Early prevention of stroke recurrence
The annual age and sex-standardised incidence of stroke has been calculated as 312 per 100,000 for the age group 45-84 years (Sudlow and Warlow, 1997), with this incidence increasing steeply with advancing years (Bonita, 1992). Community-based stroke studies have shown that approximately 80% of all strokes are ischaemic in origin (Warlow et al., 1996; Burn et al., 1994), which is slightly lower than the incidence of cerebral infarction (89%) in a hospital-based study of first stroke in Lausanne (Bogousslavsky et al., 1988). In the latter study, ischaemia was attributed to atherosclerosis in 43%, embolism from the heart in 20%, and intracranial small vessel disease in 15%. The majority of patients survive their first ischaemic stroke, with 95% alive at 7 days and 90% alive at 1 month (Warlow et al., 1996), but these patients remain at risk of stroke recurrence. Recurrence may occur “early” (Moroney et al., 1998; Sacco et al., 1989; Goldstein and Perry, 1992) or “late” after the index stroke, and the reported rate of recurrence varies depending on the aetiology of the initial stroke, the duration of follow-up, and the trial design. Early recurrence occurs in 8% to 13% of patients in the first 1 to 3 months after atherothrombotic stroke (Moroney et al., 1998; Sacco et al., 1989). The risk of recurrent ipsilateral stroke in medically treated patients with severe (>70%) symptomatic carotid stenosis is particularly high in the first year, at approximately 18%, with an overall risk of 26% over 2 years (NASCET, 1991). Early recurrence appears to be less frequent in the first 1 to 3 months after lacunar stroke (1% to 2%) (Moroney et al., 1998; Sacco et al., 1989), and although the recurrent stroke risk was as high as 9% in the first year in the Oxfordshire Community Stroke Project (Bamford et al., 1991), the overall incidence of stroke recurrence in this subgroup has also been reported to be as low as 6.5% over 2 years in a smaller hospital-based study (Clavier et al., 1994). Atrial fibrillation is the most common source of cardiogenic brain embolism (EAFT, 1993) with a stroke recurrence rate of up to 5% in the first 2 weeks (IST, 1997). Patients with nonvalvular atrial fibrillation (NVAF) have an overall risk of recurrent stroke of 12% in the first year and 5% per annum thereafter (EAFT, 1993).