J A C C : C A R D I O V A S C U L A R I M A G I N G V O L . 1 2 , N O . 3 , 2 0 1 9

ª 2 0 1 9 B Y T H E A M E R I C A N C O L L E G E O F C A R D I O L O G Y F O U N D A T I O N

P U B L I S H E D B Y E L S E V I E R

STATE-OF-THE-ART PAPER

3-Dimensional Echocardiography inImaging the Tricuspid Valve

Denisa Muraru, MD, PHD,a,b Rebecca T. Hahn, MD,c Osama I. Soliman, MD,d Francesco F. Faletra, MD,e

Cristina Basso, MD,a Luigi P. Badano, MD, PHDa,b

SUMMARY

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Tricuspid regurgitation (TR) is an independent predictor of death. Lately, emerging technologies for the treatment of

TR have increased the interest of physicians. Due to the complex 3-dimensional (3D) geometry of the tricuspid valve

(TV) and its anterior position in the mediastinum, conventional 2D echocardiography is unsuitable to study the anat-

omy and pathophysiologic mechanisms of the regurgitant TV. 3D echocardiography has emerged as a very cost-

effective imaging modality with which to: 1) visualize the TV anatomy; 2) define the mechanism of TR; 3) measure the

size and geometry of the tricuspid annulus; 4) analyze the anatomic relationships between TV apparatus and sur-

rounding cardiac structures; 5) assess volumes and function of the right atrium and ventricle; and 6) plan surgical

repair or guide and monitor transcatheter interventional procedures. (J Am Coll Cardiol Img 2019;12:500–15)

© 2019 by the American College of Cardiology Foundation.

ECHOCARDIOGRAPHIC EXAMINATION OF

THE TRICUSPID VALVE

Two-dimensional transthoracic echocardiography(2DE) of the tricuspid valve (TV) is challengingbecause of the complex, nonplanar geometry of theannulus and the highly variable anatomy of the valve(1–3). Moreover, with 2DE, it is difficult to visualize all3 leaflets simultaneously in a single tomographic view(Figure 1). Therefore, 3D echocardiography (3DE) isneeded to perform a comprehensive evaluation of theTV (4). Transthoracic 3DE (3DTTE) can often be usedin experienced centers to provide a comprehensiveinterrogation of the TV leaflets, annulus, and sub-valvular apparatus as well as to quantitate the ge-ometry and the function of the right heart chambers

N 1936-878X/$36.00

m the aDepartment of Cardiac, Thoracic, Vascular Sciences and Public

tituto Auxologico Italiano, S. Luca Hospital, University of Milano-Bicocca

w York-Presbyterian Hospital, New York, New York; dDepartment of C

tterdam, the Netherlands; and the eDepartment of Cardiology, Fondaz

raru has received research support and speaker fees from and consu

pport from TomTec Imaging Systems. Dr. Badano has received research

aging systems; and is a member of the GE Healthcare Speakers Bureau.

ationships relevant to the contents of this paper to disclose.

nuscript received June 11, 2018; revised manuscript received September

(Table 1). In patients with a suboptimal transthoracicacoustic window, during cardiac surgery or inter-ventional procedures, the 3D transesophageal(3DTEE) approach is usually used.

HOW TO USE 3DTTE TO ACQUIRE THE TV

3DTTE acquisitions of datasets including the TV canbe performed from any of the conventional acousticwindows (parasternal, apical, and subcostal). There isnot a specific acoustic window from which to acquirea 3DTTE dataset of the TV. The acoustic window fromwhich the TV is best visualized by conventional 2DE isusually used to acquire a 3D dataset of the TV. How-ever, due to the close proximity of the TV and theright ventricle (RV) to the chest wall, and the spatial

https://doi.org/10.1016/j.jcmg.2018.10.035

Health, University of Padua, Padua, Italy; bIRCCS,

, Milan, Italy; cColumbia University Medical Center,

ardiology, Thoraxcenter, Erasmus Medical Center,

ione Cardiocentro Ticino, Lugano, Switzerland. Dr.

lts for GE Healthcare; and has received research

support from GE Healthcare, Siemens, and TomTec

All other authors have reported that they have no

13, 2018, accepted October 19, 2018.

AB BR E V I A T I O N S

AND ACRONYM S

2DE = 2D echocardiography

PISA = proximal isovelocity

surface area

RV = right ventricle/ventricular

TEE = transesophageal

echocardiography

TR = tricuspid regurgitation

TTE = transthoracic

echocardiography

TV = tricuspid valve

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orientation of the leaflets perpendicular to the di-rection of ultrasonography beams, an optimal 3DTTEacquisition of the TV is often best achieved from theapical approach, using an RV focused or a fore-shortened 4-chamber view, which allows inclusion ofthe entire TV in the dataset (Central Illustration).Often, a parasternal long-axis view of the rightchambers (with the transducer angled toward theright hip) or a parasternal short-axis view can also beused to obtain good quality 3D images of the TV. Withthe parasternal approach, the TV is situated in thenear field, and the resulting 3DE images may have abetter spatial resolution than images acquired fromthe apical approach; however, because the quality ofthe apical window is usually better than that of theparasternal window in many adult patients, both ap-proaches are valid as long as all 3 TV leaflets arecompletely visualized.

