Patients who have had an ischaemic stroke are at increased risk of another stroke if their systolic blood pressure is lower than 120mmHg, compared with those whose blood pressure is between 130 and 139mmHg, an international study finds.
The results add to evidence blood pressure could follow a J-shaped curve with risk edging upwards at very low levels. The researchers said their study hadn't proven lowering blood pressure aggressively in these patients had no benefit, but did justify new research into the issue.
Researchers conducted a post hoc observational analysis of the PROFESS trial, involving 20,330 patients aged over 50 with a recent non–cardioembolic ischaemic stroke.
Participants were recruited from 35 countries from September 2003 through to July 2006, and followed up for at least 18 months.
Risk of recurrence was 14.1% with systolic blood pressures of 150mmHg or higher, 8.7% between 140 and 149mmHg, 8.0% in those lower than 120mmHg, 7.2% in those between 120 and 129mmHg and just 6.8% between 130 and 139mmHg.
Blood pressure lower than 120mmHg was associated with a 29% higher risk of having another stroke, and 31% higher risk of other vascular events, including myocardial infarction and death from vascular causes, than patients whose blood pressure was between 130 and 139mmHg.
Rates of all-cause mortality and death due to vascular causes were highest in those with blood pressure lower than 120mmHg - 9.2% and 3.1% respectively – and those at 150mmHg or higher - 9.2 and 3.2% respectively.
Researchers took mean blood pressure measurements at the end of PROFESS – during which, patients had been treated with aspirin and dipyridamole, clopidogrel and telmisartan. Their findings were independent of blood pressure at baseline, or change during follow-up.
Study author Professor Philip Bath, Stroke Association professor of stroke medicine at the University of Nottingham, said doctors caring for stroke patients needed to be ‘vigilant about how low a given patient's blood pressure is within the normal range'.
Dr Ivan Benett, a cardiology GPSI in Manchester said: ‘There is still a temptation to think lower is better but this study reaffirms it probably isn't. It behoves doctors looking after people with stroke to manage all risk factors vigorously, but in the case of BP, not too vigorously. We should certainly be managing systolic BP to less than 140, but not less than 120.'
Dr Chris Arden, a cardiology GPSI in Southampton said that these results will certainly have an impact on his practice.
He said: ‘Historically our training has always been that lower is better, and this challenges that...there is an optimal window for blood pressure management'.
Professor David Fitzmaurice, anticoagulation lead for the Primary Care Cardiovascular Society, professor of primary care research at the University of Birmingham and a GP in the city said: ‘This paper merely reinforces for me that we need to be vigilant in terms of not allowing blood pressure to rise. It remains to be seen if there is an optimum lower limit.'
The intercollegiate stroke working party guidance on secondary prevention of stroke recommends a blood pressure target of 130/80mmHg.
The Journal of the American Medical Association 2011, 16 November