Stroke and systemic embolism occur frequently in patients with rheumatic mitral stenosis (MS) in sinus rhythm (SR), but the risk and predictors of embolic events in this population are not well studied. The aim of this study was to determine if transient, subclinical atrial fibrillation (AF) increases the risk of systemic embolism in patients with MS in SR. A single-center, prospective observational study of patients with rheumatic MS in SR was performed. The rate of the composite primary outcome of stroke, transient ischemic attack, or non-central nervous system embolism was determined, as well as the predictive value of Holter-detected episodes of transient (<30 seconds), subclinical AF for this outcome. Hazard ratios were derived for subclinical AF, after adjustment for clinical and echocardiographic predictors of systemic embolism, using Cox regression. The sensitivity, specificity, and area under the receiver-operating characteristic curve of subclinical AF were determined for the primary outcome. Among 179 patients (mean follow-up 10.2 months), the rate of the primary outcome was 5.3/100 patient-years (95% confidence interval [CI] 2.6 to 10.5). In univariate analysis, subclinical AF (hazard ratio 4.54, 95% CI 1.08 to 19.0, p = 0.038) and dense spontaneous echocardiographic contrast (hazard ratio 4.32, 95% CI 1.03 to 18.09, p = 0.045) were predictors of the primary outcome. In multivariate analysis, subclinical AF remained the only significant predictor (hazard ratio 5.02, 95% CI 1.15 to 22.0, p = 0.032). Subclinical AF had an area under the receiver-operating characteristic curve of 0.68 and high negative predictive value (97.7%) for the primary outcome. In conclusion, Holter-detected, transient (<30 seconds), subclinical AF is a predictor of stroke and systemic embolism in patients with rheumatic MS in SR. Considering the high risk for embolism, randomized trials of oral anticoagulation are needed in this population.
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