Atrial pacing ECG

Atrial pacing ECG

atrial pacingECG showing atrial pacing artefact before each P wave

Pacing artefacts (stimulus artefacts or pacing spikes) are seen before each P wave. 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. Atria alone can be paced in sick sinus syndrome where the AV conduction is intact. This will prevent potential future left ventricular dysfunction due to dyssynchrony which can occur with long term right ventricular pacing.

Usual mode of pacing is AAI (pacing and sensing the atrium, inhibited mode). The same ECG pattern can be obtained even if there is a DDD (dual chamber pacing, dual chamber sensing, dual response), but only the atrial part is functioning. Physiologically this can occur if the AV conduction is intact at the time of the ECG recording. The DDD mode covers for potential deterioration of AV conduction later producing ventricular asystole.

It is mandatory to establish the presence of good conduction into the ventricles before considering single chamber atrial pacing. Simple electrophysiology study to check the HV interval will document whether the infra Hisian conduction is good. It can be rechecked after atrial pacing at a higher rate to see if it deteriorates at higher rates.

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 infrahisian disease [1].

Updated on 1st February, 2021

Reference

  1. Pentimalli F, Bacino L, Ghione M, Giambattista S, Gazzarata M, Bellotti P. 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.