Pursuing ventricular-arterial coupling: a comparison of cardiac magnetic resonance right ventricular strain analysis and novel echo-derived indexes of right ventricular myocardial work
Authors: Lacerda Teixeira B , Carvalheiro R , Neves I , Antunes M , Cardoso I , Ferreira V , Reis J , Galrinho A , Aguiar Rosa S , Cruz Ferreira R 
Published: January 2025

Abstract

Introduction
End-systolic to arterial elastance ratio (Ees/Ea) represents right ventricular-arterial coupling (RVAC) and is the gold standard for measuring right ventricular (RV) function However, this method is time-consuming and not always readily available. A simplified approach is using the stroke volume (SV) to end-systolic volume (ESV) ratio, which has shown prognostic relevance in pts with PH, with a cut-off value of 0.5. Cardiac magnetic resonance (CMR) measurements of volumetric data allow the assessment of this ratio. CMR strain analysis has also emerged as a technique to detect subtle changes in RV function, and, recently, right ventricular myocardial work (RVMW) assessed by transthoracic echocardiography (TTE) allows the study of RV pressure-strain loops. The association between indexes of RVMW and CMR derived parameters has not yet been extensively studied, namely in pre-capillary PH population.

Objectives
To evaluate the relationship between the SV/ESV ratio and CMR-derived RV strain and TTE-derived RVMW in a cohort of pts with group I and group IV PH.

Methods
Thirteen consecutive precapillary PH pts underwent CMR, TTE and right heart catheterization prospectively. CMR feature-tracking was used to track tissue voxel motion in short and long-axis cine images, in order to derive myocardial strain. In TTE, dedicated software for left ventricle myocardial work was used for the RV.

Results
69% of pts included were women, mean age 67. The average of mean PAP was 35 mmHg (± 13.5) and PVR was 4.8 WU (± 4.9). SV/ESV ratio significantly correlated with RV ejection fraction (EF) (r = 0.888, p &lt; 0.001) and circumferential peak systolic (CPS) strain (r = 0.538, p = 0.037), but not with longitudinal peak systolic (LPS) strain (p = 0.571). As for TTE-derived RVMW, SV/ESV ratio demonstrated significant correlations with RVGWI (r = 0.580, p = 0.038) and RVGCW (r = 0.654, p = 0.015) but not with RVGWW (p = 0.780) nor RVGWE (p = 0.364). Significant correlations were found between RVEF and CPS strain (r = 0.690, p = 0.009), RVEF and RVGCW (r = - 0.592, p = 0.033) and between CPS strain and RVGWI (r = 0.620, p = 0.024) and RVGCW (r = 0.718, p = 0.006). 38,5% of pts had SV/ESV ratio &lt; 0.5. These pts had lower RVEF (48 ± 7.1 vs 61 ± 5.5, p = 0.004), lower CPS strain (-10.9 ± 3.0 vs -15.8 ± 2.9, p = 0.015) but higher RVGWI (828 ± 167.4 vs 526 ± 192.0, p = 0.015) and RVGCW (1061 ± 228.5 vs 698 ± 141.0, p = 0.004) compared to pts with SV/ESV &gt; 0.5. LPS strain, RVGWW and RVGWE did not showed statistically differences between groups.

Conclusion
SV/ESV ratio correlated with both CMR-derived CPS strain and TTE-derived RVMW. Pts with a lower SV/ESV ratio had lower circumferential strain but higher work indices, suggesting potential compensatory mechanisms, where increased work may not translate to efficient pumping. Further studies with larger cohorts are warranted to validate these parameters and establish relation with outcomes.
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