Abstract: P-wave assessment is frequently used in clinical practice to recognize atrial abnormalities. However, the use of P-wave criteria to diagnose specific atrial abnormalities such as left atrial enlargement has shown to be of limited use since these abnormalities can be difficult to distinguish using P-wave criteria to date. Hence, a mechanistic understanding how specific atrial abnormalities affect the P-wave is desirable. In this study, we investigated the effect of left atrial hypertrophy on P-wave morphology using an in silico approach. In a cohort of four realistic patient models, we homogeneously increased left atrial wall thickness in up to seven degrees of left atrial hypertrophy. Excitation conduction was simulated using a monodomain finite element approach. Then, the resulting transmembrane voltage distribution was used to calculate the corresponding extracellular potential distribution on the torso by solving the forward problem of electrocardiography. In our simulation setup, left atrial wall thickening strongly correlated with an increased absolute value of the P-wave terminal force (PTF) in Wilson lead V1 due to an increased negative amplitude while P-wave duration was unaffected. Remarkably, an increased PTF-V1 has often been associated with left atrial enlargement which is defined as a rather increased left atrial volume than a solely thickened left atrium. Hence, the observed contribution of left atrial wall thickness changes to PTF-V1 might explain the poor empirical correlation of left atrial enlargement with PTF-V1.
Abstract: P-wave assessment can offer a simple and inexpensive means to diagnose left atrial enlargement, which is a predictor for atrial fibrillation. However, the underlying influence of left atrial enlargement on the P-wave is not fully understood. Furthermore, P-wave markers to assess left atrial enlargement show poor sensitivity or specificity - potentially due to other left atrial abnormalities similarly affecting P-wave morphology as left atrial enlargement. In an in silico approach, the left atrium was dilated by mechanical inflation. In another approach, the left atrial myocardium was homogeneously thickened in four patient models. To generate torso meshes containing the modified atria, an existing method to mesh tetrahedral torsos was applied for left atrial wall thickening. For left atrial dilation, a new method was developed to generate tetrahedral torso meshes from organ surfaces. Afterwards, the P-waves were simulated for the two different left atrial anatomical alterations. Left atrial wall thickening resulted in an increased P-terminal force in V1 and an increased P-wave area. For left atrial dilation, the resulting P-waves were not realistic, as the underlying electrophysiological simulation method was not es- tablished yet. Furthermore, left atrial dilation was only applied to a single model. Thus, the results were unreliable. Considering this, the results suggest a prolonged P-wave duration, P-wave notching and an increased P-wave amplitude in aV L to be correlated with left atrial dilation.