Mitral regurgitation attenuates thrombotic risk in nonrheumatic atrial fibrillation: a new CHA2DS2-VASc score risk modifier?
Authors: Van Laer SL , Winkler KM , Verreyen S , Miljoen H , Sarkozy A , Heuten H , Saenen J , Van Herck P , Van De Heyning CM , Heidbuchel H , Claeys MJ 
Published: May 2021

Abstract

Funding Acknowledgements
Type of funding sources: None.
Background/Introduction: Atrial fibrillation (AF) carries a thrombotic risk related to left atrial blood stasis. Many risk scores, such as the CHA2DS2-VASc score, have been developed to guide physicians in initiating anticoagulant therapy. However, the risk prediction with these models is modest at best (C-statistic = 0.6). The presence of mitral regurgitation (MR) has been shown to reduce thrombotic risk in patients with rheumatic AF. In nonrheumatic AF, direct evidence of a lower thrombotic risk in patients with MR is still controversial.

Purpose
The current study assessed the effect of MR on thrombotic risk in nonrheumatic AF patients.

Methods
The prevalence of atrial thrombosis, defined as the presence of left atrial appendage thrombus (LAAT) and/or left atrial spontaneous echo contrast (LASEC) grade &gt;2, was determined in 686 consecutive nonrheumatic AF patients without (adequate) anticoagulation scheduled for transoesophageal echocardiography before electrical cardioversion and was related to the severity of MR adjusted for the CHA2DS2-VASc score. The independent predictors of atrial thrombosis were assessed by stepwise multiple logistic regression analysis.

Results
A total of 103 (15%) patients had severe MR, 210 (31%) had moderate MR, and 373 (54%) had no-mild MR; the median CHA2DS2-VASc score was 3.0 (IQR 2.0-4.0). Atrial thrombosis (LAAT and/or LASEC grade &gt;2) was observed in 118 patients (17%). The prevalence of atrial thrombosis decreased with increasing MR severity: 19.9% versus 15.2% versus 11.6% for no-mild, moderate, and severe MR, respectively (p for trend = 0.03) (Figure 1). Patients with moderate and severe MR had a lower risk of atrial thrombosis than patients with no-mild MR, with adjusted odds ratios (ORs) of 0.51 (95% CI 0.31-0.84) and 0.24 (95% CI 0.11-0.49), respectively. The other independent predictors of atrial thrombosis were: the CHA2DS2-VASc score with an adjusted OR of 1.25 (95% CI 1.10-1.42), poor left ventricular ejection fraction (LVEF, &lt;40%) with an adjusted OR of 4.08 (95% CI 2.56-6.50), and large left atrial volume index (LAVI, &gt;37 ml/m²) with an adjusted OR of 1.90 (95% CI 1.19-3.03) (Figure 1, upper right corner). The C-statistic of the regression model increased significantly (p = 0.0003) from 0.62 to 0.75 by adding MR grade, LVEF, and LAVI to the univariate CHA2DS2-VASc score model. The protective effect of MR was present across all levels of the CHA2DS2-VASc score and the presence of moderate-severe MR in patients with an intermediate CHA2DS2-VASc score (2-3) lowered the atrial thrombotic risk to the level of patients with a low CHA2DS2-VASc score (0-1).

Conclusion
Our data show that the presence of MR attenuated the atrial thrombotic risk by more than 50% in patients with nonrheumatic AF, independent of the CHA2DS2-VASc risk score. Moderate to severe MR can therefore be considered a new risk modifier of the CHA2DS2-VASc score, which might help refine the indication of anticoagulants in AF patients. Abstract Figure 1. Thrombotic risk per MR grade.