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.