Risk factors for TIA and stroke

This chapter outlines the major known risk factors for TIA and stroke. Knowledge of these risk factors is necessary in order to understand the aetiology of TIA and stroke, to predict risk and to develop effective preventive strategies. 

Atrial fibrillation is a well-recognized risk factor for TIA and stroke, and many studies have identified independent prognostic factors for stroke in all patients with non-rheumatic atrial fibrillation (NRAF), irrespective of previous cerebrovascular disease (Stroke Prevention in Atrial Fibrillation Investigators 1992a, b Atrial Fibrillation Investigators 1994). The CH ADS2 score has been derived and validated to predict the risk of stroke for patients with atrial fibrillation and includes previous cerebrovascular disease as one of the independent risk factors (Gage et al. 2001) (Ch. 2). 

There are several rare familial conditions that may be complicated by ischemic stroke and TIAs (Table 3.2). However, family history of stroke is only a modest risk factor for sporadic ischemic stroke (Flossmann and Rothwell, 2004) and a family history of stroke is associated with little or no increase the risk of future stroke (Flossmann and Rothwell 2005, 2006) (Ch. 3). 

However, there is only one report specifically on which patients with a previous TIA or stroke and NRAF are at high (and low) risk, based on 375 patients with NRAF and TIA or non-disabling stroke treated in the placebo arm of the European Atrial Fibrillation Trial (van Latum et al. 1995). Independent risk factors for vascular death, stroke and other major vascular events included increasing age, previous thromboembolism, ischemic heart disease,... 

Hossmann K (1994) Viability thresholds and the penumbra of focal ischemia. Ann Neurol 36 557-565 Johnston SC, Sidney S, Bernstein AL, Gress DR (2003) A comparison of risk factors for recurrent TIA and stroke in patients diagnosed with TIA. Neurology 60 280-285 Kaplan B, Brint S, Tanabe J, Jacewicz M, Wang XJ, Pulsinelli W (1991) Temporal thresholds for neocortical infarction in rats subjected to reversible focal ischemia. Stroke 22 1032-1039... 

Currently, little is known about the cause or significance of these syndromes, and rigorous prospective data are required about the risk factors for these presentations, imaging findings and the prognosis. However, our experience is that the outcome is good and, unlike TIA or minor stroke, these are not associated with a high early risk of recurrent stroke. 

Vascular risk factors (Ch. 2) and diseases should be sought. It is unusual for an ischemic stroke or TIA to occur in someone with no vascular risk factors, unless they are very old, or are young with some unusual cause of stroke (Ch. 6). A history of heart disease may be relevant and cardiac symptoms should be specifically inquired about. 

Another important difference is the extent of the evidence base for treatments in major stroke compared with TIA and minor stroke. The concepts of stroke units and administration of thrombolysis have been researched, developed and implemented since the 1980s for patients with major stroke. Yet, although the concept of TIA arose in the 1950s and treatments such as carotid endarterectomy, anticoagulation, antiplatelet therapy and other risk factor management were subsequently proven effective, it was not until 2007 that the first reports were published on the feasibility and effectiveness of urgent assessment and treatment of TIA in specialist units (Rothwell et al. 2007 Lavallfe et al. 2007). 

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