Aortic Valve Adaptation to Aortic Root Dilatation: Insights into the Mechanism of Functional Aortic Regurgitation from Three-Dimensional Cardiac Computed Tomography
Background—The three-dimensional (3D) relationship between aortic root and cusp are essential to understand the mechanism of aortic regurgitation (AR) due to aortic root dilatation (ARD). We sought to test the hypothesis that the stretched cusps in ARD enlarge to compensate for ARD.
Methods and Results—Computed tomography imaged 92 patients, 57 with ARD: 29 with moderate to severe AR, 28 without significant AR, 35 normal controls. Specialized 3D software measured individual cusp surface areas (CSAs) relative to maximal mid-sinus cross-sectional area and minimal 3D annular area, coaptation area fraction (CAF), and asymmetry of sinus volumes and intercommissural distances. Total open CSA increased (p<0.001) from 7.6±1.4 cm2/m2 in normals to 12.9±2.2 in AR(−) and 15.2±3.3 in AR(+) patients. However, the ratio of closed CSA to maximal mid-sinus area, reflecting cusp adaptation, decreased from normals to AR(−) to AR(+) patients (1.38±0.20 to 1.15±0.15 to 0.88±0.15, p<0.001), creating the lowest CAF. Cusp distensibility (closed diastolic versus open area) decreased from 20% in controls and AR(−) patients to 5% in AR(+) patients (p<0.001). Multivariate determinants of AR and CAF reflected both sinus size and cusp-to-annular adaptation. ARD was also progressively asymmetric with root size, and individual CSAs failed to match this asymmetry.
Conclusions—Aortic cusp enlargement occurs in ARD, but cusp adaptation and distensibility become limited in prominent, asymmetric ARD, leading to AR. Optimal AR repair tailored to individual patient anatomy can benefit from appreciating valve adaptation and 3D relationships; understanding cusp adaptation mechanisms may ultimately provide therapeutic opportunities to improve such compensation.
- Received March 18, 2014.
- Accepted July 10, 2014.