Validation of Transesophageal Echocardiographic In Vitro Measurements for Bioprosthetic Aortic Valves: Implications for Percutaneous Valve-in-Valve Therapy


Percutaneous valve-in-valve therapy has become an important treatment option for failing bioprosthetic heart valves. Accurate assessment of valve internal diameter (ID) is essential for effective and safe treatment. These data may not be available in an individual patient, or the manufacturer-supplied dimensions may be incorrect because they do not allow for the space occupied by valve leaflet material.


In total, 2,332 two-dimensional and three-dimensional transesophageal echocardiographic in vitro measurements were performed using both Philips iE33 and GE Vivid E9 systems with a range of system settings on 53 bioprosthetic valves in all available sizes. Two-dimensional echocardiographic ID measurements were made in two orthogonal planes at the level of the sewing ring, and similar three-dimensional measurements were generated from multiplane reconstructions. They were compared with both manufacturer-supplied valve ID (MID) and the true ID (TID) measured with Hegar dilators.


Both the iE33 and the Vivid 9 provided comparable valve ID measurements. TID was statistically significantly smaller than MID ( P < .001). All echocardiographic measurements were closer to TID than to MID. Two-dimensional measurements were closest to TID because of higher spatial resolution.


Transesophageal echocardiographic valve ID measurements compare well with TID, which is overestimated by MID. These findings have potentially important implications for valve-in-valve procedures because an inaccurate measurement of TID might lead to the wrong choice of implanted valve.


  • The investigators analyzed differences between manufacturer-quoted internal dimensions of available BVs and the true (directly measured) internal dimensions.

  • True dimensions correlated well with those measured by TEE, whereas quoted dimensions did not.

  • More information about the internal dimensions of BVs will increase good outcomes for VIV therapy.

  • TEE plays an important role in patients being considered for VIV therapy and the manufacturer’s quoted valve size data cannot necessarily be relied upon.

Moderate or severe heart valvular diseases are most common in patients >75 years of age, and they are likely to become more common because of the aging population. Surgical valve replacement is the gold standard treatment in selected symptomatic patients. In the context of native aortic valve stenosis and very high-risk subjects, not suitable for conventional open heart surgery, transcatheter aortic valve replacement (TAVR) may be a valuable alternative treatment. Percutaneous valve-in-valve (VIV) therapy with TAVR is a less invasive approach for treating failing bioprosthetic heart valves (BV). Several successful VIV interventions have already been performed, showing that the procedure is a valid additional treatment option for a failing BV. Transesophageal echocardiography (TEE) is critical in the assessment of the aortic valve for TAVR and for VIV, especially in patient selection, monitoring during the procedure, and detecting complications. A key factor in the success of these new, noninvasive procedures is accurate measurement of the internal dimensions of the failing valve to determine the correct implant size. The size of an implantable TAVR valve is predetermined by the internal diameter (ID) of the preexisting valve, which is different for each manufacturer, and it is measured below the intra-annular portion of the valves. TEE is the most appropriate and widely used imaging modality to assess failing BVs. Therefore, in this study, we evaluated with TEE in vitro the most commonly used aortic bioprostheses.

Our hypothesis was that the manufacturer-supplied ID (MID) was greater than the true ID (TID) and that ID measurements made with TEE using contemporary ultrasound systems would correlate well with TID. To test this hypothesis, we compared ID measurements performed using TEE in vitro from two different ultrasound vendors with MID and TID.


Valve Characteristics and Imaging Modality

We analyzed in vitro 53 new and unused aortic bioprosthesis in the most commonly used available sizes: Perimount ( n = 7), Magna ( n = 1), Carpentier Edwards standard ( n = 7), Mosaic ( n = 5), Biocor ( n = 5), Biocor Supra ( n = 5), Aspire ( n = 5), Soprano ( n = 3), Trifecta ( n = 6), Hancock ( n = 5), and Mitroflow ( n = 4). In total, we performed 2,332 two-dimensional (2D) and three-dimensional (3D) TEE in vitro measurements using both Philips iE33 (Philips Medical Systems, Best, The Netherlands) and GE Vivid E9 (GE Healthcare, Little Chalfont, United Kingdom) systems with a range of system settings. TEE in vitro was performed for each aortic bioprosthesis. An iE33 echocardiographic system with an X7-2t Live 3D transesophageal echocardiographic transducer with 2- to 7-MHz operating frequency and a Vivid E9 6 TC multiplane phased-array transesophageal echocardiographic transducer with a 3- to 8-MHz operating frequency probe were used. Both systems enable real-time 3D TEE, as well as simultaneous imaging in two orthogonal planes (Live xPlane [Philips] and Multi-D [GE]) and conventional 2D multiplane TEE.


