Despite great advances in recent years, drugs can improve heart failure, but do not stop its progression. Among the surgical options for drug-resistant heart failure, heart transplantation is the treatment of choice, but application is limited by donor shortage. Alternative procedures include partial left ven-triculectomy, mitral valve surgery, and dynamic cardiomyoplasty.
Dynamic cardiomyoplasty is the technique by which autologous skeletal muscle, usually the left latissimus dorsi, is wrapped around the left ventricle to contract in systole. The plasticity of skeletal muscle enables it to be trained and transformed into fatigue-resistant tissue by chronic electrical stimulation. This is achieved by gradually increasing the frequency and duration of electrical stimulation impulses. For the first 2 weeks after operation, the muscle is left unstimulated to allow adhesions to develop between muscle and epi-cardium, and residual seroma and muscle edema to resorb. From postoperative weeks 3 to 10, muscle stimulation is gradually increased in weekly increments until the muscle receives a complete burst with six single impulses. Burst stimulation timed to coincide with the closure of the mitral valve determined by M-mode echocardiography causes tetanic contraction of the skeletal muscle.
Patients with ischemic or dilated idiopathic cardiomyopathy and severe left ventricular dysfunction are eligible for dynamic cardiomyoplasty. At operation, they should be in New York Heart Association (NYHA) functional class III. Those permanently in NYHA class IV and possibly receiving inotropic or mechanical support have a high risk of dying from the procedure and should not be submitted to cardiomyoplasty because they may not be able to wait 10 weeks for the procedure’s potential benefit. Additional eligibility criteria are recurrent hospitalization, peak exercise oxygen uptake <16 mL/kg/min, left ventricular ejection fraction <30%, cardiac index <2.5 L/min/m2 at rest, a high left ventricular filling pressure, and sufficient stability on medical therapy to withstand a wait of 2 to 3 months before effective muscle flap adaptation. Left ventricular aneurysm is a further eligibility criterion. Absolute contraindications include severe valvular dysfunction, concomitant degenerative muscle disease, left ventricular thrombus, myocarditis, coexisting disease conferring high surgical risk, severe pulmonary hypertension, and biventricular failure. Cardiomyoplasty may decrease vital lung capacity by 10% to 20%, which must be taken into account in the presence of significant pulmonary dysfunction. In patients with a history of ventricular tachycardia or ventricular fibrillation, cardiomyoplasty is combined with the implantation of an implantable cardioverter defibrillator.
Preservation of the latissimus dorsi muscle is important in the success of the procedure. Ischemia of the skeletal muscle flap may partially or totally suppress the contraction response to electrical stimulation. An excessive increase in creatine kinase levels in the immediate postoperative period indicates ischemia and a poor patient prognosis.
There have been few randomized comparisons of cardiomyoplasty vs conventional medical therapy or transplantation. Nonrandomized data suggested that cardiomyoplasty improves functional class and quality of life. The Medtronic Multicenter trial found that cardiomyoplasty improved the functional class of most patients. This has been confirmed by other studies. Hemodynamic benefits are less consistent. Improved stroke volume and stroke work indices were observed with decreased pulmonary pressures. However, most studies found no significant effect of cardiomyoplasty on the ejection fraction, or small improvements only. It should be noted that the predominant improvement in NYHA class following cardiomyoplasty is not necessarily incompatible with the hemodynamic results as there are no correlations between functional status, exercise capacity, and left ventricular ejection fraction in severe congestive heart failure.
The absence of completed randomized trials precludes conclusions about the influence of cardiomyoplasty on long-term survival. The first randomized study, the Cardiomyoplasty Skeletal Muscle Assist Randomized Trial (C-SMART), comparing cardiomyoplasty with medical treatment, was scheduled to recruit 400 patients, but recently had to be terminated due to patient recruitment difficulties. Data analysis in 51
patients undergoing cardiomyoplasty vs 52 patients on medical treatment showed an improved 6-min walk test distance, NYHA functional class, and other quality of life parameters (Minnesota Living with Heart Failureâ„¢ Questionnaire) in the cardiomyoplasty group. There was no observed difference in 6-month survival (cardiomyoplasty: 86%; medical treatment: 84%), peak V02, or left ventricular ejection fraction improvement.
Thus, clinical experience indicates that dynamic cardiomyoplasty can produce symptomatic improvement in a small percentage of patients in NYHA class III heart failure, while having no significant effect on hemodynamics or mortality. Randomized trials should determine whether dynamic cardiomyoplasty also decreases mortality, and clarify whether the functional improvement is sustained or transient. Generally speaking, however, initial enthusiasm over the procedure has recently cooled to the extent that it is no longer considered a promising alternative option to heart transplantation in severe heart failure.
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management; cardiomyoplasty; surgical option; indication; contraindication; trial