Three-dimensional echocardiographic imaging of secondary mitral
valve regurgitation
Raluca Dulgheru1, Paaladinesh Thavendiranathan2, Khalil Fattouch, Mani Vannan, Patrizio
Lancellotti1
1
GIGA Cardiovascular Sciences, Heart Valve Clinic, University of Liège, Department of
Cardiology, University Hospital Sart Tilman, Liège, Belgium , 2Peter Munk Cardiac
Center, University Health Network, Toronto General Hospital, University of Toronto,
Toronto, Canada
Keywords: secondary mitral, three dimensional echocardiographic, mitral valve
morphology.
1
Abstract
Many hypotheses regarding the mechanism of secondary mitral regurgitation (SMR) have
been made from 2D echocardiographic observations. Some have been confirmed and further
developed with the help of 3D echocardiography (1;2). 3D echocardiography, and especially 3D
transesophageal echocardiography (TEE), has much to offer in the evaluation of SMR, in
addition to 2D echocardiography. First, it offers important information regarding MV geometry,
giving insights into the mechanisms involved in the genesis of SMR in each patient. Second, it
can improve the accuracy of MR quantification (3;4). Third, it can play an important role in the
planning of surgery or percutaneous intervention.
Identifying the principal mechanism responsible for SMR, from several potential
mechanisms, in each individual patient, is very important, especially when contemplating MV
repair. Knowing which mechanism is most involved in SMR genesis and what are the possible
solutions to counterbalance and correct it may allow better tailoring of the surgical technique
potentially leading to better outcomes.
Data acquisition
Over the past few years, 3D transthoracic echocardiography (TTE) has overcome many
of its initial limitations. However, the quality of the 3D data is still highly dependent on the
acoustic window in each patient. When comprehensive and complex analyses of the MV
morphology and function are needed, the technique that is able to provide most of the answers,
and thus the most frequently used, is 3D TEE.
With 3D TEE several techniques for data acquisition are available:
2

Simultaneous Multiplane Mode or Biplane Mode – enables visualization of the
MV in two independent 2D planes simultaneously in real time (Figure 1). The
first image, usually displayed on the left side of the screen, is a reference image,
such as mid-esophageal four or five chamber view. The second image, displayed
on the right side of the screen, is a 2D image of the MV taken from a plane
rotated 30 to 150 degrees (as chosen by the user) from the reference plane. Color
flow Doppler can be added to the analysis in both planes.

Real Time 3D acquisition or Live 3D – enables a real-time display of a 30 x 60
degrees pyramidal volume of the MV. It has the disadvantage of not being able to
display the entire MV valve apparatus. However, due to the high temporal
resolution, it is the modality of choice for guiding interventions on the MV. Rapid
switch between “en face” and ventricular view of the MV leaflets can be
performed according to the clinical question to be answered. Advances to live 3D
now allow increase of the real time display to as high as a 90 x 90 degree sector;
however, this comes at the cost of reduced temporal resolution.

Focused Wide Sector or 3D Zoom – enables a real time, focused, wide-sector
view of the MV apparatus with good spatial resolution and satisfactory temporal
resolution (Figure 2). The temporal resolution can be improved by using a
“stitched” 3D acquisition over 4-6 heart beats with some vendors. Live 3D Zoom
is probably the most important 3D imaging modality for MV morphology
assessment by 3D TEE. It is the modality of choice when analyzing valvular
morphology in SMR patients. Care should be taken to optimize the spatial and
temporal resolution of the acquired images. The acquisition should be started
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from the mid esophageal bi-commissural view with the sector width adjusted to
cover the entire commissure and the elevational plane adjusted to cover the
antero-posterior aspect of the MV. The height of the volume sector should also be
adjusted to cover the entire mitral annulus, leaflets (both in systole and diastole)
and subvalvular apparatus. The key to an optimal temporal and spatial resolution
is to set the elevational plane as narrow as possible. Care should be taken to
include in the acquired volume some of the landmarks surrounding the MV, such
as the aortic valve and the left atrial appendage. This will allow the correct
recognition of each MV leaflet and a correct orientation of the MV as seen from
the atrial perspective (Supplemental material Movie 1) or ventricular perspective
(Supplemental material Movie 2)

Full Volume Gated Acquisition – enables optimal spatial and temporal resolution.
