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Paced skeletal muscle for dynamic cardiomyoplasty
G J Magovern1, F R Heckler, S B Park
1Department of Surgery, Allegheny General Hospital, Pittsburgh, PA 15212.
Insights
Left latissimus dorsi (LD) muscle flaps can be conditioned to improve cardiac function after myocardial infarction. Electrical conditioning transforms skeletal muscle into fatigue-resistant fibers, enhancing heart repair in some patients.
Area of Science:
- Cardiovascular Surgery
- Regenerative Medicine
- Skeletal Muscle Physiology
Background:
- Patients with myocardial infarction and diffuse coronary artery disease often develop heart failure.
- Surgical interventions aim to restore cardiac function and improve patient outcomes.
- The left latissimus dorsi (LD) muscle flap is a potential autologous graft for cardiac repair.
Observation:
- Four patients with myocardial infarction underwent LD muscle flap application to the left ventricle.
- Muscle conditioning, either pre- or post-operatively, was performed to enhance flap viability and function.
- Biopsies confirmed transformation of skeletal muscle to fatigue-resistant type I fibers within 6-10 weeks.
Findings:
- Three patients showed improved ejection fraction post-procedure, particularly when paced.
- Doppler echocardiography confirmed flap function in both paced and non-paced states.
- One patient experienced flap failure due to infection, leading to death from ventricular arrhythmia.
Implications:
- Electrically conditioned LD muscle flaps show potential for improving cardiac function in select patients.
- This technique may offer a novel therapeutic approach for heart failure post-myocardial infarction.
- Further research is needed to optimize patient selection and surgical techniques to mitigate risks like flap failure.
Abstract:
Four patients, each with a history of myocardial infarction and diffuse coronary artery disease, underwent application of left latissimus dorsi (LD) muscle with intact neurovascular bundle to the anterolateral wall of the left ventricle. The muscle was conditioned over a six-week period subsequent to operation in 3 patients and was conditioned preoperatively with a burst stimulus in the fourth. Biopsy specimens confirm the experimental data that human skeletal muscle can be electrically conditioned over a six- to ten-week period to contain mainly fatigue-resistant type I fibers. All patients survived the procedure, and 3 showed improvement secondary to aneurysmectomy. In Patient 1, a modified resection was performed, and at 28 months after operation, at the 75-W level of exercise, the ejection fraction was 54% paced versus 45% nonpaced. In Patient 2, at 12 months, the ejection fraction at rest was 44% paced versus 30% nonpaced. Doppler echo studies confirmed the presence of the flap and its function in the paced and nonpaced mode. The third patient died of a sudden ventricular arrhythmia 2 months following operation. An infected, nonfunctioning, degenerated flap was found at autopsy. Patient 4 did not have an aneurysm. She received a bypass graft to the right coronary artery and underwent cardiomyopexy in an attempt to relieve medically refractory incapacitating chronic congestive heart failure. Ten months postoperatively, ejection fraction at rest was 33% paced versus 25% nonpaced. Constrictive myopathy has not been encountered in any of these patients.