BACKGROUND Paravalvular aortic regurgitation (AR) after transcatheter aortic valve replacement (TAVR) has been associated with increased mortality. Precise assessment of the degree of AR within the catheterization laboratory is crucial to take counter measures, but it remains challenging. The aim of this study was to determine whether any modification to AR index can improve its performance. METHODS The study included 64 patients treated with the Sapien valve (Edwards Life Sciences, Inc., Irvine, CA). The severity of AR was evaluated using echocardiography, angiography, and invasive hemodynamic parameters. We evaluated the time-integrated aortic regurgitation (TIAR) index as follows: (LV - Ao diastolic pressure time integral)/(LV systolic pressure time integral) × 100. We analyzed the AR index and TIAR index with the receiver operating characteristic (ROC) curve. RESULTS AR was observed in 58 patients (90.7%) and graded as mild in 33 (51.6%), moderate in 20 (31.3%), or moderate to severe in 5 (7.8%) patients. No severe AR was detected. The AR index and TIAR index decreased proportionately to the increased severity of AR (P = 0.002 and P < 0.001, respectively). TIAR index < 80 was associated with a sensitivity of 86% and a specificity of 83% for ≥mild AR. The area under the curve was greater for the TIAR index compared to the AR index (0.93 vs. 0.74). CONCLUSION The TIAR index provides a better hemodynamic measure for assessing severity of AR compared to the AR index.