© 2013 Wiley Periodicals, Inc.
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NEW TECHNOLOGIES ____________________________________________________________
3D Echocardiography in Cardiac Surgery Pankaj Saxena, F.R.A.C.S., Ph.D.,* Joseph F. Malouf, M.D.,y Roger Click, M.D., Ph.D.,y and Rakesh M. Suri, M.D., D.Phil.* *Division of Cardiovascular Surgery, Mayo Clinic, Rochester, Minnesota; and yDivision of Cardiology, Mayo Clinic, Rochester, Minnesota ABSTRACT Herein, we present a patient who underwent successful repair of failed mitral valve repair in whom intraoperative 3D transesophageal echocardiography provided accurate assessment of the mechanism of mitral regurgitation. In addition, we review the potential advantages and limitations of 3D echocardiography and its role in cardiac surgery. doi: 10.1111/jocs.12256 (J Card Surg 2014;29:51–54) Annuloplasty ring dehiscence is an important cause of recurrent mitral regurgitation (MR) following valve repair. We present a patient who underwent successful redo cardiac surgery for failed mitral valve repair in whom intraoperative 3D transesophageal echocardiography (3D TEE) provided accurate assessment of the mechanism of MR. We have briefly reviewed the current status of 3D echocardiography (3DE) in cardiac surgery. CLINICAL SUMMARY An 80 year old man presented with NYHA IV dyspnea caused by recurrent severe MR following previous annuloplasty repair with Duran ring (Medtronic, Inc., Minneapolis, MN, USA) for degenerative mitral valve disease, performed at another institution four years previously. The patient’s comorbidities included pulmonary hypertension, chronic kidney disease, previous myocardial infarction, and coronary artery bypass surgery performed 20 years previously with patent bypass grafts. Preoperative 2D transesophageal echocardiography (2D TEE) identified separation of the annuloplasty ring in the region of the mid-posterior annulus with associated severe MR (Fig. 1A). Intraoperative 3D TEE confirmed the mechanism of MR with demonstration of the exact anatomic site of ring dehiscence (Fig. 1B). The patient underwent third-time sternotomy, followed by institution of cardiopulmonary bypass with
Conflict of interest: The authors acknowledge no conflict of interest in the submission. Address for correspondence: Rakesh M. Suri, M.D., D.Phil., Division of Cardiovascular Surgery, Mayo Clinic, 200 First Street SW, Rochester, MN 55905. Fax: þ1-(507)-255-7378; e-mail: suri.rakesh@ mayo.edu
peripheral cannulation due to dense intrapericardial adhesions and myocardial protection with moderate systemic hypothermia. Mitral valve exposure via left atriotomy demonstrated dehiscence of the annuloplasty ring at the nadir of valve annulus posteriorly (Fig. 1C). The area of separation of the ring was corrected using several 3-0 prolene (Ethicon, Inc., Somerville, NJ, USA) pledgetted horizontal mattress sutures. Additional reinforcement stitches were also placed in the area of right and left fibrous trigones where the annuloplasty ring had slid inferiorly. Intraoperative TEE confirmed no residual MR. The patient was discharged home on day 5.
DISCUSSION We routinely perform 3D TEE examination during intraoperative assessment of the mitral valve to identify the mechanism of MR. Three-dimensional echocardiography (3DE) provides accurate morphologic assessment of mitral valve abnormalities in complex valvular disease correlating well with intraoperative surgical findings.1 When tissue quality is satisfactory and in the absence of retraction or calcification, mitral valve rerepair is often possible and may be associated with improved late outcomes including enhanced reverse remodeling as compared to valve replacement.2 Dehiscence of a prosthetic annuloplasty device can lead to mitral valve repair failure.3 We use a 63-mm posterior annuloplasty band in all patients with degenerative mitral valve disease which restores normal annular size and is associated with durable freedom from recurrent MR.4 We believe that the nadir of posterior mitral valve annulus represents an area of potential weakness in any sutured annuloplasty system and we therefore reinforce this area of the annuloplasty ring with pledgetted prolene sutures.
