INTERINDIVIDUAL AND INTRAINDIVIDUAL VARIATIONS IN SHORTENING OF VENTRICULAR EFFECTIVE REFRACTORY PERIOD AFTER AN ABRUPT DECREASE IN PACING CYCLE LENGTH

After an abrupt decrease in pacing cycle length (PCL), the ventricular effective refractory period (VERP) shortens. The pacing protocol need ed to determine accurate and reproducible values for the VERP during t his process is elaborate and time consuming. In this study, steady-sta te values of VERP at 800 and 359 msec PCL and dynamic values of VERP d ue to an abrupt change in PCL from 800 to 350 msec were determined. Th is was done for 11 different dogs to test the interindividual variatio n and repetitively in the same dog to test the intraindividual variati on. The results for steady-state and dynamic values of the VERP show a wide range for both groups. This means that accurate prediction of st eady-state and dynamic values of VERP based on previous measurements i s not possible.