Tricuspid Valve Disease: Imaging Using Transthoracic Echocardiography


Modality

Utility

2D–TTE

Initial screening, often provides first clue for TV disease.

M-mode

Best used for tricuspid annular systolic excursion (TAPSE).

Doppler

The only modality, which provides hemodynamic and valvular regurgitation assessment.

Bi-Plane

Provides an orthogonal view of TV and right-sided chambers

iRotate

Provides a comprehensive evaluation of the TV annulus, leaflets as well as chamber quantification.

3D-TTE

Complete visualization of TV morphology; enface views as well as accurate valvular and chamber quantification.





2D–TTE


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.


Table 5.2
2D–TTE acoustic windows (views)

































Acoustic window

Utility

Parasternal right ventricular inflow tract view (RVIT)

One of the most important views to assess TV morphology, regurgitation and to measure TV annulus.

Parasternal short-axis view (SAX) at the base of the heart

Provides valuable information regarding TV morphology, regurgitation

Apical 4-chamber views

• Standard

Provides valuable information regarding TV morphology, regurgitation

• Focused

Provides valuable information regarding TV morphology, regurgitation

• Modified

Provides valuable information regarding TV morphology, regurgitation

• Subcostal 4-chamber view

Provides valuable information regarding TV morphology, regurgitation

Subcostal short-axis view

Provides comprehensive visualization of TV three leaflets as well as TV morphology and regurgitation


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Fig. 5.1
The parasternal 2D-TTE views: standard right ventricular inflow tract view from a normal subject (a) and after further angulation (b) to exclude left ventricle from the scan sector and a standard parasternal short-axis view at base of the heart (aortic valve) level (c). Corresponding views from a patient with an abnormal TV (d, e and f). LV left ventricle, RV right ventricle, RA right atrium, RVOT right ventricular outflow tract, LA Left atrium, AO aorta


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Fig. 5.2
The 2D-TTE apical views from a normal right heart (a–e): focused (a); modified (b); aortic (c); coronary sinus (d) and subcostal (e). Corresponding views from a subject with an abnormal TV (f–j). Note that in “h” LV cavity is minimally visualized due to the prominent RV (see*). Abbreviations are similar to Fig. 5.1, CS coronary sinus


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Fig. 5.3
The 2D-TTE subcostal short-axis views from a normal subject (a) and a subject (b) with a TV prolapse (arrow)


3D-TTE


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.


Acquisition


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.


Analysis and Display


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].

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Fig. 5.4
Multiple 3D-TTE views of an open TV as seen from RV aspect (a) and from RA aspect (b) and the corresponding views with the valve closed (d and e); RV inflow view (c) and a 2D multiplane reconstruction from 3D dataset (f). Note that asterisk refers to the place of TV annulus. ATL anterior leaflet, PTL posterior leaflet, STL septal leaflet, MV mitral valve, Ao aorta, RV right ventricle, RA right atrium


Incremental Value of 3D-TTE over 2D-TTE of the TV


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.

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Fig. 5.5
Visualization of TV leaflets on three standard 2D-TTE views. Percentages of the leaflet identification have been reported below each 2D view. From Anwar et al. with permission [1]

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].

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Fig. 5.6
Visualization of different etiologies and mechanisms of TR on real-time 3D-TTE : (a) a long-axis and (b) a short-axis enface TV view as seen from the RV aspect, a pacemaker lead (arrow) restricts TV leaflets from closing. (c) and (d) are from a patient with a prolapse of the posterior leaflet of the TV with elongated chordae as seen from RV aspect with TV open (c) and RA aspect TV closed (d). The arrow points to incomplete TV coaptation due to prolapsed posterior leaflet. Image (e) shows an enface view of TV, as seen from the RV aspect, with a tear in the TV leaflets (arrow) after repeated biopsies in a patient with a heart transplant. Image (f) shows lack of TV leaflets coaptation (arrow) due to carcinoid disease in enface RV view. ATL anterior leaflet, PTL posterior leaflet, STL septal leaflet, PM pacemaker lead, LV left ventricle

Tricuspid annular dilatation in patients with functional TR can be a more accurate indicator of TR severity than color Doppler of TR alone [79]. 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].


Simultaneous Multiplane Imaging


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).


Bi-plane TTE


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).

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Fig. 5.7
2D-TTE bi-plane mode assessment of the TV in two different views: (a) from a normal subject where the reference line transects the tricuspid valve annulus in a focused RV apical view allowing measurements of two axes diameters; (b) from a patient with TV disease where the reference line, transects the tricuspid valve annulus in the RV inflow view allowing measurements of two axes diameters. All measurements can be performed in the same heartbeat. RV right ventricle, RA right atrium, RVOT right ventricular outflow tract


iRotate Mode


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).

