Nondestructive determination of pacemaker sense amplifier passband

Most artificial cardiac pacemakers incorporate sense amplifiers to detect intrinsic heart activity in order to eliminate the possibility of competition between the artificial and natural pacemakers. When artificial pacemakers fail prematurely, the failure cause should be determined so that systematic failure modes can be identified and corrected. The failure analysis of any sophisticated electronic product is difficult; failure analysis of a cardia pacemaker is complicated by the sealing technologies encountered. Because access to the circuitry of implantable devices is impeded by the packaging of the device, and because the packaging may have influenced the failure, nondestructive testing techniques must be used extensively. This paper reports on a method for nondestructive determination of the pacemaker sense amplifier with a (sin x)/x waveform to which a continuous wave sinusoid is added. The amplifier passband is characterized by increasing the frequency of the sinusoid in increments of 5 Hertz and determining the amplifier sensitivity at each step.