This modality has the largest acquisition sector available (a volume size of 75 x
75 degrees) that allows imaging of the MV apparatus and of the left ventricle in
the same volume (Figure 3). It requires ECG gating. This type of acquisition may
be very important in SMR when assessing the relationship between MV
apparatus, chords, and distortion and LV with regional or global remodeling.
When used as a multi-beat stitched acquisition it has also a higher temporal
resolution, necessary when analyzing patterns of leaflet motion, such as in SMR.
However, because the acquisition modality involves stitching together several
smaller pyramidal volumes, each of them acquired during one cardiac cycle, this
type of acquisition is predisposed to stitching artifacts especially in patients with
irregular heart rhythms. Even in patients with regular heart rhythms stitching
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artifacts can often occur due to difficulties with breath-holding in a semiconscious patient during TEE. Therefore care should be taken to look through the
acquired data set to save images with minimal or no stitching artifacts to ensure
accurate analysis.

Full Volume Color Flow Doppler (Supplemental material Movie 3) – this
technique is similar to the full volume gated acquisition with color Doppler on.
With this method the full volume with color Doppler is constructed by stitching
together multiple narrow pyramidal sets, each acquired during a single cardiac
cycle (Figure 4). Inadequate breath-holding and irregular heart rhythm can lead to
stitching artifacts. With TTE this technique is highly dependent on transthoracic
image quality, being less suitable in patients with poor apical acoustic windows.
With TEE image quality is adequate but acquisition might be hampered by
stitching artifacts related to inadequate breath-holding. Real-time 3D color
Doppler acquisition and 3D zoom mode with color Doppler on are also available
techniques with 3D TEE.
Mitral Valve Morphology Assessment by 3D echocardiography
3D echocardiography offers both qualitative and quantitative information in the
evaluation of mitral valve morphology in patients with SMR.
3D TEE provides, undoubtedly, the best morphological details of the mitral valve.
However, in patients with good acoustic windows, 3D TTE is able to provide satisfactory
information regarding MV morphology and function (Figure 5, 6).
5
Through the “en face” view, 3D echocardiography allows direct examination of the atrial
surface of the mitral leaflets, coaptation line, and commissures throughout the cardiac cycle
(Figure 2). This view provides a qualitative inspection of the mitral valve geometry, as seen from
the atrial perspective, also known as the “surgeon’s view” (Figure 2, Figure 5, Panel D; Figure 6,
Supplemental material, Movie 1).
In SMR, due to the tethering of the leaflets, the geometry of the valve can be markedly
changed. The MV usually has a funnel shape, with the lowest points of the funnel at the level of
the coaptation line (Figure 6). In normal MVs the coaptation line normally describes a slightly
upward concavity as seen from the atrial side, but in SMR, it becomes even more concave
(symmetric tethering) or completely changes its shape pointing towards the LV cavity
(asymmetric tethering). This simple qualitative assessment of MV geometry from the “en face”
view by 3D echocardiography providing a quick insight into the mechanism of SMR, helping the
clinician to distinguish between symmetrical or asymmetrical tethering pattern (Supplemental
material, Movie 1).
In some cases of severe SMR, an orifice, representing the anatomic regurgitant orifice
area (AROA), can be visualized from the atrial perspective of the valve, and planimetry of this
orifice can be made using multi-planar reformat of the 3D data or with some vendors directly
from the 3D image. Care should be taken to adequately set the gain and line density on each 3D
echo machine during the acquisition to eliminate dropouts that might lead to overestimation of
the regurgitant orifice by planimetry.
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After this initial on-line qualitative assessment of MV morphology, all necessary 3D
datasets of the MV apparatus are acquired. This will enable later off line analysis, and a more
quantitative assessment of MV morphology in SMR patients.
