Standard 2D-TTE for the assessment of TV morphology and function can be performed from multiple acoustic windows. Essential 2D–TTE acoustic windows include the standard parasternal long-axis (RV inflow), the parasternal short-axis view, the apical 4-chamber view, and the subcostal view (Table 5.2 and Figs. 5.1, 5.2, and 5.3). A comprehensive TTE exam of the TV requires the use of all feasible 2D views alongside Doppler Interrogation to obtain full assessment of the TV apparatus, right heart chambers as well as venous and pulmonary circulation. A localized pathology such as a flail leaflet could be missed if all the TTE views are not attempted. Detailed transesophageal assessment of TV is provided in Chap. 6.

3D-TTE is often used in experienced centers to provide a comprehensive interrogation of the TV leaflets, annulus, subvalvular apparatus and RV size and function quantification.

3D-TTE acquisition can be performed from any of the standard 2D acoustic windows (parasternal, apical and subcostal). Using current technology cardiac structures in the axial dimension (y, azimuthal) have the best resolution (0.5 mm), in the lateral dimension (x) (2.5 mm), and in the elevation dimension (3.0 mm) the least resolution. Therefore, the parasternal short-axis window should provide the best quality for an “enface surgical” view. Consequently, TV display on 3D-TTE has an intermediate quality in the parasternal long-axis window and has the least quality in the apical window acquisition. The two most commonly used 3D-TTE modes are the real-time and the full-volume modes. The former has a relatively narrow angle (smaller scan sector) but it provides a higher resolution than the latter. Furthermore, a real-time scan is not limited to the number of heart cycles nor it is limited by respiration or arrhythmia. Moreover, it allows for focusing on a specific region of interest. On the other hand, the full volume mode allows for a wider angle (larger scan sector) that can include more structures in a single acquisition. However, structures on the full-volume mode have much lower resolution and could be limited by artifacts due to respiration or arrhythmia. The trade-offs between the two modes should be taken into consideration as per patient and according to the objectives of the 3D-TTE scan.

Similar to other 3D imaging modalities such as magnetic resonance imaging or computed tomography, real-time 3D-TTE datasets in the multiplanar reconstruction mode, display the full TV apparatus in 3D as well as right sided chambers in the 2D long-axis (coronal and sagittal) and short-axis (axial) planes. This allows for a single image displaying the TV in an enface surgical view simultaneously with a full assessment of the TV leaflets (Fig. 5.4). For uniformity it has been proposed that display of the 3D-TTE enface view of the TV should preferably be performed with the septal leaflet in the 6 o’clock position [2].

Compared with left sided structures, echocardiographic assessment of right-sided structures is more difficult due to the anterior location of the right heart and the variable position of the TV leaflets. Since 3DE is dependent on 2DE quality, 3DE acquisition of the right heart is still challenging. However, there is accumulating evidence that 3DE has incremental value in the assessment of TV disease compared with 2D-TTE.

Visualization of TV leaflets: Using 2D-TTE, it is extremely difficult to identify all leaflets in the parasternal short-axis view due to variability in their position. Anwar et al. have shown that by using a 3D mental reconstruction, both septal and anterior leaflets can be identified in all cases from the parasternal long-axis (RV inflow) and the apical 4-chamber views (Fig. 5.5). The use of an enface view from a right atrial or right ventricular aspect, “surgical view” provides a simultaneous display of the TV leaflets and their attachment to the TV annulus as well as it provides accurate assessment of leaflet morphology, thickness, leaflet defect, prolapse and fusion of commissures.

Quantification of TV annulus: Another clear advantage of 3D-TTE over 2D-TTE is the ability of the former to accurately quantify the non-planner TV annulus [1, 3]. Detailed measurements of leaflets size, intercommisural distance, and cyclic variation can be made [1].

Assessment of TR: Moreover, real-time 3D-TTE has an increasing role in the assessment of TR (Fig. 5.6). Assessment of TV leaflets and commissures morphology, annulus size and non-coaptation distance provide important clues to etiology and mechanism of TR. Furthermore, although practically difficult, quantification of vena contracta area of TR jet on real-time colour Doppler 3D-TTE has been accomplished. The authors proposed new cut-off values for TR severity: 0.5 cm² for mild, 0.5–0.75 cm² for moderate, and >0.75 cm² for severe TR [4]. However, these values need to be prospectively validated in a larger external population. Respiratory variation of TV jet regurgitant orifice area has been shown on colour Doppler 3D-TTE, as well as other TR parameters on 2D-TTE [5, 6].

