THREE DIMENSIONAL ECHOCARDIOGRAPHY IN CONGENITAL HEART DISEASES.pptx

3d echo#chd#new modality#new future

1. THREE DIMENSIONAL ECHOCARDIOGRAPHY IN CONGENITAL HEART DISEASES Presenter: Dr.Sadanand Indi Final year resident in cardiology

2. Complex intracardiac anatomy and spatial relationships are inherent to congenital heart defects (CHD). Improving transducer technology, beam forming, and miniaturization have led to significant improvements in spatial and temporal resolution using 2DE. However, 2DE has fundamental limitations. The very nature of a 2DE slice, which has no thickness, necessitates the use of multiple orthogonal “sweeps.” The echocardiographer then mentally reconstructs the anatomy, and uses the structure of the report to express this mentally reconstructed vision.it forms 3d-image of heart as virtual image echographer’s mind and translated into words. Since myocardial motion occurs in three dimensions, 2DE techniques inherently do not lend themselves to accurate quantitation.

3. In 1990, von Ramm and Smith published their early results with a matrix-array transducer that provided realtime images of the heart in three dimensions. While this was an important breakthrough, this transducer was unable to be steered in the third (elevation) dimension. Technologic advances that have facilitated the maturation of 3DE techniques include the following: Matrix transducers Beam forming and steering in three spatial dimensions Display of three-dimensional information Software for quantification Matrix Transducers Two important advances in transducer technology, namely the organization of elements and the use of novel piezoelectric materials , have been the structural basis for improvements in 3DE matrix transducers

4. ELEMENTS: Two-Dimensional Transducers Current 2DE transducers transmit and receive acoustic beams in a flat 2DE scanning plane. As opposed to M mode, which provides one spatial and one temporal dimension, 2DE scanning systems sweep a scan line to and fro within this 2DE imaging plane. The angular position of the beam is said to vary in the azimuthal dimension. Even though traditional, flat 2DE scanning comprises two spatial dimensions plus one temporal dimension, this is not three-dimensional imaging. The 2DE transducer itself consists of elements that work in concert to create a scan line. Typically, a conventional transducer consists of 64 to 128 elements arranged along a single row (technically referred to as a onedimensional array of elements). These elements are spaced according to the ultimate frequency (and hence wavelength) of the acoustic vibrations; these propagate radially along the direction of the scan line. The two spatial dimensions in the image come from sweeping the beam by firing along this row at different times.

5. ELEMENTS: PRIMITIVE MATRIX-ARRAY TRANSDUCERS An innovation applied in the last decade was to increase the number of rows of elements from one (in the 2DE transducer described above) to five to seven rows of elements. This “sparse-element” model generated a primitive matrix-array transducer with 5 x 64 = 320 elements. While this represented a dramatic increase in the number of elements, not all elements were electrically active , and the individual elements were not electrically independent from each other. As a result, this transducer did not steer in the third (elevation) dimension. Poor image quality, a large footprint and the lack of portability limited the mainstream acceptability of this approach.

6. Elements: Contemporary Matrix-Array Transducers Contemporary matrix-array transducers comprise as many elements in the elevational dimension as they do in the azimuthal dimension, with over 60 elements in each of these dimensions. While the elements are arranged in a twodimensional grid, this array generates 3DE images. In order to be able to steer in the elevational plane, each element must be electrically independent from all other elements, and each element must be electrically active.

7. As a result, the contemporary matrix-array transducer consists of thousands of electrically active elements that independently steer a scan line left and right, as well as up and down. TRANSDUCERS: PIEZOELECTRIC MATERIALS The piezoelectric material in an ultrasound transducer is a fundamental determinant of system image quality. Piezoelectric transducer elements are responsible for delivery of ultrasound energy into the scanned tissue and for converting returning ultrasound echoes into electric signals . To create an overall piezoelectric effect, allow arrangement of dipoles in line within polycrystalline materials Piezoelectric material involves growing crystals and these crystals are poled at the preferred orientation(s), near perfect alignment of dipoles (~100%) is achievable, resulting in dramatically enhanced electromechanical properties

8. The new piezoelectric materials provide both penetration and high resolution . The improved arrangement of atoms in these new piezoelectric materials, and their superior strain energy density, translate into advances in transducer miniaturization. High frequency matrix 3DE transducers that have dramatically enhanced the applicability of 3DE to pediatric populations as well as to transesophageal echocardiography.

9. THREE-DIMENSIONAL BEAM FORMING AND STEERING Beam forming consists of steering and focusing of transmitted and received scan lines. For 3DE, this means that the beam former must be steered in both the azimuthal and elevational planes This is achieved both in the ultrasound system and within the transducer itself, using highly specialized integrated circuits to create a 3D trapezoid of acoustic information that is processed.. Display of 3DE Two-dimensional computer displays consist of rows and blocks of picture elements, termed pixels, that comprise a 2D image. In contrast, a 3DE data set consists of bricks of pixels, termed volume elements or voxels . However, even for a 3DE data set, the two-dimensional nature of the display imposes restrictions on the ability to appreciate depth. The process of adding perspective is done by casting a light beam through the collection of voxels. The light beam either hits enough tissue so as to render it opaque, or it keeps shining through transparent voxels so as to render it transparent.

10. The user has the ability to rotate and tilt the data set on the computer screen. Tools are available to “cut away” interfering structures, thus performing “ virtual dissection.” A tissue colorization map has been applied to the image. This has the effect of coloring tissues in the near field (near to either the transducer or the front of the 3D image) orange. Tissues in the far field are colored blue. This is a dynamic after effect, which means that as the operator rotates, tilts, or otherwise manipulates the image, the color effect correspondingly changes in real time A tissue colorization map has been applied to the image

11. 3DE acquisitions include the entire extent of the structure, thus minimizing the possibility of foreshortening of the apex or any geometric assumptions regarding shape . Three-dimensional quantitative software tools have the potential to quantify cardiac structures accurately regardless of their shape. 3DE volumetric techniques traditionally relied on definition of chamber cavities, that is, the blood-endocardium interface. The software constructs this interface by using a process known as surface rendering, and represents it as a mesh of points and lines . This software-generated mesh is calculated for every frame of acquisition, thus providing a moving cast of the cavity of the ventricle during the cardiac cycle. Quantitative software for the mitral valve provides the ability to perform sophisticated analyses of the nonplanar shape of the mitral annulus and to measure 3D structures, including annular diameters, commissural lengths, and leaflet surface areas.

