Variations in discharge rate of demand pacemakers not due to malfunction.
D001281:Atrial Fibrillation; D004562:Electrocardiography; D004566:Electrodes; D006327:Heart Block / Q000628:therapy; D006329:Heart Conduction System / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D008280:Magnetics; D010138:Pacemaker, Artificial