title: Mitral regurgitation reduces the risk of stroke in patients with nonrheumatic atrial fibrillation.
abstract: BACKGROUND
  Significant mitral regurgitation (MR) is protective against left atrial (LA) spontaneous echo contrast formation that is associated with an increased thromboembolic risk. However, the effects of MR on the risk of stroke in patients with nonrheumatic atrial fibrillation (AF) have been unknown. We studied whether or not MR was associated with a decreased risk of stroke in patients with nonrheumatic AF.
  
  
  METHODS
  We performed an observational analysis of retrospectively collected data on 290 patients with nonrheumatic AF. Left atrial diameter (LAD) and the degree of MR were estimated by transthoracic echocardiography. Risk factors for stroke were assessed by univariate and multivariate analyses. The mean follow-up was 7.4 years.
  
  
  RESULTS
  Among these patients, 68 had a stroke during the follow-up (rate of stroke per year of follow-up 3.2%). In 95 patients with LAD of > or =48 mm, the incidence of stroke (9%) in the severe MR group (moderate or severe, n=43) was significantly lower than that (25%) of the mild MR group (none, trivial, or mild; n=52) (chi-square=3.95, p=0.047). The relative risk of stroke for increase in MR from mild to severe groups, for every 10 mm increment in LA size, for sex, and for every increase of 10 years of age was 0.45 (95% CI, 0.20 to 0.97), 1.06 (95% CI, 0.75 to 1.49), 0.98 (95% CI, 0.55 to 1.72), and 1.33 (95% CI, 1.04 to 1.71), respectively.
  
  
  CONCLUSIONS
  In patients with nonrheumatic AF, age was an independent predictor of an increased risk of stroke, and MR may be protective against stroke, especially in those patients with LA enlargement.
authors.affiliation: Department of Cardiology, Jichi Medical School, Tochigi, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Nakagami
authors.forename: K
authors.initials: K
authors.lastname: Yamamoto
authors.forename: U
authors.initials: U
authors.lastname: Ikeda
authors.forename: T
authors.initials: T
authors.lastname: Mitsuhashi
authors.forename: T
authors.initials: T
authors.lastname: Goto
authors.forename: K
authors.initials: K
authors.lastname: Shimada
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001281:Atrial Fibrillation / Q000150:complications* / Q000000981:diagnostic imaging; D004452:Echocardiography; D005260:Female; D006801:Humans; D002542:Intracranial Embolism and Thrombosis / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D008944:Mitral Valve Insufficiency / Q000150:complications* / Q000000981:diagnostic imaging; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012306:Risk; D012307:Risk Factors; D012720:Severity of Illness Index