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SAXENA, ET AL. 3D ECHO IN CARDIAC SURGERY
J CARD SURG 2014;29:51–54
Figure 1. (A) Intraoperative 2D transesophageal echocardiography with arrow pointing to the annuloplasty ring and arrow head to the posterior leaflet. Color Doppler with a wide jet of mitral regurgitation. (B) 3D echocardiography with arrow marked to identify posterior dehiscence of the ring from the annulus as seen in ‘‘Surgeon’s view’’ of the mitral valve. (C) Operative photograph with a mirror image of 3D transesophageal picture.
Figure 2. (A) Depiction of 2D sector on echocardiography. (B) 3D sector. (C) Multi-beat acquisition: four sub-volumes. Figure reproduced by permission of Mayo Foundation for Medical Education and Research. All rights reserved.
Three-dimensional echocardiography 3DE represents a major advance in cardiac imaging that complements 2DE. Whereas 2DE represents a tomographic slice through a region of interest, a 3DE encompasses the entire region of interest (Fig. 2A and B). Threedimensional echocardiography is built up from multiple 2D sectors that are acquired nearly simultaneously at various levels along the entire width and depth of the volume of interest. Spatial resolution is a function of
Figure 3. Three-dimensional TEE with stitch artifacts (arrow heads). Figure reproduced by permission of Mayo Foundation for Medical Education and Research. All rights reserved.
both the number of 2D sectors per volume of interest, and the number of ultrasound lines per 2D sectors, hence the scanning density within the volume of interest. Temporal resolution refers to the 3D image frame rate, or more accurately volume rate and is a function of the 3D volume size, image depth, and
Figure 4. Three-dimensional TEE of mitral prosthesis demonstrates a false periprosthetic defect (arrow) adjacent to ostium of left atrial appendage. Figure reproduced by permission of Mayo Foundation for Medical Education and Research. All rights reserved.
J CARD SURG 2014;29:51–54
Figure 5. Three-dimensional echo demonstrates prolapse of the tip of A2 (arrow) and chordal rupture (arrow head). Figure reproduced by permission of Mayo Foundation for Medical Education and Research. All rights reserved.
scanning density analogous to 2D imaging. The main trade off in 3DE, therefore, is between the temporal and spatial resolution. By reducing the scanning density and the associated spatial resolution, the frame rate or volume rate is increased. The frame rate can also be increased while maintaining the same scanning density simply by reducing the size of the volume of interest. When the entire 3DE volume of interest is acquired in a single beat, it is effectively real time. Because of the large amount of image data acquired, a low temporal resolution remains a major limitation of real-time 3DE. An alternative non-real-time method to increase the 3DE frame rate while maintaining the same volume size and scanning density is by dividing the 3D volume of interest into subvolumes and acquiring each subvolume separately. This is referred to as multibeat acquisition. By doing so, the 3DE frame rate will be a function of the time needed to acquire the
SAXENA, ET AL. 3D ECHO IN CARDIAC SURGERY
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Figure 7. Three-dimensional TEE of a large mitral periprosthetic leak (arrow) that is adjacent to the left atrial appendage (asterisk). The arrow head points to an aortic prosthesis anterior to the mitral prosthesis. Figure reproduced by permission of Mayo Foundation for Medical Education and Research. All rights reserved.
subvolume and not the entire volume (Fig. 2C). For example, when the 3DE is acquired over four beats that are ECG gated, the first 3DE subvolume that is ECG gated to the first beat is acquired in the usual manner. Once acquired, the next subvolume is acquired and so on until the full 3D volume is rendered complete. The four subvolumes are then electronically ‘‘stitched’’ together to form the complete volume. Patient motion, patient breathing, or arrhythmias can interfere with this process resulting in so-called stitch artifacts (Fig. 3). Since each of the subvolumes is only one-fourth the size of the entire volume, the frame rate is four times higher than would have been achieved if the entire volume was acquired in a single beat. With two beat acquisitions (that is two subvolumes) the frame rate will
Figure 6. (A) Three-dimensional TEE shows P2 prolapse (arrow) with chordal rupture (double arrow); and P3 prolapse (arrow head). A cleft can be appreciated between the prolapsing segments. (B) Operative photograph during robotic mitral valve repair in the same patient confirms the areas of prolapse. The cleft in the posterior leaflet is represented by an asterisk. Figure reproduced by permission of Mayo Foundation for Medical Education and Research. All rights reserved.
