Effect of pacing duration on right ventricular effective refractory period in man

This study was performed to assess the dependence of the effect of the duration of stimulation on the effective refractory period (ERP). ERP was determined in 12 patients after four consecutive stimuli as well as after continuous stimulation for 1 min applying a constant stimuli interval of 600 msec. After 1 min stimulation all patients showed a significant (P less than 0.01) decrease of the ERP with 236 +/- 23 SD msec in comparison to the ERP of 271 +/- 26 SD msec after four consecutive stimuli. Although it is well established that ERP depends on the previous cycle length, it is additionally influenced by the stimulation duration, as shown in this study. This must be considered when ERP or other electrophysiological parameters of the right ventricle are investigated.