To Prevent a Second Stroke, Lower Blood Pressure to Normal

All patients with stroke should have their blood pressure lowered to normal levels, including those with poor collateral blood vessel formation near the site of the stroke, according to the results of a new study.

“After a stroke, blood pressure should gradually be lowered over a period of a few weeks to a few months. Lowering it right away within a few days after a stroke provides no immediate benefit. The reduction in stroke risk occurs months to years on good blood pressure control,” William Powers, MD, Professor and Chair of the Department of Neurology at the University of North Carolina School of Medicine in Chapel Hill told ConsultantLive.

Many neurologists had suspected that blood pressure should be left high in patients with poor collateral blood vessel formation. They thought high blood pressure might force blood around the blockage and through collateral vessels, which would be beneficial and, therefore, reduce the risk of stroke.

“The collaterals are smaller vessels than the occluded or stenotic carotid artery. It was thought that higher pressures could force more blood through these smaller vessels and lowering the pressure could lead to a reduction in blood flow and thus cause a second stroke,” Dr Powers said.

After a stroke, collateral vessels can help blood flow to an area of the brain that is cut off from its normal blood supply because of a blocked blood vessel. In the 1980s, Dr Powers led positron emission tomography scan studies that characterized the importance of these collateral vessels. His team showed that patients with poor collateral flow face 6 times the risk of suffering a second stroke than do patients with good collateral vessel formation. But how to treat those patients with poor collaterals remained debatable.

For most patients with stroke, doctors agree that reducing blood pressure to the normal range is best. “We have very good studies showing that normalizing blood pressure works,” Dr Powers said. “But some doctors argue that reducing blood pressure in patients with poor collaterals would be dangerous.”

Dr Powers’ pivotal study disproved this theory. “This was an observational study of 91 patients with occluded carotid arteries on one side who had low blood flow to the part of the brain normally supplied by the occluded artery, indicating collaterals that were poor,” he said. “We showed that the stroke rate over 2 years was 8% in those whose average blood pressure was less than 130/85 mm Hg and 30% in those more than 130/85 mm Hg. Lower blood pressure was not harmful. It was actually beneficial.”

Dr Powers added, “The idea that you should let blood pressure ride high to prevent a second stroke in these patients turns out to be completely wrong. You should treat their blood pressure just like you should treat everybody else who had a stroke to reduce the risk of a second one. Lowering blood pressure to normal is the best way to prevent another stroke.”

The researchers published their results online on February 14, 2014 in the journal Neurology.