par Naeije, Robert ;Lau, Edmund M T;Celermajer, David D.S.
Référence The Right Heart, Springer-Verlag London Ltd, page (223-242)
Publication Publié, 2013-11
Partie d'ouvrage collectif
Résumé : Pulmonary arterial hypertension (PAH) is a right heart failure syndrome. The dominant symptom of PAH is shortness of breath. However, in spite of widespread pulmonary vascular remodeling and obstruction, gas exchange in PAH is generally well maintained, with moderate hypoxemia mainly caused by a low cardiac output. Patients with PAH are hypocapnic, but this is explained by increased chemosensitivity, and there is no ventilatory limitation to exercise capacity. Thus lung function is normal or near-normal in PAH. The symptomatology of PAH is principally related to right ventricular (RV) failure. Right ventricular function is altered as soon as pulmonary vascular resistance increases. In early stage PAH, the RV tends to remain adapted to afterload, with little or no increase in right heart chamber dimensions, but less than optimal RV-arterial coupling is a cause of decreased aerobic exercise capacity by limiting maximum cardiac output. In more advanced stages, homeometric adaptation of the RV becomes insufficient for daily life activities resulting in a progressive dilatation of right heart chambers and systolic dysfunction. Along with decreased contractile reserve of the RV, diastolic dysfunction occurs, due to RV fibrosis and sarcomeric stiffening; these changes lead to limitation of flow output and increased right sided filling pressures. These in turn lead to a combination of systemic venous congestion and dyspnea occurring at lower levels of exercise and, eventually, at rest. Imaging of RV function is of major diagnostic and prognostic relevance. Treatment of RV failure in PAH relies on decreasing afterload with therapies targeting the pulmonary circulation, optimal fluid management of ventricular diastolic interaction, and inotropic interventions to reverse cardiogenic shock states. The potential of chronic low-dose β-blocker therapies is currently investigated.