J Thorac Cardiovasc Surg 1995;110:1154-1155
© 1995 Mosby, Inc.
LETTERS TO THE EDITOR
Department of Cardiovascular Surgery
96 rue Didot
75014 Paris, France
To the Editor:
The invited letter by Dr. Silverman 1 regarding the results of Dr. Moreira's group after 5 years of experience with dynamic cardiomyoplasty provided a useful analysis of the study and some general comments on cardiomyoplasty. We cannot agree with his statement in the opening paragraph that the development of the technique did not conform to an idealized scientific progression. On the contrary, the evolution of cardiomyoplasty followed an unmistakable progression from observation to experimental study to clinical application. As early as the 1960s, experimental studies attempting to use the mechanical power of skeletal muscle to assist the heart are detailed, but all faced the problem of muscle fatigue. In the 1970s, Salmons and Pette demonstrated, and published in Nature and The European Journal of Physiology (Pfluegers Archives), that fatiguable fast-twitch muscle fibers could be transformed into fatigue-resistant slow-twitch fibers by slow-rate electrical stimulation. Further histochemical studies demonstrated that the metabolism of the fast-twitch muscles changed from glycolytic to oxidative, which is characteristic of slow-twitch fibers. This muscle plasticity resulted from the capacity of genes to code for various myosin isoforms. Research was initiated in our laboratory in 1980 to investigate the possibility that the same transformation could be obtained at heart frequency rates and that it could remain stable and efficient for many years. Using a goat animal model 2 and newly developed latissimus dorsi muscle (LDM) pacing electrodes and an implantable Cardio-Myostimulator device, 3 we developed the surgical technique and the concept of progressive LDM training using an original protocol of progressive sequential stimulation. 4 It is with this background of 5 years of animal experimentation in our unit, as well as several years of worldwide experimentation and observation, that the first clinical case was performed at Broussais Hospital in 1985. Despite having had the posterior wall of both ventricles replaced with an LDM flap, that patient remains well after 10 years and the flap retains fatigue-free contraction.
Current clinical experience includes 80 cases from our institution and 500 cases worldwide. The international literature is extensive; three books and more than 100 articles on basic research have been published. There is a biennial International Meeting on Dynamic Cardiomyoplasty and also an international multicentric study in conjunction with surgical centers from 15 countries. Their purpose is to evaluate results of both laboratory and clinical studies and to institute uniform protocols and postoperative schedules. Methods of evaluation continue to improve and studies involving left ventricular conductance catheters and aortic modelflow methods now demonstrate improved cardiac function 6 to 24 months after cardiomyoplasty. 5
Dr. Silverman urges participating groups to state that cardiomyoplasty may have only limited value. Jatene and Moreira 6 have previously answered Dr. Silverman on this issue, stating that their intention was not to create enthusiasm but to further present data and in the current article give reference to several studies on present limitations. In early publications Carpentier, 7 Chachques, 8 and their associates have repeatedly referred to the questionable efficiency and the future of the nascent technique. Their more recent results are more encouraging7 year's survival of 52% and hospital mortality rate of 12% between 1988 and 1995 (8/66 patients). Survival of patients with medical therapy alone in a well-matched population was significantly worse. 9
In summary, we do not agree with many of Dr. Silverman's statements regarding cardiomyoplasty. The power of contraction of the LDM is impressive, generating four times the force of cardiac muscle. The fact that it can contract without fatigue for potentially more than 10 years is a powerful stimulus for investigation and trials because of the shortage of donors for transplantation. Bearing in mind that the mean survival of the first 100 heart transplantations was 29 days, the development of dynamic cardiomyoplasty has taken great strides since its inception, both in the development of the biophysical science of adaptation of skeletal muscle and in the surgical technique. The development of cardiomyoplasty has conformed in the past to a rigorous scientific progression from observation to experimentation to patient application, 10 and it continues to conform.
This article has been cited by other articles:
G. A. Thomas, S. Isoda, R. L. Hammond, H. Lu, H. Nakajima, H. O. Nakajima, K. Greer, S. J. Gilroy, S. Salmons, and L. W. Stephenson
Pericardium-Lined Skeletal Muscle Ventricles: Up to Two Years' In-Circulation Experience
Ann. Thorac. Surg., December 1, 1996; 62(6): 1698 - 1706.
[Abstract] [Full Text]
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