Accurate visualization and identification of tricuspid valve (TV) leaflets are important for successful guidance of transcatheter TV interventions. The TV is the largest and most anterior and apically positioned of the four cardiac valves. Historically the TV has been described as having three leaflets, named according to their anatomic orientation: the anterior (the largest, with a quadrangular shape), the septal (short radially but long circumferentially, semicircular in shape), and the posterior (intermediate in size, with a triangular shape and scalloped indentations).
Echocardiographic imaging of the TV remains challenging for a number of reasons, including but not limited to its anterior location relative to the other valves, thinness of the TV leaflets compared with the mitral valve leaflets,1 and difficulty lining up the TV annular plane with the ultrasound beam. In spite of its name, pathologic specimens have shown that the TV does not uniformly have three leaflets. In one study of 36 cadaveric hearts, the TV was found to have either more or fewer than three leaflets in 30/36 patients.2
Characterization of TV leaflet number by two-dimensional (2D) transthoracic echocardiography (TTE) is not reliable due to the complex, nonplanar geometry of the tricuspid annulus and the highly variable anatomy of the TV. In addition, with 2D TTE it is difficult to visualize all the tricuspid leaflets in the same plane. The main advantage of three-dimensional (3D) TTE imaging is that all three TV leaflets can be visualized simultaneously, as compared with 2D TTE, where it is often difficult to ascertain which leaflet is being imaged. In addition, with 3D echocardiography it is possible using multiplanar reconstruction to determine where the 2D echocardiographic cut plane falls in relation to the 3D tricuspid leaflet-annulus complex and thereby to confidently determine which leaflets are being visualized.3 Given these advantages, we hypothesized that 3D TTE imaging of the TV would improve the identification of the number of leaflets when compared with 2D TTE and the frequency with which there is an abnormal number of leaflets.
Over a 2-year period, 300 patients with known or suspected right-sided or TV pathology underwent 2D and 3D TTE acquisitions of the TV from the right ventricular (RV) inflow, short-axis, and apical four-chamber views. Using 3D TTE, magnified acquisitions of the TV from the RV perspective were obtained from the standard 2D views above. Overall, 70% of studies were technically adequate for 3D TTE acquisition. We defined TV scallops of a single leaflet as having an indentation depth of less than 50% of the depth of the adjacent scallop, while separate TV leaflets had distinct and separate anatomic borders. The number of TV leaflets was compared between 2D and 3D acquisitions. Severity of tricuspid regurgitation (TR), if present, was assessed using vena contracta, and the presence or absence of pulmonary hypertension (PH) was noted. Pulmonary artery systolic pressures of 25–40, 41–55, and >55 mm Hg were defined as mild, moderate, and severe PH, respectively.
Using standard 2D TTE, no anomalies in the number of TV leaflets were identified. However, using 3D TTE, a total of 22 patients with bicuspid, four patients with quadricuspid, and one patient with pentacuspid TV were identified (Figure 1, Video 1). The interobserver variability of the number of TV leaflets was good (intraclass correlation coefficient = 0.85). Twelve of 27 patients with an abnormal number of TV leaflets were female. The average age of the patients with an abnormal number of TV leaflets was 55 ± 12 years. Cases of TV with an abnormal number of leaflets were associated with TR in all cases, with mild TR in 11 patients, moderate TR in five patients, and severe TR in 11 patients, with 64% of patients with bicuspid valves having at least moderate TR (Table 1). Of those patients with an abnormal number of TV leaflets, 63% had PH, including 73% of patients with bicuspid valves. In those patients where RV systolic pressure (RVSP) could be estimated (11/27 patients), the average RVSP was 63 mm Hg, consistent with severe PH. The average RVSP in patients with bicuspid valves was 66 mm Hg. Of note, our study population focused on patients with known or suspected right-sided pathology, and thus the presence of significant TR and PH may be overrepresented compared with the general population, which the authors acknowledge as a limitation of this study.
Figure 1.
Examples of different numbers of TV leaflets visualized on 3D TTE from RV perspective, including (A) normal (three leaflets), (B) bicuspid (two leaflets), (C) quadricuspid (four leaflets), and (D) pentacuspid (five leaflets) TV.
Table 1.
Clinical manifestations of abnormal number of TV leaflets
| Type of TV leaflet abnormality | Presence of TR | Severity of TR | Presence of PH | Severity of PH | Mean RVSP (mm Hg) |
|---|---|---|---|---|---|
| Bicuspid, 2/27(81) | 22/22 (100) | Mild, 8/22(36) | 15/22(68) | Mild, 1/15(7) | 66 |
| Moderate, 4/22(18) | Moderate, 4/15(27) | ||||
| Severe, 10/22(45) | Severe, 10/15 (66) | ||||
| Quadricuspid, 4/27(15) | 4/4 (100) | Mild, 2/4 (50) | 2/4 (50) | Mild, 1/2(50) | 49 |
| Moderate, 1/4(25) | Moderate, 0/2 (0) | ||||
| Severe, 1/4(25) | Severe, 1/2(50) | ||||
| Pentacuspid, 1/27(4) | 1/1 (100) | Mild, 1/1 (100) | 0/1 (0) | NA | NA |
| Total, 27/300 (9) | 27/27 (100) | Mild, 11/27(41) | 17/27(63) | Mild, 2/17(12) | 63 |
| Moderate, 5/27(18) | Moderate, 4/17(24) | ||||
| Severe, 11/27(41) | Severe, 11/17(65) |
The data in parentheses are percentages.
In summary, accurate determination of the number of tricuspid leaflets is highly feasible using 3D TTE but not 2D TTE. Tricuspid valves with an abnormal number of leaflets are frequently associated with TR as well as clinically significant PH. When TR is identified in patients in whom the mechanism is unclear, 3D TTE should be performed to exclude leaflet abnormalities. Accurate knowledge of the number of TV leaflets is integral to determine the feasibility of echocardiography-guided transcatheter TV intervention, to identify the optimal device size and type, and to estimate the number of TV clips required for a successful repair.
Supplementary Material
Acknowledgments
Conflicts of Interest: Dr. Lang has received a research grant from Philips Healthcare for other unrelated studies. The remaining authors have nothing to disclose.
Footnotes
SUPPLEMENTARY DATA
Supplementary data related to this article can be found at https://doi.org/10.1016/j.echo.2020.12.015.
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