title: Existence of automaticity in anomalous bundle of Wolff-Parkinson-White syndrome.
abstract: Escape beats probably arising from the anomalous bundle were documented in 2 patients with the Wolff-Parkinson-White (WPW) syndrome. A third patient, in whom complete AV block developed both in the anomalous bundle and the normal pathway, showed the occurrence of escape beats (an escape-bigeminy pattern), as well as a regular idioventricular rhythm arising from the anomalous bundle. Phase 4 block in the anomalous bundle occurred in 7 other patients, in 4 of them spontaneously and in 3 only after the administration of ajmaline or amiodarone. Only 4 of 14 fully investigated patients (out of a total number of 23) showed absence of both escape beats and phase 4 block. The escape beats were considered as direct evidence, and the phase 4 block as indirect evidence, for the existence of automaticity in the anomalous bundle. Such evidence supports the view that the anomalous bundle, like the His bundle-branch system, may be composed of specialised tissue endowed with the property of automaticity.
mesh_terms: D000293:Adolescent; D000328:Adult; D000404:Ajmaline / Q000494:pharmacology; D000638:Amiodarone / Q000494:pharmacology; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012849:Sinoatrial Node / Q000187:drug effects; D014927:Wolff-Parkinson-White Syndrome / Q000503:physiopathology*
chemical_list: D000404:Ajmaline; D000638:Amiodarone