Blood pressure variations best to predict stroke

VARIATIONS in blood pressure are better for predicting the risk of stroke than high average readings, research has shown.

They are also important indicators of vulnerability to heart attacks, heart failure, and angina chest pains, a study suggests.

The findings, reported in The Lancet medical journal, could have major implications for the prevention of strokes and heart attacks.

Experts say clinical guidelines for treating patients should now be reviewed, as currently no special importance is attached to fluctuations in blood pressure.

Researchers looked at how blood pressure variability affected stroke risk in four large groups of participants in previous international trials, each including more than 2,000 patients.

All the patients had previously experienced a so-called “mini-stroke”.

Patients with the most variation in systolic blood pressure — the pressure measured with each “surge” of the beating heart — were six times more likely to have a stroke than those with the least.

Individuals with the highest blood pressure recorded over a series of seven clinic visits had a 15-fold increased stroke risk.

Visit-to-visit blood pressure fluctuations were also warning signs of heart failure, angina and heart attacks independent of average blood pressure.

Professor Peter Rothwell, from the University of Oxford, who led the study, said: “Raised blood pressure, or hypertension, accounts for over 50% of the risk of stroke and other vascular events in the population.

“It has long been believed that it is the underlying average blood pressure that determines most of the risk of complications from hypertension and all of the benefit from the drugs that are used to lower blood pressure.

“The work that we have done shows that this hypothesis is only partly true — at least when it comes to stroke, the most common complication of hypertension.

“We have shown that it is variations in people’s blood pressure rather than the average level that predicts stroke most powerfully. Occasional high values, and what might be called episodic hypertension, carry a high risk of stroke. Previously, such fluctuations were considered to be benign and uninformative.”