ECG showing atrial pacing
Pacing artefacts (stimulus artefacts or pacing spikes) are seen before each P waves. P waves have an abnormal shape and appear biphasic in most leads. PR interval is mildly prolonged. Paced P waves have a morphology different from the normal P waves because of a different conduction sequence. Paced P waves can be wider than normal P waves for the same reason. Atrial pacing can be done in sick sinus syndrome where the AV conduction is intact. This will prevent potential future ventricular dysfunction due to dyssynchrony which can occur with long term right ventricular pacing. People used to stress the AV conduction system with ajmaline before deciding on single chamber atrial pacing in sick sinus syndrome to make sure that AV conduction is intact and likely to remain so in the near future. Ajmaline has been shown to be useful in unmasking infrahisean disease .
- Pentimalli F et al. Ajmaline Challenge To Unmask Infrahisian Disease In Patients With Recurrent And Unexplained Syncope, Preserved Ejection Fraction, With Or Without Conduction Abnormalities On Surface ECG. J Atr Fibrillation. 2016 Aug-Sep; 9(2): 1421.