To achieve the best spatial resolution, it is impor-tant that the TV is located in the center of the pyra-midal volume acquisition. The acquisition volume,size, and shape will be adjusted in order to encom-pass the entire TV complex in the dataset, includingthe leaflets and their attachments to the septum andto the anterior wall and the annulus. The initial stepfor a good 3DE acquisition is to optimize, first, the2DE image of the TV to ensure clear delineation of thevalve structures with high tissue-blood contrast and

FIGURE 1 Echocardiographic Imaging of the Tricuspid Valve With Di

2D TTE ≈ 5-10% 3

A

P

S

LV

Transthoracic 2-dimensional (left) (Video 1), transthoracic 3D (middle) (V

rates of successful visualization of the entire tricuspid valve in routine p

diography; 3D TEE ¼ 3D transesophageal echocardiography; A ¼ anterio

outflow tract; S ¼ septal tricuspid leaflet.

absent or minimal noise (Central Illustration).The next step is to ensure that the TV com-plex is encompassed within the smallestpossible acquisition volume during the entirecardiac cycle. Because of the complex anat-omy of the valve, it is recommended that theacquisition volume also encompasses sur-rounding anatomical landmarks to helprecognize the individual TV leaflets: theanterior leaflet is located close to the RVoutflow tract, left ventricular outflow tract,and aortic valve; the septal leaflet is locatedclose to the septum separating TV from the

mitral valve; and the posterior leaflet is close to theRV inferior wall. Accordingly, the region of interest isusually sized and positioned using 2 orthogonal cutplanes (Central Illustration).

Important limitations of the use of 3DE in imagingthe cardiac valves are the difficulties to appreciatetissue characteristics (i.e., presence of calcifications,fibrosis, or vegetations and so forth) and to evaluateleaflet thickness. In 3DE, color maps are used to codethe position (depth) of the voxels and not tissuetexture abnormality. Moreover, 3DE usually showsleaflets thicker than they actually are (5). This phe-nomenon is caused by blurring or amplification arti-facts. The different levels of resolution in axial,lateral, and elevation direction of the 3D volumetric

fferent Echocardiographic Techniques

A

PS

RVOT

D TTE ≈ 85-90% 3D TEE ≈ 65-70%

A

PS

RVOT

ideo 2), and transesophageal 3D (right) (Video 3) techniques with the corresponding estimated

atients. 2D TTE ¼ 2D transthoracic echocardiography; 3D TTE ¼ 3D transthoracic echocar-

r tricuspid leaflet; LV ¼ left ventricle; P ¼ posterior tricuspid leaflet; RVOT ¼ right ventricular

TABLE 1 Role of Three-Dimensional Echocardiography in Imaging the Tricuspid Valve

Imaging Acquisition/Display Informative Content

Full-volume (single- or multibeat) fromtransthoracic approach. Volumerendering of transversal cut planesfrom both ventricular (Figure 5, leftpanel) and atrial (Figure 5, right panel)approach

Number of leaflets/scallops, leafletmorphology

Full-volume (single- or multibeat) fromtransthoracic approach. Volumerendering of longitudinal cut planes(Figure 6)

Leaflet morphologyand anatomy ofsubvalvularapparatus

Full-volume, multibeat acquisition fromtransthoracic approach. Slice mode(Figure 7, left panel) or 3Dreconstruction using custom madesoftware packages (Figure 7, rightpanel)

Tricuspid annulus shapeand size

Full-volume, multibeat 3D color acquisitionfrom transthoracic approach. Slicemode

Size and shape of theregurgitant jet venacontracta

Full-volume, multibeat acquisition fromtransthoracic approach.

Surface rendering

Right ventricularvolumes, strokevolume and ejectionfraction

Continued on the next page

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TABLE 1 Continued

Imaging Acquisition/Display Informative Content

Full-volume, multibeat acquisition fromtransthoracic approach

Surface rendering

Right atrial size andphasic function

Single-beat (real-time) acquisition fromtransesophageal approach

Guiding and monitoringinterventionalprocedures

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dataset (with the axial resolution being higher thanlateral and lateral higher than elevation) actuallyproduces 3D ‘‘non-isotropic voxels.’’ In the assemblyprocess, if the system uses, in 1 specific perspectivepredominantly the elevation resolution (i.e., en faceview of the valves obtained from 3D datasets acquiredusing transthoracic approach and apical position),thin and long structures, such as tricuspid leaflets,may appear with increased thickness.

HOW TO USE 3DTEE TO ACQUIRE THE TV

The right heart and TV are located in the anteriormediastinum, quite far from the standard mid-esophageal position of the probe, with the left heartstructures interposed between the probe and the TV.Because images in the far field may be subject tobeam widening and attenuation, often 3DTEE data-sets from this position are of lower quality than3DTTE datasets obtained in patients by using a goodtransthoracic acoustic window. Because the rightheart structures in part rest on the diaphragm, thedistance between the transducer and TV can bereduced by advancing the probe to the distal esoph-agus, proximal to the gastroesophageal junction toobtain unobstructed views of the TV and acquire anoptimal 3DTEE dataset. From this position, there is noleft atrium in the near field, and only the right heartstructures are visualized (Figure 2). However, thisacquisition may provide good 3DE images of the valveleaflets only when they are in the closed position

(during systole), when leaflets are perpendicular tothe insonation beam, whereas the leaflets may bepoorly visualized in the open position (during dias-tole), when they are parallel to the insonation beam.Conversely, acquisitions from the transgastricapproach frequently allow good visualization of theTV leaflets in diastole, because they will be perpen-dicular to the insonation beam but not in systole(Figure 3). Accordingly, it is often necessary to obtainmultiple 3DTEE datasets from different probe posi-tions in order to fully assess the TV and the tricuspidannulus.

