A METHOD OF TESTING IMPLANTED CARDIAC PACEMAKERS

Abstract

In some patients with complete heart block electrical pacing has become an accepted form of treatment, and this has been well reviewed (Chardack, Gage, and Greatbatch, 1960; Chardack 1964; Zoli et al., 1961; Portal et al., 1962). The quoted battery life of pacemakers available co-mercially is from 2 to 5 years. However, experience with our first 10 cases has shown that earlier replacement of the units is sometimes necessary because of premature battery failure and either gradual or sudden failure of another component. These failures cause changes in one or more of the following output characteristics of the pacemaker: rate, amplitude, and pulse width. Measure-ment of these characteristics is easily made with the pacemaker outside the body, but after the unit is implanted this presents some difficulty. Pulse rate of the unit can be obtained from the electro-cardiogram, but output voltage and pulse width are more difficult to measure. One commercial model * provides two subcutaneous testing electrodes to which needles can be attached under local anmsthetic, but it is possible for these wires to break while the unit is functioning correctly (Par-sonnet et al., 1963). The standard electrocardiogram from a patient with an implanted pacemaker shows the stimu-lating pulses (Fig. 1), but their wave form is not accurately reproduced because of the limited fre