Aortic root anatomy is related to the bicuspid aortic valve phenotype.

BACKGROUND Bicuspid Aortic Valve (BAV) is associated with an asymmetrical (not circular) aortic root, resulting in variability in the aortic root diameter measurements obtained using different techniques. The objective of this study was to describe the aortic root asymmetry, including its orientation in the thorax, in relation to the various phenotypes of BAV and its impact on aortic root diameter measurements obtained using transthoracic echocardiography (TTE). METHODS Aortic root asymmetry, orientation of the largest root diameter, and orientation of the valve opening were studied using CT scans of BAV patients without significant aortic valve dysfunction referred for evaluation of a thoracic aortic aneurysm. 85 BAV patients were evaluated: BAV with fusion of the left and the right coronary cusps (L-R BAV), with or without raphe (n=63), were compared with BAV with fusion of the right coronary and non-coronary cusps (N-R BAV), with or without raphe (n=22). RESULTS Asymmetry of the aortic root and its orientation in the thorax can be predicted from the BAV phenotype: orientation of the valve opening differed from orientation of the largest root diameter by nearly 75° in both groups. The angle of the largest root diameter with the reference sagittal plane was 64.3° in the L-R BAV group versus 143.1° in the N-R BAV group (p<0.0001). Therefore, using TTE parasternal long axis view, in N-R BAV, the ultrasonic beam is roughly parallel to the valve opening orientation and almost orthogonal to the maximum diameter of the root. On the contrary, in the L-R BAV, the ultrasonic beam is roughly perpendicular to the valve opening orientation and almost parallel to the maximum diameter of the root. Consequently, TTE parasternal long axis view significantly underestimates the maximum aortic root diameter in the N-R BAV, and modestly underestimates the root diameter in L-R BAV (-6.1 ± 0.96 vs -2.3 ± 0.47 mm; p=0.0008). CONCLUSIONS Aortic root morphology in BAV patients can be predicted by the BAV phenotype: the largest root diameter is roughly perpendicular to the orientation of the valve opening. Therefore, echocardiographic measurements according to present recommendations (parasternal long axis view) underestimate maximal diameter in patients with N-R BAV.