Vascular Function in Fibromuscular Dysplasia

Background: There have been no studies to date on the pathophysiologic mechanisms of how fibromuscular dysplasia (FMD) affects vascular function. Due to the perturbations in the blood vessel wall and the propensity for stenosis, dissection, and aneurysms seen in arteries with FMD, subjects with FMD may have impairment in endothelial function and abnormalities in arterial compliance. Methods: Twenty-seven subjects with documented FMD of the renal and/or carotid arteries and ten age, gender, and ethnicity matched healthy control subjects were recruited for this study. Predictors of cardiovascular disease including endothelial function, brachial-ankle pulse wave velocities (baPWVs), ankle-brachial indices (ABIs), and carotid artery intima-media thickness (IMT) were evaluated. Results: For the FMD population, endothelium dependent flow-mediated vasodilation of the brachial artery was 15.91 ± 8.69% (p<0.001). Nitroglycerin produced a significant 27.69% (p=0.04) increase in time-averaged, volumetric flow through the brachial artery and resulted in an increase in brachial artery diameter from 2.66 ± 0.42 mm to 3.37 ± 0.51 mm, p<0.01. The mean baPWV for all ages was 1324.37 ± 247.55 cm/sec, the mean ABI was 1.16 ± 0.09, and the mean distal common carotid artery far wall IMT was 0.64 ± 0.15 mm. Conclusion: This is the first study to evaluate vascular function in FMD. In this small population, FMD was not associated with endothelial dysfunction, impaired arterial compliance, increased carotid artery IMT, or decreased ABIs. A prospective larger study will be required to confirm these findings.