Atrial fibrillation: prior stroke or TIA increased the risk of another stroke.

Clinical bottom line (level 2b)

  1. About a twentieth of patients with atrial fibrillation who took aspirin had an ischaemic stroke.
  2. Patients had an increased risk for ischaemic stroke if they:
    • prior stroke or TIA
    • had systolic BP >160 mmHg
    • had a history of hypertension
    • were older
    • female
  3. Patients had a decreased risk if they drank 14 or more alcoholic drinks per week.
Hart et al: Stroke 1999; 30: 1223-1229
Expires November 2003

The study

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

Setting: 25 centres, USA

2012 patients (aged mean 69 years, 72% male) adults with sustained or recurrent atrial fibrillation

Excluded if
  • mitral stenosis
  • prosthetic cardiac valves
  • lone AF



    • Factors studied:
  • ischaemic stroke, haemorrhagic stroke
  • age (per decade)
  • female
  • history of hypertension
  • systolic BP >160 mmHg
  • alcohol intake 14/week or more compared with 0-13 drinks per week
  • prior stroke or TIA


    • Patients received aspirin 325 mg/dl as part of a an RCT, and 290 also received fixed, low-dose warfarin (INR during follow-up 1.4 or less).

    Cox proportional hazards modelling was used to adjust for confounding factors.

    100% followed for mean 2 years
    Outcomes studied:
  • ischaemic stroke
  • haemorrhagic stroke

    • The evidence

    outcome time to outcome number of patients/total number %
    (95% CI)
    ischaemic stroke mean 2 years 130/2012 6.46%
    (5.39% to 7.54%)
    haemorrhagic stroke mean 2 years 10/2012 0.50%
    (0.19% to 0.80%)

    prognostic factor for
    ischaemic stroke     		time to outcome adjusted RR
    (95% CI)    		 p-value
    age (per decade) mean 2 years 1.8
    ( to )     		0.001
    female mean 2 years 1.6
    ( to )     		0.01
    history of hypertension mean 2 years 2.0
    ( to )     		0.001
    systolic BP >160 mmHg mean 2 years 2.3
    ( to )     		0.001
    alcohol intake 14/week or more mean 2 years 0.4
    ( to )     		0.04
    prior stroke or TIA mean 2 years 2.9
    ( to )     		0.001

    • Left ventricular dysfunction was not found to be independently associated with stroke.

    Comments

    1. The inclusion of patients with an INR of <1.5 should not alter the results, as this is not independently associated with a risk of further stroke.
    2. Results should be viewed with some caution as the patients were part of a randomised controlled trial.
    3. For moderate and low-risk patients, their own preferences may strongly influence the choice of opting for anticoagulation or otherwise - studies like these assist in more accurately detailing stroke risk.

    Citation

    1. Hart RG, Pearce LA, McBride R, et al: Factors associated with ischemic stroke during aspirin therapy in atrial fibrillation. Analysis of 2012 participants in the SPAF I-III clinical trials. Stroke 1999; 30: 1223-1229
    Contributor: Clare Wotton and Bob Phillips, November 2000
    Reviewer: Santiago Alvarez Montero

    Clinical Question.
    Patient AF with aspirin therapy
    Intervention or Exposure risk factors
    Outcome ischaemic stroke