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SAXENA, ET AL. 3D ECHO IN CARDIAC SURGERY
J CARD SURG 2014;29:51–54
Figure 8. (A and B) Three-dimensional reconstructions of left ventricular outflow tract and aortic valve annulus. Note elliptical shape of annulus in B. Figure reproduced by permission of Mayo Foundation for Medical Education and Research. All rights reserved.
double and with a six beat acquisition typical for multibeat 3DE with color Doppler, the frame rate is increased by sixfold. Another 3DE imaging limitation is drop out artifacts that may simulate an actual defect such as a periprosthetic leak or leaflet perforation (Fig. 4). Color Doppler documentation of flow through a defect, particularly if fixed, is therefore absolutely necessary to establish diagnosis of a true defect. It is important to emphasize at this juncture that the quality of a 3DE depends on the intrinsic quality of the 2DE. Therefore, suboptimal 2D images result in suboptimal 3D images. Of all the intracardiac structures, the mitral valve lends itself best to 3D imaging particularly by TEE. Enface views of the mitral valve from the left atrium (socalled surgeon’s view) can be readily obtained in a single image acquisition, thus eliminating the extensive manipulation necessary when using 2D imaging to obtain similar information. Enface views of the mitral valve from the left ventricle can also be readily obtained. Three-dimensional TEE is almost always an adjunct to a standard 2D TEE. The additional time required to capture the images and interpretation is quite variable, but usually adds another 10–15 minutes to the study. Personnel trained to perform standard 2D TEE will find 3D TEE very easy to do. The challenge is to understand the 3D anatomy, orient the images so they are standard and adjust the equipment settings to maximize the structure being reviewed. In patients with degenerative mitral valve disease, 3DE provides accurate information regarding the location and extent of prolapse/flail segments in a format that is readily appreciated by cardiac surgeons (Fig. 5). Additional 3DE information crucial to planning of the repair procedure that may be missed on 2DE includes presence of concomitant leaflet clefts and commissural MR. Figure 6 illustrates the excellent correlation between 3DE and actual pathology as seen during robotic mitral valve repair in a patient with a large flail P2 segment, a posterior leaflet cleft, and a small prolapsing P3 segment. Three-dimensional echocardi-
ography is also very useful in assessing the mechanism of failed mitral repair and the suitability for redo repair. In patients with a periprosthetic leak, the full extent of the periprosthetic defect, hence suitability for percutaneous device closure may be better appreciated with 3D as opposed to 2D echocardiography (Fig. 7). In some centers, TEE is used to guide valve deployment during transcatheter aortic valve replacement. Advantages of 3DE over 2DE include superior delineation of the aortic valve and subvalvular pathology including, more accurate annular measurements (Fig. 8), better visualization of location of calcium deposits, superior visualization of the guidewire, and catheter device positioning and deployment.5 In conclusion, 3DE improves and expands the diagnostic capabilities of cardiac ultrasound in a manner that complements traditional 2DE. Three-dimensional echocardiography allows visualization of cardiac anatomy and pathology in a format that is readily appreciated by cardiac surgeons, and is very helpful in guiding and assessing the results of mitral valve repair surgery.
REFERENCES 1. Chen X, Sun D, Yang J, et al: Preoperative assessment of mitral valve prolapse and chordae rupture using real time three-dimensional transesophageal echocardiography. Echocardiography 2011;28:1003–1010. 2. Suri RM, Schaff HV, Dearani JA, et al: Recurrent mitral regurgitation after repair: Should the mitral valve be re-repaired? J Thorac Cardiovasc Surg 2006;132:1390– 1397. 3. Shekar PS, Couper GS, Cohn LH: Mitral valve re-repair. J Heart Valve Dis 2005;14:583–587. 4. Brown ML, Schaff HV, Li Z, et al: Results of mitral valve annuloplasty with a standard-sized posterior band: Is measuring important? J Thorac Cardiovasc Surg 2009; 138:886–891. 5. Smith LA, Dworakowski R, Bhan A, et al: Real-time threedimensional transesophageal echocardiography adds value to transcatheter aortic valve implantation. J Am Soc Echocardiogr 2013;26:359–369.
