Background
Accurate identification of tricuspid valve (TV) leaflets by two-dimensional (2D) transthoracic echocardiography is difficult because of variability in the intersection between the imaging plane and leaflets. Using information obtained from multiplanar reconstruction (MPR) of three-dimensional (3D) data sets, the investigators sought to define “novel” 2D views that would allow targeted interrogation of TV leaflets using 2D transthoracic echocardiography.
Methods
Images of the TV in the standard 2D views (apical four chamber, right ventricular focused, right ventricular inflow, and parasternal short axis) and 3D data sets were acquired from the same probe position in 106 adults. Three-dimensional MPR was used to determine which leaflet combination was seen in the 2D image: anterior and septal, anterior and posterior, anterior alone, or posterior and septal. Using this analysis, 2D landmarks were identified to define nonstandard TV views tailored to depict specific leaflets. Two-dimensional images in these views and 3D data sets were then prospectively collected in 54 additional patients. Three independent readers analyzed these 2D views to determine TV leaflet combinations, and their interpretation was compared with 3D MPR–derived reference.
Results
Three-dimensional MPR views made it possible to define six nonstandard 2D views on the basis of anatomic clues and landmarks, which consistently depicted all the aforementioned leaflet combinations. When these six views were prospectively tested, the agreement of TV leaflet identification against 3D MPR was excellent (κ = 0.88, κ = 0.93, and κ = 0.98).
Conclusion
The nonstandard 2D views defined in this study allow accurate TV leaflet identification and may thus be useful when localization of TV leaflet pathology is clinically important.
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Methods
Patient Population and Study Design
One hundred sixty patients with a wide range of RV sizes and function and tricuspid annular sizes without previous TV surgery were prospectively studied. All patients had undergone clinically indicated TTE. Of these patients, the first 106 patients became the study group, and the following 54 became the test group. Table 1 summarizes the baseline characteristics of both groups. The study group was used to address the first and second aims, whereas the test group was used to address the third aim. Specifically, using data obtained from the MPR analysis of the study group, 2D view-specific details were identified to describe nonstandard 2D views tailored to depict specific TV leaflets. Two-dimensional acquisitions of these “novel” views combined with the 3D data sets obtained from the identical transducer position were subsequently prospectively collected in the test group. These nonstandard views were reviewed by three independent observers, whose determination of which leaflets were visualized were compared with 3D MPR reference. The study was approved by the institutional review board.
| Study group ( n = 106) | Test group ( n = 54) | |
|---|---|---|
| Age (y) | 54 ± 20 | 48 ± 23 |
| Men | 52 (49%) | 25 (46%) |
| BSA (m 2 ) | 1.8 ± 0.2 | 1.8 ± 0.2 |
| Tricuspid annular diameter (mm) | 33 ± 7 | 34 ± 8 |
| RV basal diameter (mm) | 55 ± 6 | 53 ± 6 |
| TAPSE (cm) | 1.9 ± 0.5 | 1.9 ± 0.5 |
| S′ (cm/sec) | 11 ± 3 | 11 ± 3 |
Protocol I: The Study Group
In the study group, digital cine loops of the TV were acquired in the three standard 2D views: A4C, RVIF, and PSAX, as well as in the RVF view (iE33; Philips Medical Systems, Andover, MA) by a single sonographer using the fully sampled matrix-array X5 transducer. For each of the four transducer positions on the chest wall, a full-volume 3D data set was acquired immediately after the 2D acquisition ( Figure 1 ). Full-volume or zoomed acquisitions were performed using electrocardiographic gating over four consecutive cardiac cycles during a single breath-hold.
MPR of 3D Data Sets
Digital 3D data sets were analyzed offline using commercial software (QLAB version 9.0; Philips Medical Systems) to determine which combination of leaflets (anterior and septal [A-S]; anterior and posterior [A-P]; posterior and septal [P-S]; posterior, anterior, and septal; or anterior alone [ANT]) was visualized in each 2D image. This was done by manipulating the data set using QLAB with 3DQ functionality ( Figure 2 ). The green plane ( Figure 2 , top left ) represented the original 2D input. The position of this plane was not adjusted. To determine which leaflets were depicted in the original 2D image, the red (orthogonal) and blue (cross-sectional) planes were adjusted to depict a cross-section of the TV as viewed from the RV perspective. The leaflets seen in the original 2D imaging plane were then determined by carefully assessing the intersection between the green plane and the blue plane in systole and diastole ( Figure 2 ). In the study group, the combinations of TV leaflet pairs were counted to obtain the percentage frequency of each combination for each of the standard views.
