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Acquired atrioventricular block in a patient with sinus node disease on single-chamber atrial pacing.

Single-chamber atrial pacing is the most physiological and yet economical modality of treatment in patients with symptomatic sinus node disease with normal atrioventricular conduction. However, because of the possibility of future development of a high-degree atrioventricular block and atrial fibrillation, most patients are implanted either dual- or single-chamber right ventricular pacemakers. We report a patient with symptomatic sinus node disease on single-chamber atrial pacing for the past 7 years who developed a progressive increase in the PR interval and ultimately presented with symptomatic high-degree atrioventricular block requiring pacemaker upgradation. The pacemaker was upgraded to the single-chamber ventricular mode with one additional ventricular lead introduced from the same side percutaneously.