The rapid generation of strength-interval curves under computer control.
A system was developed to allow for the rapid evaluation of myocardial excitability and conduction in canine preparations. The stimulus strength required to excite a propagated response, as a function of time since the last depolarization, can be summarized by a strength--interval curve. Our system generates strength-interval curves under computer control with high accuracy and efficiciency. The conduction time of each ventricular response is also determined. At a heart rate of 2.5 Hz, the average time for curve generation is 94 s, an efficiency which is 85% of the theoretical maximum. This system has been employed in over 120 dogs to generate strength--interval curves during rapidly changing periods of myocardial ischemia and during interventions with various drugs.
D000818:Animals; D003201:Computers; D004285:Dogs; D004594:Electrophysiology / Q000295:instrumentation*; D006329:Heart Conduction System / Q000502:physiology*; D008991:Monitoring, Physiologic / Q000295:instrumentation*