VASCULAR ALTERATIONS IN FIBROMUSCULAR DYSPLASIA: INSIGHTS FROM CAROTID AND AORTIC PULSE WAVE ANALYSIS

Objective: Fibromuscular dysplasia (FMD) is a non-atherosclerotic, multi-arterial condition of unknown origin, typically associated with hypertension. Changes in elastic and structural properties of the carotid and radial arteries have been observed in FMD, which may influence wave patterns differently compared to those seen in essential hypertension (HTN) and healthy individuals (HS).Design and method: Carotid and Aortic wave separation and wave intensity analysis were performed in patients with FMD (n = 16), age and blood-pressure matched HTN (n = 21) and age-matched HS (n = 22). Right and left carotid and aortic (transfer function from radial measurement) pressure waveforms were acquired using tonometery. Carotid blood flow velocity was measured using doppler ultrasound and aortic flow was simulated using the ARCSolver algorithm. Comparisons were adjusted for site of measurement, height and mean carotid diameter. Results: Carotid backward wave amplitude (ampPb) was comparable between HTN and FMD 14.82±4.71 vs 13.45 ± 5.36 mmHg, p =0.13) but higher in HTN compared to HS (11.69±3.78.mmHg, p =0.03). Backward compression wave intensity (dIb_R) (FMD -5.68 (-9.32,-3.23), HS -6.43 (-8.58,-3.59), HTN -8.38 (-11.46,-5.37)) and energy (Area_R) (FMD 0.33 (0.21,0.46), HS 0.35 (0.24,0.52), HTN 0.43 (0.29,0.66)) was higher in HTN compared to HS (p =0.04 and 0.02) and FMD (p =0.006 and <0.001) respectively. Aortic ampPb (FMD 17.5(13.6,23.0), HS 14.2(11.2,17.8), HTN 18.22(15.26,21.54)mmHg, and Area_R (FMD 0.96(0.71,1.51), HS 0.76(0.56, 1.08), HTN 1.06(0.72, 1.45) were significantly higher in patients with FMD compared to HS (p =0.008 and 0.04) but comparable to HTN (p =0.41 and 0.13) respectively. Conclusions: The results indicate two major alterations in patients with FMD. First, despite similar blood pressure, wave reflection at the carotid level is higher in patients with essential HTN compared to FMD. This could indicate a greater transmission of pulsatility to the cerebral circulation, leading to vascular damage and development of aneurisms in FMD. Second, wave reflections at the aortic level are increased, which could increase the risk of cardiovascular disease in these patients.