Lowering blood pressure in acute stroke: the SCAST trial

In The Lancet, Else Sandset and colleagues report the results of the Scandinavian Candesartan Acute Stroke Trial (SCAST), in which they aimed to fi nd out whether careful lowering of blood pressure, with the angiotensin-receptor blocker candesartan, would be benefi cial in patients with acute ischaemic and haemorrhagic stroke. The rationale for the study was that raised blood pressure is common in patients with acute stroke, associated with a poor outcome, and how it should be managed is uncertain. In theory, lowering blood pressure in acute ischaemic stroke should reduce further vascular damage, cerebral oedema, and haemorrhagic transformation of the fresh brain infarct, and forestall early recurrent stroke. In acute haemorrhagic stroke, lowering blood pressure should reduce hydro static expansion of the haematoma, perihaematoma oedema, and early re-bleeding into the brain. Conversely, lowering blood pressure could increase the ischaemic penumbra and size of any brain infarction or perihaematomal ischaemia. In healthy individuals, a fall in systemic blood pressure is accompanied by compensatory dilatation of the cerebral arteries to maintain constant cerebral perfusion. However, patients with acute stroke might have impaired cerebral autoregulation in the region surrounding the stroke; so any reduction in systemic blood pressure might be accompanied by a similar reduction in cerebral blood fl ow to the ischaemic brain. Within the fi rst 24 h after stroke, systolic blood pressure spontaneously falls by about 28% (SD 11%) in most patients, particularly when they are moved to a quiet room, they are allowed to rest, their bladder is empty, and any pain and increased intracranial pressure is controlled. Until now, however, there has been no reliable evidence from large clinical trials about the benefi ts and risks of lowering blood pressure with drugs in acute stroke. A systematic review of interventions to alter blood pressure within 1 week of acute ischaemic or haemorrhagic stroke, which included 12 randomised trials and 1153 patients, concluded that there was insuffi cient evidence to reliably assess eff ects on functional outcome or death. However, one small trial (342 patients with acute stroke) did suggest that early treatment for the fi rst week with candesartan could reduce later vascular events and death at 1 year (odds ratio 0·48, 95% CI 0·25–0·90); but there was no work that furthers our understanding of myocardial infarction triggers. Their work stands as a warning against overlooking the public health relevance of risk factors with moderate or weak strength that have high frequency in the community.