Atrial Conduction Disorders

Abstract

Atrial conduction disorders result from impaired propagation of cardiac impulses from the sinoatrial node through the atrial conduction pathways. Disorders affecting interatrial conduction alter P-wave characteristics on the surface electrocardiogram. A variety of P-wave indices reflecting derangements in atrial conduction have been described and have been associated with an increased risk of atrial fibrillation (AF) and stroke. Interatrial block (IAB) is the most well-known of the different P-wave indices and is important clinically due to its ability to predict patients who are at risk of the development of AF and other supraventricular tachycardias. P-Wave Axis is a measure of the net direction of atrial depolarization and is determined by calculating the net vector of the P-wave electrical activation in the six limb-leads using the hexaxial reference system. It has been associated with stroke and it has been proposed that this variable be added to the existing CHA2DS2-VASc score to create a P2-CHA2DS2-VASc score to improve stroke prediction. P-Terminal Force in V1 is thought to be an epiphenomenon of advanced atrial fibrotic disease and has been shown to be associated with a higher risk of death, cardiac death, and congestive heart failure as well as an increased risk of AF. P-wave Dispersion is defined as the difference between the shortest and longest P-wave duration recorded on multiple concurrent surface ECG leads on a standard 12-lead ECG and has also been associated with the development of AF and AF recurrence. Pwave voltage in lead I (PVL1) is thought to be an electrocardiographic representation of cardiac conductive properties and, therefore, the extent of atrial fibrosis relative to myocardial mass. Reduced PVL1 has been demonstrated to be associated with new-onset AF in patients with coronary artery disease and may be useful for predicting AF. Recently a risk score (the MVP risk score) has been developed using IAB and PVL1 to predict atrial fibrillation and has shown a good predictive ability to determine patients at high risk of developing atrial fibrillation. The MVP risk score is currently undergoing validation in other populations. This section reviews the different P-wave indices in-depth, reflecting atrial conduction abnormalities.

Keywords: Atrial fibrillation; Morphology-Voltage- P-Wave Duration Score; P-wave axis; P-wave indices; atrial conduction abnormalities; interatrial block.

Fig. (1)

Measurement of P-Terminal Force in V1 (the product of the duration (in seconds) and amplitude (in millimeters) of the negative terminal deflection of the P-wave in lead V1). (A higher resolution / colour version of this figure is available in the electronic copy of the article).

Fig. (2)

Component Variable Measurements of the MVP ECG Risk Score. P-Wave Duration (measured in milliseconds) and Morphology (normal or biphasic) are measured in the inferior leads and P-Wave Voltage (in milliVolts) is measured in Lead I. Reproduced with permission from Alexander B, Milden J, Hazim B, et al. New electrocardiographic score for the prediction of atrial fibrillation: The MVP ECG risk score (morphology-voltage-P-wave duration). Ann Noninvasive Electrocardiol. 2019;24(6):1-7. © 2019 Wiley Periodicals, Inc. [34] (A higher resolution / colour version of this figure is available in the electronic copy of the article).