BP Variability After Stroke Therapy Linked to Poor Outcomes

Nancy A. Melville

September 28, 2015

CHICAGO — Increases in systolic blood pressure (SBP) in the initial days following endovascular thrombectomy are significantly linked to worse functional outcomes, a new study shows.

"In a cohort of acute ischemic stroke patients who were treated with endovascular therapies, we found a consistently robust association between increased systolic blood pressure and worse neurologic outcomes," said Alicia Bennett, DO, from the Neurology Department, University of Utah, Salt Lake City.

Blood pressure variability following acute ischemic stroke has been shown in previous research published in Neurology to be linked to infarct growth leading to worse outcomes, symptomatic intercerebral hemorrhage, and even death, but similar patterns following endovascular therapies have not been demonstrated, Dr Bennett said.

The results were presented here at the American Neurological Association (ANA) 2015 Annual Meeting.

For this retrospective study, Dr Bennett and her colleagues reviewed data on 161 patients with ischemic stroke who underwent endovascular thrombectomy from 2005 to 2013.

Calculations included blood pressure variation as the standard deviation and coefficient of variation of SBP in a total of 14,986 readings. The patients had a mean age of 64 years, and 81% had an anterior circulation stroke.

The results showed that each increase of one quartile of SBD standard deviation was associated with a 1-point increase in modified Rankin Scale (mRS) score at discharge, as well as at follow-up at six different time points in the first 5 days of hospitalization.

"An increase in 10 mmHg of the SBP standard deviation in the first 4 days of hospitalization was associated with a 1.9- to 2.7-fold higher odds of a 1-point increase in mRS at follow-up," Dr Bennett said.

Among the strongest risk factors for a 1-point increase in mRS score for every 10-mmHg increase in SBP deviation were age, a history of diabetes mellitus, postprocedural Thrombolysis In Cerebral Infarction score, and admission glucose levels (all P < .01).

Dr Bennett speculated that blood pressure variation may play an important role in the brain's ability to regulate in the first days after a stroke.

"Worse outcome is potentially a result of impaired cerebral autoregulation following stroke, especially in the first 4 days, and we're wondering if this impaired autoregulation is a result of these fluctuations in blood pressure," she said.

Novel Insights

The findings offer important, novel insights into the role of blood pressure in relation to endovascular thrombectomy, Shyam Prabhakaran, MD, director of stroke research at Northwestern University's Feinberg School of Medicine, Chicago, Illinois, told Medscape Medical News.

"Blood pressure variability as opposed to absolute levels of blood pressure has been linked to stroke risk and poststroke outcomes. [However,] the role of blood pressure variability after endovascular therapy has not been previously reported," he said.

While the Neurology paper showed a similar effect with blood pressure variability linked to increased infarct growth with intravenous tissue plasminogen activator (IV tPA), such findings are not widely known, Dr Prabhakaran said.

"Since this concept is not intuitive and not clinically utilized — we don't track variability on a daily basis in hospitals — clinicians may not grasp its importance."

He speculated that because the authors controlled for symptomatic hemorrhage and found that did not explain their findings, other mechanisms must exist.

"For example, it may be similar to [the Neurology study], which found infarct growth was common in patients with increased variability."

"Or, alternatively, non-neurological mechanisms such as cardiac complications may explain the association."

Further work exploring mechanisms of the association should include looking at various potential factors. In addition, the causes of variability, whether intrinsic (such as side of brain affected or posterior vs anterior circulation) or iatrogenic (due to medications administered), should be evaluated.

"The authors should also assess the relationship of blood pressure variation on outcomes in those with recanalization vs nonrecanalization," he added.

Known Marker

Anthony Kim, MD, medical director of the UCSF Stroke Center at the University of California, San Francisco, who chaired the session, noted that blood pressure variability is a known marker of autonomic tone and hemodynamic instability, yet ideal targets in acute care remain elusive.

"Acute blood pressure management is likely to be important for large-vessel strokes because we are trying to maintain collateral flow but still want to minimize the risk of reperfusion hemorrhage," he told Medscape Medical News.

"It's just that we don't have good evidence on the right targets for acute blood pressure management, nor do we really understand the factors which may modify these acute targets for individual patients."

He added that a caveat of the study is that, despite the link between increased blood pressure variation and worse outcomes, efforts to decrease that variation still may not change outcomes.

"There is limited ability to make causal inference with these observational data, even though important confounders, such as initial stroke severity and hemorrhage, were adjusted for," he said.

"But it still is possible that blood pressure variability is an innocent bystander and it could indeed be a marker of disease severity with residual confounding."

Dr Bennett, Dr Prabhakaran, and Dr Kim have disclosed no relevant financial relationships.

American Neurological Association (ANA) 2015 Annual Meeting. Abstract S255WIP. Presented September 27, 2015.


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