Spike or not a spike? That is the question in a patient with single lead pacemaker.

Dual-chamber pacing is feasible via the floating atrial sensor electrodes of a single-pass VDD lead but the atrial lead threshold is higher than the accepted clinical standard. Furthermore, due to the floating nature of the system, atrial sensing and pacing thresholds may vary during the follow up. For these reasons this strategy is seldom considered a common pacing solution in routine clinical practice. Alternatively, this phenomenon is likely to be observed as a result of incorrect generator configuration. As shown in our case, this inadequate setting can be suspected just by the analysis of the surface ECG and the post implantation chest X-ray.