[Influence of exercise on the permeability of accessory pathways and supraventricular arrhythmia in Wolff-Parkinson-White syndrome].

The influence of adrenergic stimulation on the effective anterograde refractory period of the accessory pathways and on supraventricular arrhythmias, was studied in 20 patients (average age 38 +/- 16 years) with an untreated permanent Wolff-Parkinson-White syndrome and a resting anterograde refractory period < or = 400ms. Repeated electrophysiological studies with a single endocavity catheter positioned near the atrial pole of the accessory pathway were performed under basal conditions and during a standardised exercise test on a bicycle ergometer. The effective anterograde refractory period of the accessory pathway, the length of the tachycardia cycle during reciprocating orthodromic tachycardia, the average heart rate, the percentage of preexcited QRS complexes during induced atrial fibrillation, were measured in all patients under basal conditions and at the peak of exercise. Exercise significantly reduced the anterograde refractory period of the accessory pathway (287 +/- 49 ms at rest versus 238 +/- 24 ms on exercise: p < 0.001), the cycle of orthodromic tachycardia (302 +/- 32 vs 260 +/- 22 ms p < 0.001), the minimal R-R interval (270 +/- 65 vs 227 +/- 46 ms: p < 0.05) and % of preexcited QRS complexes (75 +/- 33 vs 51 +/- 39: p < 0.05) in atrial fibrillation whilst increasing the average heart rate (165 +/- 42 vs 202 +/- 39 bpm: p < 0.02). Adrenergic stimulation significantly improves anterograde conduction in the accessory pathway. The reduction in the % of preexcited QRS complexes in atrial fibrillation could indicate a preferential action of catecholamines on the nodo-hisian pathway.(ABSTRACT TRUNCATED AT 250 WORDS)