Relationship between the Left-to-right Ventricular Volume Ratio and Aortic Regurgitation Severity: An Echocardiographic and Cardiac Magnetic Resonance Imaging Study

Background Left ventricular (LV) enlargement in chronic aortic regurgitation (AR) is commonly assessed using diameters and volumes. However, these measures are influenced by body size, sex, and age. The left-to-right ventricular end-diastolic volume ratio (LV/RV ratio), assessed by cardiac magnetic resonance imaging (CMR) and known to remain close to 1 in healthy individuals, could provide a more individualized marker of LV remodeling in chronic AR. Methods and results This bi-center study included 258 patients with chronic AR (median age: 55 years, 18% women) who underwent echocardiography (Echo) and CMR. LV and RV volumes were measured from cine-CMR images. Associations between the LV/RV ratio, conventional LV measures, and significant AR, defined as grade 3-4 on Echo or Regurgitant fraction (AR-RegFrac) ≥ 33% on CMR, were analyzed using area under the curves (AUC) and logistic regression. The median LV/RV ratio was 1.5 [1.3-1.9], increased with AR severity (p<0.001), and correlated more strongly with AR-RegFrac (r=0.67, p<0.001) than conventional LV measures. The LV/RV ratio identified significant AR with good accuracy (Echo: AUC 0.77, CMR: AUC 0.83). A threshold of 1.5 provided balanced sensitivity and specificity (Se 71–84%, Sp 77–75%), while 1.8 ruled in significant AR with high specificity (Sp 91% for both modalities). The LV/RV ratio did not vary significantly by age or sex and showed consistent performance across subgroups. Conclusion The LV/RV ratio is a reliable and individualized marker of LV remodeling in chronic AR. These findings support its potential role in clinical assessment and further evaluation in outcome studies.