Association between left atrial appendage fibrosis and thrombus formation: A histological approach

Abstract

Introduction: Although recent echocardiographic studies have suggested that left atrial appendage (LAA) remodeling contributes to the development of LAA thrombus (LAAT), histological evidence is absent. The objective of this study was to examine clinical parameters and histological findings to clarify the factors involved in LAAT formation. Methods: A total of 64 patients (no atrial fibrillation [AF], N = 22; paroxysmal AF, N = 16; nonparoxysmal AF, N = 26) who underwent LAA excision during surgery were enrolled. Transthoracic and transesophageal echocardiography were performed before surgery. We evaluated the fibrosis burden (%) in the excised LAA sections with Azan-Mallory staining in patients with a LAAT compared with those without.Results: Patients with paroxysmal and non-paroxysmal AF had a higher LAA fibrosis burden than those without AF (p = .005 and p < .0001, respectively). Among the patients enrolled, 16 had a LAAT and 15 of them had nonparoxysmal AF. Among the nonparoxysmal AF patients, those with a LAAT had significantly higher LAA fibrosis burden than those without (23.8% [14.8%-40.3%] vs. 12.8% [7.4%-18.2%], p = .004) and echocardiographic parameters of the left atrial volume index (R = 0.543, p = .01), LAA depth (R = 0.452, p = .02), and LAA flow velocity (R = − 0.487, p = .01) were correlated with the LAA fibrosis burden. Conclusion:This study provided histological evidence that LAA fibrosis is related to LAAT formation. Echocardiographic parameters of LAA remodeling and function were correlated with the LAA fibrosis burden.

Study of the Biomechanical Properties and Microstructure of Trabecular Musculi Pectinati in the Left Atrial Appendage for patients with Atrial Fibrillation

“…Endocardial thickness was measured. Referring to the formula for calculating the degree of myocardial fibrosis [24], the TMP cross-section PFB (5) was calculated using the percentage of blue collagen fibers in the entire cross-sectional area under Masson staining of transverse sections, and its correlation with the EMLS and EMHS of the sample was analyzed. (5)…”

Machine Learning and the Conundrum of Stroke Risk Prediction

“…Histologically quantified LAA fibrosis burden is higher in patients with AF than in those in sinus rhythm, and in patients with LAA thrombus than in those without. 24,25 The mechanism by which atrial fibrosis contributes to thrombogenesis is not completely understood. A decrease in left atrial strain was shown in the presence of extensive late gadolinium enhancement MRI (LGE-MRI) fibrosis.…”