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Fig. 5.8
A schematic drawing of the cut planes for the four iRotate RV views. Left: as visualized in the transvers plane viewed from the RV aspect. Right: as visualized in the RV sagittal plane


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Fig. 5.9
The 2D-iRotate image acquisitions of the four RV views from a normal TV valve, left, and right the corresponding views from a patient with Ebstein’s anomaly (a, e) the mitral view: visualizing the RV lateral wall; (b, f) the coronary sinus view: visualizing the RV anterior wall; (c, g) the aortic view: visualizing the RV inferior wall; (d, g) the coronal view: visualizing the RV inferior wall and RVOT anterior wall. Note the position of the chordal attachments, towards the RVOT, of the Ebstein TV in (h)

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.


TTE Approach to Tricuspid Valve Disease


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.


Table 5.3
Comprehensive tricuspid valve assessment on transthoracic echocardiography


































Item

Utility

Leaflets

Thickening, doming, restriction

Coaptation

Flail

Annulus

Diameter, area, changes over cardiac cycle

Gradient

Mean gradient

Tricuspid regurgitation

Severity of regurgitation.

Septum

Septal flattening

Right atrium

Chamber quantification

Right ventricle

Chamber quantification

Pulmonary artery

Pulmonary artery pressure


TTE Approach to Tricuspid Valve Stenosis


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).

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Fig. 5.10
Example of a stenotic tricuspid valve on 2D-TTE (a); flow acceleration on colour-Doppler (b) and typical pattern on spectral continuous-wave Doppler (c)



Table 5.4
Estimation of TV cross-sectional area on transthoracic echocardiography


















 
Formula

Continuity equation

TV cross sectional area in cm2 = [A1*V1/V2]
 
TV cross sectional area in cm2 = [A1*VTI1/VTI2]

TV cross sectional area in cm2 = [Stroke volume/VTI2]

PHT

TV cross sectional area in cm2 = 190/PHT


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 and VT1 is the velocity time integral from the pulsed-wave Doppler of either right or left ventricular outflow tracts; VT2 is the the velocity time integral from the pulsed-wave Doppler of blood flow at the tricuspid valve annulus. TV cross sectional area in cm2 = stroke volume/TV-VT1. Stroke volume as above-mentioned is derived from left or right ventricular outflow PHT, Pressure half time; TV, Tricuspid valve; VTI, Velocity time integral. Although there are similarities between mitral and tricuspid stenosis, the P1/2t method has not been as extensively validated for the calculation of tricuspid valve area [34]

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.


Table 5.5
Signs of hemodynamically significant TV stenosis on transthoracic echocardiography


































Item

Cut-off value

Specific findings
 

Mean pressure gradient

≥5 mmHg

RV inflow velocity-time integral

≥60 cm

RV inflow PHT

≥190 ms

TV area

≤1 cm2

Supporting findings
 

Dilated right atrium

≥Moderate

Dilated inferior vena cava
 


TV tricuspid valve, RV right ventricle, PHT pressure half time


TTE Approach to Tricuspid Valve Regurgitation


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.


TTE Diagnostic Algorithm of TR


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].


Etiology and Mechanisms of TR


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).


Table 5.6
Etiology and mechanisms of tricuspid regurgitation




















Aetiology

Feature

Mechanism(s)

Primary

Less common (10–25%)

Structural abnormality of tricuspid valve leafletsAcquired disease or congenital

Cleft leaflet (congenital)

Perforation (endocarditis)

Mal-coaptation (pacemaker leads)

Retraction (rheumatic, radiation, drug, carcinoid)

Prolapse (degenerative)

Ruptured chordae (traumatic or endocarditis)

Congenital Ebstein’s anomaly or prolapse

Other congenial etiologies:

TV dysplasia

TV tethering (perimembranous ventricular septal defect and ventricular septal aneurysm)

Repaired tetralogy of Fallot

Congenitally corrected transposition of the great arteries

Other (giant right atrium)

Secondary

(Functional)

Most frequent (80–90%)

Morphologic normal leaflets with impaired leaflets coaptation

Annular dilatation and or RV dilatation

Leaflet tethering due to left sided heart disease or pulmonary hypertension

RV dysfunction (RV ischemia; RV volume overload, RV cardiomyopathy)

RA abnormalities (atrial fibrillation)


RV right ventricular


Grading of TR Severity


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


Table 5.7
Assessment of chronic tricuspid regurgitation severity on transthoracic echocardiography





























Parameter

Mild

Moderate

Severe

Structural

TV morphology

Normal or mildly abnormal leaflets

Moderately abnormal leaflets

Severe valve lesions (e.g., flail leaflets severe retraction, large perforation)

RV, RA

Usually normal

Normal or mild dilatation

Usually dilateda

RV eccentricity index

Usually normal

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Dec 30, 2017 | Posted by in CARDIOLOGY | Comments Off on Tricuspid Valve Disease: Imaging Using Transthoracic Echocardiography
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