Personal computer based software operated dual chamber cardiac stimulator

The authors describe some of the technical and algorithmical decisions which have been taken when developing a software-based external pacemaker which utilizes a standard IB AT compatible personal computer. The core of the hardware is a universal state machine which permits accurate timing of 16 internal states. The programming of the state machine enables different pacing pulses to be generated. The software part of the stimulator is composed of several program segments which create an open package. The computer communicates with the unit by means of special commands which are decoded by input circuits of the hardware unit, the communication from the unit to the computer uses parallel port interrupts. Another part of the software package implements pacing algorithms which can be operated in an interactive way