LIMITATIONS OF 3D TEE IMAGING OF THE TV

There are a number of limitations to 3D TEE imagingof the tricuspid valve. First, the position of theesophagus in relation to the plane of the tricuspidannulus typically places the annular plane from 0� to45� to the insonation beam from every imaging plane.Differences in resolution in axial, lateral, and eleva-tion directions of the 3D volumetric dataset (with theaxial resolution being higher than lateral, and lateralhigher than elevation) actually produces 3D ‘‘non-isotropic voxels.” When the leaflets are more parallelto the insonation beam (i.e., at 0�), lateral andelevation gain resolution will limit structural defini-tion. Patients with an annular plane perpendicular tothe insonation beam (i.e., at 90�) may provide betterimaging of the tricuspid leaflets in systole, whereasthe reverse is true for imaging leaflets in diastole.

CENTRAL ILLUSTRATION Stepwise Acquisition of Tricuspid Valve Complex Using the Matrix Probe byTransthoracic 3D Echocardiography

Muraru, D. et al. J Am Coll Cardiol Img. 2019;12(3):500–15.

(Left) Cardiac scanning bed with an apical cutout is essential for apical acquisition, as it allows positioning the patient with the chest in a steep lateral position or even

facing slightly downward and proper placement of the probe in an almost vertical position, lateral to the cardiac apex and pointing toward the patient’s right shoulder

(left middle panel). (Middle) Regardless of the scanning approach (parasternal or apical), the operator should select the view in which the tricuspid valve leaflets are

best visualized in the center of the image sector (“tricuspid valve focused view”). (Right) The time gain compensation (aligned at 50%) and the overall gain are set to

a slightly higher level than usual to avoid dropout artifacts of tricuspid leaflets (middle panel). Respiratory maneuvers (commonly asking the patient to hold their

breath during full inspiration) are extremely useful to ensure that all valve components are well visualized in both simultaneous orthogonal views (azimuth and

elevation) for a complete visualization of the valve leaflets in 3D images. The volume size and depth are reduced to preserve both spatial and temporal resolution while

keeping relevant adjacent structures in the view field for helping with the orientation (right ventricular outflow, septum, superior part of right atrium, medial part of

mitral valve) (Video 4). During or after acquisition, the multislice view display is useful to finally check that the whole tricuspid valve apparatus is encompassed in the

dataset with no stitching, noise, or dropout artifacts. The acquired 3D dataset is then cropped and rotated to display the valve from both the ventricular (right)

(Video 1) and atrial (Video 5) perspectives in the anatomical orientation (see text for details regarding tricuspid valve orientation).

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Second, the tricuspid leaflets are much thinner thanthe mitral leaflets, resulting in poor echocardio-graphic definition of the body of the leaflets and sig-nificant echo dropout. The thin leaflets and theiroblique orientation with respect to the ultrasonogra-phy beam produce echoes that are weaker and scat-tered rather than strong and specular. The assemblyalgorithms therefore are unable to reconstruct valveleaflet surfaces without dropout artifacts (5).

If, however, the system optimizes the elevationalplane, then thin and long structures, such as tricuspidleaflets, may appear with indistinct edges andincreased thickness. Third, the fibrous body of theheart as well as any prosthetic material in the leftheart (i.e., prosthetic valves) may cause acousticshadowing or reverberations in the far field ofimaging, commonly masking the TV. Although thiscan frequently be overcome by inserting the probe

FIGURE 2 3D Transesophageal Volume Rendered Display of the Tricuspid Valve

(Low Esophageal Position)

A

B

RA

RVRV

RA

A

PS

A

P

S

A

Simultaneous biplane image from the low esophageal position with only the right heart

structures seen (A). The S and A leaflets of the tricuspid valve can be seen in the left

quadrant of A. In the right quadrant of A, which is the orthogonal view of the left, the A

and P tricuspid valve leaflets are seen. From this position of the transesophageal probe,

the 3D dataset of the tricuspid valve can be acquired (B), in this instance, shown from

the atrial perspective and rotated into the “surgical” en face view with the septal leaflet

at the 6-o’clock position. A ¼ anterior; P ¼ posterior; RA ¼ right atrium; RV ¼ right

ventricle; S ¼ septal.

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farther into the esophagus (thus removing the nearfield left-heart structure causing the artifact), thisalso changes the angle of insonation resulting in theproblems already mentioned. All of these issuesbecome even more problematic for 3D color Dopplerimaging.

3DE ACQUISITION MODES FOR THE TV

The 2 most commonly used 3DE acquisition modesare real-time and multibeat full-volume (6). Thetrade-offs between the 2 modes should be consideredaccording to each patient and according to the ob-jectives of the 3D scan.