Each of the possible mechanisms involved in SMR are carefully inspected while
performing the off-line analysis of the acquired data to measure: mitral annulus size and shape,
mitral annulus dynamics (change in shape between diastole and systole), MV leaflet surface area
computation, and subvalvular apparatus geometry and its relative position to the MV annular
plane.
Mitral annular geometry in SMR
For a more comprehensive analysis of MV morphology in SMR, off line reconstruction
of the MV leaflets and annulus is possible from the 3D data sets with the help of various
commercial software applications available on the market (Figure 7). Mitral annulus anteroposterior diameter, the inter-commissural diameter, the perimeter of the mitral annulus, the
length of each annular segment (anterior annulus length vs. posterior annulus length), the
height of the annulus, i.e. the distance between the highest and the lowest points on the annulus,
can be measured during each frame of the cardiac cycle to characterize mitral annular
morphology and its dynamic properties in patients with SMR. Many of these measurements can
be obtained without any geometric assumptions.
Studies that analyzed MV annular morphology, by 3D echocardiography, have shown
that annular perimeter and area are increased, and that the annulus is less elliptical and more
flattened in patients with SMR as compared to normal subjects (5;6). These studies have also
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shown that the degree of mitral annular deformation in ischemic SMR is more pronounced
following anterior MI than inferior MI (7).
An attenuation of the sphincter function of the mitral annulus, i.e. the annular area change
between diastole and systole, has been described as one of the mechanisms that contribute to
SMR (8). The annular sphincter function is decreased in these patients (9), while in normal
subjects annular contraction is around 25% (10).
3D echocardiography has also proven that in healthy individuals, caudal displacement of
the mitral annulus occurs during systole and is more accentuated in the posterior region, while in
patients with SMR, this displacement is reduced, most notably in the posterior region (11).
Mitral leaflet morphology in SMR
Optimal coaptation of the MV leaflets throughout systole requires perfect match between
MV leaflet’s surface and the MV orifice. SMR is characterized by suboptimal leaflet coaptation
related to increased MV leaflets tethering. Through 3D reconstruction of the MV the
measurement of mitral leaflets surface area, mitral leaflets coaptation area (CA), coaptation
height (CH), and coaptation index (CI) is possible. Mitral leaflets surface computation (Figure
8) form 3D data sets, using dedicated software has helped us understand that mitral valve leaflets
are not inert structures, and that they are capable of adapting dynamically to maintain adequate
coaptation. This was first elegantly shown using 3D echocardiographic studies in animal models
where this dynamic enlargement of the leaflets was shown to increase mitral valve coaptation
surface, explaining at least in part, why in some cases with significant leaflets tethering, SMR
may be only mild in severity (12). This adaptive remodeling of the leaflets was felt to be a
response to the chronic mechanical stress exerted by leaflet tethering (12).
8
This finding was confirmed by another “in vivo” study which demonstrated that despite
increased leaflet size to compensate for the increased mitral leaflet tethering, coaptation can be
significantly decreased in patients with LV remodeling and significant SMR as compared to
patients without significant SMR and similar degrees of LV remodeling. In this study, all indexes
of coaptation, as assessed by 3D TEE (CA, CI and coaptation length) were related to SMR
severity (13). CA was defined as the difference between total leaflet area (MV leaflet surface
measured at the onset of mitral leaflet closure) and closed leaflet area in mid-systole (MV leaflet
surface measured form the mid-systolic frame). Since it has been demonstrated that mitral
leaflets stretch during systole (14), leading thus to an underestimation of the coaptation area,
another parameter, namely the CI, was calculated to account for the “dynamic” increase in mitral
leaflets surface during systole. The CI was defined as the ratio of CA to total leaflet area and
multiplied by 100. CI was also associated with the SMR severity in this study (13).
In addition, the tenting volume, which is the volume encompassed between the surface of
the MV leaflets and the mitral annulus plane in mid-systole, can be calculated from the 3D
datasets with a dedicated software (Figure 9). The software is able to reconstruct the tenting
volume shape and render it in its 3D shape. A simple eyeball examination of the tenting volume
shape gives valuable hints regarding the pattern of tethering on the MV leaflets. Asymmetric
tethering usually exhibits a tenting volume shape deformed toward the most tethered segment of
the leaflet, pointing out the part of the leaflet that is predominantly stretched.
