Wenckebach phenomenon within the atria.
D000368:Aged; D002037:Bundle-Branch Block / Q000503:physiopathology; D006328:Cardiac Catheterization; D004562:Electrocardiography; D006325:Heart Atria; D006327:Heart Block / Q000175:diagnosis*; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans