Eleven trials including 2487 patients were included in a Cochrane review [Abstract] 1. One trial included only transient ischaemic attack patients, the remainder included mainly patients with previous strokes. Five trials excluded patients with a possible cardiac embolic source. Oral anticoagulants were used in all but one trial where low-dose heparin was compared with usual therapy. Only 3 trials defined a scheduled treatment period (two years) whilst in the others the treatment period varied from 3 to 42 months. The quality of 9 trials which predated routine computerised tomography (CT) scanning and the use of the INR to monitor anticoagulation was poor. Anticoagulant therapy did not significantly reduce the odds of death or dependency ( OR 0.83, 95% CI 0.52 to 1.34; 2 trials) or of non-fatal stroke, myocardial infarction, or vascular death (4 trials, OR 0.96, 95% CI 0.68 to 1.37). There was no evidence of an effect of anticoagulant therapy on the risk of recurrent ischaemic stroke (OR 0.85, 95% CI 0.66 to 1.09). However, fatal intracranial haemorrhage increased (odds ratio 2.54, 95% CI 1.19 to 5.45), as did major extracranial haemorrhage (OR 3.43, 95% CI 1.94 to 6.08). Death from any cause (OR 0.95, 95% CI 0.73 to 1.24) and death from vascular causes (OR 0.86, 95% CI 0.66 to 1.13) were not significantly different between treatment and control groups. This is equivalent to anticoagulant therapy causing about 11 additional fatal intracranial haemorrhages and 25 additional major extracranial haemorrhages per year for every 1000 patients given anticoagulant therapy.
Comment: The quality of evidence is downgraded by study quality (inadequate allocation concealment), inconsistency (heterogeneity in patients and interventions), imprecise results (limited study size for comparisons) and indirectness (differences in interventions; 9 trials performed before 1980).
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