Protocol II: The Test Group
Three independent readers were requested to analyze the nonstandard 2D views obtained in the test group and to identify the TV leaflets in each image. This was done after a brief teaching session, which described the novel 2D views and the TV leaflets expected to be visualized in each of these novel views. The interpretation of these readers was compared with the 3D MPR–based analysis, which was performed by an independent investigator.
Statistical Analysis
In protocol II, κ statistics of agreement between categorical variables were used to compare the 2D and 3D MPR determinations. The calculated κ coefficients were judged as follows: 0 to 0.20, low; 0.21 to 0.40, moderate; 0.41 to 0.60, substantial; 0.61 to 0.80, good; and >0.80, excellent.
Methods
Patient Population and Study Design
One hundred sixty patients with a wide range of RV sizes and function and tricuspid annular sizes without previous TV surgery were prospectively studied. All patients had undergone clinically indicated TTE. Of these patients, the first 106 patients became the study group, and the following 54 became the test group. Table 1 summarizes the baseline characteristics of both groups. The study group was used to address the first and second aims, whereas the test group was used to address the third aim. Specifically, using data obtained from the MPR analysis of the study group, 2D view-specific details were identified to describe nonstandard 2D views tailored to depict specific TV leaflets. Two-dimensional acquisitions of these “novel” views combined with the 3D data sets obtained from the identical transducer position were subsequently prospectively collected in the test group. These nonstandard views were reviewed by three independent observers, whose determination of which leaflets were visualized were compared with 3D MPR reference. The study was approved by the institutional review board.
| Study group ( n = 106) | Test group ( n = 54) | |
|---|---|---|
| Age (y) | 54 ± 20 | 48 ± 23 |
| Men | 52 (49%) | 25 (46%) |
| BSA (m 2 ) | 1.8 ± 0.2 | 1.8 ± 0.2 |
| Tricuspid annular diameter (mm) | 33 ± 7 | 34 ± 8 |
| RV basal diameter (mm) | 55 ± 6 | 53 ± 6 |
| TAPSE (cm) | 1.9 ± 0.5 | 1.9 ± 0.5 |
| S′ (cm/sec) | 11 ± 3 | 11 ± 3 |
Protocol I: The Study Group
In the study group, digital cine loops of the TV were acquired in the three standard 2D views: A4C, RVIF, and PSAX, as well as in the RVF view (iE33; Philips Medical Systems, Andover, MA) by a single sonographer using the fully sampled matrix-array X5 transducer. For each of the four transducer positions on the chest wall, a full-volume 3D data set was acquired immediately after the 2D acquisition ( Figure 1 ). Full-volume or zoomed acquisitions were performed using electrocardiographic gating over four consecutive cardiac cycles during a single breath-hold.
MPR of 3D Data Sets
Digital 3D data sets were analyzed offline using commercial software (QLAB version 9.0; Philips Medical Systems) to determine which combination of leaflets (anterior and septal [A-S]; anterior and posterior [A-P]; posterior and septal [P-S]; posterior, anterior, and septal; or anterior alone [ANT]) was visualized in each 2D image. This was done by manipulating the data set using QLAB with 3DQ functionality ( Figure 2 ). The green plane ( Figure 2 , top left ) represented the original 2D input. The position of this plane was not adjusted. To determine which leaflets were depicted in the original 2D image, the red (orthogonal) and blue (cross-sectional) planes were adjusted to depict a cross-section of the TV as viewed from the RV perspective. The leaflets seen in the original 2D imaging plane were then determined by carefully assessing the intersection between the green plane and the blue plane in systole and diastole ( Figure 2 ). In the study group, the combinations of TV leaflet pairs were counted to obtain the percentage frequency of each combination for each of the standard views.
Protocol II: The Test Group
Three independent readers were requested to analyze the nonstandard 2D views obtained in the test group and to identify the TV leaflets in each image. This was done after a brief teaching session, which described the novel 2D views and the TV leaflets expected to be visualized in each of these novel views. The interpretation of these readers was compared with the 3D MPR–based analysis, which was performed by an independent investigator.
Statistical Analysis
In protocol II, κ statistics of agreement between categorical variables were used to compare the 2D and 3D MPR determinations. The calculated κ coefficients were judged as follows: 0 to 0.20, low; 0.21 to 0.40, moderate; 0.41 to 0.60, substantial; 0.61 to 0.80, good; and >0.80, excellent.
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