Tricuspid annular dilatation in patients with functional TR can be a more accurate indicator of TR severity than color Doppler of TR alone [7–9]. Therefore; the ability to accurately quantify TV annulus with 3D-TTE is important in the assessment of TR severity [10, 11].

Display and assessment of TV enface area, similar to mitral enface area; in patients with suspected TV stenosis is required for accurate diagnosis of TV pathology, and of course only feasible on 3D-TTE [12, 13].

With the introduction of the MATRIX transducer, simultaneous multiplane imaging has become available. This new modality permits the use of a full electronic rotation of 360° (adjustable by 5° steps) of the 2D image (iRotate) and a simultaneously adjustable bi-plane 2D image (xPlane).

In the bi-plane mode an orthogonal view can be obtained through the midline of the primary image, such as the tricuspid valve, and displayed as a secondary image. If necessary, from the midline additional secondary images can be visualized by a lateral tilt of up to maximal +30° to −30° (Fig. 5.7).

2D- iRotate echocardiography is a relatively new echo modality aiming at maximizing the benefits of using 2D- and 3D-TTE in routine clinical practice by combing the advantages of the two echo modalities. It allows for full assessment of a cardiac structure such as the right ventricle from a single transducer position. The iRotate images retain the advantages of a better quality and a higher frame rate than 3D-TTE. The feasibility of 2D-TTE iRotate has been examined by our group for the assessment of right ventricular function using fixed anatomic landmarks [14] as well as right ventricular strain assessment [15].

McGhie et al. proposed a novel 13-segment model to assess right ventricular function from a single apical acquisition using the iRotate mode . The proposed protocol uses four anatomic landmarks to identify the different right ventricular walls, namely: mitral valve for RV lateral free wall, coronary sinus for RV anterior wall, aortic valve for RV inferior wall and RVOT for RVOT anterior and inferior wall. From the apical window, a standard apical 4-Chamber view can be adjusted to acquire a focused non-foreshortened RV view with the tricuspid valve centered along, or as near as possible, to the midline of the sector. With the iRotate mode a full electronic rotation can be performed. Using the anatomic landmarks, as defined above, four standard TV annulus views can be acquired (Figs. 5.8 and 5.9).

The 2D-TTE iRotate mode provides a standard methodology for serial assessment of RV function [16]. High quality image acquisition using the 2D-TTE iRotate mode could be achieved after a relatively short learning curve of 20 cases. The feasibility of segmental RV wall analysis approached 95% in subjects with normal- and patients with dilated-RVs. Furthermore, quantification of RV function using tricuspid annular plane systolic excursion (TAPSE) and Doppler tissue velocities were feasible in more than 90% of subjects with normal RV size and in all patients with dilated RVs. Likewise, assessment of RV strain in subjects with normal and dilated RV has been shown feasible and reproducible using the 2D-TTE iRotate mode [15].

Translating those initial feasibility studies of the 2D-TTE iRotate mode into direct TV assessment could be speculated in several aspects. It could be used for more robust serial follow up of disease progression before- and reverse remodeling after percutaneous interventions or surgery involving the TV. Likewise, recovery of RV function after TV repair or replacement could be more accurately quantified. The 2D-TTE iRotate mode could be used as well for comprehensive and robust serial assessment of TV annulus size and function.

Tricuspid pathology can be broadly described as stenotic, regurgitant or both. TV disease varies widely from asymptomatic lesions to advanced cases with generalized anasarca due to severe TR. Congenital TV disease is beyond the scope of this book chapter.

A diagnostic approach begins with morphologic assessment and localization of the underlying TV pathology. Once the etiology of TV lesion is established, assessment of disease severity is the next step. Impact of TV disease on right sided chambers size and function as well as pulmonary and hepatic circulation should follow. Finally, associated valvular lesions and assessment of left sided chambers should be performed. Table 5.3 lists the comprehensive assessment of the TV with 2D-TTE.

TV stenosis can be due to rheumatic, infiltration such as in carcinoid disease, or rarely, due to compression by external structure such as tumor, thrombus or the aorta. When suspected, morphologic assessment with 2D-TTE and colour-Doppler, spectral pulsed- and continuous-wave Doppler is required (Fig. 5.10). Tracing of Doppler flow envelopes should be performed and averaged from three to five cardiac cycles. Velocity timed integral (VTI) and mean gradient can then calculated automatically. There are several methods for calculation of the TV cross sectional area (Tables 5.4 and 5.5).