A metal bowl lined with a soft, thick cloth to minimize reverberation artifacts was filled with water and stood for 24 hours to allow degasification. A purpose-built frame was attached to the bowl and supported the transesophageal echocardiographic probe so that the transducer surface was under the water facing downward and approximately 5 cm above the valves that were placed on the cloth at the bottom of the bowl ( Figure 1 ). This essentially provided an in vitro simulation of midesophageal imaging of an aortic bioprosthesis. On the Philips iE33 system, Live xPlane imaging was used to obtain two orthogonal 2D views of the valves. We performed the measurements using simultaneous orthogonal planes because we believe that most operators would use this mode to check the orientation of the 2D scan planes relative to the prosthetic valve sewing ring plane. The 2D line density is the same as nonsimultaneous imaging. In all cases, the frame rate was >30 Hz, which we believe is quite adequate, assuming the patient is not tachycardic. The planes were adjusted to intersect the midpoint of the valve. Therefore, measurements were made from the edge of the strongest (brightest) and most consistent echo signal, ignoring the softer (darker) signals inside the valve ring. Images were acquired using three different system settings, resolution, general, and penetration, maintaining overall gain power at 60%. These settings are equivalent to high, medium, and low fundamental. Three-dimensional mode data sets were acquired using the 3D zoom modality in fundamental mode with the overall gain power maintained at 50% for penetration, general, and resolution modes. A second 3D data set was obtained for each valve using resolution mode, with overall gain at 60% and a high volume rate, to determine the impact of lowering line density and hence spatial resolution. All 3D and four-dimensional zoom data sets were obtained in single-beat mode to replicate the in vivo situation in which this would be used to avoid stitching artifacts.

Figure 1

Experimental setup of water tank. This is an image of the in vitro setup with a transesophageal echocardiographic probe suspended above a BV in a water tank lined with toweling to minimize reverberation artifacts.

All valves were also imaged with a GE Vivid E9 BT12 machine. Multi-D was used and is comparable with Live xPlane imaging on the Philips system. We acquired images using three different frequencies, 8, 6, and 4 MHz, which are comparable with the Philips resolution, general, and penetration modes, maintaining overall gain power at −20 dB. We also used the four-dimensional zoom modality. Initially, data sets were obtained using frequencies of 8, 6, and 4 MHz, with a low volume rate. Then we acquired further images using a frequency of 8 MHz with a high frame rate, which again lowers the line density and, potentially, the spatial resolution.

The internal surface of the valve sewing ring was determined to be the most appropriate and likely landing zone for a VIV implant. The valve sewing ring is the narrowest internal dimension of the valve and is the point chosen by all operators performing this procedure to be the best landing zone for the implant. It is relatively easy to visualize this point on TEE and is analogous to the virtual aortic annulus used as a landing zone during TAVR procedures. Therefore, 2D echocardiographic ID measurements were made for the Philips iE33 machine in Live xPlane at the level of the sewing ring using Xcelera software (R3.2L1 SP2 ( Figure 2 ); 3D echocardiographic ID measurements, made at the same level, were generated using the manufacturer’s software (QLAB version 9-3DQ) ( Figure 3 ). Multiplane reconstruction from the 3D data sets was used to facilitate geometrically oriented measurements of the internal dimensions of the sewing rings using three orthogonal and perpendicular axes. Equivalent 2D and 3D echocardiographic ID measurements were also made at the same level of the sewing ring using analysis software on the GE Vivid E9 (version 112.2013) ( Figures 4 and 5 ). Two experienced operators performed the ID measurements on the iE33, and a third experienced operator performed the ID measurements on the Vivid E9. All 2D and 3D echocardiographic measurements of the anatomic ID were compared with the MID and the TID. MID was derived from the published information supplied by the valve companies, and TID was obtained by using Hegar dilators, which is a standard surgical sizing technique ( Table 1 ). Hegar dilators are adjustable and were used in increments of 0.5 mm. Multiple measurements were taken. There is no other practical way to measure TID, as other methods have greater margins of error.

Figure 2

Hancock 25 bioprosthetic aortic valve imaged in vitro. Transesophageal echocardiographic in vitro 2D measurements in resolution mode using a Philips iE33 echocardiographic machine. The left-hand image depicts the equivalent of a midesophageal long-axis view at approximately 120°, whereas the right-hand image is the equivalent transverse image plane at approximately 30°. Sample measurements of the valve internal dimensions are depicted in red, green, and yellow . In the right-hand (short-axis) image, there is some dropout of the valve ring in the medial and lateral aspects due to acoustic shadowing, which frequently occurs in vivo. Therefore, two orthogonal measurements were made at angles at which the ring is more clearly visualized. Because the valve is circular, the precise angle of measurements is not critical, but we recommend that the average of a minimum of two measurements be used.

Figure 3

Hancock 25 bioprosthetic aortic valve imaged in vitro. This is the same valve shown in Figure 1 , imaged using 3D TEE in resolution high-frequency mode imaged with the Philips iE33 echocardiographic machine. A series of multiplane reconstructions were made from the 3D image depicted in the bottom right frame. On the top left (green frame) is a longitudinal plane with measurement (D14 = 2.18 cm). Top right is a transverse (red, short-axis) frame with measurements (D11 = 2.18 cm, D12 = 2.23 cm), and bottom left is a coronal plane (blue) with measurement (D16 = 2.14 cm). Measurements were made from the edge of the strongest (brightest) and most consistent echo signal, ignoring the softer (darker) signals inside the valve ring, and we recommend that an average of all measurements be used to obtain a value for the valve internal dimension.

Figure 4

Trifecta 23 bioprosthetic aortic valve imaged in vitro. Transesophageal echocardiographic in vitro 2D measurements with F6 using a GE Vivid E9 echocardiographic machine. The acquired image sequence is played backward and forward to help identify the appropriate landmarks to use in making measurements. In a single still frame (as displayed), it can be more difficult to be confident about the landmarks, so the replay process is important during measurements.

Figure 5

Trifecta 23 bioprosthetic aortic valve imaged in vitro. Transesophageal echocardiographic in vitro 3D measurements with F4 using a GE Vivid E9 echocardiographic machine. Measurements are made using multiplane reconstructions created to simulate long-axis, short-axis, and coronal planes. As previously described, the entire image sequence is viewed to help identify which landmarks on an individual frame (as displayed) represent the valve ring.

Table 1

Bioprosthetic aortic valves

Valve model and size (mm) TID (mm) MID (mm)
Perimount 19 17 18
Perimount 21 19 20
Perimount 23 21 22
Perimount 25 23 24
Perimount 27 25 26
Perimount 29 27 28
Perimount EU 29 27 28
Magna 29 27 28
Mosaic 21 16.5 18.5
Mosaic 23 18.5 20.5
Mosaic 25 20.5 22.5
Mosaic 27 22 24
Mosaic 29 24 26
Carpentier Edwards 19 17 18
Carpentier Edwards 21 19 20
Carpentier Edwards 23 20 22
Carpentier Edwards 25 21 24
Carpentier Edwards 27 23 26
Carpentier Edwards 29 25 28
Carpentier Edwards 31 27 30
Biocor 21 16.5 19
Biocor 23 18.5 21
Biocor 25 20.5 23
Biocor 27 22.5 25
Biocor 29 24.5 27
Biocor Supra 19 16.5 19
Biocor Supra 21 18.5 21
Biocor Supra 23 20.5 23
Biocor Supra 25 22.5 25
Biocor Supra 27 24.5 27
Aspire 20 16.5 18.2
Aspire 21 17.5 19.2
Aspire 23 19 21
Aspire 25 20 23
Aspire 27 22 25
Trifecta 19 16 17
Trifecta 21 18 19
Trifecta 23 20.5 21
Trifecta 25 22 23
Trifecta 27 24 25
Trifecta 29 26 27
Hancock 21 16.5 18.5
Hancock 23 18.5 20.5
Hancock 25 22.5 22.5
Hancock 27 24 24
Hancock 29 26 26
Soprano 20 20 19.8
Soprano 22 22 21.7
Soprano 24 23.5 23.7
Mitroflow 21 17 17.3
Mitroflow 23 19 19
Mitroflow 25 21 21
Mitroflow 27 23 22.9

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Apr 21, 2018 | Posted by in CARDIOLOGY | Comments Off on Validation of Transesophageal Echocardiographic In Vitro Measurements for Bioprosthetic Aortic Valves: Implications for Percutaneous Valve-in-Valve Therapy

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