A baseline systolic blood pressure (SBP) between 145 and 180 mmHg before the initiation of oral anticoagulant therapy may more than double the hemorrhagic stroke risk in patients with atrial fibrillation, according to research published in the Journal of Hypertension.
Researchers conducted an observational cohort study in order to evaluate the risk for hemorrhagic stroke at different levels of baseline SBP before the initiation of oral anticoagulant therapy in patients with hypertension and atrial fibrillation.
Participants were part of the Swedish Primary Care Cardiovascular Database of Skaraborg (SPCCD-SKA), which included primary healthcare patients from a rural area of southwest Sweden, between 2006 and 2016. Patients with atrial fibrillation and hypertension treated with an oral anticoagulant during the study period were eligible for inclusion; the primary study outcome was hemorrhagic stroke.
A total of 3972 patients (mean age, 77±8.5 years; 47.8% women) with atrial fibrillation, hypertension, and newly initiated oral anticoagulant treatment were included in the study, which had a total follow-up of 17,264 person-years (mean, 4.3 per patient). Patients were stratified by SBP levels: <130 mmHg (n=1031), 130 to 139 mmHg (n=829), 140 to 159 mmHg (n=1440), 160 to 179 mmHg (n=479) and at least 180 mmHg (n=175).
The most common baseline comorbidities were coronary heart disease, cerebrovascular disease, congestive heart failure, and diabetes, found in 34%, 26.4%, 29.1%, and 24.7% of patients, respectively. In terms of oral anticoagulant therapy, 87.7% of patients took warfarin; 11.6% took rivaroxaban, apixaban, or edoxaban; and 1% took dabigatran; 34.2% of patients used platelet inhibitors at baseline.
Forty patients experienced hemorrhagic stroke, with the highest incidence rate (5.8 per 1000 person-years) in the 160 to 179 mmHg blood pressure category. Lowest incidence rates (1.2 per 1000 person-year) were found in the <130 mmHg blood pressure group.
Curve of the restricted cubic spline indicates that the hazard ratio (HR) for hemorrhagic stroke was below 1 in the 120 to 130 mmHg blood pressure group (nadir, approximately 125 mmHg). HR in this blood pressure range was not significantly lower than the reference (130 mmHg). In the 145 to 180 mmHg range, though, the risk for hemorrhagic stroke more than doubled — a statistically significant difference.
A diagnosis of any stroke — either ischemic or hemorrhagic — was noted in 208 patients. The 160 to 179 mmHg blood pressure group experienced the highest incidence rate (18.7 per 1000 person-years), while the lowest incidence rate was 10.6 per 1000 person-years in the <130 mmHg group. Those in the 155 to 170 mmHg group experienced an increased risk of any stroke type.
There were 312 bleeding events of any type. The highest bleed incidence rates were in the 160 to 179 mmHg blood pressure group (24.7 per 1000 person-years) while the lowest incidence rates were in the at least 180 mmHg group (8.5 per 1000 person-years).
Investigators identified 590 deaths during the follow-up period. Highest mortality rates were in the <130 mmHg group (37.4 per 1000 person-years), while the 160 to 179 mmHg group had the lowest mortality rate (29.5 per 1000 person-years). Systolic blood pressure below 105 mmHg was associated with an increased risk for death in the continuous analysis when compared with the reference (130 mmHg).
Study limitations include those inherent to observational cohort research, the equation of medication dispensing with treatment, which may result in misclassification errors due to patients who received, but did not take their medications, and limitations of external validity due to the high number of warfarin users within the cohort.
“[P]atients with hypertension, atrial fibrillation, and a SBP above 145 mmHg prior to initiation of anticoagulant treatment are at an increased risk of hemorrhagic stroke,” the researchers concluded.
“This suggests that lowering SBP to below 145 mmHg, prior to the initiation of [oral anticoagulation therapy], may decrease the risk of hemorrhagic stroke in patients with hypertension and atrial fibrillation.”
Bager J-E, Hjerpe P, Schiöler L, et al. Blood pressure levels and risk of haemorrhagic stroke in patients with atrial fibrillation and oral anticoagulants: Results from The Swedish Primary Care Cardiovascular Database of Skaraborg. Published online March 11, 2021. J Hypertens. doi: 10.1097/HJH 0000000000002838