Activation Mapping and Functional Properties of Single Premature Ventricular Beats in Asymptomatic Patients: Electrophysiologic Evidence of Supernormal Conduction and Latency

Abstract

Conduction times (CT) of single premature ventricular beats (PVBs) delivered at the right ventricular apex (RV A) and outflow tract (RVOT) were measured at different right ventricular sites in seven asymptomatic patients during sinus rhythm. CT were similar during RVA and RVOT stimulation. Ventricular conduction curves were constructed by plotting coupling interval against CT at all recording sites (including that close to the stimulation site). Two types of curves were observed: in type I, CT of PVBs was constant until 35–105 msec before the effective refractory period, when a progressive delay of appearance of activation was observed at all recording sites; this phenomenon was called latency and was observed in all patients. In type II curve, a decrease of CT of PVBs with a coupling interval ranging between 470 and 320 msec was observed and lasted 50–150 msec; this phenomenon was thought to represent supernormal conduction, and was observed in four patients. We concluded that in asymptomatic patients: 1. homogeneity of right ventricular endocardial activation of single PVBs is independent of site of origin and coupling interval; 2. latency, not conduction delay, is responsible for the delayed appearance at distant sites of early PVBs; 3. supernormal conduction can be observed in the right ventricle.