Instructions: In this task, you are given a passage which has a question and the context. You have to generate an answer to the question based on the information present in the context.
Input: Context: Severe mitral regurgitation (MR) reduces left atrial thrombus formation in patients with mitral stenosis (MS) and atrial fibrillation (AF). Plasma D-dimer levels represent a biochemical marker for fibrinolytic activity in prothrombotic states. The prothrombotic burden in patients with mitral valve disease and/or AF was assessed using plasma D-dimer levels.', 'The study population included 89 patients with mitral valve disease, 21 with AF but normal valves, and 15 healthy controls. The mitral valve group was subdivided into patients with MS (n = 27), severe MR (n = 26), and MS with concomitant with severe MR (MS/MR; n = 36). These subgroups were further subdivided according to the atrial rhythm (sinus rhythm (SR)+AF).', 'The mean left atrial size was increased in all groups with cardiac disease. D-dimer levels were highest in the MS+AF subgroup (527 +/- 134 microg/l). Patients with MS+AF, MS+SR, and nonvalvular AF had significantly higher D-dimer levels than controls (p < 0.01, by ANOVA). Patients with MR had normal levels of D-dimer. The atrial rhythm did not influence D-dimer levels in the MS/MR subgroup, or in the pure MR subgroup (p = NS).\Question: Does mitral regurgitation reduce systemic coagulation activity in patients with rheumatic heart disease?
Output:
Plasma D-dimer levels correlated with the embolic risk in mitral valve disease and non-valvular AF. The highest levels were found in patients with MS+AF and non-valvular AF. Severe MR decreased the D-dimer levels in MS and/or AF to control levels.