The tenting volume proved to be closely related to SMR severity and a reliable marker of
leaflets tethering severity.
MV subvalvular apparatus morphology in SMR
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3D echocardiography allows also a comprehensive evaluation of the MV subvalvular
apparatus and its position relative to the mitral annular plane.
The distance between each PM tip and a point located in the center of a plane with least
deviation of annular hinge point about it, the inter-papillary muscle distance, and the distance
between each PM tip and its contralateral or ipsilateral commissure, are all methods that can be
used to characterize the pattern of the MV tethering and to estimate its severity in SMR patients.
One of the most important parameters that can be evaluated with the use of 3D
echocardiography to describe MV apparatus deformation in SMR is the tethering distance. It is
the distance measured between the intervalvular fibrosa (the middle anterior part of the MV
annulus that extends between the anterior mitral valve leaflet and the aortic valve) and the head
of the posteromedial PM at mid-systole. This parameter proved to be a reliable indicator of the
severity of distortion of the MV apparatus, and a strong predictor of SMR after MI (2;15). The
distance between the head of the anterolateral PM and the intervalvular fibrosa can be also
measured. Classically this is named the “lateral tethering distance”, while the distance between
the posteromedial PM and the intervalvular fibrosa is referred to as the “medial tethering
distance”. The advantage of 3D echocardiography over 2D echocardiography in the
measurement of this parameter is the accurate identification of the PMs tips closest to the base of
the heart, which lowers the variability of the measurement.
SMR Severity Assessment by 3D echocardiography
In the current guidelines (16), the quantification of SMR severity is still based on several
well validated parameters derived from 2D echocardiography: the vena contracta width (VC) and
the PISA method for effective regurgitant orifice area (EROA) and regurgitant volume (RV)
10
estimation. According to current guidelines, SMR is considered severe whenever EROA is > 20
mm² or/and the regurgitant volume (RV) is > 30 mL, as assessed by 2D echocardiography.
Using 3D color Doppler echocardiography, several small studies have shown that 2D
echocardiography might underestimate the EROA as well as the RV in certain cases of SMR.
There are several limitations of the PISA method and VC width, as assessed by 2D
echocardiography that should be acknowledged. 3D echocardiography seems to be able to
overcome these limitations and improve the accuracy of assessing EROAs and RVs in patients
with SMR. In the years to come, paralleling the improvement in 3D echocardiography, a higher
availability of this technique in daily clinical practice is expected. Thus, the need for establishing
3D derived cut off values for the parameters used to quantify SMR severity is imperative. The
reader should keep in mind that the cut of values for EROA and RV derived from 2D
echocardiography and those derived from 3D echocardiography are not interchangeable.
In SMR, the regurgitant orifice is usually not circular and is more commonly elliptical in
shape. Therefore using the vena contracta width the severity of SMR may be overestimated if
measured by 2D echocardiography along the long-axis of the regurgitant orifice (e.g from a 2
chamber view), or underestimated if measured from a plane perpendicular to the regurgitant
orifice (e.g. 4 chamber view) (Figure 9). 3D echocardiography can overcome this limitation by
being able to provide the area of the vena contracta with no geometric assumptions by direct
planimetry in the plane perpendicular to the direction of the regurgitant jet using reconstructed en
face view of the 3D regurgitant jet (Figure 10). 3D derived VC area measurement is a method of
measuring the effective regurgitant orifice area. 3D derived VC area has been shown to correlate
more closely with Doppler-derived EROA than 2D VC width. There are some limitations of this
technique that have to be acknowledged. The limited spatial resolution of the reconstructed
11
images may make measurement of VC area particularly challenging in mild to moderate SMR.
The choice of the systolic frame for VC area measurement may lead to important interobserver
variability because SMR is highly dynamic throughout systole and depending on the chosen
frame computed values might be very different between observers. Color bleeding into gray
scale and cropping of the regurgitant jet in a nonorthogonal manner can overestimate VC area
(17).
