INTRODUCTION Fasciculoventricular (FV) pathways are rare variants of preexcitation, and their ECGs may be misinterpreted as Wolff-Parkinson-White syndrome with anteroseptal accessory pathways (WPW-AS). We analyzed the electrocardiographic characteristics of the patients with FV pathways to find out the different findings from WPW-AS.

METHODS AND RESULTS Five patients with FV pathways and four patients with WPW-AS who underwent electrophysiologic studies were evaluated. Intervals and amplitudes of each wave and QRS morphologies were analyzed in standard 12-lead ECGs of these patients by two independent cardiologists without the information of the electrophysiologic findings. PR intervals were longer in FV pathways (122 +/- 11.0 vs 83 +/- 21 ms, FV pathways vs WPW-AS, P = 0.017). In lead V1, narrower width of R waves (25 +/- 6 vs 45 +/- 13 ms, P = 0.037) and smaller amplitude of S waves (12.8 +/- 8.3 vs 26.6 +/- 7.4 mm, P = 0.037) were observed in FV pathways. The polarity of delta waves in V1 was flat or negative in contrast with the cases of WPW-AS in which the polarity was positive. Three of five patients had notching in the descending limb of S waves in V1, which was not observed in WPW-AS.

CONCLUSION FV pathways have different ECG characteristics from WPW-AS in PR interval and morphology of QRS complexes in lead V1 of the standard 12-lead ECG.