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NEW TECHNOLOGIES ____________________________________________________________
3D Echocardiography in Cardiac Surgery Pankaj Saxena, F.R.A.C.S., Ph.D.,* Joseph F. Malouf, M.D.,y Roger Click, M.D., Ph.D.,y and Rakesh M. Suri, M.D., D.Phil.* *Division of Cardiovascular Surgery, Mayo Clinic, Rochester, Minnesota; and yDivision of Cardiology, Mayo Clinic, Rochester, Minnesota ABSTRACT Herein, we present a patient who underwent successful repair of failed mitral valve repair in whom intraoperative 3D transesophageal echocardiography provided accurate assessment of the mechanism of mitral regurgitation. In addition, we review the potential advantages and limitations of 3D echocardiography and its role in cardiac surgery. doi: 10.1111/jocs.12256 (J Card Surg 2014;29:51–54) Annuloplasty ring dehiscence is an important cause of recurrent mitral regurgitation (MR) following valve repair. We present a patient who underwent successful redo cardiac surgery for failed mitral valve repair in whom intraoperative 3D transesophageal echocardiography (3D TEE) provided accurate assessment of the mechanism of MR. We have briefly reviewed the current status of 3D echocardiography (3DE) in cardiac surgery. CLINICAL SUMMARY An 80 year old man presented with NYHA IV dyspnea caused by recurrent severe MR following previous annuloplasty repair with Duran ring (Medtronic, Inc., Minneapolis, MN, USA) for degenerative mitral valve disease, performed at another institution four years previously. The patient’s comorbidities included pulmonary hypertension, chronic kidney disease, previous myocardial infarction, and coronary artery bypass surgery performed 20 years previously with patent bypass grafts. Preoperative 2D transesophageal echocardiography (2D TEE) identified separation of the annuloplasty ring in the region of the mid-posterior annulus with associated severe MR (Fig. 1A). Intraoperative 3D TEE confirmed the mechanism of MR with demonstration of the exact anatomic site of ring dehiscence (Fig. 1B). The patient underwent third-time sternotomy, followed by institution of cardiopulmonary bypass with
Conflict of interest: The authors acknowledge no conflict of interest in the submission. Address for correspondence: Rakesh M. Suri, M.D., D.Phil., Division of Cardiovascular Surgery, Mayo Clinic, 200 First Street SW, Rochester, MN 55905. Fax: þ1-(507)-255-7378; e-mail: suri.rakesh@ mayo.edu
peripheral cannulation due to dense intrapericardial adhesions and myocardial protection with moderate systemic hypothermia. Mitral valve exposure via left atriotomy demonstrated dehiscence of the annuloplasty ring at the nadir of valve annulus posteriorly (Fig. 1C). The area of separation of the ring was corrected using several 3-0 prolene (Ethicon, Inc., Somerville, NJ, USA) pledgetted horizontal mattress sutures. Additional reinforcement stitches were also placed in the area of right and left fibrous trigones where the annuloplasty ring had slid inferiorly. Intraoperative TEE confirmed no residual MR. The patient was discharged home on day 5.
DISCUSSION We routinely perform 3D TEE examination during intraoperative assessment of the mitral valve to identify the mechanism of MR. Three-dimensional echocardiography (3DE) provides accurate morphologic assessment of mitral valve abnormalities in complex valvular disease correlating well with intraoperative surgical findings.1 When tissue quality is satisfactory and in the absence of retraction or calcification, mitral valve rerepair is often possible and may be associated with improved late outcomes including enhanced reverse remodeling as compared to valve replacement.2 Dehiscence of a prosthetic annuloplasty device can lead to mitral valve repair failure.3 We use a 63-mm posterior annuloplasty band in all patients with degenerative mitral valve disease which restores normal annular size and is associated with durable freedom from recurrent MR.4 We believe that the nadir of posterior mitral valve annulus represents an area of potential weakness in any sutured annuloplasty system and we therefore reinforce this area of the annuloplasty ring with pledgetted prolene sutures.
