Assessment of accessory pathway and atrial refractoriness by transoesophageal and intracardiac atrial stimulation - An analysis of methodological agreement

Aims Measurement of the refractory properties of asymptomatic overt accesso ry pathways is performed to assess the risk for significant arrhythmias. We hypothesized that a transoesophageal atrial stimulation (TAS) protocol wou ld accurately predict simultaneously measured invasive intra cardiac stimul ation (ICS) of the anterograde effective refractory period of the accessory pathway (AP-ERP) Methods and Results Fourteen single pathway Wolff-Parkinson-White (WPW) syn drome patients underwent TAS during ICS and 24 h prior to it. The AP-ERP wa s measured using incremental atrial extra stimuli from TAS, the right atriu m (RA) and the coronary sinus (CS) using drive trains of 500 and 600 ms. St imulus latency was measured from intracardiac electrocardiograms. For metho dological comparison, Altman-Bland analysis was used to create the limits o f agreement (within-patient mean of differences +/- two standard deviations ). There were no or small differences in the AP-ERP, as assessed by TAS, co mpared to RA and CS. Methodological disagreement between the three sites we re common, however, and the limits of agreement ranged from +/- 30 to +/- 7 6 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 R A and CS sites. The two TAS procedures performed a day apart, revealed a co efficient of variation of 9% and a coefficient of reproducibility of 63 ms. Conclusions Despite adequate reproducibility, TAS fails to predict the AP-E RP by ICS. Differences in stimulus latency is responsible, in part, for the disagreement. Invasive ICS cannot be replaced by TAS for risk stratifying WPW patients.