0164: Validation of two-dimensional speckle tracking strain for assessment of early right ventricular dysfunction: in vivo and ex vivo study

Abstract

Right ventricular (RV) dysfunction is a major determinant of long-term survival in congenital heart diseases. Early echo detection of RV failure is mandatory, but recent indices need to be validated. Objectives were to: (1) validate standard and strain echo indices for evaluation of RV systolic function, compared to hemodynamic parameters; (2) assess the accuracy of these indices for early detection of RV failure. Combined RV overload as observed in repaired tetralogy of Fallot was surgically reproduced in 2-month-old piglets (n=6). Age-matched piglets were used as controls (n=4). RV function was evaluated at baseline and 4 months of follow-up by standard and strain echo indices, compared to conductance catheter. Sarcomere shortening and calcium transients were recorded in RV isolated myocytes (IonOptix). Contractile reserve was assessed by in-vivo (dobutamine 5µg/kg) and ex-vivo (isoprenaline 100nM) β adrenergic stimulation. The integrity of T-tubules was controlled after Di-4-Anepps labeling. 4 months after surgery, hemodynamic RV ejection fraction (FEVD) was significantly decreased (29.7% [26.2-34] vs 42.9% [40.7-48.6], p<0.01), and inotropic responses to dobutamine were blunted (contractile reserve ΔEmax=51% vs 193%, p<0.05). On echocardiography FAC, TAPSE, S’ peak and RV free wall longitudinal strain rate were significantly reduced and correlated with FEVD. Peaks strain rate and S’ were correlated with ΔEmax (r=0.75 and 0.78, p<0.05). Isolated RV myocytes from operated animals showed hypertrophy, decreased sarcomere shortening peak in response to isporenaline (ΔL=7.8±2.8% vs 10.7±2.9%, p<0.05), and increased spontaneous calcium waves suggesting perturbations of calcium homeostasis. In this model, both standard and strain echo indices allowed the detection of early impairments of RV function and cardiac reserve, which are associated with cardiac excitation-contraction coupling alterations.