REAL-TIME 3DE ACQUISITION OF TV. Real-time 3DE re-fers to a volume of information acquired over a singleor multiple heart beats. Real-time single-beat 3DEacquisition is not limited by motion artifacts (i.e.,respirophasic or patient movement) or electrocar-diographic cyclic variability (i.e., arrhythmia).Because the TV in the parasternal views is in the nearfield, the scan sector can be increased with lessreduction of volume rate due to the minimal depthrequired for the acquisition, and it is sometimespossible to visualize the complete TV with a single-beat real-time 3DTTE acquisition. Real-time single-beat 3DTEE, with and without color Doppler, may bemost useful when assessing respiratory variations ofthe regurgitant orifice size and for intraproceduralguidance of interventional procedures on the TV.

MULTIBEAT 3DE ACQUISITION OF TV. Multibeat full-volume datasets are composed of several sub-volumes that are then stitched together to create asingle, larger volumetric dataset with higher temporaland spatial resolution than the same volume acquiredusing single-beat real-time acquisitions. Multi-beat3DE datasets may be acquired with or without colorDoppler. The 3DE color Doppler acquisition is usuallyperformed to obtain an assessment of the severity oftricuspid regurgitation independent of the geometricassumptions about the shape of the regurgitantorifice affecting the measurements of the diameter ofthe vena contracta or the calculation of the effectiveregurgitant orifice area by proximal isovelocity sur-face area (7). However, multibeat acquisitions couldbe limited by stitching artifacts due to respiration,arrhythmia, or the patient’s movements. Stitchingartifacts could be an issue that precludes accurateinterpretation of the 3DE dataset and can be avoidedby acquiring the dataset during relatively stable R-Rintervals on the electrocardiographic (ECG) breath-holding, with the patient immobile and withoutmoving the probe (6). The number of cardiac cycles to

acquire depends on the patient’s characteristics (car-diac rhythm, ability to cooperate, and so forth), thesize of the TV complex, and the acquisition depth.However, for quantitative analyses, a dataset shouldhave a minimum temporal resolution of 20 volumes/s,with higher frame rates needed for assessing normalannular dynamics or in presence of tachycardia. Tocapture the volume with minimal stitched artifacts,

FIGURE 3 3D Transesophageal Volume Rendered Display of the Tricuspid Valve

(Transgastric Position)

A

B

RARV

AA

P PS

A P

S

Simultaneous biplane image from the transgastric position (A). The short-axis view of the

tricuspid valve (left quadrant) images all 3 leaflet tips; the S, A, and P leaflets, the long-

axis orthogonal view (right quadrant) images the anterior and posterior leaflets. From

this position of the transesophageal probe, the 3D dataset of the tricuspid valve can be

acquired (B), shown from the atrial perspective and rotated into the “surgical” en face

view with the septal leaflet at the 6-o’clock position. Abbreviations as in Figure 2.

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imaging the elevational plane (either by 2D or 3D enface view) can be used (Figure 3).

3DE display and quantitative analysis of the TV. To assessthe anatomy of the TV, 3DE datasets are typicallydisplayed in volume rendering mode, visualizing thevalve en face from both the ventricular and the atrialperspectives (Figure 4). Usually, the atrial perspective

(also called the “surgical view” because it resemblesthe view of the surgeon when the right atrium isopened) is used to assess patients with primary TR(degenerative, traumatic, and others). The ventricu-lar perspective is mainly used to evaluate the com-missures and the regurgitant or stenotic orifice inpatients with functional TR or stenotic tricuspidvalves. Additional longitudinal cut planes can be usedto evaluate the motion of single leaflets, the chordaetendineae and the papillary muscle position(Figure 5).

Despite the fact that current recommendations (6)advocate orienting the 3D en face view with the TVseptal leaflet placed inferiorly (at the 6-o’clock posi-tion), regardless of the atrial or ventricular perspec-tive, these recommendations were written at the endof the last decade, when interventional proceduresfor the TV were not available, and the proposedorientation of the TV was aimed to replicate the sur-gical view. Today, when 3DE is used mainly to guideinterventional procedures in the catheterization lab-oratory, the present authors propose a moreanatomically oriented display of the TV (Figure 4).Alternatively, Hausleiter et al. (8) recently proposedorienting the en face volumes in a way similar to theorientation of a 2D transgastric image; with the septalleaflet between 12- and 5-o’clock and the aorta at 5-o’clock. This orientation eliminates the third step(rotation of the image) that is always required bycurrent guidelines because the anterior leaflet (notthe septal leaflet) is in the far field of imaging from allimaging planes.

Because there is no commercially available, dedi-cated software with which to perform an echocar-diographic quantitative analysis of either TV leaflets’size and position or annulus geometry, measure-ments are obtained from dedicated cut-planes ob-tained by slicing the 3DE dataset.