12. MODES OF 3DE Electronically-steered 3DE systems have two major modes of scanning: live and EKG-gated. The live mode is the only one where the system scans in 3D realtime . A defining characteristic of this mode is: if the transducer comes off the chest, the image disappears . The live 3D mode can also be operated within a three-dimensionally shaped zoom box. Live 3DE modes provide narrow (20 to 30 degrees in the elevation plane) datasets that have high voxel density. Live 3DE can be obtained on patients with arrhythmias or with an active precordium; this mode eliminates the potential for motion or stitch artifact . Currently, EKG-gated modes are required to provide wider volumes while maintaining adequate frame rates. Gating allows for anywhere from two to eight smaller volumes to be stitched together to generate volumes that are greater than 90 degrees wide in the elevation plane, at frame rates exceeding 30 Hz Gated modes have comparatively lower voxel density, and are subject to both motion and stitch artifacts. Recent enhancements have improved the ability to acquire gated full-volume data among patients with arrhythmias.

13. Conventional 2DE is shown in the left panel. Live 3DE imaging (center panel) adds the elevation plane. The shape of the image is therefore trapezoidal rather than pie-shaped. The right panel depicts ECG-triggered (full-volume) 3DE imaging, which provides a wider trapezoid. Given the potential for motion and stitch artifacts with gated modes and the need for high spatial and temporal resolution, it has been our practice to use live 3DE to delineate anatomy in children . We also use live 3DE for the purpose of image-guidance of interventions , because instant visual feedback is critical in this application. We reserve the use of gated modes for the following: ■ Targets that do not fit within a live 3DE window ■ Quantitation of chamber volumes 3DE color flow demonstrations of regurgitant jets or shunt flows

14. CLINICAL APPLICATIONS IN CONGENITAL HEART DISEASE 3DE imaging has three broad areas of clinical application among patients with congenital heart disease: visualization of morphology, volumetric quantitation of chamber sizes and flows, and image-guided interventions. Visualization of Morphology Dating from an early stage in the development of 3DE technology, the structural complexity that is inherent to congenital heart disease has been identified as fertile substrate for exploration using 3DE.

15. THE ATRIOVENTRICULAR VALVES 3DE is valuable in delineating the morphology of the atrioventricular valves. Espinola-Zavaleta et al. described the role of 3DE in delineating congenital abnormalities of the mitral valve . Rawlins et al. demonstrated the additive value of 3DE and improved image quality using intraoperative epicardial 3DE to delineate the anatomy of atrioventricular valves. Seliem et al. studied 41 patients with AV valve abnormalities and found that 3DE imaging was helpful in delineating the morphology of the valve leaflets and their chordal attachments, the subchordal apparatus, the mechanism and origin of regurgitation, and the geometry of the regurgitant volume. Vettukatil et al. examined the role of 3DE in patients with Ebstein anomaly of the tricuspid valve. They demonstrated that 3DE provided clear visualization of the morphology of the valve leaflets, including the extent of their formation, the level of their attachment, and their degree of coaptation . They were also able to visualize the mechanism of regurgitation or stenosis. 3DE provides unparalleled views of cor triatriatum as well as en face views of the tricuspid valve

16. ATRIOVENTRICULAR SEPTAL DEFECT Hlavacek et al. studied 52 datasets on 51 patients with atrioventricular septal defects (AVSD) and showed that gated 3DE views could be cropped to obtain en face views of the atrial and ventricular septa. These views provide a clear understanding of the relationships of the bridging leaflets to the septal structures. These views have been useful to determine the precise location of the interventricular communication relative to the bridging leaflets, and to demonstrate how these relationships determine the level of shunting (atrial, ventricular, or both). They found that 3DE on unrepaired balanced AVSD and repaired AVSD with residual lesions was more often additive/useful (33/36; 92%) than on repaired AVSD without residual lesions or unbalanced AVSD (9/16 (56%), P=0.009). 3DE was additive or useful in all three patients with unbalanced AVSD being considered for biventricular repair.

17. THE ATRIAL AND VENTRICULAR SEPTA Tantengco et al. showed that 3DE reconstructions provided unique en face views of atrial and ventricular septal defects. Cheng et al. studied 38 patients with atrial and/or ventricular septal defects using 3DE, and compared their results to 2DE and surgical findings. They demonstrated novel 3DE views of both atrial and ventricular septal defects and improved accuracy of quantification of the size of the defect by 3DE compared to 2DE We have found live 3DE to be of great value in evaluating the ventricular septum en face and to assess malformations of the outflow tract that involve malalignment of the outlet septum Sivakumar et al. have recently published an elegant series demonstrating a simplified subxiphoid 3DE acquisition technique to visualize ventricular septal defects. Similarly, Faletra et al. and Saric et al. have published elegant practical guidelines on how to demonstrate atrial septal defects.

18. THE AORTIC ARCH, PULMONARY ARTERIES, AND AORTOPULMONARY SHUNTS 3DE color flow Doppler has been used to provide echocardiographic “angiograms” of flow patterns in the aortic arch (coarctation of the aorta), the branch pulmonary arteries (the Lecompte maneuver), and across Blalock-Taussig shunts.These authors examined echocardiographic “angiograms” in 26 patients. 3DE provided additional diagnostic information in 10 of 26 patients (38%). In 17 of 26 patients (65%), validation of the 3DE diagnosis was available at surgery, cardiac catheterization, MRI, or CT angiography. Echocardiographic angiogram

19. THE AORTIC VALVE AND OUTFLOW TRACT Sadagopan et al. examined the role of 3DE in 8 children who subsequently underwent surgery for congenital aortic valvar stenosis. They showed that 3DE was accurate in providing measurements of aortic valve annulus and number of valve leaflets, and in identifying sites of fusion of the leaflets as well as nodules and excrescences that characterized dysplastic valves. Bharucha et al. studied 16 patients with subaortic stenosis. Using a form of 3DE reconstruction , demonstrated abnormalities of mitral valve leaflet or chordal apparatus attachments (14 patients), abnormal ventricular muscle band (11 patients), and abnormal increased aortomitral separation (2 patients). CHARACTERIZATION OF LEFT VENTRICULAR NONCOMPACTION Baker et al. evaluated four patients with left ventricular noncompaction using 3DE. Characterized the Left Ventricular Noncompaction.

