title: Exercise-induced distal atrioventricular block.
abstract: Three patients with 1:1 atrioventricular (AV) conduction at rest developed fixed 2:1 or 3:1 AV block during treadmill exercise testing. Electrophysiologic study documented block distal to the AV node in all three patients, and suggested that the exercise-induced block occurred because of increased atrial rate and abnormal refractoriness of the His-Purkinje conduction system. The findings in these three patients suggest that high grade AV block appearing during exercise reflects conduction disease of the His-Purkinje system rather than of the AV node, even in the absence of bundle branch block. Patients with this diagnosis should be considered for permanent cardiac pacing.
mesh_terms: D000368:Aged; D001283:Atrioventricular Node / Q000503:physiopathology; D004562:Electrocardiography; D004594:Electrophysiology; D006327:Heart Block / Q000209:etiology* / Q000503:physiopathology; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D005082:Physical Exertion