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Table of Contents
RESEARCH ARTICLE
Year : 2018  |  Volume : 3  |  Issue : 1  |  Page : 1-7

Role of three-dimensional transesophageal echocardiography in transcatheter aortic valve implantation of bicuspid aortic valve stenosis: A controlled study and comparison with tricuspid aortic valve stenosis


1 Department of Echocardiography, Zhongshan Hospital of Fudan University, Shanghai Institute of Medical Imaging, Shanghai Institute of Cardiovascular Diseases, Shanghai, China
2 Department of Cardiology, Zhongshan Hospital of Fudan University, Shanghai Institute of Cardiovascular Diseases, Shanghai, China
3 Department of Anesthesiology, Zhongshan Hospital, Fudan University, Shanghai, China
4 Department of Interventional Radiology, Zhongshan Hospital, Fudan University, Shanghai Institute of Medical Imaging, Shanghai, China

Date of Web Publication16-May-2018

Correspondence Address:
Cuizhen Pan
Department of Echocardiography, Shanghai Institute of Medical Imaging, Shanghai Institute of Cardiovascular Diseases, Zhongshan Hospital of Fudan University, Shanghai
China
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/cp.cp_4_18

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  Abstract 


Aims: This study aims to investigate the application of three-dimensional transesophageal echocardiography in aortic valve stenosis for the assessment of aortic valve ring size, to monitor the procedure of transcatheter aortic valve implantation (TAVI), and perform postoperative follow-up. Methods: Eighteen patients with bicuspid valve malformation and severe aortic stenosis bicuspid aortic valve (Group BAV-AS) and 23 patients with a tricuspid valve and severe aortic stenosis trileaflet aortic valve (Group TAV-AS) were enrolled in this study. Preoperative routine transthoracic echocardiographic (TTE) examination and two- and three-dimensional transesophageal echocardiography (2D and 3DTEE) were performed, followed by perioperative 2D and 3D TEE monitoring and postoperative routine TTE at 6-month follow-up. Results: Both BAV-AS and TAV-AS patient groups were successfully implanted with bioprosthetic valves under 3DTEE guidance. Parameters at 6-month postoperatively, including prosthetic valve orifice area, mean aortic transvalvular pressure gradient, and left ventricular ejection fraction, showed significant improvement compared with baseline measures (P < 0.0001) in both the groups. No differences were observed between the groups. The maximum diameter of the aortic annulus and eccentricity index were larger in the BAV-AS group than in the TAV-AS group, whereas the minimum diameter of the aortic annulus was larger in the latter (both P < 0.0001) after TAVI. Moreover, the values of maximum and minimum diameters on 3DTEE were strongly correlated with those on multidetector computed tomography. Conclusions: TEE is capable of clearly displaying the morphology of aortic valves and valve rings and precisely quantifying the size of the aortic annulus, thereby playing an essential role during preoperative and perioperative periods. The postoperative shape of the prosthetic valve ring was more oval (larger than normal eccentricity index) in the BAV-AS group and more circular (smaller than normal eccentricity index) in the TAV-AS group.

Keywords: Aortic stenosis, bicuspid, transcatheter aortic valve replacement


How to cite this article:
Zhou N, Pan C, Zhao W, Zhou D, Pan W, Zhang X, Guo K, Shu X, Wang X, Ge J. Role of three-dimensional transesophageal echocardiography in transcatheter aortic valve implantation of bicuspid aortic valve stenosis: A controlled study and comparison with tricuspid aortic valve stenosis. Cardiol Plus 2018;3:1-7

How to cite this URL:
Zhou N, Pan C, Zhao W, Zhou D, Pan W, Zhang X, Guo K, Shu X, Wang X, Ge J. Role of three-dimensional transesophageal echocardiography in transcatheter aortic valve implantation of bicuspid aortic valve stenosis: A controlled study and comparison with tricuspid aortic valve stenosis. Cardiol Plus [serial online] 2018 [cited 2018 May 24];3:1-7. Available from: http://www.cardiologyplus.org/text.asp?2018/3/1/1/232550




  Introduction Top


Transcatheter aortic valve implantation (TAVI) is an alternative for patients with severe aortic valve stenosis who cannot undergo surgery.[1] Currently, TAVI is only used for inoperable or high-risk surgical patients with trileaflet aortic valve (TAV) stenosis. The safety and efficacy of TAVI in patients with a congenital bicuspid aortic valve (BAV) with severe stenosis is unclear.[2],[3],[4] Nonetheless, recent studies have suggested that TAVI surgery is safe for BAV patients. No significant difference in mortality rate or occurrence of major complications, such as the need for permanent cardiac pacemaker implantation or major hemorrhage, has been observed between BAV and non-BAV patients. The presence of BAV is a logical indication for TAVI since the proportion of patients with BAV is high among those with severe AS.[5],[6] It is worth noting that patients with BAV undergoing valvular surgery are at increased risk of mild-to-moderate paravalvular aortic regurgitation requiring secondary valve implantation compared with those with TAV, indicating that not every BAV is appropriate for TAVI surgery. It remains clinically challenging to screen for BAV patients who are anatomically suitable for TAVI as well as precise implantation of a prosthetic valve.

Preoperative TAVI evaluation includes echocardiography, multidetector computed tomography (MDCT), and cardiac magnetic resonance imaging. MDCT is the most commonly used method.[1],[7],[8] However, MDCT exposes the patient to radiation and is contrast agent dependent, time-consuming, and relatively expensive. 3DTEE is capable of comprehensively evaluating aortic root anatomy before TAVI. It is comparable to MDCT when used for aortic valve measurements.[8],[9],[10] Most importantly, 3DTEE is useful for guidewire passage through the aortic valve orifice during TAVI, enabling precise implantation and real-time monitoring of the valve location, stability, and orifice. 3DTEE can also visualize paravalvular regurgitation, as well as incidents of cardiac perforation, pericardial effusion, aortic rupture, aortic dissection, mitral regurgitation, and other complications. Immediately following the procedure, 3DTEE is useful for detecting the maximum flow and mean gradient across the implanted valve and can evaluate valve motion, left ventricular stroke volume, and left ventricular ejection fraction (LVEF). These functions cannot be achieved with other imaging examination methods. Few researchers have focused on the application of 3DTEE in BAV TAVI, specifically relating to preoperative assessment, perioperative evaluation of the morphology and function of the aortic valve ring, or during the follow-up period. Moreover, a comparative study with patients undergoing TAVI for TAV aortic stenosis has not been reported.


  Methods Top


Patients

From May 2013 to September 2016, 42 patients with severe aortic stenosis were recruited for TAVI therapy with the Department of Cardiology in our hospital. Three days after TAVI, one patient died of aortic dissection. Eighteen patients (77.56 ± 4.25 years old; 12 males and 6 females) had BAV with severe aortic stenosis and 23 (81.17 ± 4.85; 15 males and 8 females) had TAV with severe aortic stenosis. All patients underwent preoperative transthoracic echocardiography (TTE), two- and three-dimensional transesophageal echocardiography (2D and 3D TEE) and MDCT, perioperative 2D and 3D TEE, and 6-month follow-up with routine TTE. The protocol of this study complied with the Declaration of Helsinki and was approved by the Ethics Committee of the Fudan University. All patients gave written informed consent.

Instruments and methods

Philips iE33 ultrasonic imaging system, with S5-1 transthoracic probe and X7-2 transesophageal probe, was used for real-time 3D imaging of the mitral and aortic valves. Real-time focusing and amplification, full-volume imaging of single and four cardiac cycles, and 3D color Doppler flow imaging, at frequencies of 1-5 MHz or 2-7 MHz, were performed. An ACUSON SC2000 PRIME ultrasonic imaging system, with Z6MS1-6 transesophageal probe at a frequency of 1–6 MHz, was used for real-time single cardiac cycle 3D imaging and real-time 3D color Doppler flow imaging [Figure 1]. Imaging was performed with patients in the left decubitus or supine positions and an S5-1 probe was attached for routine echocardiography. After general anesthesia, the X7-2 or Z6MS1-6 probe was inserted slowly into the esophagus for detection of the long-axis, short-axis, and five-chamber view through the middle segment of the esophagus. The collected data were then stored in an optical disk for online or offline analysis. 3DTEE measurement of the aortic annulus was performed using the following two methods:
Figure 1: Real-time two-dimensional (a) and three-dimensional (c) transesophageal echocardiography showed thickening and reduced motion of the bioprosthetic leaflets. Two-dimensional transesophageal echocardiography clearly (b and d) showed CoreValve implantation in bicuspid valve (arrows)

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  1. Viewed from the standard LV long axis, a 3D image of the aortic ring was acquired with the ZOOM mode. QLAB-3DQ software was used to quantify the maximum and minimum diameters of the aortic rings. The eccentricity index was calculated using the following equation: Eccentric index = (maximum diameter – minimum diameter)/maximum diameter
  2. Viewed from the standard LV long axis, SC2000 Workplace eSie Valves software was applied to quantify the diameters and calculate the eccentricity index with the same equation as above [Figure 2].
Figure 2: Three-dimensional transesophageal echocardiography measurement of the aortic annulus was performed using the SC2000 Workplace eSie Valves software. Viewed from the standard left ventricular long axis, a three-dimensional image of the aortic ring was acquired with the ZOOM mode (a and b). QLAB-3DQ software was used to quantify the maximum and minimum diameters of the aortic rings (c and d)

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Statistical analysis

SPSS 19 and MedCalc 16.2 software were used for statistical analysis. The data are expressed as mean ± standard deviation (x ± s). Data between groups were compared with a t-test. Paired or nonpaired t-tests were used for data comparison. The partial correlation coefficient between the two variables was calculated and tested. Linear correlation analysis was used to measure the association between two variables. Variation within the group was described with an intraclass coefficient (ICC). P< 0.05 indicated statistical significance.


  Results Top


General health conditions and clinical outcomes are shown in [Table 1]. All patients in the BAV-AS and TAV-AS groups were successfully implanted with a bioprosthetic aortic valve and no abnormality of function was observed. In the BAV-AS group, the transvalvular pressure gradient decreased from 58.38 ± 10.05 mmHg to 10.66 ± 3.81 mmHg and the valve orifice area increased from 0.59 ± 0.12 cm 2 to 1.72 ± 0.18 cm 2 following TAVI. There was no paravalvular leakage in 6 cases (33%), mild paravalvular leakage in 10 (56%), moderate paravalvular leakage in 2 (11%), no prosthetic valve regurgitation in 10 (55%), slight prosthetic valve regurgitation in 7 (39%), and mild-to-moderate regurgitation in 1 (5%). In the TAV-AS group, the mean transvalvular pressure gradient decreased from 60.21 ± 13.70 mmHg to 10.21 ± 3.91 mmHg, while the valve orifice area increased from 0.68 ± 0.12 cm 2 to 1.84 ± 0.21 cm 2 following TAVI. There was no paravalvular leakage in 7 cases (30%), mild paravalvular leakage in 16 (70%), no prosthetic valve regurgitation in 16 (70%), and mild prosthetic valve regurgitation in 7 (30%) [Table 2].
Table 1: Baseline demographic and clinical characteristics

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Table 2: Procedural characteristics and clinical outcomes

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TAVI significantly improved valve hemodynamics (P< 0.0001) at 6-month postoperatively, as shown by the following parameters: valve orifice area (BAV-AS: 0.59 ± 0.16 vs. 1.72 ± 0.24, TAV-AS: 0.68 ± 0.16 vs. 1.84 ± 0.28), mean aortic transvalvular gradient (BAV-AS: 58.39 ± 12.95 vs. 10.67 ± 4.58, TAV-AS: 60.22 ± 18.27 vs. 10.22 ± 4.79), and LVEF (BAV-AS: 55.33 ± 14.78 vs. 61.28 ± 8.66, TAV-AS: 59.22 ± 8.98 vs. 62.13 ± 9.15). No significant difference was observed between the BAV-AS and TAV-AS groups [Figure 3].
Figure 3: Transcatheter aortic valve implantation significantly improved valve hemodynamics at 6-month postoperatively: aortic valve orifice area (upper), mean aortic transvalvular gradient (middle), and left ventricular ejection fraction (lower). No significant difference was observed between the bicuspid aortic valve-AS and trileaflet aortic valve-AS groups

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At 6-month post-TAVI, the maximum diameter of the prosthetic aortic annulus was larger in the BAV-AS group (25.06 ± 1.70 vs. 22.70 ± 1.84) than in the TAV-AS group. The eccentricity index was also larger in the BAV-AS group (0.32 ± 0.07 vs. 0.08 ± 0.04) than in the TAV-AS group. The minimum diameter was significantly smaller in the BAV-AS group (17.00 ± 1.94 vs. 20.78 ± 1.88) than in the TAV-AS group (P< 0.0001). No baseline differences were detected between the BAV-AS and TAV-AS groups before surgery [Figure 4].
Figure 4: At 6 months after transcatheter aortic valve implantation, the maximum diameter of the prosthetic aortic annulus was larger in the bicuspid aortic valve-AS group. The eccentricity index was also larger in the bicuspid aortic valve-AS group. The minimum diameter was smaller in the bicuspid aortic valve-AS group

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There was strong correlation and consistency between 3DTEE and MDCT when measuring minimum diameter [r = 0.92, P< 0.0001, ICC =0.929 (0.870–0.961)] and maximum diameter [r = 0.95, P< 0.0001, ICC = 0.955 (0.918–0.976)] of the aortic annulus [Figure 5].
Figure 5: There was a strong correlation and consistency between three-dimensional transesophageal echocardiograph and multidetector computed tomography for the measurement of minimum diameter and maximum diameter of the aortic annulus

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  Discussion Top


BAV is a common congenital anomaly of the aorta and is the second most common heart abnormality present at birth, with an incidence rate of 0.9%–2%.[1] It is one of the primary causes of aortic stenosis, especially in the Chinese population. TAVI offers the advantage of less trauma, faster recovery, no need for thoracotomy or cardiopulmonary bypass, and shorter hospital stay compared with standard aortic valve surgery.[11],[12],[13] Data indicate that the survival rate of TAVI is neither inferior to nor better than that of surgical valve replacement. Therefore, it has been extensively used as an alternative therapy for high-risk AS patients.

It is essential to systemically examine aortic structure and function before TAVI,[14],[15] 3DTEE plays an increasingly important role in the precise and reproducible measurement of valve ring diameter, including maximum and minimum diameters, as well as 3D morphologic assessment of valves and roots. During the TAVI procedure, 3DTEE can display intracardiac devices, guide the localization of prosthetic valves, and monitor perivalvular leakage and valve regurgitation, as well as other complications.[16],[17]

Although most TAVI procedures utilize X-ray imaging for real-time guidance of valve implantation, 3DTEE can also be used for this purpose. The combination of 3DTEE and X-ray imaging was performed in all patients recruited in our study. 3DTEE successfully aided guidewire and sheath passage through the original aortic valve, guided the positioning and release of the prosthetic valve, and was used for monitoring possible complications, including cardiac perforation, pericardial effusion, aortic rupture, aortic dissection, and mitral regurgitation. Incorrect wire position can cause acute severe mitral regurgitation due to tendon contraction. Too high a location of the prosthetic valve can cause coronary artery occlusion and rupture of the aorta, whereas too low a position can interfere with the mitral valve opening and closing or lead to atrioventricular block. Immediate postoperative evaluation with 3DTEE for valve opening and closing, flow velocity, pressure gradient, and valvular and paravalvular regurgitation is essential for planning treatment.

In the current study, all patients who underwent TAVI had preoperative 3DTEE and MDCT examinations. In accordance with prior reports, 3DTEE was found to be an accurate means for determining maximum and minimum diameters of the aortic valve rings and showed good correlation with data from MDCT. 3DTEE was conducted to measure the maximum and minimum diameters of aortic valve rings, as well as the eccentricity index, in all patients before TAVI.[7],[18] The aortic valve ring was found to be oval in our study. Importantly, prior detection of the minimum diameter of an oval aortic valve ring by TTE and 2DTEE is associated with an underestimation of the diameter and is inconsistent with MDCT values.

All patients displayed normal valve opening and closing properties at the 6-month follow-up of prosthetic valve function and aortic annulus morphology. The eccentricity index in BAV-AS patients with a prosthetic aortic annulus was larger than that in normal controls, but smaller in TAV-AS patients, with a nearly circular shape. Therefore, the morphology of the implanted prosthetic aortic annulus is dependent on the leaflet number of the endogenous aortic valve and is more oval in BAV and more circular in TAV. The long-term outcome of prosthetic valves in both groups remains to be determined, even though function at 6 months appeared normal in this study. At the 6-month post-TAVI follow-up of 18 BAV-AS patients, mild perivalvular leakage occurred in 10 cases (56%) and moderate leakage in 2 (11%), whereas 16 of 23 TAV-AS patients (70%) had mild leakage; this is consistent with previous data.[19],[20],[21] The pathological changes likely leading to mild or moderate perivalvular leakage include the following: (1) severe calcification of aortic valve and annulus, forming a gap between the prosthetic valve and the endogenous aortic valve ring; (2) a prosthetic valve that is too small; and (3) an oval aortic annulus is present. To reduce the occurrence of valve leakage, we recommend using the mean value of the maximum and minimum diameters of the aortic annulus or the diameter calculated by the oval perimeter as the reference for selection of a prosthetic valve.

Limitations

The number of patients in this study was small. More patients should be involved in a follow-up study. Moreover, the patients in this study had relatively good health status since high-risk cases were excluded at an early stage. This might have contributed to the high success rate and few complications. Variation in surgical skills and proficiency among surgeons also has the potential to affect procedural outcomes.


  Conclusions Top


TEE is capable of clearly displaying the morphologies of the aortic valves and valve rings and precisely quantifying the size of the aortic annulus, thereby playing an essential role during preoperative and perioperative processes. The morphology of the implanted prosthetic aortic annulus is dependent on the leaflet number of the endogenous aortic valve and is more oval in BAV and more circular in TAV.

Acknowledgments

This study was supported by grant #16441908100, #16441901502 from Science and Technology Committee Foundation of Shanghai.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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