20. 3D-Transthoracic Echocardiography (TTE) uses Views Subxiphoid (Subcostal) views Apical views Left parasternal views Right parasternal views Suprasternal notch views

21. The first step of the examination, is to determine visceral and atrial situs and cardiac position within the chest (normal or levo cardia, dextrocardia, or mesocardia ). Second, both systemic and pulmonary venous connections to the atria should be determined. In adults, only three pulmonary veins are generally visualized on TTE (best seen in the apical views). The right inferior pulmonary vein is not seen. All pulmonary venous drainage into the left atrium can be easily identified on transesophageal imaging. Third, abnormalities of ventricular inflow such as tricuspid atresia or cor triatriatum are assessed. Fourth, ventricular number, morphology, relative size, position, and concordance with the atria are determined. The number of ventricles is determined by the presence or absence of an interventricular septum. The morphology of the ventricle should be classified as right, left, or indeterminate.

22. Fifth, abnormalities of cardiac septation such as ASD, ventricular septal defect (VSD), and AV septal defect (AV canal or endocardial cushion defect), including direction and magnitude of shunt, are assessed. Sixth, ventriculoarterial concordance and great vessel number and relationships are elucidated. Seventh, the right and left ventricular outflow tracts , including subvalvular , valvular, supravalvular, and distal great arteries must be evaluated for the presence of obstructive lesions such as pulmonary valve stenosis, branch pul monary artery stenosis, discrete subaortic membranes, and even coarctation of the aorta. Finally, attention is turned to the evaluation of native shunts (e.g., patent ductus arteriosus, aortopulmonary windows, ruptured sinus of Valsalva aneurysm, or systemic to pulmonary artery collaterals), and postoperative structures (patches, conduits, surgically created systemic to pulmonary shunts, Fontan circuits, etc.).

23. OUTLINES OF ABNORMALITIES Abnormalities of Cardiac Septation ASD ,VSD AVSD/ECD Abnormalities of Right ventricular inflow Tricuspid atresia, Ebsteins anomaly Abnormalities of Left ventricular inflow Cor triatriatum , Mitral supravalvular ring, Congenital mitral stenosis, or mitral atresia

24. Abnormalities of Ventricular Number or Morphology Double- inlet left ventricle. Double- inlet right ventricle. Conotruncal Abnormalities TOF DORV D-TGA L- TGA Patent Truncus Arteriosus Obstruction to Ventricular Outflow Right ventricle outflow obstruction Left ventricle outflow obstruction

25. ABNORMALITIES OF CARDIAC SEPTATION

26. The most commonly diagnosed congenital cardiac defect in adulthood, aside from bicuspid aortic valve, is ASD, which accounts for almost 30% of all first congenital cardiac diagnoses in adults Ostium primum defect (characterized by the absence of the primum septum at the AV junction or crux of the heart, represents approximately 15% of ASD in adults.) Ostium secendum defect (75%) type, which is caused by a defect in portions of the membranous fossa ovalis (secundum septum). The atrial septal aneurysm , which may be congenital or acquired, occurs when the membranous flap of the fossa ovalis protrudes with a “wind-sock”- like appearance into one or the other atrium and may demonstrate mobility during the cardiac cycle. Sinus venosus ASD , caused by absence of the basal segment of the interatrial septum most commonly at the superior vena cava (SVC) and rarely at the inferior vena cava (IVC) junction with the atrium, accounts for 10% to 15% of ASD in adulthood

27. Parasternal short axis view of the ventricles demonstrating paradoxical septal motion of right ventricular volume overload. In diastole (A), right ventricular pressure equals left ventricular pressure, the interventricular septum is flat (arrow), and the left ventricle is D- shaped. In systole (B), left ventricular pressure is greater than right ventricular pressure and the ventricle resumes its normal circular geometry. The appearance of a color flow signal from the left to right atrium in the apical view can assist in the diagnosis of secundum defects. Trans esophageal echocardiography is excellent for localizing the defect. Right-sided chamber enlargement is the hallmark of an atrial level shunt. When seen on echocardiographic imaging, this should prompt a comprehensive evaluation of the atrial septum and definition of pulmonary venous return.

28. Primum ASD 15-20% Secundum ASD 75% Sinus venosus ASD 5-10% Coronary sinus ASD <1% Sinus venosus asd

29. A defect in the atrial septum results in a direct communication between the left atrium (LA) and right atrium (RA). During embryologic development, the primitive atrium undergoes a complex septation process. The septum primum extends inferiorly from the middle of the atrium toward the region of the endocardial cushions, initially leaving an opening called the ostium primum. The inferior portion of the septum primum subsequently fuses with the developing endocardial cushions to close the inferiorly located ostium primum. Tissue reabsorption (or programmed cell death) in the middle of the septum primum leads to a second central opening, or ostium secundum. Concurrently, development of the septum secundum occurs, and once joined with the endocardial cushions, the inferior portions of the two atria are separated. The remaining defect in the septum secundum is the foramen ovale , which allows flow from the fetal RA to LA during gestation. SECUNDUM ASD

30. Once birth occurs, fusion of these two septa should occur, functionally closing the foramen ovale ; however, probe patency is present in approximately 25% to 30% of the population. Secundum ASDs, typically occurring in the central or secundum portion of the atrial septum, actually result from a true deficiency in the septum primum. A secundum ASD produces characteristic dropout in the central-most portion of the atrial septum. Most defects are relatively elliptical in shape. Assessment from multiple views is needed to fully evaluate the maximum ASD dimensions, septal rims, and relationship of the ASD to surrounding cardiac structures. It is very important to rule out any defects that would require surgical attention: 1) primum ASD is typically associated with cleft anterior mitral valve leaflet;, 2) sinus venosus ASD is associated with anomalies of right pulmonary venous return; and 3) coronary sinus ASD is associated with left superior vena cava to the left atrium. None of these are appropriate for consideration of device closure.

