Biomechanical properties of common carotid arteries assessed by circumferential two-dimensional strain and beta stiffness index in patients with ankylosing spondylitis.

OBJECTIVE Ankylosing spondylitis (AS) is associated with an elevated risk of cardiovascular disease (CVD) related to atherosclerosis, preceded by arterial stiffness. We aimed to examine common carotid artery (CCA) biomechanical properties using ultrasound to calculate β stiffness index (indicating arterial stiffness) and, a more recently developed technique, two-dimensional (2D) speckle tracking strain (indicating arterial motion and deformation, strain) to 1) compare with age- and sex-matched controls and to 2) analyze relationships between strain and stiffness with disease characteristics and traditional risk factors for CVD in AS patients. METHODS In this cross-sectional study, a cohort of 149 patients with AS, mean age 55.3±11.2 years, 102(68.5%) men, 146 (98%) HLA-B27 positive, were examined. Bilateral CCAs were examined for circumferential 2D strain and β stiffness index. A subgroup of 46 patients were compared with 46 age- and sex-matched controls, both groups without hypertensive disease, diabetes, myocardial infarction or stroke. RESULTS Mean bilateral circumferential 2D strain was lower in AS patients compared with controls, 7.9±2.6% vs 10.3±1.9%, p<0.001 whereas mean bilateral β stiffness index was higher, 13.1±1.6mmHg/mm vs 12.3±1.3mmHg/mm, p=0.018. In multivariable linear regression analyses strain was associated with age, erythrocyte sedimentation rate, history of anterior uveitis and treatment with csDMARD and/or bDMARD (R2 0.33), while stiffness was associated with age (R2 0.19). CONCLUSION Both CCA circumferential 2D strain and β stiffness index differed between AS patients and controls. Strain was associated with AS-related factors and age while stiffness with age, suggesting that the obtained results reflect different pathogenic vascular processes.