Abstract Objective: Analysis of mechanical changes characteristic of the mitral-aortic valve commissure (MAC) in patients with chronic severe aortic valve closure insufficiency (AR) with preserved ejection left ventricular blood fraction. Methods: A total of 40 patients with chronic severe AR and 40 normal individuals were included in this study. MAC parameters, such as angle, velocity, and displacement-related indicators, were estimated. Two-dimensional strain techniques were utilized to acquire Global longitudinal strain (GLS), Global transverse strain (GCS), Global circumferential strain (GRS), Anterolateral papillary muscle strain (ALPMS), Posterior medial papillary muscle strain (PMPMS) and Left ventricular torsion Angle (LV-Twist), Aortic ring torsion Angle (A-Twist), Mitral annulus orsion Angle (M-Twist). Results: MAC displacement and angle were smaller in the AR group than in the control group (P<0.05). GLS, GCS, GRS, ALPMS, PMPMS, LV-Twist, A-Twist, and M-Twist were significantly lower in the AR group than the control group (P<0.05). MAC displacement, angle, and papillary muscle strain were correlated with GLS, and LV-Twist was positively correlated with A-Twist and M-Twist (P<0.05). The ROC curve showed that MAC displacement, angle, A-Twist, and M Twist had good diagnostic efficacy for severe AR. Conclusion: Left ventricular papillary muscle strain and MAC angle, displacement, A-Twist, and M-Twist are reduced in patients with chronic severe AR, and a correlation was established among these and changes in the left ventricular (LV) systolic function and the underlying mechanics.