31. SECUNDUM ASD

32. Ventricular septal defect (VSD) Ventricular septal defect (VSD), the most common form of congenital heart disease. The normal ventricular septum is a curved structure extending from the posterior interventricular groove at its inferior and rightward aspect to the pulmonary outflow tract and anterior interventricular groove superiorly and leftward. The ventricular septum can be divided into four regions: the membranous, inlet, outlet, and trabecular septa. VSDs can be divided into two fundamental types. In the first type, there may be adequate septal tissue, but there is malalignment of portions of the ventricular septum causing a “gap” or VSD. The second fundamental type of VSD is due to a deficiency in septal tissue. This deficiency either can be congenital or can be acquired following myocardial infarction or trauma.

33. THE CLASSIFICATION SYSTEMS

34. VSD CLASSIFICATION SCHEME 1.Outlet (33% Asia) 6% 2.Membranous 80% 3.Muscular (20% infants) 10% 4.Inlet 4%

35. MUSCULAR DEFECT Spontaneous closure common Small- observation Large defect-close Operation Device closure

36. Anterior muscular defects are located anterior to the septal band (or trabeculum septomarginalis ), which extends along the mid-septum from the insertion of the moderator band toward the membranous septum . The septal band bifurcates into an anterior and a posterior limb to surround the membranous septum and a portion of the outlet septum. Mid-muscular defects are posterior to the septal band, anterior to the septal attachment of the tricuspid valve , and superior to the moderator band. Posterior muscular defects are located posterior to the septal attachment of the tricuspid valve ; posterior-inlet muscular defects are located immediately below the AV valves but separated from the valves by muscle tissue. Ventricular septal defects and aortic arch abnormalities keep close company. From 17% to 33% of patients with coarctation of the aorta have an associated VSD , as do nearly all patients with an interrupted aortic arch.

37. A double-chambered right ventricle (DCRV) has an associated VSD in 63% to 90% of patients. Two-dimensional and color flow mapping show the “napkin ring” of muscle bundles and flow disturbance (arrow) superior to the VSD. This VSD is on the “high pressure” side of the obstructing muscle bundles DCRV WITH VSD

38. MEMBRANOUS VSD Association- Infective Endocarditis AV and TV regurgitation

39. The membranous septum is a small fibrous portion of the ventricular and atrioventricular (av) septum located at the base of the heart , adjacent to the anteroseptal tricuspid commissure, the right posterior aortic valve commissure, and the anterior mitral valve leaflet. because of the relative apical placement of the tricuspid valve compared with the mitral valve, a portion of the membranous septum, the membranous av septum, separates the left ventricle (lv) from the right atrium. Anterior deviation and rotation of the outlet septum results in the ventricular septal defect, an enlarged aortic outflow overriding the main body of the ventricular septum, and narrowed subpulmonary outflow in TOF case. A perimembranous VSD may be related to deficiency of tissue in the region of the membranous septum or may be due to malalignment of the outlet septum with the muscular ventricular septum. The gap caused by malalignment of the outlet septum can be due to either anterior or posterior deviation of the outlet septum. Anterior deviation creates a VSD of the type seen in tetralogy of Fallot with override of the aorta.

40. Because of their location adjacent to the tricuspid valve, perimembranous defects can be associated with tricuspid septal leaflet distortion and tricuspid regurgitation . Accessory tissue from the septal leaflet of the tricuspid valve, or a part of the septal leaflet itself, can partially or completely close the defect; this tissue is sometimes referred to as a ventricular septal aneurysm Blood flow traverses through the VSD from the LV, through the aneurysmal tissue, and across the tricuspid valve and enters the right atrium resulting in LV–to–right atrial shunt. Misinterpretation of this high-velocity flow from this LV–to–right atrial shunt as tricuspid regurgitation can lead to an erroneous overestimation of RV pressure . A related, but distinct, type of LV–to–right atrial shunt is the Gerbode defect , which is an LV–to–right atrial connection created by a defect in the portion of the membranous ventricular septum separating the LV from the right atrium.

41. GERBODE’S DEFECT

42. OUTLET VSD Infundibular/ supracristal /doubly commited Subarterial defects make up 5% to 10% of VSDs and are more common in the Asian population . These defects are located beneath both semilunar valves and result from a deficiency in the conal , or outlet, septum. Subarterial defects are seen by echocardiography to be immediately beneath the aortic valve in long axis views and immediately adjacent to both the aortic and pulmonary valves in short-axis views (doubly-committed VSD). Prolapse of the right coronary cusp of the aortic valve into the defect, with distortion of the aortic valve, is present in up to 60% to 70% of subarterial VSDs . Prolapse is demonstrated as a diastolic bulging of the right aortic cusp and portion of the sinus into the RV in the long-axis and short-axis views. It can be mild and transient during early systole, or severe, encompassing the entire cusp with tethering to the VSD throughout systole and diastole.

