Effects of isoflurane on conduction velocity and maximum rate of rise of action potential upstroke in guinea pig papillary muscles.

This study was undertaken to determine whether isoflurane, a volatile anesthetic that is reported to possess a wide margin of cardiovascular safety, exerts electrophysiological effects on cardiac tissue. By use of standard microelectrode techniques, effects of isoflurane on the maximum rate of rise of action potential upstroke (Vmax) and conduction velocity were examined in guinea pig papillary muscles. Isoflurane decreased action potential amplitude and action potential duration in a concentration-dependent fashion. Isoflurane at 1.5 and 2.0 MAC decreased conduction velocity with as little influence on the maximum rate of rise of action potential upstroke as that exerted by halothane and enflurane. However, the effect of isoflurane in slowing intraventricular conduction was less than that of halothane and enflurane when compared at equi-MAC concentrations. Thus, isoflurane may be a safer anesthetic for the patients with intraventricular conduction abnormalities.