title: Changes in morphology of the paced QRS complex related to atrial contraction.
abstract: A patient with 2:1 AV block underwent temporary ventricular pacing. All the paced stimuli resulted in ventricular capture, but a marked variability in morphology of the paced QRS complexes occurred. Two different types of paced QRS complex (labeled A and B) were recognized. Type B complexes were manifest only when the pacing stimulus was preceded by a sinus P wave within a time interval ranging from 0.15 to 0.52 sec. The P wave-induced changes in morphology of the paced QRS complexes were interpreted as due to displacement of the pacing ventricular lead caused by atrial systole.
mesh_terms: D000368:Aged; D002304:Cardiac Pacing, Artificial; D004562:Electrocardiography; D006325:Heart Atria / Q000503:physiopathology; D006327:Heart Block / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D008297:Male; D009200:Myocardial Contraction