Assessment of the Relations Between Endothelial and Venous Dysfunctions and Left Ventricular Obstruction in Genetic Hypertrophic Cardiomyopathies

Overview

Left ventricular obstruction is an invalidating complication of hypertrophic cardiomyopathies (HCM), and endothelial dysfunction has also been observed in these pathologies. However, the relation between obstruction and endothelial and venous dysfunctions has not been previously studied. The main objective is to investigate the relations between endothelial and venous dysfunctions and symptomatic left ventricular outflow-tract obstruction in HCM patients.

Hypertrophic cardiomyopathies (HCM) secondary to sarcomeric gene mutation or to Anderson-Fabry disease can be complicated by left ventricular (LV) outflow-tract obstruction responsible of disabling exercise symptoms. LV outflow-tract obstruction is a complex, multifactorial and dynamical phenomenon influenced by the degree of LV hypertrophy but also by mitral valve elongation and hemodynamical components including venous return (LV preload). The clinical and research team of Dr Réant, responsible of the Bordeaux Competence Center in hereditary or rare Cardiomyopathies, has recently demonstrated that LV outflow-tract obstruction can also be influenced by the conditions of realization of exercise echocardiography tests (position: upright versus supine, type: bicycle versus treadmill), and by an abnormal venous return capacity. In parallel, it has also been demonstrated, by other research teams, that HCM can be associated to endothelial and microvascular peripheral dysfunctions. However, to date, the relation between these two elements, and with sudden cardiac death risk, have not been previously studied. The tests which will be performed during normal recommended follow-up of the HCM patients will be: Brain Natriuretic Peptide (BNP) blood sample test, electrocardiogram (ECG), Holter ECG, echocardiography at rest and during exercise. The tests realized in addition will be: * air venous plethysmography: non invasive, and non painful test evaluating different parameters of venous filling by inflation of an armband around the leg, upright positioning, flexion-extension of the leg. Total duration estimated at 30-45 minutes. * upper member arterial Doppler echography with analysis of Flow Mediated Dilatation (FMD) : measurement of the evolution of brachial artery diameter before and after inflation of a armband during 5 minutes. Non invasive and non painful test, duration 30 minutes.. * endothelial function biomarkers: blood sample test, 5 minutes. No follow-up is required for this study.