A transversal cut plane positioned at the level ofthe tricuspid annulus and oriented in order to crossthe junction with TV leaflets in 2 orthogonalplanes, will allow the planimetry of tricuspidannulus area and perimeter, and to obtainanatomically sound measurements of its major andminor axes (Figure 6). These measurements arelikely to be relatively accurate in patients with se-vere functional TR in whom the tricuspid annulusis flattened (9). Conversely, in normal subjects andin patients in whom the 3D geometry of thetricuspid annulus is preserved, measurements ob-tained by 3D reconstruction of the annulus aresignificantly different from those obtained by directplanimetry of tomographic cut planes (10). Softwarededicated to the 3D reconstruction of the tricuspid

FIGURE 4 Volume Rendering of the Tricuspid Valve Obtained With Transthoracic 3D Echocardiography

RVOT

LVOT

MV

LAAAV

A

SP

A

S PMV

Ventricular view Atrial view

En face views from the right ventricular (left) (Video 1) and atrial (right) (Video 5) perspectives show the spatial relationship of the tricuspid

leaflets with the surrounding structures. AV ¼ aortic valve; LAA ¼ left atrial appendage; LVOT ¼ left ventricular outflow tract; MV ¼ mitral

valve; other abbreviations as in Figure 2.

FIGURE 5 Volume Rendering of the Tricuspid Valve Complex

Obtained With Transthoracic 3D Echocardiography

RVOT

APM

MB

SA

RA AV

Ch

Tricuspid valve complex

Longitudinal cut planes of the datasets allow the assessment of

leaflet motion and of the anatomy of subvalvular apparatus

(Video6). APM¼ anterior papillarymuscle; Ch¼ chordae tendineae;

MB ¼ moderator band; other abbreviations as in Figures 1 to 4.

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annulus will allow initialization of the annulus in aseries of rotated planes around it to factor thenonplanar nature of the TV into the tricuspidannulus measurements. This feature is not possiblewith the commercially available slicing method oftricuspid annulus assessment, which provides onlyplanar tomographic views (11). When performingannular measurements using the slicing method,the position of the annular plane is chosen by theoperator. However, the choice of the position ofthis plane is difficult because of the nonplanarity ofthe annulus. If the chosen annular plane is locatedat the hinge points of the annulus in 1 longitudinalview, it may not be possible to ensure that it is atthe hinge points in the orthogonal plane. As acompromise, the plane is often placed above theannulus, toward the right atrium. As a result: 1) theoperator measures a projected or planar areainstead of the actual annular area; and 2) part ofthe right atrial wall will be incorrectly identified astricuspid annular boundary, resulting in smallerend-diastolic measurements, because at this timethe right atrium is the smallest (10,11). These find-ings explain why there is a need for dedicatedsoftware that accounts for the nonplanarity of theTV annulus to provide a more reliable and semi-automated quantification of tricuspid annulus sizeand dynamics.

In addition, dedicated longitudinal cut planespositioned in the center of each leaflet will allowmeasurements of the length of the leaflets, the

leaflet-to-annular plane tethering angle of eachleaflet, and of the coaptation depth of TV leaflets(Figure 7). The tenting volume of TV leaflets by 3DE,accounting for both annulus dilation and leaflet

FIGURE 6 Slicing of the 3D Data Set of the Tricuspid Valve to Obtain a Cut Plane at the Level of the Tricuspid Annulus to Assess its Size

and Geometry

RA

RV

RV

RA

LV

LA

RVOT

AV

AV

Tricuspid annulus

MV

MV

The 3DE dataset (left upper) is sliced in 2 orthogonal cut planes: the 4-chamber (yellow right upper quadrant) and its orthogonal view (white

lower left quadrant) crossing at the center of the tricuspid annulus (white and yellow vertical lines). Then, the green plane (horizontal

dashed line) is positioned at the level of the tricuspid annulus in both views to obtain a transversal cut plane at the level of the annulus (green

right lower quadrant) on which the diameters, the perimeter, and the projected 2D areas of the tricuspid annulus can be measured. LA ¼ left

atrium; LV ¼ left ventricle; MV ¼ mitral valve; RA ¼ right atrium; RV ¼ right ventricle; RVOT ¼ right ventricular outflow tract.

FIGURE 7 Slicing of the 3D Echocardiography Dataset of the Tricuspid Valve to Obtain Cut Planes in the Center of Each Tricuspid Valve Leaflet to Measure Their

Diastolic Length and Tethering Angle in Systole

In the example, the cut planes have been oriented to pass through the center of the septal (yellow line and right upper quadrant) and the anterior (white line and left

lower quadrant) leaflets.

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FIGURE 8 Different Aspects of Tricuspid Valve Anatomy in Patients With Organic Tricuspid Regurgitation Illustrated by Volume Rendered En Face 3DE

Transthoracic Images

A B DC

E F HG

(A) Septal leaflet prolapse (white arrow) caused by tricuspid chordal damage after endomyocardial biopsy in a heart transplant recipient (Video 7). (B) Large vegetation

and anterior leaflet flail (white arrow) due to Staphylococcus spp infective endocarditis in a drug abuser (Video 8). (C) Diffuse tricuspid leaflet prolapse with loss of

coaptation in Barlow disease (Video 9). (D) Pacemaker lead (white arrow) interference with the septal leaflet motion (Video 10). (E) Vegetation on the posterior leaflet

(Video 11). (F) Tricuspid valve involvement in carcinoid disease showing the typical “frozen” appearance of leaflets in a semi open position (Video 12). (G) Rheumatic

tricuspid stenosis with restricted opening due to commissural fusion (Video 13). (H) Extensive bioprosthetic endocarditis with vegetations (white arrows) and cusp

thickening (Video 14). 3DE ¼ 3-dimensional echocardiography.

