A case series of patients with poorly-tolerated arrhythmias related to a preexcitation syndrome and presenting with atypical ECG.

Unlabelled: The aim of study was to report different and unusual patterns of preexcitation syndrome (PS) noted in patients referred for studied for poorly-tolerated arrhythmias and their frequency. Electrophysiologic study (EPS) is an easy means to identify a patient with PS at risk of serious events. However the main basis for this diagnosis is the ECG which associates short PR interval and widening of QRS complex with a delta wave.

Methods: ECGs of 861 patients in whom PS related to an atrioventricular accessory pathway (AP) was identified at electrophysiological study (EPS), were studied.

Results: The most frequent unusual presentation (9.6%) was the PS presenting with a normal or near normal ECG, noted preferentially for left lateral AP and rarely for posteroseptal or right lateral location. More exceptional (0.1%) was the presence of a long PR interval, which did not exclude a rapid conduction over AP. The association of a complete AV block with symptomatic tachycardias was exceptional (0.3%) and was shown related to a rapid conduction over AP after isoproterenol. Most of the presented patients were at high-risk at EPS.

Conclusion: The diagnosis of PS is not always evident and symptoms should draw attention to minor abnormalities and lead to enlarge indications of EPS, only means to confirm or not PS.