Observations of Interatrial Conduction in Healthy Individuals Using Signal-averaged P-wave ECG: A Clinical Perspective

University dissertation from Faculty of Medicine, Lund University

Abstract: Disturbances of interatrial conduction are linked to supraventricular arrhythmias. Previous studies have shown that these disturbances can be detected non-invasively as distinctive appearances of the orthogonal P wave using signal-averaged P-wave analysis (PSAECG). Orthogonal recordings (VCG) are however scarce in clinical practice for practical reasons. The aim of the presented study was to explore the possibility of mathematically transforming conventional 12-lead ECGs into orthogonal P-wave data with preserved information content regarding P-wave morphology. If feasible, the method would then be used to analyse P-wave data from healthy adult men and women of all ages in order to provide a first reference material of the “normal” P wave for future studies. Study I evaluated the feasibility of lead conversion (ECG into VCG) in both healthy individuals and arrhythmia patients. The study compared P waves from recorded and derived VCG and it was found that information of interatrial conduction disturbances is preserved. Study II further evaluated this method in a similar material. Different variations of ECG data mimicking true clinical conditions were explored regarding the preservation of P-wave data. It was found that PSAECG is a robust analysis method also in a proposed clinical setting. Study III and IV were devoted to the analysis of P-wave data retrieved from a large material of healthy individuals using the previously validated method. The main finding of Study III was that P-wave morphologies previously observed in arrhythmia patients were commonly observed also in this normal population. The changes were, however, mostly found in the higher age groups, which is in keeping with the known fact that many arrhythmias are more common with increasing age. In Study IV, a long-term follow-up of the “normal” P-wave morphology was conducted, where it was found that P-wave morphology is mostly unaltered after three years. However, in a small number of individuals, discrete changes were observed that support the theory that age-related changes influence interatrial conduction and may implore susceptibility for developing arrhythmias. The presented study adds to the increasing knowledge about interatrial conduction. It provides a validated method for non-invasive exploration of he impulse propagation and also a reference material of the “normal” signal-averaged P-wave morphology.

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