抄録
A battery-type automatic defibrillator with temporary pacing function has been developed. The pacing function is activated after defibrillation to work as a high-output ventricular demand pacemaker. To minimize the number of circuit devices and battery size, the output circuit of the implantable defibrillator, which has been developed by our group using a gate turn-off thyristor, has been improved and a small size oscillator has been added to the pacing circuit for the defibrillator. Moreover, the residual energy in the output capacitor has been used after the defibrillation for the high-output pacing.
The developed system has been tested in animal experiments. Three mongrel dogs were anesthetized with pentobarbital and mechanically ventilated. After thoracotomy, a catheter type blood pressure sensor was inserted into the right ventricle through the right auricle, and a catheter, which has two electrodes made of stainless steel (surface area of 260mm2 and 100mm apart), was introduced through a jugular vein into the apex of the right ventricle. The catheter was used for both defibrillation and pacing.
In the animal experiments, fibrillation was electrically induced, and the automatic defibrillation and pacing function were confirmed. After defibrillation, as the high-voltage converter did not work during the pacing, the capacitor voltage in the defibrillator decreased exponentially. However, it was possible to continue the fixed-rate pacing (60ppm) for more than three minutes after defibrillation. The main reason for the decreasing voltage was due to the voltage measuring resistor (1MΩ), connected to the capacitor in parallel. The pacing pulse was inhibited during sinus rhythm using blood pressure signal.
From the results, it was possible to accomplish pacing function using residual energy after defibrillation by improvement and addition of the circuit in the defibrillator.
