Cystatin C, vascular biomarkers and measured glomerular filtration rate in patients with unresponsive hypertensive phenotype: a pilot study

Background: Biomarkers are commonly used to estimate the presence of subclinical cardiovascular disease (CVD) in patients with essential arterial hypertension (HT). In addition to known association between cystatin C and glomerular filtration rate (GFR), elucidating the association between cystatin C and vascular biomarkers (intima-media thickness of common carotid arteries (CCIMT), carotid plaque and renal artery resistance index (RRI)) in patients with unresponsive hypertensive phenotype could be of significant clinical interest. Methods: Participants (n = 200, median age 58 (52-64) years, 49% female) under treatment with antihypertensive drugs were stratified into two subgroups based on their blood pressure level as having responsive hypertension (RHT - compliant and responsive to treatment, n = 100), or nonresponsive (URHT - compliant but nonresponsive to treatment, n = 100). GFR was measured by isotopic (slope-intercept) method (99m Tc diethylene triamine penta-acetic acid - mGFR). Results: The URHT group had significantly higher median cystatin C serum concentration (p = 0.02) and CCIMT (p = 0.00) compared to the RHT group, with no significant difference in RRI (p = 0.51) and mGFR among subgroups [69.9 ± 28.2 vs 76.74 ± 23.61 ml/min/1.73m 2 , p = 0.27]. In the URHT group, cystatin C was found to be associated with CCIMT (p = 0.02), hsCRP (p = 0.01) and duration of HT (p = 0.02), independently of mGFR and age. Independent predictors of URHT phenotype were CCIMT (p= 0.02) and hsCRP (p= 0.04). Conclusion: In addition to GFR, cystatin C serum concentration is positively and independently associated with CCIMT in patient with URHT phenotype and subclinical CVD. Prospective larger studies should further investigate the clinical importance of this relationship.