Abstract 167: Consistency of Blood Pressure Control Predicts Vascular Outcome after Ischemic Stroke
Authors: Towfighi Amytis , Markovic Daniela , Ovbiagele Bruce 
Published: March 2022

Background:
Hypertension is the leading modifiable risk factor for stroke. Uncontrolled hypertension increases cardiovascular risk, independent of type of treatment. Analysis of blood pressure (BP) control using mean follow-up BP may not provide a complete picture of BP control during a study, because BP may be in control at one visit and out of control at the next visit or vice versa.

Objective:
To assess the independent association between consistency of BP control at follow-up encounters and occurrence of future vascular events among recent ischemic stroke patients.

Methods:
We reviewed the trial dataset of 3680 recent (<120 days) ischemic stroke patients, aged ≥ 35 years, recruited from 56 centers from 1996 to 2003, and followed for 2 years. Consistency of BP control was defined as the proportion of visits in which BP was in control (<140 mm Hg systolic and 90 mm Hg diastolic). Patients were grouped according to proportion of visits in which BP was in control (<25%, 25-49%, 50-74% and ≥75%). The primary outcome was time to stroke, myocardial infarction (MI) or vascular death; while time to stroke alone was the secondary outcome. Stepwise Cox proportional hazard models were used to determine the relationship between BP control and primary and secondary outcomes before and after adjusting for demographic (age, sex, and race-ethnicity) and clinical variables (vascular risk factors and cardiovascular medications use). Interaction effects were assessed for age, sex, race, history of hypertension, history of diabetes, and baseline (measured after the qualifying stroke) systolic BP (SBP).

Results:
Among the cohort, 35%, 16%, 19%, and 30% had BP controlled <25%, 25-49%, 50-74%, and ≥75% of the time. After adjustment for covariates, those who maintained their BP within the target range ≥75% of the time did not have significantly lower rates of primary or secondary outcomes compared to those with BP within target range <25% of the time; however, there was an interaction with baseline SBP such that a higher proportion of visits within target BP control was significantly associated with vascular risk reduction benefit starting from a baseline SBP of 132 mm Hg. Among patients with baseline SBP in the 75
th
percentile (≥ 153 mmHg), having BP controlled at least 75% of the time conferred a lower risk of stroke, MI or vascular death (HR 0.51, 95% CI 0.32-0.83, p=0.007) and stroke (HR 0.48, 95% CI 0.26-0.87, p=0.02), compared to having BP controlled <25% of the time. Individuals with mean follow-up BP under control had a lower risk of stroke, MI or vascular death (HR 0.76, 95% CI 0.62-0.92, p=0.006) and stroke (HR 0.76, 95% CI 0.59-0.98, p=0.03).

Conclusions:
While achieving a mean follow-up BP within target range is independently associated with a reduction in stroke, MI or vascular death, consistency of BP control among those with elevated baseline SBP is independently linked to an even greater reduction in vascular events. These findings highlight the importance of ensuring BP is controlled at each post-stroke clinical encounter, particularly among those patients who have elevated baseline SBP in the post-acute period following their index stroke.