43. INLET VSD Inlet VSDs are located posteriorly immediately adjacent to both AV valves. These defects are often best imaged from an apical four-chamber view or a parasternal short-axis view. They most commonly occur as part of atrioventricular septal defects (AVSD) but can be isolated. Inlet VSDs should be distinguished from posterior muscular (also called inlet muscular) VSDs, which are located near the inlet septum but are separated from the AV valves by a rim of muscle. Inlet VSDs may be formed by malalignment of the atrial and ventricular septa, resulting in some degree of AV valve override and frequently with straddling of AV valve chordal attachments AV valve override occurs when an AV valve is positioned over a VSD and relates to both ventricles. AV valve straddling occurs when chordal attachments from an AV valve cross the VSD to the opposite side of the ventricular septum or contralateral ventricle. An AV valve can override, straddle, or both. Tricuspid valve straddling with chordal attachments to the left ventricular side of the septum can be seen with inlet VSDs

44. A: Parasternal long-axis view showing muscular, perimembranous outlet, and subarterial VSDs. B: Parasternal short-axis view at the base showing perimembranous and subarterial VSDs. C: Parasternal short-axis view at the level of the left ventricular (LV) papillary muscles showing muscular VSDs. D: Apical four-chamber view showing inlet and muscular VSDs. E: Apical fivechamber view showing muscular and perimembranous VSD

45. ABNORMALITIES OF RIGHT VENTRICULAR INFLOW

46. TRICUSPID ATRESIA Tricuspid atresia is the third most common form of cyanotic congenital heart disease , with a prevalence of 0.3% to 3.7%, and is characterized by absence of a direct communication between the right atrium (RA) and the RV . The anatomic form of atresia is most commonly fibromuscular. In the majority of patients, the floor of the RA is entirely muscular with separation from the hypoplastic RV by fibrofatty tissue. Although we use the term “tricuspid atresia” for lesions with an echogenic plate-like area beneath the floor of the right atrium and above the right ventricle, this echogenicity is usually not the result of an atretic tricuspid valve but rather it results from fibrofatty tissue in the AV groove, So the tricuspid atresia is likely a result of failure of formation of the tricuspid valv e rather than fusion of formed tricuspid valve leaflets. OTHER ANOMALIES An opening in the atrial septum, either a patent foramen ovale or a secundum atrial septal defect (ASD), is obligatory for survival.

47. Historically, based on the great artery relationship, tricuspid atresia is classified into three types, with subclassification based on the anatomy of the ventricular septal defect (VSD) and pulmonary valve

48. SUBCOSTAL FOUR-CHAMBER (CORONAL) VIEW Subcostal examination begins with a determination of abdominal viscera and atrial situs in all patients. Subcostal four-chamber (coronal) views will show dilation of the RA with absence of the connection to the RV. As foreshortening of the RV may occur in this plane, short-axis (sagittal) plane imaging is useful for “ threedimensional ” assessment of right ventricular size. The atrial septum is best visualized from subcostal imaging planes, and characterization of the ASD should be performed. An atrial shunt is obligatory for survival. Evaluation of the great arteries from multiple imaging planes to determine ventriculoarterial connections is important. An enlarged, posterior great artery (PA) that bifurcates early is consistent with transposed great arteries (ventriculoarterial discordance).

49. Examination of the ventricular septum may provide information on the size and location of the VSD, but orthogonal views will be needed. In tricuspid atresia, the VSD is usually muscular; rarely, the VSD can be doubly committed and subarterial or outlet in nature. The mitral valve and left ventricular function can be assessed initially from the four-chamber subcostal plane. A left-juxtaposed right atrial appendage is visualized in the subcostal fourchamber scan plane. Both atrial appendages are located more leftward than normal. Juxtaposition of the appendages should not be confused with an ASD. SUBCOSTAL SHORT-AXIS (SAGITTAL) VIEW Subcostal short-axis views demonstrate the absent connection between the floor of the RA and the hypoplastic RV. Orthogonal views are very useful for evaluation of the atrial septal anatomy.

50. The RA and the hypoplastic RV, and the size of the RV is more easily assessed in the subcostal short-axis view than in the four-chamber imaging plane. Evaluation of the size of the VSD between the LV and hypoplastic anterior RV is important for documenting sites of obstruction to arterial outflow. Careful sweeps from right to left are important to obtain complete information about the location and degree of right ventricular outflow obstruction. Assessment of the ventriculoarterial connection is performed from the short-axis view,the proximal bifurcation of the PA should be assessed. The presence of parallel great arteries suggests transposition (ventriculoarterial discordance). PARASTERNAL LONG AXIS Parasternal long-axis scans typically demonstrate a small anterior RV and a large posterior LV . This scan plane also provides excellent views of the ventricular septum. The size and position of the VSD should be noted.

51. The position and origin of the great arteries are confirmed. In the presence of transposed great arteries, the arteries appear parallel in their proximal course from the ventricles, with the posterior vessel (PA) bifurcating early. If the VSD is present in the outlet portion of the septum, anterior deviation of the septum, seen most commonly with normally related great arteries may produce subpulmonary obstruction. Posterior deviation is seen more often with transposed great arteries . Muscular ridges or membranes can also cause ventricular outflow obstruction and should be evaluated from multiple imaging planes. Doppler and color Doppler evaluation of the gradient from the LV to RV and into the RVOT should be used to provide information about the degree of restriction, either to the PA (for an estimation of the PA pressure) or to the anterior aorta in transposition.

52. The parasternal short-axis view is useful for further characterization of the hypoplastic RV and VSD and position of the great arteries. Left ventricular function should be evaluated. Scanning apically from the base of the heart toward the midventricular level, the right ventricle is seen in front of the dominant, large LV. In addition to orthogonal subcostal views , the size of the RV and the anatomy of the VSD can be assessed in the short-axis plane. The presence of additional VSDs should be assessed with both imaging and color Doppler. Pulsed-wave Doppler interrogation can provide an estimation of the gradient between the LV and RV as well as aid in assessing the restrictive VSD.

53. Scanning superiorly toward the base of the heart to the level of the great arteries will again confirm their arrangement. If transposed, both great vessels are seen in short-axis, represented by two semilunar valves seen in the same imaging plane. In transposition, one can evaluate whether the anterior aorta is located rightward (d-transposition, more common) or leftward (l-transposition, less common). An apical four-chamber view provides excellent definition of the absent right AV connection. Angling the transducer posteriorly demonstrates the muscular atresia of the tricuspid valve appearing as an echo- dense plate of tissue in the floor of the RA. Again, assessment of the hypoplastic RV and its communication from the LV (VSD) is important . In the presence of juxtaposed atrial appendages, one can again see an abnormal atrial septal configuration. Mitral valve morphology and function are well visualized from the apical approach. Angling the transducer anteriorly facilitates development of a “five-chamber view,” providing further assessment of the outflow tracts and sites of potential obstruction.

