A simple microcomputer-controlled device for automated measurement of refractory period of excitable tissue

A computer-controlled tissue stimulator interface will be described. This device can generate a basic train at a predetermined rate. An extra pulse is introduced after a selected number of pulses. The initial latency of this extra pulse is shorter than the tissue refractory period. The latency is increased, automatically, until the tissue produces a conducted response. This is made possible by the computer checking the tissue response. The device is inexpensive and can be readily controlled by any 8 bit microcomputer, such as the Commodore PET or VIC-20. The use of a signal conditioner has been discussed. Such a circuit facilitates detection of the often slowly occurring action potential of the premature beat riding on the repolarization phase of the normal action potential.