Consistent BP Control Reduces Recurrent Stroke Risk

April 04, 2014

Consistency of blood pressure (BP) control was strongly associated with a reduced risk for recurrent stroke in a new study.

The post hoc analysis of the VISP (Vitamin Intervention for Stroke Prevention), published online in Stroke on March 27, found that fewer than one third of stroke patients enrolled in the trial had BP controlled for 75% or more of the time.

However, those who did have their BP controlled for 75% or more of the time had half the risk for recurrent stroke during the 2-year study period compared with patients whose BP was controlled for less than 25% of the time.

Lead author, Amytis Towfighi, MD, University of Southern California, Los Angeles, commented to Medscape Medical News: "We know that raised blood pressure is a risk factor for stroke. We generally just look at office visit value and take an average over time. But emerging data show that variability in blood pressure is associated with worse outcomes."

She continued: "In coronary artery disease patients, it has been shown that the consistency with which blood pressure is kept below 140/90 is associated with better outcomes. Now we have shown a similar finding in patients with stroke."

Noting that this was a post hoc analysis and the population in the trial is not representative of the overall stroke population, Dr. Towfighi acknowledged that the analysis was "not the best evidence." But she pointed out that this is the first study to show the importance of consistency of BP control among individuals with previous stroke.

"By looking at variability we are picking up different people than if we just look at average values. Average blood pressure results also showed an association with outcomes but this was not as profound as that linked to variability," she told Medscape Medical News.

Fluctuating BP Signals High Risk

"More and more data are now accumulating that variability in blood pressure itself has detrimental effects. There might be two people with the same average blood pressure, but one always has similar readings while the other may fluctuate wildly. We believe the fluctuating one is at higher risk. We are advocating that variability of blood pressure is included in assessments, not necessarily instead of average readings but as well as."

She added: "It is not enough to do one-time measurements at a clinic visit. Much more frequent measurements are needed, which could be brought about with more extensive use of home monitoring."

For the current study, the researchers analyzed data from the VISP trial, which involved 3680 patients within 120 days of having sustained a stroke, and who were followed or 2 years. They were divided according to proportion of visits in which BP was controlled (<140/90 mmHg): less than 25%, 25% to 49%, 50% to 74%, and 75% or greater. Multivariable models adjusting for demographic and clinical variables determined the association between consistency of BP control and recurrent stroke (primary outcome) and stroke, myocardial infarction, or vascular death (secondary outcomes).

Results showed that only 30% of participants had BP controlled for 75% or more of the time. Consistency of BP control affected outcomes in individuals with baseline systolic BP greater than 132 mmHg.

Among individuals with baseline systolic BP greater than 75th percentile (>153 mmHg), risks for primary and secondary outcomes were 2-fold lower in those with BP controlled for 75% or more of the time compared with those whose BP was controlled less than 25% of the time.

Table 1. Risk for Primary and Secondary Outcomes in Patients With BP Controlled 75% or More vs Less Than 25% of Visits

Endpoint Hazard Ratio (95% Confidence Interval)
Stroke 0.46 (0.26 - 0.84)
Stroke/myocardial infarction/vascular death 0.51 (0.32 - 0.82)

 

When mean BP was used to assess risk, this also showed an association with outcomes, but was not as clear as the consistency data.

Table 2. Risk for Stroke and Secondary Outcomes in Patients With Mean Follow-up BP Less Than 140/90 mmHg vs 140/90 mmHg or Greater

Endpoint Hazard Ratio (95% Confidence Interval)
Stroke 0.76 (0.59 - 0.98)
Stroke/myocardial infarction/vascular death 0.76 (0.62 - 0.92)

 

"Consistency of BP control offers information above and beyond mean BP," the researchers state in the paper. They add that these results highlight the importance of ensuring that BP is controlled at each poststroke clinical encounter, particularly among patients with elevated baseline systolic pressure.

With the combination of home BP monitors and mobile health technology, healthcare teams will be able to use home measurements to more reliably determine adequacy of BP control and to make subsequent treatment decisions, they add.

They point out that the finding that so few patients had consistent control in this study has important implications: "If BP is so inconsistently controlled in a randomized controlled trial with close follow-up, one can imagine that in the overall stroke population, a small minority of individuals have consistent BP control."

Stroke. Published online March 27, 2014. Abstract

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