Geert Kleinnibbelink

RV Strain in Pulmonary Hypertension 6 153 DISCUSSION The purpose of this systematic review and meta-analysis was to examine whether RVLS has prognostic value for future events in patients with PH. The key finding was that RVLS has independent prognostic value for all-cause mortality ( Figure 3 ). To a lesser extent, RVLS also demonstrated independent predictive capacity for the combined endpoint of mortality and PH-related events ( Figure 2 ). Collectively, these findings emphasize that RVLS is a valuable tool with independent prognostic value for all-cause mortality in PH patients. Impact of PH on RVLS The thin RV walls consist of longitudinal, circumferential and oblique oriented muscle fibers. 35 The free wall predominantly consists of transverse fibers with scanty subendocardial longitudinal oriented fibers, while in the septal wall the oblique fibers are in a helical shape. 35 Coiling and shortening of the helical-shaped oblique fibers determine the shortening of the RV, producing 80% of RV systolic function. In contrast, contraction of the transverse fibers accounts for just 20% of RV systolic function. 35 In a healthy RV, contraction is therefore predominantly driven by shortening of the RV in the longitudinal direction 35, 36 , highlighting the importance of examining RVLS 35 in clinical and research scenarios. In PH, an increase in afterload influences the mechanical function of the RV, which subsequently leads to a decrease in longitudinal shortening 37 , indicating insufficient contraction and leading to a reduction of RV stroke volume. The increased afterload forces the RV to adapt, causing either hypertrophy and/or increased contractility to preserve function and stroke volume. 38 Ultimately, however, these processes may lead to maladaptive remodelling, which causes dilation of the chamber and altering of the helical orientation of the oblique fibers, leading to (progressive) attenuation of function. 35 This maladaptive process ultimately contributes to clinical progression and/or mortality. The strong relation between an increase in afterload and/or ventricular maladaptation alongside a decrease in RVLS likely explains the strong and independent prognostic value for RVLS for all-cause mortality in PH patients.