title: Alternating left and right bundle branch block aberration of atrial extrasystoles in bigeminal rhythm.
abstract: We report two cases of atrial extrasystolic bigeminy manifesting with alternating right and left bundle branch block aberration. The manifestation is explained on the basis of cycle-dependent variations of the bundle branch refractory period with alternate resetting of bundle branch refractoriness.
mesh_terms: D000293:Adolescent; D002037:Bundle-Branch Block / Q000503:physiopathology*; D005117:Cardiac Complexes, Premature / Q000503:physiopathology*; D004562:Electrocardiography; D004594:Electrophysiology; D005260:Female; D006325:Heart Atria; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged