Eccentricity of Aortic Annulus and Distance of Origin of Left Main and Right Coronary Arteries from Adjacent Aortic Leaflets in Non-Stenotic Aortic Valves by TEE 3D Echocardiography

Eccentricity of Annulus and Distance of Origin of Left Main and Right Coronary Arteries from Adjacent Aortic Leaflets in Non-Stenotic Aortic Valves by TEE 3D Echocardiography. Cardiology and Cardiovascular Medicine 6 (2022): 196-205. Abstract To measure the size of the aortic Annulus (AN) and Left Ventricular Outflow Tract (LVOT) in different views and distance between right and left coronary ostia from aortic annulus by Transesophageal (TEE)3D echocardiography in patients with normal aortic valves. Method: 31 patients (51.5% F) underwent TEE3D.Full-volume of aortic valve was saved by TEE3D.AN was measured in 3 planes: two orthogonal lines in short-axis plane (D1 & D2), sagittal (D3) and coronal (D4) planes,diameter of LVOT 5-10 mm below AN was measured in sagittal and coronal views (D5 & perimeter is equal to mean D1&D2 and D3&D4 and D area is equal to D3. Mean distance of left main and RCA ostia from AN is 14.2±2.97 and15.25±3.60 mm respectively.Mean length of left coronary cusp is 12.75±2.1 mm. Conclusion: Aortic annulus is oval shape in normal aortic valves and is larger in coronal than sagittal view in most subjects,D perimeter is equal to mean aortic annulus. D LVOT is non-significantly smaller than the following annulus D. Distance of LM ostium from aortic annulus is longer than RCA,length of left coronary cusp is shorter than left main-annulus distance.


Introduction
It has been identified that aortic annulus is not completely round in normal and stenotic aortic valves, a few studies have described the eccentricity of aortic annulus both by CT and by 3D echocardiography [1][2][3][4]. Although many studies have predominantly found that aortic annulus is non-circular, commercially available transcatheter aortic heart valve prostheses are circular [5]. With rising ovality, the pressure difference across the prosthesis increased.
Slight ovalities were well tolerated by a self-expanding prosthesis, but more significant ovality led to worsening of prosthesis function and regurgitation [5]. Traditionally, aortic annulus is measured in sagittal view before TAVI and final device size should be oversized compared to annular diameter. Most procedures are performed according to the annular diameter measurement by 2D TTE or TEE, but these methods assume annular circularity, which may result in erroneous dimensions in patients whose annuli are more ovals shaped. This limitation can be overcome using multiplanar tools of either 3D TEE or MSCT [6]. But the precise detection of aortic annulus in different echocardiographic views, diameter according to perimeter and area, distance of LM and RCA ostia from adjacent aortic annulus and length of left coronary cusp by 3D echo are mentioned in few articles [2][3][4]7]. It has been already studied that aortic annulus size is not different between aortic stenosis patients and normal subjects, so precise evaluation of aortic annulus in normal subjects can lead us to better understanding of aortic valve annulus shape, ovality and different sizes in different views [2][3][4]. The aim of this study is to measure aortic annulus and LVOT diameter in different views, and to measure distance of LM and RCA ostia from aortic annulus and length of left coronary cusp and diameter of LVOT in sagittal and coronal views in normal aortic valves.   If TEE long-axis full volume 3D view was used, RBG upright modality was used and then by grabbing the blue line in sagittal view and rotating 90-degree counter clock wise, the right upper view is coronal view and left lower view is short-axis view and the measurement were done like described above [1].
The following measurements were done in above described views:  D6: LVOT diameter 5-10 mm below aortic annulus in coronal view (below D4).
Perimeter: Circumference of aortic annulus in short-axis view (cm).
Area: Area of aortic annulus in short-axis view (cm 2 ).
Diameter of Aortic annulus according to perimeter: Perimeter of aortic annulus/π.
LM distance from aortic annulus: The distance between left main and aortic annulus in coronal view ( Figure 2a).
RCA distance from aortic annulus: The distance between RCA and aortic annulus in TEE long-axis view ( figure   2b).
Length of left coronary cusp: The length of left coronary cusp in TEE coronal view ( Figure 2a).
All measurements are performed in mid-systole.

Statistical Analysis
The Statistical Software Package (SPSS for Windows, version 22, SPSS Inc, Chicago, Illinois, USA) was used for the statistical analyses. The continuous variables are presented as mean ± SD, and the categorical variables are or smaller than 0.05 was considered statistically significant. To assess reproducibility of data, data of 5 patients were randomly measured by the second observer for inter-observer variability control and by the first observer at an interval of two weeks for intra-observer variability. Inter-and intra-observer variability was calculated via dividing the mean difference between observations by their average measurement [8].
Inter and Intra observer variability: Inter and intra observer variability was as follows:  Empiric distribution of difference between D4 and D3 in each subject is demonstrated by figure 2, median difference is 1.9 mm, maximum difference is 9.3 mm and minimum difference is -3.5 mm (It means that D3 is larger than D4). In 71.9 % of subjects, D4 is larger than D3 and 28.1% D4 is smaller than D3.