54. In the presence of juxtaposed atrial appendages, one can again see an abnormal atrial septal configuration. Mitral valve morphology and function are well visualized from the apical approach. SUPRASTERNAL VIEWS Beginning with the long-axis view of the aortic arch, careful evaluation for evidence of arch obstruction is very important. In the setting of transposition of the great arteries , coarctation is more common , particularly when the VSD is restrictive and the aorta is small Short-axis suprasternal imaging demonstrates the branching pattern of brachiocephalic arteries and the sidedness of the aortic arch. The PA bifurcation is also seen from short-axis imaging, with branch sizes measured. The absence of an innominate vein should raise the possibility of a left SVC. A typical “crab” view should demonstrate normal pulmonary venous connections.

55. EBSTEIN’S MALFORMATION AND TRICUSPID VALVAR DYSPLASIA Ebstein’s malformation is often thought of as a primary disorder of the tricuspid valve. In reality, it is a manifestation of a more global aberration in myocardial development. The hallmark of Ebstein’s malformation is displacement of the annular attachments (hinges) of the septal and inferior leaflets, away from the atrioventricular junction. This results from failure of these leaflets fully to separate from the underlying ventricular wall during cardiac development. The normal separation process is referred to as “delamination” Delamination begins at the tips of the embryonic leaflets and proceeds “back” toward the atrioventricular junction. A completely delaminated leaflet will have a hinge point at (or very near) the anatomic tricuspid valvar annulus. Failure of delamination results in the leaflets remaining variably adherent to the underlying right ventricular and septal myocardium.

56. Rotation is spiral in nature and is directed both toward the apex and, more important, anteriorly toward the outflow tract. The displacement seen in Ebstein’s malformation is not simply a linear shift of the tricuspid valve toward the cardiac apex. The displacement is actually rotational in nature , following the contours of the right ventricular cavity Rotational shift of the functional tricuspid orifice away from the atrioventricular junction to the plane that divides the trabecular and outlet zones of the ventricle. The observed planes of the effective valvar orifices of the hearts with Ebstein’s malformation studied by Schreiber and colleagues are shown. The effective displacement of the functional tricuspid valve away from the atrioventricular junction is rotational, not linear .

57. These subcostal, sagittal plane images demonstrate the anatomic relationships of the three tricuspid valve leaflets. Normal tricuspid valve. The septal tricuspid leaflet (STL) lies parallel to the ventricular septum, and the anterior tricuspid leaflet (ATL) is positioned parallel to the anterior free wall of the right ventricle and separates the posterior inlet from the anterior outlet of the ventricle. The inferior tricuspid leaflet (ITL) is parallel to the diaphragmatic surface of the right ventricle and lies in the most inferior portion of the ventricle . This leaflet has often been referred to as the “posterior” leaflet, which is anatomically incorrect B:From an examination of the patient with Ebstein’s malformation. The ATL remains parallel to the anterior free wall. The STL and ITL are more difficult to recognize in this diastolic image because they are adherent to the myocardium of the septum and right ventricular inferior wall.

58. APICAL FOUR-CHAMBER The hinge point (septal insertion) of the normal STL is positioned slightly more toward the cardiac apex, compared with the septal hinge point of the anterior mitral leaflet (bottom left, arrow). This displacement is exaggerated in hearts with Ebstein’s malformation

59. Normal delamination process that gives rise to the tricuspid valve leaflets. During embryonic valve formation, the inner layer of endomyocardium separates (delaminates) from the underlying cardiac muscle and gradually loses its myocardial components. As development progresses,we begin to recognize the supportive chordal structures and leaflet of the mature valve. When a failure of delamination occurs (bottom), it results in adherence of the “tricuspid valve” tissues to the right ventricular myocardium. This is the hallmark of Ebstein’s malformation. The four diagrams, progressing from mild to severe, demonstrate the spectrum of abnormality that can be associated with failed delamination.

60. ECHOCARDIOGRAPHIC RECOGNITION AND EVALUATION OF EBSTEIN’S MALFORMATION The single most sensitive and specific diagnostic feature is the displacement of the annular hinge of the septal leaflet. This displacement is most easily appreciated by comparison to the annular hinge of the mitral leaflet as seen in the apical four-chamber view The distance between the valvar hinge points can easily be measured in systole . This distance, when divided by the body surface area in square meters, is known as the displacement index In a heart with evidence of failed delamination, an index value greater than 8 mm/m2 reliably distinguishes those with Ebstein’s malformation from both normals and from patients with other disorders associated with enlargement of the right ventricle

61. The tricuspid valve is displayed as if the examiner is standing in the apex of the right ventricle looking toward the right atrium. The leaflet texture, thickening of the leading edges, and a direct muscular insertion into the middle of the anterior leaflet were more easily appreciated in the three-dimensional scan. A coaptation gap was also easily appreciated three- dimensionally.The abnormal papillary muscle attachment to the anterior leaflet and the rudimentary nature of the septal leaflet combined to create a single, posterior regurgitant orifice in this case

62. COR TRIATRIATUM Cor triatriatum , an unusual form of abnormal atrial septation, occurs within the LA. Cor triatriatum may result from abnormal incorporation of the common pulmonary vein into the LA, causing obstruction between the pulmonary vein confluence and the LA. A membrane is seen within the LA as a linear echo, located above the mitral valve in orthogonal views. As the membrane is somewhat curvilinear, it should be visualized from multiple imaging planes. In classic cor triatriatum , the proximal chamber communicates only with the LA and not with the RA. There may be a PFO or an ASD between the lower LA chamber and the RA. Another variant of cor triatriatum exists in which all of the pulmonary veins return to the proximal chamber, which does not communicate with the distal LA directly . In this setting, an ASD provides egress to the RA, and a separate more inferior PFO/septal defect allows flow from the RA back to the LA.