The 2D echocardiography derived PISA method, used to estimate the EROA and RV,
assumes that the flow convergence area is hemispheric. As demonstrated by 3D
echocardiography, flow convergence area is frequently hemielliptic or more complex in SMR
(18). Applying a 2D PISA radius method with a hemispheric assumption in patients with SMR
might lead to underestimation of EROA and RV (Figure). Using 3D color Doppler
echocardiography the EROA and RV can be calculated more accurately in SMR. Several
methods can be applied. The 3D VC area, 3D PISA based EROA (see paragraph below) coupled
with the MR velocity time integral (MR-VTI) obtained from the continuous wave Doppler can
be used to derive RV. In patients with less than mild aortic regurgitation, the RV calculated with
one of the 3D methods or by 2D PISA method, can be combined with the 3D LV stroke volume
obtained by automated/semiautomated endocardial tracking algorithms, to derive the RF. In
addition, subtraction of the conventional 2D Doppler derived LV outflow tract stroke volume
(using LVOT area and PW Doppler) from the 3D LV stroke volume from endocardial contouring
is an alternate way to calculate the RV in patients with SMR.
With 3D TTE computation of the true 3D proximal isovelocity surface area without any
specific geometric assumptions is also possible. Instantaneous “Full Volume” 3D color Doppler
echocardiography with the ACUSON SC2000TM volume imaging ultrasound system provides a
12
new technology that allows calculation of EROA and RV applying the same equations used in
2D echocardiography, but with the advantage of PISA being directly measured as a 3D (Figure
11). This approach was validated against “in vitro” phantoms, showing higher accuracy when
compared with results obtained from the conventional spherical approximation method (19). One
of the limitations of this technique is that PISA measurement is made in one fixed frame, as
chosen by the sonographer, thus missing the dynamic character of SMR throughout systole.
Interobserver variability may be encountered due to this limitation. However, in the future,
instantaneous calculation of the 3D PISA in each frame during systole might become available,
as 3D echocardiography techniques are constantly improving. A mean value for EROA and RV
calculated frame by frame being probably more close to the real EROA and RV in patients with
SMR.
Validation studies on large populations of these techniques and outcome studies are also
expected.
Role of 3D echocardiography in pre-procedural selection of patients and
intervention guiding
3D TEE proved to be useful both in the selection of the patients for the percutaneous
catheter based edge-to-edge MV repair and for procedure guiding. It should be emphasized that
candidates for the percutaneous repair of the MV in severe SMR are only patients in whom the
coaptation length of the MV leaflets is higher than 2 mm and coaptation depth lower than 11
mm. Pre-procedural 3D TEE increases the confidence that the selected patient is suitable for
such a procedure because it allows measurement of the coaptation length and coaptation depth in
multiple image planes, with less chance of “missing” the lowest value of the coaptation length
13
and highest value of coaptation depth that would make the patient unsuitable for the procedure.
Guiding of the procedure is also facilitated by 3D TEE because it can optimize the selection of
the transseptal puncture site and the steering of the device towards the center of the MV orifice.
These aspects will be discussed in another chapter of this book (see “The role of the “edge-toedge” in mitral valve repair” chapter).
Figure legend:
Figure 1. Biplane Mode (X-plane) acquisition with 3D transoesophageal echocardiography. Left
side panel: the reference plane is mid-oesophageal 4 chamber view. Right side panel: 2D image
of the mitral valve from a plane rotated 95⁰ from the reference plane. AML- anterior mitral
leaflet; PML – posterior mitral leaflet.
Figure 2. 3D Zoom acquisition of the mitral valve as seen from the atrial perspective by 3D
transoesophageal echocardiography. The image is then rotated in such a way that the aorta is
located anteriorly (flipped image indicated by arrow). Ao –aorta.
Figure 3. Full Volume Gated Acquisition with 3D transoesophageal echocardiography.
Acquisition is done over 4 cardiac cycles that enables a good temporal resolution (32 volumes
per second).
Figure 4. Full Volume Color Flow Doppler acquisition with 3D transthoracic echocardiography.