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tethering, is a predictor of residual TR followingsurgical tricuspid annuloplasty (12).Normal values of TV complex components and right heartchambers. European recommendations report anormal 2DE diameter of the tricuspid annulus in adultsof 28 � 5 mm when measured in diastole, using anapical 4-chamber view (13); however, no reference hasbeen reported to support this value. Both EuropeanAssociation of Cardiovascular Imaging and AmericanSociety of Echocardiography agree that significanttricuspid annulus dilation should be defined by adiastolic diameter >40 mm or >21 mm/mm2 in theapical 4-chamber view (13,14). These numbers havelimited scientific evidence and have been cited from apaper by Dreyfus et al. (15) in which the only mea-surements were the intraoperative, stretched annulardiameters. Moreover, due to the noncircularity oftricuspid annulus, its dimensions inherently dependon the view used to obtain the measurement

(parasternal long- and short axes, apical 4-chamber orsubcostal) (9,11), with the apical 4-chamber viewshowing the highest feasibility (76%) and the highestreproducibility (9). Three recent studies in healthysubjects have reported that the end-diastolic diameterof the normal tricuspid annulus in 4-chamber view islarger than 3.0 cm and that it depends on sex,body size, and view (i.e., standard vs. RV-focused4-chamber) and also on the diastolic frame in whichthe measurement is performed (10,11,16). Addetiaet al. (2) reported that measurements of tricuspidannulus obtained from RV-focused view in healthysubjects (maximal diameter 35 � 6 mm at late diastole)correlated more closely with right-heart chambervolumes than the same measurements taken from thestandard 4-chamber view (maximal diameter 34 � 6mm at late diastole), implying that the former may bemore representative of maximal TA size (10). Of note,it has been demonstrated that, regardless of the view,

TABLE 2 Additive Diagnostic Value of 3-Dimensional Echocardiography Over Current 2-Dimensional Technique in Various

Tricuspid Valve Diseases

Tricuspid Valve Disease Added Diagnostic Value of 3-Dimensional Echocardiography

Functional tricuspid regurgitation Exclusion of organic etiology of tricuspid regurgitationMeasurement of size and shape of tricuspid annulusRight ventricular volumes and ejection fractionRight atrial volumeMeasurement of tricuspid valve tenting volumeEstimation of regurgitation severity independent on geometric assumptions about regurgitant orifice

geometry

Tricuspid valve prolapse Precise identification of the prolapsing leaflet(s)Extent of the prolapse/flailEstimation of regurgitation severity independent on geometric assumptions about regurgitant orifice

geometryRight ventricular volumes and ejection fractionRight atrial volume

Traumatic tricuspid regurgitation Visualization of papillary muscle and/or chordal rupture

Ebstein anomaly Precise morphology of tricuspid leaflets, extent of development of their formation, level of theirattachment, and degree of coaptation.

Visualization of the mechanism of regurgitation or stenosisVisualization of subvalvular apparatusVolume of the functional right ventricle

Interference from cardiac implantableelectronic devices

Precise identification of regurgitation mechanism:Valve injury during lead placement or manipulation (e.g., leaflet perforation or laceration)Mechanical interference of leads with normal leaflet excursion/coaptationLeaflet entrapmentSubvalvular apparatus structure entanglement (e.g., transection of papillary muscles or chordaetendineae)

Endocarditis

Infective endocarditis Comprehensive assessment of TV anatomyLocation of vegetation point of attachmentVegetation characteristics and sizing (volume)Regurgitation mechanism

Rheumatic heart disease Detailed leaflet anatomyExtent of commissural fusionLeaflet shortening and thickeningInvolvement of subvalvular apparatusDirect planimetry of residual orifice areaRight atrial volume

Carcinoid disease Comprehensive assessment of TV anatomyIdentification of the regions of ineffective leaflet coaptation and the lack of commissural fusion.Better assessment of regurgitation severityDirect planimetry of residual orifice area

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2DE still underestimates significantly the maximaldimension of tricuspid annulus in comparison with3DE, cardiac magnetic resonance, and multidetectorcomputed tomography measurements (9,17,18). Thus,tricuspid annulus diameter measured in apical4-chamber view is smaller than the maximal diameterobtained from 3DTTE (11) or 3DTEE (9) datasets, but2DTTE and 3DE measurements are closely correlated(r ¼ 0.84) with a systematic 4-mm underestimation by2DTTE (9).

Furthermore, in healthy subjects, tricuspidannulus size and shape change significantly duringthe cardiac cycle (10,11). On average, tricuspidannulus linear dimensions and perimeter show >20%systolic shortening, whereas tricuspid annulus areashrinks by 35% during the cardiac cycle. Of this, 49 �29% occurs during atrial systole (between late- andend-diastole) (10). Tricuspid annulus area reaches aminimum in mid-to-late systole then increases during

isovolumic relaxation and diastole reaching amaximum value in late diastole after the onset ofatrial contraction (end of P-wave) (19,20). At latediastole (after atrial systole), normal maximal andminimal linear dimensions of normal tricuspidannulus were 40 � 5 mm (23 � 3 mm/m2) and 33 � 5mm (19 � 3 mm/m2). Tricuspid annulus circularity(minimum/maximum diameters) is approximately0.84 in late diastole, reflecting its elliptical shape.Furthermore, normal values of tricuspid annulus ge-ometry are 11 � 3 cm2 (6 � 1 cm2/m2) for maximal areaat late diastole, 12 � 1 cm (7 � 1 cm/m2) for maximalperimeter, whereas annular height between thehighest and lowest point is approximately 7 mm(10,21).

