The Influence of Interatrial Conduction Disorders on Atrial Mechanical Function - Atrial Strain and Pulmonary Veins Reversal Flow in Patients with COVID-19.

Background: The physiological activation of the left atrium (LA) happens through the Bachmann bundle, which is crucial for the heart's proper functioning. Bayes de Luna first described interatrial blocks (IABs) in 1979, noting their disruption of atrioventricular (AV) synchrony. This study aims to evaluate LA mechanics by analyzing LA strain in cases of normal and impaired interatrial conduction, focusing on retrograde flow in the pulmonary veins (PV).

Methods: The study included 51 patients who tested positive for SARS-CoV-2 and exhibited related symptoms. Six patients with persistent atrial fibrillation (AF) were excluded from the study (45 patients qualified in total: 23 males, 22 females; mean age 69.0 ± 12.9 years).

Results: IABs were more frequently observed in COVID-19 patients. Thus, they were included despite SARS-CoV-2 being a potential limitation of the study. All participants underwent clinical evaluation, electrocardiography (ECG) (200 mm/s ×256), and echocardiography to assess left ventricular ejection fraction (LVEF), mitral regurgitation (MR), LA volume, global and regional strain, and retrograde flow in the PV. A statistical dependency was found between LA global strain and P-wave morphology, MR, heart failure (HF), and paroxysmal atrial fibrillation (PAF). However, no clear correlation was found between retrograde flow in the PV and LA strain. The mean P-wave duration correlated with its morphology. Additionally, correlations were observed between P-wave morphology and hypertension, being overweight, and PAF.

Conclusions: LA mechanics are negatively influenced by IABs. LA global strain correlates with P-wave duration, ejection fraction (EF), and MR independently. Regional LA strain examination is potentially effective for assessing LA mechanics and complements precise ECG.