par Naeije, Robert ;Lamia, Bouchra
Référence The Right Heart, Springer-Verlag London Ltd, page (99-114)
Publication Publié, 2013-11
Partie d'ouvrage collectif
Résumé : Echocardiography allows for accurate measurements of pulmonary vascular resistance and hydraulic load, and thus the estimation of afterload in severe pulmonary hypertension as a cause of right ventricular (RV) failure. The procedure also provides a series of estimates of RV systolic function, such as fractional area change, tricuspid annular plane excursion, tricuspid annulus tissue Doppler imaging of the velocities of isovolumic contraction and ejection, strain and strain rate. These indices help to evaluate the adequacy of RV systolic function adaptation to afterload (Anrep mechanism) but suffer from variable degrees of preload-dependency. Failure of RV-arterial coupling results in Starling's mechanism of preservation of stroke volume through increased myocardial fibre length, or end-diastolic volume. This can be appreciated by echocardiographic measurements of increased right heart chamber dimensions, dilatation and loss of inspiratory collapsibility of the inferior vena cava, and pericardial effusion, along with altered indices of left ventricular diastolic function such as prolonged isovolumic relaxation time, deceleration of E waves, and decreased ratio of E over A waves. Echocardiographic dimension measurements are currently limited to a series of planes, with difficult instantaneous volume reconstruction of the RV, which has an irregular crescent shape and inhomogenous contraction. Echocardiography is limited by operator-dependency, and is sometimes implemented in low clinical probability contexts. This may be a cause of false positive or negative diagnosis of RV failure. Recent advances in echocardiography technology open the perspective of RV volume measurements with assessment of regional function and asynchrony.