63. Right-sided cardiac structural enlargement is characteristic of cor triatriatum . The RV is typically hypertrophied. RV function may be severely reduced if cardiac decompensation is present with severe membrane obstruction and little atrial communication for decompression of the proximal LA chamber. In the subcostal “coronal” view, an abnormal line of tissue is visualized within the LA. The pulmonary veins connect proximal to this line of tissue, and may be distended. When the membrane is patent, and communicates with the distal LA, color Doppler interrogation will reveal turbulent continuous flow across the obstructed membrane within the LA. In the absence of a communication between the proximal chamber and the LA, there may be a large ASD between the proximal chamber and the RA with a large left-to-right shunt ; a PFO communication between the RA and the distal LA is necessary for maintaining cardiac output and consequently shunts from right to left.

64. Systolic frame with mitral valve closed; there is distance between the membrane and the mitral valve, which suggests cor triatriatum rather than supramitral ring. PARASTERNAL VIEWS The enlarged right ventricle can be seen in both the parasternal long-axis and short-axis views. Septal motion is abnormal, depending on the degree of pressure overload , again directly related to the degree of obstruction and to the presence of a decompressing atrial communication between the proximal pulmonary venous chamber and the RA. In the long-axis view,there is a linear membrane visualized in the mid-portion of the LA , again seen above the appendage and below the pulmonary veins. Color Doppler may be used to demonstrate the communication with the distal chamber

65. APICAL VIEW Imaging of the left atrial membrane from the apical view will show a linear echo appearing above the base of the left atrial appendage and the mitral valve. From this view, the membrane may have a funnel-like appearance and mobile. If there is a large ASD communicating with the proximal LA chamber, the majority of flow will enter the RA, rather than the distal LA, and may reduce the measured gradient. If there is no communication between this proximal chamber and the LA, an ASD will be seen decompressing from left to right into the RA. SUBCOSTAL SAGITTAL VIEW Short-axis imaging demonstrates an abnormal horizontal line of tissue separating the LA into two functional chambers. The atrial septum should be evaluated from both orthogonal subcostal views, to determine the presence or absence of communication between the RA and either the proximal or distal chambers. The RVOT can be easily visualized in the short-axis view, typically showing a dilated main pulmonary artery.

66. SUPRASTERNAL NOTCH VIEWS Confirmation of pulmonary venous return to the proximal left atrial chamber should be performed from the suprasternal notch view. A high parasternal shortaxis view may be used to evaluate for the presence of a patent ductus arteriosus.

67. CONOTRUNCAL ABNORMALITIES

68. TETRALOGY OF FALLOT (TOF) A single morphologic abnormality—namely, anterior deviation or malalignment of the conal septum VENOUS CONNECTIONS About 10% of patients may have a left superior vena cava (L-SVC) draining to the right atrium via the coronary sinus. The parasternal long-axis view typically demonstrates a dilated coronary sinus—a finding that should prompt the echocardiographer to suspect a L-SVC .

69. In the parasternal short-axis view, a prominent venous structure is identified anterior to the left pulmonary artery. Slight clockwise rotation of the transducer will typically display the entire course of the left SVC in its long axis with drainage to the coronary sinus along the posterior aspect of the heart. Color flow mapping and pulsed-wave Doppler confirm that this blood vessel is venous and demonstrates low-velocity phasic systolic and diastolic flow toward the heart. The one third of Unrepaired TOF have an ASD . Many additional patients have a small patent foramen ovale . Defects in the atrial septum are best imaged from the subcostal scan planes because the atrial septum is perpendicular to this imaging plane.

70. The atrial septum can be visualized in orthogonal subcostal planes (coronal and sagittal) to optimally define the ASD. A subcostal sagittal (short-axis) view provides excellent visualization of the inferior vena cava (IVC) and SVC connections and the ASD It is important to remember that for color flow mapping of right-to-left atrial level shunt the Nyquist limit must be reduced to as low as 30 to 50 cm/s to optimally demonstrate the shunt ATRIOVENTRICULAR CONNECTIONS Most cases of tetralogy of Fallot have concordant atrioventricular connections. The tricuspid and mitral valves are usually structurally normal. Significant atrioventricular valve pathology is uncommon The apical four- chamber view demonstrates a typical image of a large primum atrial defect and a large inlet VSD.

71. By rotating the transducer clockwise, a parasternal short-axis view at the base of the heart is obtained. The extent of the VSD is well seen in this view extending from the area of aortic-tricuspid continuity often up to the crista supraventricularis (“12 o’clock” position in the parasternal short-axis view). A prominent “knuckle” of the anteriorly malaligned conal septum is often evident in this view leading to the os infundibulum where the RVOT obstruction typically begins A prominent “ knuckle” of the anteriorly malaligned conal septum is often evident in this view leading to the os infundibulum where the RVOT obstruction typically begins . The demonstration of a pulmonary valve in this view with antegrade flow across it excludes the possibilities of pulmonary atresia with VSD and truncus arteriosus Doubly committed subarterial defect (5%): In this setting, there is a complete lack of conal septum. In the parasternal short-axis view, the VSD is noted to extend beyond the crista supraventricularis (“12 o’clock position”) up to the pulmonary valve. This VSD is usually separated from the tricuspid valve by a muscular rim. RVOT obstruction is most commonly due to pulmonary valve stenosis and concomitant annular hypoplasia and not due to infundibular stenosis.

72. Perimembranous VSD without aortic-tricuspid fibrous continuity due to a muscular rim (18%) Atrioventricular septal defect in continuity with the subaortic defect (2%) Inlet VSD with straddling tricuspid valve (1%) THE VENTRICULOARTERIAL CONNECTIONS In TOF are typically concordant . However, the aorta does characteristically override the ventricular septum. This override is best demonstrated in the parasternal long-axis view It must be pointed out that even in normal individuals, there can be some degree of aortic override. A spectrum exists in the setting of this anomaly from less than 50% override in patients with TOF to greater than 50% aortic override (predominant RV origin of the aorta) in patients with double-outlet right ventricle.

