Effect of mitral regurgitation on stroke risk in patients with non-rheumatic atrial fibrillation

Atrial fibrillation (AF) carries a thrombotic risk related to blood stasis in the left atrium. In patients with rheumatic valve disease and AF, the presence of severe mitral regurgitation (MR) has been shown to reduce the risk of atrial thrombosis and stroke. However, in patients without rheumatic disease, the results are controversial.To analyse the association between MR and the incidence of stroke in patients with non-rheumatic AF.We analysed data from the retrospective CardioCHUVI-AF registry, which includes 15,720 patients with AF (without mechanical prostheses or rheumatic valvular disease) in the Vigo area of Spain, during 2014-2018. We grouped the patients according to MR grades: 0-2 (n=15,194) and 3-4 (n=526). We performed univariate and multivariable competitive risk analyses to analyse the association between MR and stroke, with death as the competitive event.During a median (interquartile range [IQR]) follow-up of 4.9 (2.8-4.9) years, 859 patients (5.5%) suffered a stroke. The stroke incidence was 1.3 per 100 person-years (95% confidence interval [95% CI]: 1.2-1.4), with no difference between the MR groups. In univariate analysis, no relationship was observed between MR grade and stroke (subdistribution hazard ratio [sHR]: 1.12, 95% CI: 0.79-1.60; P=0.53); likewise after multivariable analysis (sHR: 0.98, 95% CI: 0.68-1.41; P=0.90). This same relationship was evaluated in subgroups of interest (patients with and without: oral anticoagulation, CHA2DS2-VASc≥2, prior heart failure, aortic valve disease, left ventricular ejection fraction≤40%, and moderate-severe left atrial dilation), with results consistent with the overall population.In our large registry of patients with non-rheumatic AF, we did not find a protective effect of grade 3-4 MR on the risk of stroke.