Occasional high blood pressure ‘a risk for stroke’

By Lilian Anekwe

Hypertension guidance is set to change after ‘revolutionary' new research suggested patients with only occasional high blood pressure readings – who are not currently diagnosed as hypertensive - are at increased risk of stroke and should be considered for treatment.

Three linked studies published in The Lancet and The Lancet Neurology last week found patients with the highest variation in blood pressure readings were up to 12 times more likely to have a stroke than those with the least variation.

Leaders of the British Hypertension Society (BHS) told Pulse the research would ‘undoubtedly' prompt a change in the Joint British Societies' JBS3 guidance on hypertension, due this summer. NICE also said it would take BP variability into account when revising its hypertension guidance next year.

The first of the three studies, all led by Professor Peter Rothwell, found BP variability was strongly linked to stroke risk among patients who either had a history of TIA or were being treated for hypertension.

Among the TIA group, patients in the top decile of systolic BP variability over seven visits had a six-fold higher risk of stroke than those in the lowest decile, and those in the top decile over 10 visits a 12-fold higher stroke risk than those in the lowest decile - regardless of their mean SBP reading.

The two other studies looked at the effects of different classes of antihypertensives on BP variability and concluded that calcium channel blockers produce greatest benefit. In one study, amlodipine reduced the risk of stroke by 22% compared with atenolol.

The other study - a meta-analysis of 389 randomised controlled trials – found that, compared with other drugs, calcium-channel blockers reduced variation in systolic blood pressure by 19%, while thiazide diuretics reduced it by 13%.

But ACE-inhibitors and ARBs raised SBP variability by 8% and 16% respectively, while did beta-blockers raised it by 17%.

Professor Rothwell, professor of clinical neurology at the University of Oxford concluded: ‘Visit-to-visit variability in systolic blood pressure is a powerful predictor of stroke and coronary events independent of mean systolic blood pressure. These findings challenge the usual blood-pressure hypothesis and have implications for diagnosis, treatment, and monitoring of patients with hypertension.'

He told Pulse that GPs might be justified in treating an apparently normotensive patient with a one-off high BP reading on the basis of raised stroke risk. He added: ‘Probably about half of all hypertensive patients show inconsistency between visits. It's certainly not a small minority and we should take them very seriously and start them on medication earlier.'

GPs could tailor drug choice according to BP variability, he suggested: ‘If you are prone to variable blood pressure it's much better to be put on a calcium-channel blocker or thiazide diuretic, and GPs should actively avoid ARBs, ACEis or beta-blockers.'

Former BHS president Professor Neil Poulter, professor of cardiovascular medicine at Imperial College London, said: ‘This tells us that the approach that is absolutely ingrained in all of us is probably wrong. This is revolutionary research that is going to prompt a fundamental look at the guidance, and rightly so.'

Professor Bryan Williams, professor of medicine at the University of Leicester, and chair of the BHS guidelines working party, said: ‘This data provides evidence that we should be moving towards more comprehensive monitoring of blood pressure away from the doctor's office, with wider use of home monitoring.'

Stroke risk
Highest visit to visit variability in systolic blood pressure over 7 visits - 6.2x increased risk
Maximum systolic blood pressure over 7 visits - 15.0x increased risk

Effect of antihypertensives on systolic blood pressure variability
Calcium channel blockers - 19% reduction
Thiazide diuretics - 13% reduction
ARBs - 16% increase
ACE inhibitors - 16% increase
Beta-blockers 17% increase

Sources: Rothwell et al, The Lancet 2010;375:895-905 & 906-915, The Lancet Neurology published online March 12