A portable microprocessor-based triggering device for cardiac muscle electrical stimulation.
We describe a microprocessor-based programmable triggering instrument designed to control the distribution in time of electrical stimuli delivered to a heart muscle preparation. Sequences of stimuli may be selected among those stored in the non-volatile memory of the instrument and new sequences may be programmed using a repertory of 25 commands. The instrument was used to study the inotropic effects of three irregular sequences of stimuli applied to the isolated rat left atrium. The mean peak tension developed by the tissue was unaltered by stimulus sequence, provided the mean stimulatory frequency (2 or 5 Hz) was maintained. The instrument may be useful to study the effect of different stimulatory patterns on cardiac inotropism, as well as for controlling the electrical stimulation of other biological preparations.