Of note, the most significant reduction in tricuspidannulus size occurs in the pre-systolic phase of thecardiac cycle (after right atrial contraction and duringisovolumic RV contraction), with subsequent

FIGURE 9 3D Printing of a Transthoracic 3DE Data Set of the Tricuspid Valve

(Left to right) Surface rendering of the tricuspid valve leaflets and annulus (left). Creation of a virtual 3D model and stereolithographic file that can be printed using any

commercially available 3D printer (center). The printed 3D solid model of the valve can be used to appreciate valve morphology and perform qualitative and

quantitative analysis useful for pre-procedural (surgical or interventional) planning and teaching (right and lower panels). Abbreviations as in Figure 8.

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shortening during the first part of systole. As seen incross-section, tricuspid annulus shape becomes morecircular during systole, and returns to more ellipticalshape during diastole due to a relatively greater in-crease in antero-posterior dimension than in septo-lateral dimension.

Tricuspid annulus size and function depend alsoon gender, women having smaller and more dynamictricuspid annuli than men, and body size (i.e., bodysurface area) (10).

Finally, tricuspid annulus size depends on the di-mensions of right heart chambers, being more closelycorrelated with right atrial, than with RV volumes(10,11).

In addition to the annulus size and the extent ofleaflet tethering, another parameter has recently beenreported to be associated with the severity of TR inpatients with pulmonary hypertension: the ability ofthe TV leaflets to grow in order to match the totalleaflet area to the closure area (the minimal leafletarea separating the RV and the right atrium necessaryto occlude the tricuspid orifice, as required by annulardilatation and ventricular tethering) (22). Afilalo et al.(22) reported that tricuspid leaflet area played a sig-nificant role in determining which patient with

pulmonary hypertension developed significant TR.The tricuspid leaflet area-to-closure area ratio was themain determinant of the severity of the regurgitationin those patients (22). Accordingly, normal values ofTV total leaflet area (the sum of the areas of the 3leaflets measured at mid-diastole, in the open posi-tion) may be of interest to distinguish those patientswho develop effective remodeling of the leaflets fromthose who do not. The authors report a median valueof 14.4 cm2 of total leaflet area in healthy controls,which increased by 49% (21.4 cm2) in patients. How-ever, the way the controls were selected was notdescribed in the paper, and healthy controls had amedian tricuspid annulus area of 6.9 cm2, whichseems quite small compared to other studies report-ing reference values of tricuspid annulus size(10,11,21). Therefore, these data and their patho-physiological significance need confirmation.

Finally, the extent of the distortion of the TVcomplex, leading to TR, is also related to the size ofright heart chambers: the RV and the right atrium(23,24).Incremental value of 3DE over 2DE to define abnormal TVmorphology. The complex and variable morphology ofthe TV complex (25,26) and the difficulty to visualize

FIGURE 10 Fusion Imaging of Fluoroscopic and 3D Echocardiography Imaging of the Tricuspid Valve From LAO 30� and Cranial 18�

A S

P

A S

P

A S

P

A S

P

A B

DC

*

* *

The valve is visualized from a ventricular perspective. (A, B, C, and D) Still are shown still frames obtained from different phases of cardiac cycle

from diastole to systole. The asterisks mark the commissures. LAO ¼ left anterior oblique view; other abbreviations as in Figures 2 and 3.

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all 3 TV leaflets in the same tomographic view make2DE (either transthoracic or transesophageal) a sub-optimal imaging technique for evaluating the mecha-nisms and the severity of pathologies affecting the TV.

Conversely, the acquisition of 3DE datasetsincluding the various components of the TV com-plex, by careful cropping and anatomic orientationof the cutting planes, will allow the user to obtainany desired view to optimally appreciate themorphology of the TV components in the beatingheart and perform a quantitative assessment of itsgeometry. The en face TV views from the right atrialor RV perspectives will provide a simultaneous

display of all TV leaflets and their attachment to thetricuspid annulus to assess the morphology of eachindividual leaflet (native or prosthetic in case ofbioprosthesis dysfunction), presence of leafletstructural abnormalities (such as prolapse, flail,ruptured chords or vegetations attached on leaflets),pacemaker lead interference, coaptation defects orcommissural fusion, with the possibility ofmeasuring the anatomical regurgitant or stenotictricuspid orifice area, respectively (Figure 8). Longi-tudinal cut planes will allow assessment of thethickness and/or the extent of the tethering of theleaflets, and the status of the subvalvular apparatus

FIGURE 11 Fusion of Multislice Computed Tomography, Coronary Angiography, and 3DE for Pre-Procedural Planning of Transcatheter Tricuspid Valve

Intervention

A B

E

C D

TARA

RA

RALA

RV

RV

RV

LV

LVLA

The 3DE geometry of the TV annulus, with the characteristic saddle shape (red lines) has been obtained from a 3DE dataset (E). The course of the right coronary artery

(green line) has been obtained from coronary angiography (C). Both are then modeled on a volume rendered 3D reconstruction of right heart anatomy (D) obtained by

multislice computed tomography (A, B). Courtesy of Pie Medical, the Netherlands. 3DE ¼ 3D echocardiography; TV ¼ tricuspid valve; other abbreviations as in Figure 6.

