0048: A long accessory pathway refractory period measured by oesophageal atrial stimulation is always associated with a benign form of preexcitation syndrome

Abstract

Measurement of accessory pathway (AP) refractory period (RP) is required for the evaluation of preexcitation syndrome (PS). The purpose of study was to evaluate the measurement of AP-RP by transesophageal electrophysiological study (EPS) and intracardiac EPS. EPS was performed in 51 patients aged from 13 to 50 years (mean 30±16) for a PS. Atrial stimulation was performed in control state (CS) at a cycle length of 400ms and coupling was decereased until AP6RP or atrial RP. Measurement was repeated after isoproterenol when AP-RP≥250ms in CS. Measurement was performed by transesophageal route and then by intracardiac route, with a delay not >3 months. AP-RP’s were 267±50ms in CS, 233±49ms after isoproterenol at transesophageal EPS, 309±72ms in CS, 280±64ms after isoproterenol at intracardiac EPS (p<0.002). Among 31 patients with initially AP-RP ≥250ms at transesophageal EPS, AP-RP was ≤220ms after isoproterenol in 12 patients. All, but one had an AP-RP≥250ms in CS at intracardiac EPS; one patient with AP-RP of 270ms at esophageal EPS had a value of 240ms at intracardiac EPS in CS but value was 250ms after isoproterenol. Three patients with transesophageal AP-RP in CS and after isoproterenol ≥280ms had lost their anterograde conduction. At transesophageal EPS, AP-RP was <250ms in 20 patients of which only 8 had a short AP-RP at intracardiac EPS and 3 had a short AP-RP after isoproterenol. There was no significant difference for the induction of orthodromic tachycardia at transesophageal and intracardiac EPS (72%) and there was a similar induction of atrial fibrillation at transesophageal EPS (32%) and intracardiac EPS (28%). A long AP refractory period measured at transesophageal EPS excluded the presence of an AP with a short refractory period at intracardiac study even after isoproterenol. There was an adrenergic factor during transesophageal EPS and isoproterenol produced a significant shortening of AP refractory periods in only 39% of patients with AP-RP ≥250ms. When AP-RP is ≥280ms at transesophageal EPS, the loss of anterograde conduction in AP can be expected in the following weeks (15%).