An unusual pacemaker malfunction: spontaneous mode change from VVI to VVT.
D000368:Aged; D001919:Bradycardia / Q000628:therapy*; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate; D006801:Humans; D010138:Pacemaker, Artificial / Q000009:adverse effects*; D013610:Tachycardia / Q000628:therapy*