Assessment of accessory pathway and atrial refractoriness by transoesophageal and intracardiac atrial stimulation

Aims Measurement of the refractory properties of asymptomatic overt accessory pathways is performed to assess the risk for significant arrhythmias. We hypothesized that a transoesophageal atrial stimulation (TAS) protocol would accurately predict simultaneously measured invasive intra cardiac stimulation (ICS) of the anterograde effective refractory period of the accessory pathway (AP-ERP) Methods and Results Fourteen single pathway Wolff-Parkinson-White (WPW) syndrome patients underwent TAS during ICS and 24 h prior to it. The AP-ERP was measured using incremental atrial extra stimuli from TAS, the right atrium (RA) and the coronary sinus (CS) using drive trains of 500 and 600 ms. Stimulus latency was measured from intracardiac electrocardiograms. For methodological comparison, Altman–Bland analysis was used to create the limits of agreement (within-patient mean of differences±two standard deviations). There were no or small differences in the AP-ERP, as assessed by TAS, compared to RA and CS. Methodological disagreement between the three sites were common, however, and the limits of agreement ranged from ±30 to±76 ms. The concordance between TAS and RA, with regards to the AP-ERP value of 270 ms, was 63% when measured as S1S2 and was 67% when measured as A1A2. The stimulation site delay was significantly shorter for TAS compared to RA and CS sites. The two TAS procedures performed a day apart, revealed a coefficient of variation of 9% and a coefficient of reproducibility of 63 ms. Conclusions Despite adequate reproducibility, TAS fails to predict the AP-ERP by ICS. Differences in stimulus latency is responsible, in part, for the disagreement. In-vasive ICS cannot be replaced by TAS for risk stratifying WPW patients.