Relation of the severity of mitral regurgitation to thromboembolic risk in patients with atrial fibrillation.

ABSTRACT

BACKGROUND: Patients with atrial fibrillation (AF) are at risk for thromboembolism. Although mitral regurgitation (MR) could be protective against left atrial (LA) blood stasis, the relationship between the severity of MR and thromboembolic risk has not been clarified in patients with AF. METHODS: 271 patients with permanent AF underwent transesophageal echocardiography (TEE). The severity of MR was assessed by Doppler echocardiography. LA blood stasis on TEE and plasma D-dimer levels were used to evaluate the thromboembolic risk. RESULTS: Patients with severe MR (n=20) had significantly higher LA appendage peak flow velocity compared to those with no MR (n=114) and those with only mild MR (n=92) (p<0.05). The grade of LA spontaneous echo contrast (SEC) was lower in patients with severe MR compared to those with no, mild or moderate MR (severe MR 0.7±0.7 grade vs moderate MR 1.7±1.0 grade, mild MR 2.2±1.3 grade, and no MR 1.9±1.3 grade, p<0.05). Multivariate analysis revealed severe MR as a negative predictor of LA blood stasis on TEE findings (odds ratio 0.27; 95% confidence interval 0.09-0.86, p<0.05). By contrast, D-dimer level was significantly higher in patients with moderate MR compared to those with any other type of severity of MR (moderate MR 1.72±1.45 µg/ml vs severe MR 0.76±0.95 µg/ml, mild MR 0.97±1.09 µg/ml, and no MR 0.82±1.15 µg/ml, p<0.05). CONCLUSIONS: There is a protective effect of MR on LA blood stasis, but this beneficial effect on thromboembolic risk appears to be limited to patients with severe MR.