Experience with Implanted Pacemakers: Technical Considerations.

Between April 1960 and September 1964, 79 patients were treated with implanted pacemakers. We record here the technical difficulties encountered and the steps taken to overcome them. In all cases the indication for artificial pacing was failure of medical treatment to prevent Stokes-Adams attacks or to relieve cardiac failure due to a slow pulse. Most, but not all, patients were in complete heart block. Fuller clinical details are being published elsewhere (Harris, Bluestone, Busby, Davies, Leatham, and Siddons, in press). Throughout the period under consideration (up to 30 September 1964) 143 pacemakers were implanted in these 79 patients. The first two were of Swedish make*. but subsequently pacemakers designed by one of us (J.G.D.) have been used exclusively, some of them having been made in the electronics department of St. George's Hospital and some to our designt. In treating 19 of our early patients a number of prototype units were tried, some from outside with only a receiver unit implanted, and others containing their own battery for power; some could be turned on and off, speeded up, and slowed down from outside. However, as a result of experimental work done in this hospital (Sowton, 1963), an early decision was taken to concentrate on the development of a fixed-rate pacemaker powered by miniature mercury cells within the implanted unit. There was no time for prolonged laboratory or animal trials since patients with complete heart block in whom Stokes-Adams attacks threatened life required pacing without delay. Thus it has proved necessary to modify the apparatus as faults revealed themselves during clinical use (see Table 1). The earliest patients were treated with a pacemaker implanted in the rectus sheath with wires leading to the surface of the heart (epicardial system) (Fig. 1). A high proportion developed sinuses and many of the pacemakers had to be taken out. Before this complication reached serious propor-