Association Between MRI-Derived Right-to-Left Ventricular Volume Ratio and Regional Left Ventricular Myocardial Dysfunction in Patients With Pulmonary Arterial Hypertension.

BACKGROUND: Right ventricular (RV) to left ventricular (LV) end-diastolic volume ratio (RV/LV) is a validated marker of RV dilation in pulmonary arterial hypertension (PAH), yet its impact on LV myocardial function and the underlying mediating pathway is incompletely characterized. PURPOSE: To investigate the association between RV/LV volume ratio and LV dysfunction in PAH patients, with a focus on regional strain patterns and mediating pathways. STUDY TYPE: Retrospective. POPULATION: 188 PAH patients were divided into normal (ratio < 1.27, n = 74) and elevated (ratio ≥ 1.27, n = 114) RV/LV volume ratio groups, and 81 age- and sex-matched controls. FIELD STRENGTH/SEQUENCE: 3.0-T/balanced steady-state free precession cine sequence. ASSESSMENT: LV global longitudinal, circumferential, and radial strains (LVGLS, LVGCS, and LVGRS, respectively) and regional strains were measured using feature tracking. Strain parameters were compared among controls and PAH subgroups. STATISTICAL TESTS: One-way ANOVA with Bonferroni-corrected post hoc tests, Kruskal-Wallis test, and Pearson or Spearman correlation. Multivariable linear regression was used to identify independent determinants and mediation analysis to examine the mediating pathways. A two-tailed p < 0.05 was deemed statistically significant. RESULTS: PAH patients with elevated volume ratio had significantly reduced LVGCS and LVGLS. Regional analysis showed that the most extensive strain impairment was at the mid-ventricular septum. The RV/LV volume ratio was independently associated with LVGCS (β = -0.194) and LVGLS (β = -0.307). Mediation analysis demonstrated that the mPAP-LVGLS relationship was statistically mediated by the RV/LV volume ratio, with a significant indirect effect (β = -0.192, 95% confidence interval: -0.302 to -0.096) and a non-significant (p = 0.544) direct effect. DATA CONCLUSION: Elevated RV/LV volume ratio in PAH is associated with spatially heterogeneous LV strain impairment, with the mid-septum being most vulnerable. The ratio mediates the adverse impact of pulmonary pressure on LV longitudinal strain and may serve as an imaging marker for assessing LV dysfunction. EVIDENCE LEVEL: 3. TECHNICAL EFFICACY: Stage 3.