Background
An understanding of aortic root anatomy in bicuspid aortic valve (BAV) has not been well established. The aims of this three-dimensional transesophageal echocardiographic study were (1) to examine whether aortic root geometry differs between BAV and tricuspid aortic valve (TAV) and (2) to analyze the dynamic motion of the aortic annulus throughout cardiac cycle.
Methods
A total of 66 patients with BAV (38 with severe aortic stenosis [AS]) and 66 age-, gender-, and body surface area–matched patients with TAV (36 with severe AS) who underwent three-dimensional transesophageal echocardiography were retrospectively enrolled. The dynamic motion of the aortic annulus was also analyzed in 40 selected patients (10 with BAV with severe AS, 10 with BAV without AS, 10 with TAV with severe AS, and 10 with TAV without AS).
Results
The area of the aortic root in patients with BAV was larger than in those with TAV (aortic annulus, P < .001; sinus of Valsalva, P < .05; sinotubular junction, P < .01). There was a significant difference in circularity (4π × area/[perimeter] 2 ) of the sinus of Valsalva between patients with BAV and those with TAV ( P < .001), although there were no differences in the shapes of the aortic annulus and the sinotubular junction between the two groups. In both patients with BAV and those with TAV, the aortic annulus in mid-systole was largest and most circular in cardiac cycle; on the other hand, in end-diastole, the aortic annulus was smallest and most elliptical ( P < .001).
Conclusions
Three-dimensional transesophageal echocardiography successfully demonstrated significant differences in the size of the aortic root and the shape of the sinus of Valsalva between patients with BAV and those with TAV.
Bicuspid aortic valve (BAV) is a most common congenital cardiovascular malformation, with a prevalence ranging from 1% to 2% of the entire population. BAV is also a most common cause of aortic valve disease, such as aortic stenosis (AS), in young adult patients. Although surgical aortic valve replacement has been the gold standard treatment for aortic valve disease with BAV, transcatheter aortic valve replacement (TAVR) for AS with BAV is now available. Along with the development of treatment for aortic valve disease with BAV, the understanding of aortic root anatomy and dynamic motion of aortic annulus in patients with BAV must be advanced and detailed.
In an aortic root geometry, particularly that of the aortic annulus, two-dimensional (2D) assessment is known to fail to appreciate the noncircular geometry. On the other hand, three-dimensional (3D) assessment, such as 3D transesophageal echocardiography (TEE) and multidetector computed tomography (MDCT), appears superior in the evaluation of the aortic annulus. Moreover, it was reported that precise preoperative 3D assessment of the aortic annulus had an impact on the results of TAVR for patients with AS with tricuspid aortic valve (TAV). However, the aortic root geometry and the dynamic motion of the aortic annulus in BAV have not been evaluated adequately. The aims of this 3D transesophageal echocardiographic study were (1) to examine whether aortic root geometry differs between patients with BAV and those with TAV and (2) to analyze the dynamic motion of the aortic annulus in patients with severe AS and those without AS with BAV and TAV throughout the cardiac cycle.
Methods
Study Population
We retrospectively enrolled 66 patients with BAV (38 with severe AS) who underwent 3D TEE from June 2009 to April 2013. The diagnosis of BAV was judged by both of two independent physician readers experienced in the assessment of 3D TEE. We also included 66 patients with TAV matched for age, gender, and body surface area (BSA) (36 with severe AS) in this study. All characteristic data were retrieved from our computerized database. As a substudy, we selected 40 patients (10 with severe AS and BAV, 10 without AS with BAV, 10 with severe AS with TAV, and 10 without AS with TAV), in whom 3D transesophageal echocardiographic data sets were acquired at >15 frames/sec throughout the cardiac cycle. Patients in these four groups were selected so that age, gender, and BSA would be matched. The study was approved by the institutional review board.
Comprehensive Transthoracic Echocardiography
Comprehensive 2D and Doppler transthoracic echocardiography was performed at our institution. The iE33 ultrasound system (Philips Medical Systems, Andover, MA) equipped with an S5-1 phased-array transducer (Philips Medical Systems) was used. In accordance with the guidelines of the American College of Cardiology and American Heart Association, severe AS was determined quantitatively on the basis of aortic valve area < 1.0 cm 2 , mean aortic gradient > 40 mm Hg, or aortic jet velocity > 4.0 m/sec. Left ventricular mass was calculated using the M-mode method. The left ventricular mass index was calculated by dividing left ventricular mass by BSA.
TEE
TEE was performed using the iE33 ultrasound system equipped with an X7-2t transesophageal echocardiographic ultrasound probe, which provides a frequency range of 2.0 to 7.0 MHz and has 2D and 3D matrix array (Philips Medical Systems). Bland sedation using either intravenous propofol or the combination of midazolam and fentanyl with hemodynamic monitoring was performed in all patients.
After introducing the probe into the esophagus, we performed 2D and color Doppler imaging using the standard methods. Two-dimensional aortic annular diameter was measured by a zoomed long-axis (120°–150°) frame hinge point–to–hinge point measurement. Two-dimensional aortic annular area was defined as area assumed to be a circle using aortic annular diameter. Real-time 3D zoom data sets and, if necessary, full-volume data sets with electrocardiographically triggered sequential volumes were acquired for late analysis.
3D TEE Analysis
All volumetric images were analyzed offline using commercial software (QLAB; Philips Medical Systems). The cardiovascular mode was used for correct alignment of the aortic root geometry ( Figure 1 ). Two orthogonal long-axis views of an aortic root were extracted from the 3D data sets ( Figures 1 A and B). A third plane perpendicular to both of the long-axis planes was manipulated to obtain the 2D short-axis cutting plane of the aortic annulus, which was defined as the plane including each lowest cusp hinge point, the sinus of Valsalva, and sinotubular junction (STJ). After choosing the frame of proper timing, the 2D short-axis cutting plane was shifted to find each level.