Doppler estimation of TV cross-sectional area is based on the conservation of mass theory. Using the continuity equation, TV cross-sectional area can be calculated from the standard formula (TV cross sectional area in cm² = [A₁*V₁/V₂]) where A₁ is the cross-sectional area from left or right ventricular outflow, V₁ is the peak flow velocity from left or right ventricular outflow on pulsed-wave Doppler. V₂ is the peak flow velocity from forward TV flow on continuous-wave Doppler. Another method for estimation of TV cross-sectional area can be derived from the formula TV area in cm² = stroke volume/TV-VTI. Stroke volume, mentioned above, is derived from left or right ventricular outflow. Stroke volume can be estimated from the formula (stroke volume = cross sectional area * velocity time integral) based on Doppler interrogation of either left or right outflow tracts.

TV area can also be estimated from the formula 190/PHT, where PHT is the pressure half time from forward TV flow on continuous-wave Doppler. In the presence of mild or more TR, the derived area will be underestimated. Furthermore, the stroke volume calculation becomes inaccurate in cases of aortic or pulmonary regurgitation. Tricuspid inflow velocities are largely dependent on respiration, heart rate and rhythm. Therfore, all measurements must be averaged throughout the respiratory cycle or recorded at endexpiratory apnea. As a rule of thumb, Doppler measurements from a minimum of three (sinus rhythm) or five cardiac cycles (atrial fibrillation) should be averaged. Likewise, pressure half-time is not reliable in case of tachycardia.

TR is the most frequently seen TV pathology. It can be organic due to leaflet pathology or functional secondary to annular dilatation and/or ventricular dysfunction. The latter is the predominant form mostly encountered in clinical practice. Trivial TR is considered physiologic and it is very often seen on routine echocardiography. Mild TR has been reported in 80–90% of echocardiograms. The prevalence of moderate or severe TR was 0.8% in the Framingham heart study with an increased prevalence with age and was fourfold more frequent in females than males [17]. One-third of patients with mitral valve stenosis have at least moderate TR [18]. Severe TR has been reported in 23–37% of patients who underwent mitral valve replacement for rheumatic mitral valve disease [19, 20]. This form of TR is defined as “functional” or “secondary” since no primary TV pathology could be seen in most of these patients. Likewise, functional TR is often seen in patients with advanced left heart disease [21].

Residual moderate or severe TR after correction of left sided lesions is not benign; it does not often regress and is associated with reduced cardiac output and right-sided heart failure. Redo surgery is associated with up to 10% mortality. More importantly, it has been associated with poor long-term outcome [22]. Therefore, surgical TV repair or replacement is indicated for patients with stages C and D functional severe TR undergoing left sided valve surgery [23]. Details on TR clinical spectrum are described in Chap. 2 of this book.

According to the current guidelines, TTE is the primary modality for TR assessment. Complete TR assessment requires; identification of etiology, severity and impact on right ventricle (and vice versa) size and function as well as right atrial size and assessment of inferior vena cava. Furthermore, pulmonary artery systolic pressure should be estimated and any associated left heart disease should be assessed [23, 24].

TR can be due to a primary cause such as a structural abnormality of the TV or incomplete leaflet closure secondary to a dilated TV annulus or a dilated right ventricle or to mal-coaptation and/or tethering of the TV leaflets (Table 5.6).

Similar to all other valves, TR is first assessed by visual inspection of the return of blood from the right ventricle into right atrium using colour Doppler. As recommended by the ASE guidelines, the use of a multi-parametric approach is mandatory [26, 40]. TR severity is determined according to 2D chamber measurements and function and Doppler recordings of jet characters. There are a few colour Doppler jet characteristics including jet area, vena contracta (VC) width and area, proximal isovelocity area (PISA) radius and flow convergence. Continuous-wave Doppler parameters include TR Doppler jet envelope shape and density. Furthermore, Doppler interrogation of hepatic venous flow is an integral part of 2D echocardiographic estimation of TR severity. However, Doppler cut-off values, which are used for grading TR severity, are largely not well validated, nor in respect all aspects of TR severity, particularly functional TR (Table 5.7