The sequence of normal ventricular recovery.

Abstract Functional refractory periods (FRP's) were measured at epicardial, intramural, and septal sites in pentobarbital anesthetized dogs. The sinus node was crushed and the atria were driven at a fixed rate. Activation times at the test sites were measured from electrograms recorded from closely spaced bipolar electrodes. The test stimuli were cathodal “make” stimuli delivered to one pole of the pairs of electrodes. FRP's at the base of the free wall of the left ventricle and of the septum were shorter than FRP's at the apex. FRP's on the epicardium were shorter than those on the endocardium, and FRP's on the right side of the septum were shorter than those on the left side of the septum. The findings indicate that normal ventricular recovery properties are systematically distributed and inversely related to activation sequence. Areas of the ventricle activated early have the longest FRP's, and areas activated late have the shortest FRP's. This distribution of recovery properties tends to make all portions of the ventricles complete recovery at about the same time, and may play a protective role in the prevention of reentrant arrhythmias. This distribution of recovery properties is also applicable to an explanation of the configuration of normal T waves.