Figure 2:
Empiric distribution of difference D4 and D3 in each subject by a plot, median difference is 1.9 mm, maximum difference is 9.3 mm and minimum difference is -3.5 mm.
In 50% of subjects, D4 was greater than D3 more than 1.9 mm, of which, in 50% this difference was between 1.9-3.8 mm and in 50% this difference was between 3.8 to 9.3 mm. In 50% of subjects, the difference between D3 and D4 was less than 1.9mm of them, in 50%, the difference was between 1.9 to -0.95 and in 50%, this difference was between -0.95 to-3.5 mm (D3 is greater than D4). In one quarter of patients, D4 is greater than D3 between 1.9 to 3.83 mm. In one quarter of patients, D4 is greater than D3 between 3.83 to 9.3 mm, in one quarter of patients, the difference between D3 and D4 is between 1.9 to -0.95 mm. In one quarter of patients, D4 is smaller than D3 between 0.95 to 3.5 mm. Mean distance between left main ostium and aortic annulus is 14.2±2.94 mm.
Distance of LM from aortic annulus is longer than distance between RCA and aortic annulus, mean difference=1.05, P=0.052.
Length of left coronary cusp is shorter than distance of left main from aortic annulus, mean difference =1.05, P=0.001 (Table 2).

Discussion
The results of our study showed that the coronal diameter of aortic annulus is about 2mm larger than sagittal diameter in normal aortic valve. Although the median difference between coronal and sagittal aortic annulus is 1.9 mm, in 50% of subjects, D4 is greater than D3 more than 1.9 mm, in 25% this difference was between 1.9-3.8 mm and in 25% this difference was between 3.8 to 9.3 mm. In 50% of subjects, the difference between D3 and D4 was less than 1.9mm, in 25%, the difference was between 1.9 to -0.95 and in 25%, this difference was between -0.95 to-3.5 mm (coronal diameter is smaller than sagittal diameter of aortic annulus). The aortic annulus diameter according to area is similar to the aortic diameter in sagittal view and aortic diameter according to perimeter is equal to mean aortic annulus. D1 is the smallest aortic diameter according to our study as reported before [9]. Mean RCA distance from aortic annulus is 1mm greater than mean left main distance from aortic annulus and mean left coronary cusp is about 1.2 mm smaller than distance of left main from aortic annulus.
The results of our study showed that D1 is significantly smaller than D3, so the annulus in short-axis (smaller diameter) is smaller than the aortic annulus in sagittal view and they are not the same measurement and cannot be replaced by each other. Also, the difference between D2 and D4 is not statistically significant, so the aortic annulus in coronal view and short-axis view (greater diameter) are the same. The aortic annulus in sagittal view is about 2 mm smaller than the aortic annulus in coronal view. So the aortic annulus in normal valves is not round in systole and is oval shape. Although the difference between D3 and D5 is not statistically significant, but mean difference is 0.66 mm and P=0.07, it is probable that with a larger study population and especially in patients with significant aortic stenosis with left ventricular hypertrophy, this difference would be significant [10]. In the study by Otani et al, the minimum diameter of LVOT was not different between AS and normal but maximum diameter of LVOT was significantly smaller in AS group compared to normal [3]. D perimeter in our study is larger than D area which is comparable with study by Blank P et al [11], but in the study by Khalique at al,D perimeter and area was not different by TEE3D but D area is smaller than D perimeter by CT scan [1].According to our results, D perimeter is equal to mean D coronal and D sagittal. The results of our study showed that D1 is significantly smaller than D3, so the annulus in short-axis (smaller diameter) is smaller than the aortic annulus in sagittal view and they are not the same measurement and cannot be replaced by each other. Also, the difference between D2 and D4 is not statistically significant, so the aortic annulus in coronal view and short-axis view (greater diameter) are the same. The aortic annulus in sagittal view is about 2 mm smaller than the aortic annulus in coronal view. So the aortic annulus in normal valves is not round in systole and is oval shape. Although the difference between D3 and D5 is not statistically significant, but mean difference is 0.66 mm and P=0.07, it is probable that with a larger study population and especially in patients with significant aortic stenosis with left ventricular hypertrophy, this difference would be significant [10]. In the study by Otani et al, the minimum diameter of LVOT was not different between AS and normal but maximum diameter of LVOT was significantly smaller in AS group compared to normal [3]. D perimeter in our study is larger than D area which is comparable with study by Blank P et al [11], but in the study by Khalique at al,D perimeter and area was not different by TEE3D but D area is smaller than D perimeter by CT scan [1].According to our results, D perimeter is equal to mean D coronal and D sagittal.

Future Studies
1)According to the results of this study, the difference between sagittal and coronal diameter of aortic annulus is between 3.8 to 9.3 mm in 25 percentile of normal aortic valves, so ovality of aortic annulus even in normal aortic valve is remarkable and ovality of aortic valve in AS patients may be a real cause of paravalvular leakage after TAVI, future studies need to describe the relationship between ovality of aortic valve and paravalvular leakage post TAVI.
2)Smaller diameter of LVOT diameter compared to aortic annulus as a probable cause of LBBB and some other complication post TAVI should be evaluated.
3) The design of self-expandable aortic valve prosthesis which LVOT end is smaller than mid-portion may be a cause of LBBB in the patients with smaller LVOT diameter compared to annulus and may be a guide for designing the self-expandable devices which mid-portion and LVOT end have the same diameter.

Declaration
None of the authors have any conflicts of interest to declare and this study has been ethically approved by Tehran Heart Center. This study is not funded by any organization.