Inadvertent atrial location of a sutureless epicardial pacemaker electrode

A 70-year-old woman had an epicardial pacing system implanted after transvenous right ventricular endocardial pacing resulted in cardiac perforation. At the time of revision of the epicardial system for pacing failure, it was noted that one of the bipolar epicardial electrodes was pacing atrial tissue. The differential diagnosis of this unusual finding is discussed and recommendation urged for systematic analysis of pacing system function at the time of implant, in order to avoid inadvertent electrode placement.