The development of a microprocessor controlled implantable device [pacemaker]

The basic system of the rate-responsive dual-chamber Kelvin II pacemaker is described. The Kelvin-II consists of two custom integrated circuits (a micro chip and a pacer chip), a hybrid circuit, a battery, and a case. The complexity of the pacemaker required that the circuit functions be divided into two separate custom integrated circuits. The hybrid circuit holds the two integrated circuits and external components and functions as a means of connecting these components in a very small, hermetically sealed package. The pacer chip contains the pulse generator output circuitry, sense amplifiers, detectors, rate limiter, analog-to-digital converter, programming and telemetry circuitry, watchdog (continuous high-reliability testing and backup circuit), and clock circuitry. The micro chip contains a complete 8-b microprocessor, 4 kB of read-only memory, 2 kB of random-access memory, and one external port