Slow recovery of the maximal rate of rise ($\dot V_{max}$) of the action potential in sheep cardiac Purkinje fibers

Abstract

Measurements of the maximal rate of rise ($\dot V_{\max }$) of the action potential in cardiac Purkinje fibers were made at different intervals following an action potential or a long-duration depolarization. Recovery of$\dot V_{\max }$ is fast after a short depolarization but is composed of a fast phase and a very slow phase (time constant order of 1 s) after a long-duration depolarization. The existence of a slow phase in the recovery explains the shift of the ($\dot V_{\max }$ - E_m) relationship to negative potentials in fibers with reduced resting potential.