Electrophysiologic characteristics of the Crista terminalis and implications on atrial tachycardia in rabbits

The objective of this study was to evaluate the electrophysiologic characteristics of Crista terminalis (CT) and their implication in the pathogenesis of atrial tachycardia in rabbits. For this purpose, 27 New Zealand rabbits were used. Using standard glass microelectrode technique, cellular action potentials (APs) of CT and pectinate muscle (PM) were recorded in normal Tyrode's perfusion and Tyrode's perfusion with 4 μM isoproterenol. Longitudinal conduction velocity (V(L)) and transverse conduction velocity (V(T)) of CT were measured. As our data show, CT tissue had a trend of spontaneous phase IV depolarization. Conduction anisotropy (V(L)/V(T)) of CT was 4.53 ± 0.91. The duration of the AP of CT was longer than that of PM cells. APD(20) and APD(90) for CT were 28.1 ± 3.5 and 145.3 ± 7.1 ms; and for PM cells were 21.8 ± 4.1 and 125.3 ± 6.3 ms, respectively (all P values < 0.01). The early and delayed action depolarizations were recorded after isoproterenol perfusion. A fast paroxysmal irregular rhythm was recorded which could be arrested by 0.1 mmol/l Isoptin. It was, therefore, concluded that the latent autorhythmicity, trigger activity, and conduction properties of CT might provide the electrophysiologic basis for the occurrence and sustenance of atrial arrhythmia.