Relationship between left atrial fibrosis and function in a selected cohort undergoing surgery for severe primary mitral regurgitation

BACKGROUND: In primary mitral regurgitation (MR) atrial dysfunction is believed to be the result of atrial interstitial fibrotic replacement, and left atrial (LA) strain has been suggested as a non-invasive tool to identify a maladaptive atrial remodelling beyond LA enlargement. We aim to investigate the association between LA function and the extent of interstitial fibrosis within the atrial wall in patients undergoing surgery, and their relation with MR characteristics and clinical profiles. METHODS: 49 consecutive patients (61 ± 10 years, men 75%) with severe primary MR due to prolapse or flail were enrolled the day before surgery and a complete echocardiographic examination with LA strain analysis was performed. During surgery, a single-site full-thickness sample of the LA free wall was obtained from each patient. RESULTS: Areas of interstitial fibrosis were detected in all atrial specimens (median degree 6.5% [4.75-9.25]). No correlation was found between fibrosis degree and echocardiographic parameters like LA strain, LA volume, quantitative parameters of MR degree, regurgitant jet direction, estimated pulmonary artery pressure (sPAP), or clinical parameters like NYHA class or NTproBNP. However, lower LA reservoir and contractile strain values were associated with higher sPAP (p = 0.002 and p = 0.01, respectively), NTproBNP values (p < 0.0001) and symptoms severity (p < 0.05). CONCLUSIONS: In this selected cohort with severe primary MR and relatively low single-site histological LA fibrosis, LA strain was associated with markers of haemodynamic burden but not with biopsy-derived fibrosis percentage.