Ultrasound Assessment and Vascular Mechanics in Takayasu Arteritis and Systemic Lupus Erythematosus

Abstract: Takayasu arteritis (TAK) and systemic lupus erythematosus (SLE) are inflammatory diseases that primarily affect young women. TAK is a rare vasculitis that affects the aorta and its main branches, whereas SLE is a chronic autoimmune disease that effects multiple organs. Both diseases are associated with premature cardiovascular disease (CVD), and a wish to understand these associations prompted the studies of this thesis.The macrocirculation, microcirculation and vascular haemodynamics were studied in patients with TAK (N=25 in Paper I, N=17 in Paper II) and SLE (N=60 in Papers III and IV), and compared with age- and gender-matched controls. Vessel wall thickness (intima-media thickness (IMT)), vessel wall appearance, and occurrence of atherosclerotic plaques were evaluated in multiple vascular areas using high-frequency ultrasound (US). Microcirculation in the skin was studied after induced ischaemia employing a new method that combines laser Doppler flowmetry (LDF) and diffuse reflectance spectroscopy (DRS). The measured microcirculatory value was defined as the peak oxygen saturation (OxyP). Pulse wave analysis was used for calculation of the central augmentation index (AIx). Cerebrovascular reserve capacity (CVR) was analysed using transcranial Doppler (TCD).Paper IIn this study, TAK patients were examined with US, including follow-up studies. Clinically active cases of TAK showed significantly increased IMT compared to stable patients with TAK and healthy controls. The arteries of patients with active disease showed signs of intra-mural micro-vessels, oedema, or increased vessel diameter, whereas these signs were not seen in cases of stable disease. The Takayasu US index (based on the summation of the IMT in three arterial areas) was higher in active disease than in stable disease, and was valuable for the assessment of relapse.Paper IIIn this study of vascular haemodynamics in patients with TAK we observed impaired microcirculation, as compared with controls. CVR was preserved regardless of proximal arterial stenosis. The AIx, reflecting arterial stiffness, was increased, also in the arms without proximal stenosis or occlusion.Papers III and IVIncreased IMT with predominantly medium echogenicity was observed in multiple arteries of the 60 patients with SLE, predominantly in vascular areas that are not usually part of the IMT measurements. The patients with SLE developed plaques more frequently and earlier in life compared to the controls. Correlation with traditional cardiovascular risk factors was observed, indicating atherosclerotic mechanisms rather than inflammation. The patients with SLE had higher AIx values and lower OxyP levels, even at younger ages, and both these methods correlated with the IMT and plaque occurrence.ConclusionsFor patients with TAK, US can be valuable both for the diagnosis of the disease and for distinguishing between the active and stable disease forms. The microcirculation and degree of arterial stiffness in the arms are affected also in patients with TAK without proximal stenosis/occlusion, indicating a more widespread arterial wall dysfunction.In patients with SLE, increased IMT, an affected microcirculation, increased arterial stiffness, and premature atherosclerotic plaques indicate vascular affection coupled with increased risk for cardiovascular disease. All these evaluated methods may be used for longitudinal studies with or without intervention.