title: [Postextrasystolic sinus responses after autonomic blockade in patients with sinus node dysfunction].
abstract: The interpretation and significance of postextrasystolic responses obtained in human electrophysiological examinations of patients with sinus node dysfunction has long been a matter of controversy. We carried out programmed atrial stimulation by the method of Strauss et al. in 54 patients with sinoatrial disorder, before and after pharmacologic autonomic blockade (with propranolol 0.2 mg/Kg and atropine sulfate 0.04 mg/Kg intravenously). There were two responses, as follows: computable sinoatrial conduction times and chaotic patterns. Patients were divided into groups on the basis of their intrinsic heart rate (IHR). If the total estimated sinoatrial conduction time over greater than or equal to 200 msec and greater than or equal to 147 msec after autonomic blockade and chaotic pattern were considered to be pathologic, so the ratio of abnormal parameters decreased from 73 to 44% in patients of normal IHR, and increased from 70 to 90% in patients of abnormal IHR. The latter 90% was mostly to the expense of the incalculable chaotic patterns. Interpreting a postextrasystolic curve, the existence of reset zone refers to the functional integrity of the sinoatrial node, to the organisation and synchronism of sinus potentials, which depends on the balance of autonomic nervous system and on the intrinsic electrophysiological integrity of the pacemaker cells.
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D004594:Electrophysiology; D005260:Female; D006327:Heart Block / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012848:Sinoatrial Block / Q000503:physiopathology*; D012849:Sinoatrial Node / Q000503:physiopathology*
vernacular_title: Comportamento del ciclo di ritorno dopo blocco neurovegetativo in soggetti con disfunzione sinusale.