title: Limiting factor for the initiation of reentrant tachycardia in concealed Wolff-Parkinson-White syndrome.
abstract: We studied the limiting factor for the initiation of reentrant tachycardia in 14 patients with concealed Wolff-Parkinson-White syndrome by comparing atrial refractoriness and echo times. When relatively late atrial premature beats (A2) were not accompanied by an atrial echo (Ae), the echo times were estimated from the antegrade A2-V2 conduction time of A2, since the retrograde conduction time via the accessory pathway remained constant regardless of the degree of prematurity. Thus, A2-Ae curves including the minimal echo time and the longest A2-Ae without Ae could be drawn in all patients. Then the curve was compared with the atrial effective refractory periods and the functional refractory periods of A2 in each patient. Atrial refractoriness which might limit the occurrence of an Ae is not that of basic beats (A1) but that of premature beats (A2). In all patients the atrial effective refractory periods of A2 were much shorter than the minimal echo time and the longest A2-Ae without Ae, suggesting that the atrial effective refractory period is not responsible for limiting the initiation of an Ae. Also in 13 of 14 patients, the atrial functional refractory periods were shorter than the minimal echo time and the longest A2-Ae without Ae. In one patient, the atrial functional refractory period was sandwiched between the minimal echo time and the longest A2-Ae without Ae suggesting the atrial functional refractory period of Ae might be responsible for limiting the occurrence of an Ae in this patient.
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012032:Refractory Period, Electrophysiological; D013610:Tachycardia / Q000503:physiopathology*; D014927:Wolff-Parkinson-White Syndrome / Q000503:physiopathology*