The Hypertension of Hemophilia Is Associated with Vascular Joint Remodeling and Cannot be Explained By the Usual Cardiovascular Risk Factors

Patients with hemophilia (PWH) have a higher prevalence of hypertension and intracranial hemorrhage than the general male population. However, the etiology of the hypertension, and to what extent blood pressure and associations with cardiovascular risk factors vary from the general population, is incompletely understood. We therefore investigated the prevalence of hypertension as well as the associations of blood pressure measurements with usual cardiovascular risk factors, in a cross-sectional analysis of a cohort of 486 PWH. The PWH (median age 38 years) came from 3 geographically different areas in the United States. They were compared against males from the contemporary National Health and Nutrition Examination Survey (NHANES), matched for age and race in a 1:5 ratio. Subsequently, at the University of California San Diego, a pilot cohort of PWH (n=28; median age 37 years) was examined prospectively for hypertension and associations with hemophilia-specific risk factors pertaining to joint health.

PWH had a significantly higher prevalence of hypertension compared to subjects from NHANES. The prevalence of hypertension was 53.4% in PWH compared to 28.8 % in NHANES (p<0.01). In untreated (not taking anti-hypertensive medications) and treated subjects median systolic blood pressure (SBP) and diastolic blood pressure (DBP) were significantly higher in PWH than in NHANES. Differences in prevalence of hypertension and blood pressure measurements were most pronounced in the youngest age group (18-29 years). In untreated PWH median SBP and DBP were 125 and 78 mmHg (118 and 72 mmHg in NHANES), and in treated PWH 134 and 84 (127 and 76 mmHg in NAHES), respectively; all p-values <0.0001. However, despite higher blood pressures the usual cardiovascular risk profile was better in PWH compared to NHANES, in that body mass index (BMI), total cholesterol, smoking and diabetes were lower and renal function was better.

While the usual cardiovascular risk factors were associated with blood pressure in both PWH and NHANES, they did not account for the differences between the two groups. Whether each risk factor was considered by itself, or in combination with the others in multivariate models, the blood pressure differences remained. Therefore, to elucidate to what extent hemophilia-specific factors might play a role in the pathophysiology of hypertension, we assessed hypertension and blood pressures in association with joint health parameters in a pilot cohort of young adult PWH. These patients underwent prospective baseline examination of 6 joints (both elbows, knees and ankles, n=168) for joint pain (Visual Analogue Scale 0-10), radiographic Pettersson score (maximum score 78), clinical Hemophilia Joint Health Score (HJHS, maximum score 120), severity of hemophilia (severe vs mild/moderate), clotting factor usage, and joint vascular perfusion quantified with Power Doppler (PD, maximum score 54) and high resolution musculoskeletal ultrasound. We found that 54% were hypertensive, similar to the larger cohort. In univariate analysis, PD score was the risk factor most strongly associated with hypertension (p = 0.07). After adjustment for confounders, the odds for hypertension increased by 1.29 (95% CI: 1.04, 1.60; p = 0.02) for each unit increase in PD score. Moreover, there was a strong association of PD scores with SBP when adjusted for confounders.

In conclusion, our findings demonstrate that PWH not only have a significantly higher prevalence of hypertension, but also significantly higher blood pressures compared to the general population, even when treated with anti-hypertensive medications. The difference in blood pressures could not be explained by the usual cardiovascular risk factors but appeared to be strongly associated with the degree of vascular changes in the joint. Based on previous findings that vascular remodeling is a prominent feature of hemophilic arthropathy and may be mediated systemically, we postulate that vascular remodeling is associated with the etiology of hypertension in hemophilia. These findings warrant further basic and clinical investigation.