Externally Rechargeable Cardiac Pacemaker

Abstract

otally implantable cardiac pacemakers currently available are powered by self-contained mercury batteries having a relatively T short life. T h e estimated period of useful function is not inore than five years, and experience has shown that actual lifetime may be much less than this [3, 7, 151. This means at least another operative procedure to replace the battery, with the attendant risk of infection and, probably, recurrent cardiac arrhythmia such as heart block or tachycardia. Older patients can therefore anticipate several replacements, and the child with surgically produced heart block could expect more than ten replacements in the course of a normal human life span. With the intent of extending the period between required replacements or of completely eliminating the necessity of replacement, an experimental model of a constant-rate pacemaker using rechargeable nickel-cadmium batteries has been developed. This type of battery can be completely sealed with no danger of leakage and may be repeatedly recharged without damage. Power to recharge the batteries is supplied by induction from an externally produced magnetic field. This magnetic field can pass through tissue and clothing unattenuated [ l , 81. This principle was used earlier by Elmqvist and Senning in 1959 to construct a rechargeable unit [5] but problems arose in its clinical application [ l l , 121. Current technology and improved methods of pacemaker manufacture may now overcome the obstacles encountered previously. T h e pacemaker package contains the additional circuitry necessary to convert the magnetic field into useful charging current and to give