Intermittent atrial undersensing in single-lead VDD pacemakers in patients with bradycardia-sensitive repolarization: a possible mechanism for ventricular arrhythmia.

Intermittent atrial undersensing in patients with single-lead VDD pacemakers is regarded as being of limited clinical significance. Nevertheless, in patients with bradycardia-mediated repolarization abnormalities, undersensing could result in RR-interval oscillations due to changes in pacemaker mode and this could act as a trigger for the initiation of torsades de pointes. We report our findings in three patients, which demonstrate the functioning of this trigger mechanism for ventricular arrhythmias.