Associate Professor of Surgery, Division of Cardiothoracic Surgery University of Pennsylvania Philadelphia, Pennsylvania
AN ALTERNATE FORM OF cardiac assistance is known as dynamic cardiomyoplas-ty (DCMP), a promising but un-proven surgical treatment for patients with end-stage heart failure (Fig. 11.5). The procedure was first performed in a human by Drs. Alain Carpentier and Juan Carlos Chachques of Paris, France, in 1985.
It involves freeing up a back muscle called the latissimus dorsi. The main blood supply and nerve supply are left intact. The muscle is then placed inside the chest and wrapped around the heart, where it is stimulated with a pacemaker for several weeks to make it more fatigue resistant. After this period, the muscle is stimulated with a special type of pacemaker so it contracts in synchrony with the heart in hopes of helping the function of the patient's own failing heart muscle.
Over the last fourteen years, more than one thousand patients worldwide have had dynamic cardiomyoplasty performed. The
vast majority have demonstrated substantial improvement in symptoms of heart failure.
Despite this dramatic improvement, however, consistent evidence of improvement in heart function has not been found. Also, there is no good evidence that patients undergoing this procedure live longer than similar patients who have not had dynamic cardiomyoplasty. Lack of clear survival advantage and ongoing misunderstanding of the procedure's mechanism of action has so far hindered dynamic cardiomyoplasty's ac ceptance as a treatment alternative for patients with end-stage heart failure.
In more than six hundred cardiomyoplasty patients implanted with Medtronic electrical stimulators, clinical improvement in signs and symptoms of heart failure has been noted in 80 percent to 85 percent of surgery survivors. Improvement in symptoms of heart failure usually begins within the first six months after the surgery. In addition, the number of hospitalizations for heart failure decrease. A similar clinical improvement was found in a Phase II trial of cardiomyoplas-ty in the United States conducted under the auspices of the FDA.
During the recently completed Phase III trial, patients undergoing cardiomyoplasty had an operative mortality of less than 3 percent.
Today, the sickest patients who have heart failure symptoms at rest or who are confined to bed or to sitting in a chair are considered at too high a risk for
cardiomyoplasty, so those patients are more likely to be referred for a heart transplant.
The Phase III randomized, clinical trial, again under the auspices of the FDA, commenced in June 1995 and was finished near the end of 1998. Slightly more than one hundred patients entered the study. It was a study designed to determine the safety of cardiomyoplasty as a treatment for heart failure due to dilated cardiomyopathy or ischemic cardiomyopathy (secondary to coronary artery blockages). In both dilated cardiomy-opathy and ischemic cardiomy-opathy, the main problem is that the heart muscle itself is failing. The study was designed to provide a clearer picture of the role of cardiomyoplasty as a treatment alternative for patients with endstage heart failure.
Legitimate doubts about the efficacy of dynamic cardiomy-oplasty remain. Although patients improve and have less severe symptoms of heart failure, no consistent improvement in heart function or survival benefit has been demonstrated.
Although many heart failure patients can be managed effectively with medicine alone, there are clearly many other patients receiving medical therapy whose quality of life and exercise capacity have worsened yet who are not sick enough to be considered for transplantation. It is clear that a more potent treatment alternative for these patients must be sought. Unfortunately, recruitment into this Phase III randomized trial, which perhaps would have been the definitive study, was too slow to allow definitive data to be collected.
With the trial's termination in the United States, cardiomy-oplasty's potential clinical benefit may never be totally known. Its ultimate role in the treatment of heart failure depended on the outcome of a properly designed, controlled study with a minimum of four hundred patients. Clinical cardiomyoplasty has ceased being done in the United States, although in Europe, the procedure is still performed. The lessons learned from cardiomy-oplasty, however, may still prove to be of greater significance.
A similar surgical procedure, in which the skeletal muscle is wrapped directly around the aorta, is called aortomyoplasty (Fig. 11.6). This operation has been performed in more than twenty-eight humans worldwide and shows some promise.
The difference between aor-tomyoplasty and cardiomy-oplasty is that the latissimus is wrapped around the aorta instead of the heart. In some of these procedures, it has been wrapped around the ascending aorta just as it comes out of the heart. In other procedures, it's wrapped around the descending aorta after the major blood vessels to the head and to the upper extremities branch off it.
Because the two procedures work on different parts of the anatomy, the muscle is trained to contract at different times. In car-diomyoplasty, the muscle is stimulated to contract at the same time as the heart ventricles. In aortomyoplasty, the latissimus muscle is stimulated to contract while the heart ventricles are relaxing. If the muscle was stimulated to contract to compress the aorta at the same time the heart ventricles were contracting, it would be working against the heart because they'd both be trying to pump blood in different directions at the same time.
One advantage this procedure has over cardiomyoplasty is that the sick heart itself does not need to be manipulated. In some cases, the heart is so large that the latissimus muscle can not even be wrapped around it. In this case, cardiomyoplasty would not be performed, but an aortomyoplasty could be performed.
Although there are reports that patients with failing hearts have benefited from this procedure, it should be considered experimental, particularly until more long-term information is obtained.
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