Anatomical regurgitant orifice area in aortic regurgitation: a quantitative key to severity assessment?

Abstract Introduction Evaluating chronic aortic regurgitation (AR) severity remains challenging, even for experienced imaging specialists. While transthoracic echocardiography (TTE) is the first-line modality, relying on a multiparametric approach, limitations exist in cases with suboptimal acoustic windows or discordant findings. Left ventricular (LV) dilatation reflects chronic volume overload and is a key criterion for intervention in asymptomatic patients. Cardiac CT, though not included in current guidelines for AR, can directly measure the anatomical regurgitant orifice (ARO) using diastolic planimetry, offering a potentially reproducible and quantitative marker. Previous studies have reported its correlation with AR severity, but data on its association with LV volume overload and comparison to echocardiographic indices remain limited. Objectives To assess whether ARO measured by cardiac CT correlates with LV volume overload in patients with severe AR. Secondary objective: identify which echocardiographic parameters best predict ARO dimensions. Methods Thirty-seven patients with severe AR by TTE were consecutively enrolled. All underwent cardiac CT within 12 months. AR was graded as severe per ASE/ESC guidelines using vena contracta (>6 mm), AR jet/LVOT ratio (>65%), descending aorta flow reversal (VTI >15 cm), and peak end-diastolic velocity (>20 cm/s). LV volumes were assessed by 3D/biplane Simpson’s methods (TTE) and ECG-gated CT. ARO was measured during diastole on orthogonal CT planes aligned with the aortic coaptation defect. Pearson correlation assessed relationships between ARO and LV volumes/diameters. Linear regression identified echocardiographic predictors of ARO. Results All patients showed LV dilation by both imaging modalities. Mean ARO was 0.33±0.03 cm². ARO correlated strongly with CT-derived LV end-diastolic volume (LVEDV; r=0.7, p<0.05) and moderately with end-systolic volume (r=0.45, p<0.05). Similar results were seen with echocardiographic volumes (LVEDV r=0.65; LVESV r=0.5, both p<0.05). ARO also correlated with LV end-diastolic diameter (r=0.6, p<0.01), but only weakly with systolic diameter (r=0.3). Vena contracta was the best predictor of ARO (R²=0.57, p<0.01), followed by AR jet/LVOT ratio (R²=0.47) and descending aortic end-diastolic velocity (R²=0.45). These results suggest that ARO integrates anatomical and functional severity components, correlating with both volume overload and established echocardiographic indices. Conclusions ARO measured by cardiac CT is a robust quantitative parameter reflecting AR severity. Its strong association with LV volume overload and echocardiographic predictors supports its clinical relevance. ARO may enhance multimodality assessment, particularly in patients with inconclusive or conflicting data, and could be integrated into future AR diagnostic algorithms to improve risk stratification and therapeutic decision-making.