Prolongation of conduction time during premature stimulation in the human afrium is primarily caused by local stimulus response latency

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Abstract
Conventional clinical electrophysiological techniques cannot accurately differentiate between local stimulus response latency and propagation time of the atrial response. The purpose of this study was to identify and distinguish local stimulus response latency from impulse propagation time in the human right atrium during programmed electrical stimulation. Pacing was performed from two atrial sites (high and low right atrium) in 19 patients, using monophasic action potential recording/pacing combination catheters (interelectrode distance PP<0.0001). The impulse propagation time between the stimulation site and the remote recording site was on average 54.5 ± 14.3 ms during basic stimulation, and increased up to 62.1 ± 13.5 ms (14.0 ± 8.4%), which was not significant. The intra-atrial impulse propagation remained essentially unchanged during the entire range of premature stimulation. Local stimulus response latency was negligible and constant during late coupling intervals but increased dramatically when extrastimulation approached the preceding repolarization phase. This has the following clinical impact: first, local stimulus response latency during premature extrastimulation curbs the targeted a trial response interval; second, local stimulus response latency, not propagation time, seems responsible for the greater functional than effective refractory period during electrical stimulation; third, local stimulation; response latency should be considered in pace mapping for accurate comparison of conduction time before pacing with that during pacing.

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