The full volume color Doppler is reconstructed by stitching together 4 narrow pyramidal sets.
Off line analysis enables evaluation of vena contracta area by direct planimetry.
Figure 5. 3D transthoracic echocardiography evaluation in a patient with dilated cardiomyopathy
and secondary mitral regurgitation. Apical systolic displacement of the mitral valve leaflets
14
coaptation point as seen from a lateral aspect (Panel A, yellow arrow, the blue dotted line
represents the mitral annulus plane). Apical and lateral displacement of the papillary muscles
exerting a tethering effect on the mitral leaflets in mid-systole as seen from the ventricular view
(Panel B, yellow arrows). For rapid recognition of the anatomic landmarks the ventricular aspect
of the mitral valve apparatus is also shown in diastole (Panel C). Funnel shape morphology of
the mitral valve as seen from the atrial perspective in the same patient (Surgeon’s view, Panel
D). All images are reconstructed from the same 3D pyramidal data set. AML- anterior mitral
leaflet; PML- posterior mitral leaflet; Ao- aorta.
Figure 6. Surgeon’s view of the mitral valve in a patient with secondary mitral regurgitation
(SMR) and idiopathic dilated cardiomyopathy showing the funnel shape of the mitral valve as
seen from the atrial perspective (3D transthoracic echocardiography, Panel A). The chosen frame
is in mid-systole, tethering on the MV leaflets being maximal (Panel A, yellow arrow indicating
mid-systole on the ECG tracing). For easy recognition of the anatomic landmarks the valve is
also shown in diastole (Panel B). Ao-aorta; ALC –anterolateral commissure; PMC –
posteromedial commissure.
Figure 7. Mitral annular reconstruction from 3D transoesopageal datasets with measurement of
the antero-posterior diameter of the mitral annulus (green continuous line).
Figure 8. Mitral valve morphology reconstruction in a patient with secondary mitral
regurgitation from 3D transoesopageal datasets: measurement of the mitral valve tenting volume
and height, intercommissural diameter, and anterior and posterior leaflet area.
Figure 9. 2D transthoracic evaluation from the parasternal short axis view at the level of the
mitral valve in a patient with secondary mitral regurgitation showing the elliptical shape of the
15
vena contracta (VC) of the regurgitant jet (green dotted line). Measurement of VC from the
parasternal long axis view (PSLA) would underestimate the severity of the MR (white line)
while measurement from the 2-chamber view (2-Ch) would overestimate its severity (black
arrow). PSLA- parasternal long axis view; 2-Ch – 2 chamber view.
Figure 10. Vena contracta (VC) area measurement by 3D transthoracic echocardiography in a
patient with secondary mitral regurgitation and dilated cardiomyopathy. After full volume color
Doppler acquisition with the 3D transthoracic probe from the apical window the 3D data set is
cropped to derive the area of the vena contracta of the regurgitant jet. Direct planimetry of the
vena contracta area is possible (white line enclosed area). The dotted green line represents the
orthogonal plane in which the VC area measurement was done.
Figure 11. Instantaneous “Full volume” 3D transthoracic echocardiography with the assessment
of the effective regurgitant orifice (ERO) area and regurgitant volume of a secondary mitral
regurgitation by direct 3D measurement of proximal isovelocity surface area.
Supplemental material Movie 1. 3D Zoom mode acquisition of the mitral valve as seen from
the atrial perspective (“surgeon’s view) by 3D transoesophageal echocardiography. The
displayed image is then rotated in such a way that the aorta is located anteriorly.
Supplemental material Movie 1. 3D Zoom mode acquisition of the mitral valve as seen from
the ventricular perspective by 3D transoesophageal echocardiography. The displayed image is
then rotated in such a way that the anterior mitral leaflet is seen opening in diastole towards the
interventricular septum, while the posterior leaflet is almost fixed during the cardiac cycle.
16
Supplemental material Movie 3. Full Volume Color Flow Doppler Gated Acquisition with 3D
transoesophageal echocardiography in a patient with ischemic mitral regurgitation and a
centrally oriented regurgitation jet, indicative of symmetric tethering pattern.
17
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