Relationship between the left-to-right ventricular volume ratio and aortic regurgitation severity

Introduction Left ventricular (LV) enlargement in chronic aortic regurgitation (AR) is typically assessed using LV diameters and volumes. However, these measurements are influenced by body surface area, sex, and age. We hypothesized that the CMR-assessed left-to-right ventricular end-diastolic volume ratio (LV/RV volume ratio), which remains close to 1 in healthy individuals regardless of age and sex, could offer a more individualized marker of adverse LV remodeling in chronic AR patients. Purpose We aimed to determine whether the LV/RV volume ratio correlates more strongly with AR severity than conventional LV measurements. Methods In this bi-center study, 258 patients (median age: 55 years, 18% women) with chronic AR underwent both echocardiography (Echo) and cardiac magnetic resonance imaging (CMR). LV and right ventricular (RV) volumes were measured from short-axis steady-state free precession cine-CMR images. Significant AR was either defined as grade 3-4 by Echo or AR Regurgitant fraction (RegFrac) ≥ 33% by CMR. A control group of 100 consecutive healthy individuals was used to define normal LV/RV volume ratio values. Associations between the LV/RV volume ratio, conventional LV metrics (Echo-assessed absolute and indexed LV end-systolic diameters, CMR-assessed indexed LV end-diastolic and end-systolic volumes), and AR severity were assessed using areas under the curve (AUC) and logistic regression models. Results In healthy individuals, the median LV/RV volume ratio was 1 [25th-75th percentile: 0.9-1.1], with no significant differences by age or sex (all p>0.178). In chronic AR patients, the median LV/RV volume ratio was 1.5 [25th-75th percentile: 1.3-1.9], increasing with AR severity grading (p<0.001, Fig. 1A). The LV/RV volume ratio correlated more strongly with CMR AR-RegFrac (r=0.67, p<0.001, Fig. 1B) than LV diameters or volumes. It showed strong associations with significant AR, both by Echo (AUC 0.77, 95% CI [0.70-0.83], Fig. 2A) and CMR (AUC 0.83, 95% CI [0.78-0.88], Fig. 2B), which remained significant after adjustment for age and sex (Echo: OR 4.25, 95% CI [2.44-7.41], p<0.001; CMR: OR 6.28, 95% CI [3.77-10.47], p<0.001, [OR for 1 increase in standard deviation]). A threshold of 1.5 for the LV/RV volume ratio identified significant AR with good diagnostic accuracy (Echo: Sensitivity [Se] 71%, Specificity [Sp] 77% ; CMR: Se 84%, Sp 75%). The LV/RV volume ratio did not significantly differ by age (≥ or < 55 years) or sex (all p>0.160), and its diagnostic performance was consistent across sex and age subgroups. Conclusion The LV/RV volume ratio showed a stronger relationship with AR severity than conventional LV metrics, with a threshold value of 1.5 identifying significant AR. Therefore, the LV/RV volume ratio could provide a more tailored assessment of adverse LV remodeling in chronic AR. These findings support further investigation into its clinical prognostic value in patients with chronic AR.