not calculated for subsequent long-term follow-up no statistical calculations for the secondary end points such as left ventricular dimensions in the recently published one-year follow-up were made (1).
The placebo effect can be described as the sum of the treatment effect and the true placebo. The placebo effect by pacemaker implantation was described by us in 1999 in a study with similar crossover design as the present and of patients paced for hypertrophic obstructive cardiomyopathy (5). Like in the MUSTIC trial, long-term follow-up demonstrated a sustained beneficial effect on both objective and subjective parameters (4,5). The placebo effect has been shown to fade by time, rarely lasting more than six months. For the MUSTIC study, sustained two-year benefits by biventricular pacing in both groups of patients (6,7) have been reported. Therefore, we strongly believe that the observations found in the present study reflect the treatment effect induced by biventricular pacing rather than the placebo effect.
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References
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1. Linde C, Leclercq C, Rex S, et al. Long-term benefits of biventricular pacing in congestive heart failure. results from the MUSTIC (Multisite Stimulation In Cardiomyopathy) study. J Am Coll Cardiol. 2002;40:111–118[Abstract/Free Full Text]
2. Cazeau S, Leclercq C, Lavergne T, et al. Clinical effects of multisite biventricular stimulation in heart failure patients without conventional indication for cardiac pacing. N Engl J Med. 2001;334:873–880
3. Leclercq C, Linde C, Cazeau S, et al. Sustained clinical efficacy of biventricular pacing in patients with advanced heart failure and stable sinus rhythm. 2-year follow-up from the MUSTIC (Multisite Stimulation in Cardiomyopathy) study. Pacing Clin Electrophysiol. 2002;24:601A
4. Leclercq C, Linde C, Cazeau S, et al. Long-term (2-year) clinical results of permanent biventricular pacing in patients with advanced heart failure and chronic atrial fibrillation. Results from the (Multisite Stimulation in Cardiomyopathy) study. Pacing Clin Electrophysiol. 2002;24:716A
5. Linde C, Gadler F, Kappenberger L, Rydén L. Does pacemaker implantation carry a placebo effect? Am J Cardiol. 1999;83:903–907[CrossRef][Medline]
6. Gadler F, Linde C, Kappenberger L, et al. Significant improvement in quality of life following atrioventricular synchronous pacing in patients with hypertrophic obstructive cardiomyopathy. Eur Heart J. 1999;20:1044–1050[Abstract/Free Full Text]
7. Kappenberger L, Linde C, Daubert C, et al. Clinical progress after randomised on/off pacemaker treatment for hypertrophic obstructive cardiomyopathy. Europace. 1999;1:77–84[Abstract/Free Full Text]
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References