52
SAXENA, ET AL. 3D ECHO IN CARDIAC SURGERY
J CARD SURG 2014;29:51–54
Figure 1. (A) Intraoperative 2D transesophageal echocardiography with arrow pointing to the annuloplasty ring and arrow head to the posterior leaflet. Color Doppler with a wide jet of mitral regurgitation. (B) 3D echocardiography with arrow marked to identify posterior dehiscence of the ring from the annulus as seen in ‘‘Surgeon’s view’’ of the mitral valve. (C) Operative photograph with a mirror image of 3D transesophageal picture.
Figure 2. (A) Depiction of 2D sector on echocardiography. (B) 3D sector. (C) Multi-beat acquisition: four sub-volumes. Figure reproduced by permission of Mayo Foundation for Medical Education and Research. All rights reserved.
Three-dimensional echocardiography 3DE represents a major advance in cardiac imaging that complements 2DE. Whereas 2DE represents a tomographic slice through a region of interest, a 3DE encompasses the entire region of interest (Fig. 2A and B). Threedimensional echocardiography is built up from multiple 2D sectors that are acquired nearly simultaneously at various levels along the entire width and depth of the volume of interest. Spatial resolution is a function of
Figure 3. Three-dimensional TEE with stitch artifacts (arrow heads). Figure reproduced by permission of Mayo Foundation for Medical Education and Research. All rights reserved.
both the number of 2D sectors per volume of interest, and the number of ultrasound lines per 2D sectors, hence the scanning density within the volume of interest. Temporal resolution refers to the 3D image frame rate, or more accurately volume rate and is a function of the 3D volume size, image depth, and
Figure 4. Three-dimensional TEE of mitral prosthesis demonstrates a false periprosthetic defect (arrow) adjacent to ostium of left atrial appendage. Figure reproduced by permission of Mayo Foundation for Medical Education and Research. All rights reserved.
J CARD SURG 2014;29:51–54
Figure 5. Three-dimensional echo demonstrates prolapse of the tip of A2 (arrow) and chordal rupture (arrow head). Figure reproduced by permission of Mayo Foundation for Medical Education and Research. All rights reserved.
scanning density analogous to 2D imaging. The main trade off in 3DE, therefore, is between the temporal and spatial resolution. By reducing the scanning density and the associated spatial resolution, the frame rate or volume rate is increased. The frame rate can also be increased while maintaining the same scanning density simply by reducing the size of the volume of interest. When the entire 3DE volume of interest is acquired in a single beat, it is effectively real time. Because of the large amount of image data acquired, a low temporal resolution remains a major limitation of real-time 3DE. An alternative non-real-time method to increase the 3DE frame rate while maintaining the same volume size and scanning density is by dividing the 3D volume of interest into subvolumes and acquiring each subvolume separately. This is referred to as multibeat acquisition. By doing so, the 3DE frame rate will be a function of the time needed to acquire the
SAXENA, ET AL. 3D ECHO IN CARDIAC SURGERY
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Figure 7. Three-dimensional TEE of a large mitral periprosthetic leak (arrow) that is adjacent to the left atrial appendage (asterisk). The arrow head points to an aortic prosthesis anterior to the mitral prosthesis. Figure reproduced by permission of Mayo Foundation for Medical Education and Research. All rights reserved.
subvolume and not the entire volume (Fig. 2C). For example, when the 3DE is acquired over four beats that are ECG gated, the first 3DE subvolume that is ECG gated to the first beat is acquired in the usual manner. Once acquired, the next subvolume is acquired and so on until the full 3D volume is rendered complete. The four subvolumes are then electronically ‘‘stitched’’ together to form the complete volume. Patient motion, patient breathing, or arrhythmias can interfere with this process resulting in so-called stitch artifacts (Fig. 3). Since each of the subvolumes is only one-fourth the size of the entire volume, the frame rate is four times higher than would have been achieved if the entire volume was acquired in a single beat. With two beat acquisitions (that is two subvolumes) the frame rate will
Figure 6. (A) Three-dimensional TEE shows P2 prolapse (arrow) with chordal rupture (double arrow); and P3 prolapse (arrow head). A cleft can be appreciated between the prolapsing segments. (B) Operative photograph during robotic mitral valve repair in the same patient confirms the areas of prolapse. The cleft in the posterior leaflet is represented by an asterisk. Figure reproduced by permission of Mayo Foundation for Medical Education and Research. All rights reserved.
