CO-28: Flow-mediated dilatation (FMD) and endothelium-independent dilation (EID) in patients with multifocal fibromuscular dysplasia: a cross-sectional study.

BACKGROUND: Fibromuscular dysplasia (FD) is a rare idiopathic, segmental, non-atherosclerotic non-inflammatory vascular disease, which occurs mostly in middle-aged patients and affects medium-sized arteries (renal and carotid arteries). We previously showed that FD is a general arterial disease with focal exacerbation of the trait. However, whether endothelial dysfunction may be involved in the pathophysiology of FD is unclear.

METHODS: In a cross sectional study, we compared the endothelial function between 50 patients with multifocal FD of renal/carotid arteries confirmed by CT-angiography, 50 essential hypertensive (EH) patients matched for age, sex, ethnicity and BP and 50 healthy subjects (HS) matched for age, sex and ethnicity. Exclusion criteria were: tobacco consumption, hypercholesterolemia, diabetes, aspirin or statin treatment. Brachial artery (BA) FMD after release of hand ischemia and glyceryl trinitrate (GTN)-induced EID were measured using a high-resolution radiofrequency - based echotracking system blind to the diagnosis.

RESULTS: FD, EH and HS were well matched. FD and EH had significantly higher SBP than HS despite antihypertensive treatments. BA external diameter was significantly lower in FD than in both HS and EH before, during and after hand ischemia and after GTN. BA intima media thickness (IMT), internal diameter and distensibility did not differ between the 3 groups. The percent changes in BA diameter after release of hand ischemia (FMD) or GTN administration (EID) did not significantly differ between the 3 groups. BA flow velocity did not significantly differ in any experimental condition.

CONCLUSIONS: In conclusion, despite showing similar acute vasodilatory responses to flow and GTN, FD patients differed from EH and HS in terms arterial morphology with smaller BA diameter associated with similar IMT. The similarity of the IMT between the groups, combined with the reduction of the BA diameter in FD patients suggests that the BA underwent inward eutro-phic remodeling despite normal blood flow velocity. This paradoxical remodeling may suggest a chronic defect in the endothelium-dependent pathways involved in arterial remodeling in FD patients.