Cardiomyoplasty is a method for managing patients with dilated cardiomyopathy. We evaluated the means of carbon fiber electrode stimulation of the nerve to the latissimus dorsi muscle (LDM) in dogs to increase skeletal muscle contractility. Histochemical examination of biopsies of muscle electrically conditioned by a single pulse stimulator via the thoracodorsal nerve demonstrated transformation of muscle into fatigue resistant slow fibers without damage to muscle or nerve tissue. Canine experiments confirmed that carbon fibers are one of the best electrodes for chronic LDM stimulation. Between 1988 and 1992, we operated on ten patients, New York Heart Association (NYHA) Class III (4 patients) and Class IV (6 patients), with a mean left ventricular ejection fraction (LVEF) of 23%. The indications for cardiomyoplasty were idiopathic (7 patients) and ischemic (3 patients) cardiomyopathy refractory to maximum medical therapy. The operative procedure was performed via median sternotomy (5 patients) and left thoracotomy (5 patients). There was one operative mortality and two additional deaths during the late follow-up period. The mean postoperative LVEF increased to 27%. Functional class, quality-of-life, and ventricular performance were improved after cardiomyoplasty. Two of the surviving patients are in NYHA Class I, four in Class II, and one in Class III.

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To improve electrode construction the following main problems have been considered: (1) reliable initial fixing in the endocardium, and (2) reducing the area of contact surface and improving threshold values. In this article we have described three original electrodes: 1) an endocardial electrode with a multi-edged tip (contact area 28 mm2), which gives high electric field strength and low thresholds; 2) a spreading tip electrode, which was created on the basis of morphological data. The tissues grow into the spread spaces of this tip and ensure better stability (contact area 17.8 mm2); and 3) a double-screw-in electrode which differs from the other corkscrew types. The contact end (surface area--10.4 mm2) consists of two sickle-shaped hooks. The sickle handle is 0.7 mm in length which prevents further hook penetration in the wall of the heart. It was found that a multi-edged electrode and electrodes supplied with a fixation device are, in terms of energy consumption, more effective compared to electrodes with spherical or cylindrical tips of the same area of contact surface. The double-screw-in endocardial electrode has useful features: reliable fixation and a small contact surface area and, therefore, a low threshold value. Thirty-five double-screw-in electrodes were inserted into an atrial position and 28 into a ventricular position. We have not observed any displacement of such electrodes during the past two years.

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