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SAXENA, ET AL. 3D ECHO IN CARDIAC SURGERY
J CARD SURG 2014;29:51–54
Figure 8. (A and B) Three-dimensional reconstructions of left ventricular outflow tract and aortic valve annulus. Note elliptical shape of annulus in B. Figure reproduced by permission of Mayo Foundation for Medical Education and Research. All rights reserved.
double and with a six beat acquisition typical for multibeat 3DE with color Doppler, the frame rate is increased by sixfold. Another 3DE imaging limitation is drop out artifacts that may simulate an actual defect such as a periprosthetic leak or leaflet perforation (Fig. 4). Color Doppler documentation of flow through a defect, particularly if fixed, is therefore absolutely necessary to establish diagnosis of a true defect. It is important to emphasize at this juncture that the quality of a 3DE depends on the intrinsic quality of the 2DE. Therefore, suboptimal 2D images result in suboptimal 3D images. Of all the intracardiac structures, the mitral valve lends itself best to 3D imaging particularly by TEE. Enface views of the mitral valve from the left atrium (socalled surgeon’s view) can be readily obtained in a single image acquisition, thus eliminating the extensive manipulation necessary when using 2D imaging to obtain similar information. Enface views of the mitral valve from the left ventricle can also be readily obtained. Three-dimensional TEE is almost always an adjunct to a standard 2D TEE. The additional time required to capture the images and interpretation is quite variable, but usually adds another 10–15 minutes to the study. Personnel trained to perform standard 2D TEE will find 3D TEE very easy to do. The challenge is to understand the 3D anatomy, orient the images so they are standard and adjust the equipment settings to maximize the structure being reviewed. In patients with degenerative mitral valve disease, 3DE provides accurate information regarding the location and extent of prolapse/flail segments in a format that is readily appreciated by cardiac surgeons (Fig. 5). Additional 3DE information crucial to planning of the repair procedure that may be missed on 2DE includes presence of concomitant leaflet clefts and commissural MR. Figure 6 illustrates the excellent correlation between 3DE and actual pathology as seen during robotic mitral valve repair in a patient with a large flail P2 segment, a posterior leaflet cleft, and a small prolapsing P3 segment. Three-dimensional echocardi-
ography is also very useful in assessing the mechanism of failed mitral repair and the suitability for redo repair. In patients with a periprosthetic leak, the full extent of the periprosthetic defect, hence suitability for percutaneous device closure may be better appreciated with 3D as opposed to 2D echocardiography (Fig. 7). In some centers, TEE is used to guide valve deployment during transcatheter aortic valve replacement. Advantages of 3DE over 2DE include superior delineation of the aortic valve and subvalvular pathology including, more accurate annular measurements (Fig. 8), better visualization of location of calcium deposits, superior visualization of the guidewire, and catheter device positioning and deployment.5 In conclusion, 3DE improves and expands the diagnostic capabilities of cardiac ultrasound in a manner that complements traditional 2DE. Three-dimensional echocardiography allows visualization of cardiac anatomy and pathology in a format that is readily appreciated by cardiac surgeons, and is very helpful in guiding and assessing the results of mitral valve repair surgery.
REFERENCES 1. Chen X, Sun D, Yang J, et al: Preoperative assessment of mitral valve prolapse and chordae rupture using real time three-dimensional transesophageal echocardiography. Echocardiography 2011;28:1003–1010. 2. Suri RM, Schaff HV, Dearani JA, et al: Recurrent mitral regurgitation after repair: Should the mitral valve be re-repaired? J Thorac Cardiovasc Surg 2006;132:1390– 1397. 3. Shekar PS, Couper GS, Cohn LH: Mitral valve re-repair. J Heart Valve Dis 2005;14:583–587. 4. Brown ML, Schaff HV, Li Z, et al: Results of mitral valve annuloplasty with a standard-sized posterior band: Is measuring important? J Thorac Cardiovasc Surg 2009; 138:886–891. 5. Smith LA, Dworakowski R, Bhan A, et al: Real-time threedimensional transesophageal echocardiography adds value to transcatheter aortic valve implantation. J Am Soc Echocardiogr 2013;26:359–369.
