Call for overhaul of blood pressure monitoring

12th March 2010 - A fundamental change in the way GPs monitor high blood pressure is being urged, as experts say fluctuations in readings may be a better indicator of the risk of strokes and heart attacks than relying on single recordings showing high blood pressure, otherwise known as hypertension.

The findings could lead to major changes in the prevention of strokes and heart attacks.

Established medical practice is to estimate usual blood pressure to obtain a guide to cardiovascular risk.

Evidence from four separate trials

Professor Peter Rothwell, of the Stroke Prevention Research Unit at Oxford’s John Radcliffe Hospital and colleagues examined how variations in blood pressure affected the risk of stroke in previous international trials involving people who had experienced a ‘mini stroke’, known as a transient ischaemic attack.

They sifted through evidence from four separate trials, each involving more than 2,000 patients.

“The hypothesis that has come to dominate is that we each have an underlying average ‘true’ blood pressure, which is difficult to measure precisely, but which accounts for the vast majority of the complications of hypertension, and explains the benefits of blood-pressure-lowering drugs,” Rothwell says in a statement. “Variability in blood pressure is dismissed as uninformative and ‘random’, only noteworthy as an obstacle in the measurement of the true underlying blood pressure,” he adds.

Strong predictor of stroke and heart attack

However, Rothwell’s study showed that variations in systolic blood pressure (the pressure caused by each heart beat) provided a strong indication of stroke, heart failure, angina, and heart attack (myocardial infarction).

In fact, patients with the most variation - measured over seven visits to a clinic - were six times more likely to have a stroke. That compared to patients with the highest blood pressure, over the same number of visits, who were 15 times more likely to have a stroke.

Episodic high blood pressure “should no longer be ignored”

The findings challenge the current clinical guidelines that patients with only occasional high readings, known as ‘episodic hypertension’, do not require treatment. The researchers say that, quite to the contrary, such patients have a high risk of stroke and other complications.

“Persistent hypertension is a major cause of vascular disease and must be treated appropriately, but episodic hypertension is at least as common in routine practice and should no longer be ignored,” says Rothwell. “We have shown that episodic hypertension is just as risky, and that patients and their doctors shouldn't be reassured by the fact that blood pressure is sometimes normal,” he warns.

The research is published in the latest edition of The Lancet.

Commenting on the study, Professor Peter Weissberg, Medical Director at the British Heart Foundation, tells us in an email that it would be wrong to assume that current clinical guidelines are wrong, but says “this might add a new measure to help doctors make decisions on who to treat for hypertension”.

Weissberg adds that “From a public health perspective, the biggest issue remains that many people with hypertension are not diagnosed, and many who are diagnosed are not receiving any treatment. So we’ve much to do and conventional assessment and treatment still has a lot to offer.”