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(ruptured chordae, position of papillary muscles,and others). Slicing the 3D datasets will allow thequantitative analysis of tricuspid annulus shape andsize, extent of the global tethering of the valve(tenting volume), and length and tethering angle ofeach leaflet (Figure 7, Table 2).

ROLE OF 3D PRINTING AND FUSION IMAGING IN TV

DISEASES. Recently, both the increased awareness ofcardiologists and cardiac surgeons about the negativeimpact of TR on patients’ outcome (27) and thecurrently reported perioperative mortality fortricuspid surgery of 8% to 15% (28), have fueled thedevelopment of transcatheter procedures that couldpotentially treat high surgical risk patients (29).Despite a large array of transcatheter-based devicesdesigned to treat severe functional TR, significantcontroversy still remains about how, when and inwhom to intervene. A more robust understanding of

the anatomy and pathophysiology of TR in variousclinical settings is needed to improve clinical man-agement and selection of the most appropriate devicefor the appropriate patient.

Despite the technical advancements and the in-cremental clinical use of 3DE that has definitelyimproved our understanding of pathophysiology andfunctional anatomy of the regurgitant TV (4,24,30),the effectiveness of displaying 3DE datasets as pro-jections on 2D, flat screens has been questioned (31).3D printing of the TV (32) (Figure 9) has the potentialto allow cardiac imagers and interventional cardiol-ogists to move a step forward in understandingand quantifying tricuspid annulus geometry,elevating their impressions from textured flat-screencolored perspectives to actual exploration of thecomplex geometry of the TV, with the potentialto guide personalized care of patients with severeTR (33,34).

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The tissues of the various components of TVapparatus are soft and transparent to radiography. Inpatients with severe TR, only exceptionally there arecalcium deposits on the TV and usually these patientsare considered unsuitable for transcatheter proced-ures. Accordingly, the interventional cardiologistcannot rely on fluoroscopic imaging only to guide andmonitor procedures on the TV. However, fluoroscopyhas its own strengths in the catheterization labora-tory: interventional cardiologists are more familiarwith fluoroscopy than with other imaging modalities;wires, guide catheters, and devices have beendesigned to be radiopaque in order to optimize fluo-roscopic guidance (conversely, they create artifactswhen imaged with echocardiography); the system hasa large field of view allowing the operator to followlong segments of catheters; the temporal resolution(up to 30 fps) is adequate to maneuver the catheters.On the other end, 2DE and 3DE can offer detailedanatomical assessment of the TV structures and arepivotal for guiding catheter navigation during trans-catheter procedures (35). However, when images ob-tained from fluoroscopy (to manipulate catheters anddevices) and echocardiography (to visualize thecomponents of the TV apparatus) are shown onseparate screens, the anatomical relationships be-tween the position/orientation of the wires andcatheters and the anatomy of the TV can be lost (alsobecause, particularly for the TV, the projections of thefluoroscopy seldom mimic the views of echocardiog-raphy). Advances in the management of digital im-ages have allowed to merge patient-specific imagingdata from both fluoroscopic projections and either2DE views or 3DE cut planes, and align them in the 3Dspace and time in order to obtain a fusion between 2

imaging modalities that can be displayed in a singlemonitor and used by the interventional cardiologistto obtain: 1) an easier localization of the anatomicalstructures of interest; 2) an improved localization ofdevices and an easier navigation inside the right-heart chambers; 3) a facilitated assessment of trajec-tories and axial alignment of catheter and devices;and 4) a more precise localization of the landing zoneof devices (36) (Figure 10).

Further advances in digital imaging manipulationhave recently allowed the fusion of data/imagesobtained 3 imaging modalities (3DE, angiographyand computed tomography) to provide a multi-modality imaging reconstruction of the stereoscopicanatomy of the TV and surrounding structures (i.e.,the right coronary artery) with the possibility of aquantitative analysis of their spatial relationships(Figure 11).

CONCLUSIONS

Because echocardiography is the primary noninvasiveimaging modality for assessing the patient with TVdisease, 3DE is becoming essential for assessing theanatomy and function of TV complex, as a mandatorytool for better understanding of the TR mechanism,for more precise quantification of abnormal valvegeometry, for guiding patient selection and thedevelopment of effective and durable TV repairprocedures.

ADDRESS FOR CORRESPONDENCE: Dr. Luigi P.Badano, IRCCS, Istituto Auxologico Italiano, S. LucaHospital, University of Milano-Bicocca, Milan, Italy.E-mail: lpbadano@gmail.com.

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KEY WORDS 3D echocardiography, 3Dprinting, fusion imaging, tricuspid annulus,tricuspid regurgitation, tricuspid valve

APPENDIX For supplemental videos,please see the online version of this paper.