Stroke: thromboembolism rate increased with increasing numbers of risk factors.

Clinical bottom line (level 2b)

  1. Patients with nonrheumatic atrial fibrillation were at increased risk of thromboembolism if they had:
    • left ventricular dysfunction
    • left atrial M-mode
    • history of hypertension
  2. Patients had an increasing risk of thromboembolism with increasing numbers of risk factors.
  3. Congestive heart failure and previous thromboembolism did not clearly increase the risk of thromboembolism.
The Stroke Prevention in Atrial Fibrillation Investigators : Annals of Internal Medicine 1992; 116 (1): 6-12
Expires November 2001

The study

Prospective cohort study with objective outcomes, adjusted for confounding factors, not validated in an independent set of patients.

Setting: fifteen medical centres, USA

568 patients (aged mean 67 years, 70% male) nonrheumatic atrial fibrillation

Excluded if
  • described in stroke_Stroke_Prevention_AF_92



    • Factors studied:
  • global left ventricular dysfunction
  • left atrial M-mode (cm/ m ² )
  • history of hypertension
  • recent congestive heart failure
  • previous thromboembolism


    • Patients were from the placebo arm of a randomised trial of warfarin, aspirin and placebo.

    Multivariate analysis was used to adjust for confounding factors. Items were selected on the basis of statistical significance in univariate analysis (which was performed on hypothetically important variables).

    100% followed for mean 1.3 years
    Outcomes studied:
  • thromboembolism

    • The evidence

    outcome time to outcome number of patients/total number %
    (95% CI)
    thromboembolism mean 1.3 years 46/568 8.1%
    (5.9% to 10.3%)

    prognostic factor for
    thromboembolism     		time to outcome adjusted RR
    (95% CI)
    global left ventricular dysfunction mean 1.3 years 2.0
    (1.0 to 4.0)
    left atrial M-mode (cm/ m ² ) mean 1.3 years 1.6
    (1.0 to 2.5)
    history of hypertension mean 1.3 years 1.9
    (1.0 to 3.9)
    recent congestive heart failure mean 1.3 years 2.0
    (0.8 to 4.7)
    previous thromboembolism mean 1.3 years 1.9
    (0.9 to 4.2)

    • Risk stratification using clinical and echocardiographic predictors:
      • no risk factors: thromboembolism rate (% per year) 1.0% (0.2 to 4.0)
      • 1 or 2 risk factors: thromboembolism rate 6.0% (4.1 to 8.8)
      • three or more risk factors: thromboembolism rate 18.6% (11.6 to 30.1)

    Comments

    1. Results should be viewed with some caution as the data was taken from patients in a randomised controlled trial.

    Citation

    1. The Stroke Prevention in Atrial Fibrillation Investigators , : Predictors of thromboembolism in atrial fibrillation: II. Echocardiographic features of patients at risk. Annals of Internal Medicine 1992; 116 (1): 6-12
    Contributor: Clare Wotton and Bob Phillips, November 2000
    Reviewer:

    Clinical Question.
    Patient nonrheumatic atrial fibrillation
    Intervention or Exposure risk factors
    Outcome thromboembolism