title: Atrial pacing by a ventricular-inhibited (VVI) myocardial unipolar pacemaker.
abstract: A patient with sinoatrial node disease is reported who demonstrated inadvertent atrial pacing from a ventricular unipolar myocardial electrode and a VVI Intermedics pacemaker. Atrial refractory and vulnerable periods are addressed in this context as possibly providing the environment for an atrial arrhythmia, secondary to competition between the non-sensed impulse and the unipolar cathodal stimulus falling in the atrial vulnerable period.
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000209:etiology* / Q000503:physiopathology; D001281:Atrial Fibrillation / Q000209:etiology; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects*; D004562:Electrocardiography; D005260:Female; D006325:Heart Atria / Q000503:physiopathology; D006801:Humans; D012032:Refractory Period, Electrophysiological; D012849:Sinoatrial Node / Q000503:physiopathology