EXPERIENCE WITH INDUCTIVE COUPLED CARDIAC PACEMAKERS

I n June, 1960, Ahrams, Hudson, and Lightwood' reported the use of the inductive coupled cardiac pacemaker for the treatment of three patients with complete heart block. T h e method is illustrated in FIGURE 1. A pulse generator is attached by a flexible lead to a n external primary coil that is strapped to the skin over the implanted secondary coil, the ends of which are the myocardial electrodes. The pulse in the primary coil produces a pulse in the secondary coil by simple electromagnetic induction. The secondary coil consists of a thousand turns of 38 gauge standard copper wire wound to form a ring with a n inner apperture of 2 cm. The ends of the wire are welded to braided No. 26 gauge stainless steel leads armed with atraumatic needles. The coil and leads are covered by silicone rubber. The appearance of these coils in a patient is shown in FIGURE 2, which is a lateral chest X-ray taken six days after the operation. T h e lead from the pulse generator is seen going to a solid external coil that overlies the subcutaneous ringshaped secondary coil. The secondary coil must be firmly fixed in a position in which it has a stable base. I n patients who are not fat the best place is o n the front of the left third intercostal space, but if there is a considerable depth of subcutaneous fat the internal coil is placed on the front of the sternum. The leads are laid in a full turn around the coil before being passed back through the intercostal space to the heart, which is exposed through a n anterior fourth space thoracotomy. The silicone rubber can be peeled off the stainless steel wire so that the right length to form a sweeping curve between the chest wall and the area on the heart chosen for the implantation of the electrodes can be used. The electrodes are fixed by taking three one centimeter bites with the atraumatic needle so that they all fall in a n area of myocardium about 1 cm. by 0.6 cm. The insulation is pulled right up to the muscle, and none of the wire should show through the surface. The excess wire is cut off under slight tension so that the end retracts into the myocardium; thus the lead itself forms the electrode. A patch of Teflon felt, 2.5 cm. long by I cm. wide, is sutured to the heart, covering the area containing the electrode and holding the first centimeter of the insulated lead. FIGURE 3 shows the internal wires in the postero-anterior X-ray. The loop at the end is the buried wire. FIGURE 4 shows the patient on the sixth postoperative day wearing his coil and pacemaker. The strapping on the lower part of the chest covers temporary thin, braided wire, direct pacemaking electrodes, which are always put in so that direct pacemaking can be used while any postoperative swelling and tenderness settles down and the patient becomes accustomed to the use of the inductive coupled system. This patient, who was 41 and had had many Stokes-Adams attacks every