73. The pulmonary annulus is often hypoplastic and the pulmonary valve may be acommissural , unicommissural , bicommissural , or tricommissural with thickening/dysplasia. Accurate measurement of the pulmonary annulus is important and may determine the necessity for transannular patch repair if significant hypoplasia exists. Great Arteries Often there is supravalvar stenosis noted in the main pulmonary artery. Typically, this is located at the tips of the open pulmonary valve in systole and the valve may have attachments in this region. Recognition of this narrowing is important because patch angioplasty of the main pulmonary artery may be needed to relieve this obstruction during surgical repair. The anatomy of the branch pulmonary arteries is important to define . These pulmonary artery branches are best visualized in the parasternal short-axis view as well as the high left parasternal and suprasternal short-axis views In fact, measurements of the right pulmonary artery from the suprasternal short-axis view correlate better with angiography-derived measurement s than those from parasternal views.

74. A continuous left-to-right ductal shunt is suggestive of severe RVOT obstruction, particularly if significant antegrade flow is not demonstrated. Continuous multiple tortuous channels of systemic-to-pulmonary artery flow are typical of aortopulmonary collaterals and are far more common in pulmonary atresia with VSD rather than in TOF Finally, the side of the aortic arch must be defined . Up to 25% to 30% of patients with TOF have a right-sided aortic arch, usually with mirror image branching. A right aortic arch is more common with increasing degrees of RVOT obstruction.

75. Congenitally corrected transposition of the great arteries (CCTGA) The discordance of both the AV and VA connections No subpulmonary infundibulum because this is a morphologic LV and therefore there is mitral valve–pulmonary valve fibrous continuity. The pulmonary veins connect to the left atrium (LA) The LA is then connected to a morphologic right ventricle (RV) via a tricuspid valve The aorta is usually positioned anterior and leftward of the pulmonary artery with a well-developed subaortic infundibulum resulting in discontinuity between the tricuspid and aortic valves.

76. Transposition of the great arteries, the initial (unbranched) segments of the great arteries run parallel to each other Unlike the normal heart, the ventricles assume more of a side-by-side relationship , and as result, the ventricular septum is oriented in a straight anterior–posterior plane The diagnosis of CCTGA is based on demonstrating discordance of both the AV and VA connections [RA → LV → PA, and LA → RV → aorta]. The spatial relationship of the great arteries supports the diagnosis of CCTGA; however, it should not be considered the sole diagnostic criterion .

77. The subcostal plane is used to define the atrial and visceral situs and the cardiac position . Twenty-five percent of patients with CCTGA have dextrocardia or mesocardia The subcostal views allow excellent imaging of the great arteries and their relationships to the ventricular chambers . From the subcostal coronal imaging plane, the parallel arrangement of the great arteries can be easily identified. In addition, the unique relationship of the LV outflow tract and the PA can be seen with pulmonary outflow tract deeply wedged between the right and left AV valves.

78. The apical four-chamber plane is extremely useful in the setting of CCTGA. In fact, the key anatomic feature of AV discordance is best visualized in the four-chamber plane . In this imaging plane, the septal hinge points of the AV valves are readily appreciated In situs solitus of the atria and concordant AV connections, the AV valve associated with the RA and RV will have a septal hinge that is displaced toward the apex when compared to the contralateral valve. In situs solitus of the atria and CCTGA, due to the discordant AV connection, it is the left-sided AV valve hinge point that is closer to the ventricular apex

79. The side-by-side relationship of the ventricles, more vertical orientation of the ventricular septum , and side-by-side relationship of the great arteries all make the parasternal long-axis views in CCTGA confusing. Unlike in the normal heart, the long axis in CCTGA is more vertically oriented. This allows easy confirmation of the parallel arrangement of the great arteries. The long-axis imaging plane is useful for evaluating the great artery relationships and for detecting the presence of outflow tract obstruction.

80. The short-axis imaging plane in the setting of CCTGA is also very helpful . The ventricular septum in CCTGA is more horizontally oriented than it is in the normal heart . At the level of the aortic and pulmonary valves, the relationship of the great arteries can be confirmed . In the majority of cases, the aortic valve will be leftward, anterior, and superior to the pulmonary valve. With slight superior angulation from the level of the aortic valve, the coronary arteries can be identified. In 85% of cases, the coronary arteries will be inverted. The coronary artery that arises from the left posterior– facing sinus has the epicardial distribution of a morphologic right coronary artery.

81. ABNORMALITIES OF VENTRICULAR NUMBER OR MORPHOLOGY

82. DILV exists when the greater part of both AV junctions is supported by the same ventricular chamber . Malformation likely originates embryologically from a partial or complete block in the left-to-right expansion process of the AV canal, resulting in connection of both atria to the primitive ventricle, which then forms the LV and a hypoplastic RV. In DILV, the hypoplastic RV lacks the inlet portion and has either a bipartite (trabecular and outlet) or monopartite (trabecular) morphology. Typically, both left and right AV valves have mitral valve morphology with deeper anterior leaflets and shallower posterior leaflets. Both AV valves lie posteriorly in fibrous continuity with a semilunar valve . Typically, the AV connections are committed to the dominant posterior LV . The inlet septum is absent and both AV valves are in close proximity to each other, posterior to the trabecular septum.

83. DOUBLE-INLET LEFT VENTRICLE WITH TRANSPOSED GREAT ARTERIES When there is a dominant LV and a hypoplastic RV, the ventriculoarterial connections are usually discordant . In this form of DILV, the aorta arises from the rudimentary RV or outlet chamber. This chamber is connected with the LV through a VSD, which is the embryologic remnant of the bulboventricular foramen . This is seen in approximately 85% of DILV cases. The aorta is usually leftward and anterior in position, with l-looping of the right ventricular outlet chamber There may be obstruction of the bulboventricular foramen and it may be associated with coarctation of aorta DOUBLE-INLET LEFT VENTRICLE WITH NORMALLY RELATED GREAT ARTERIES Concordant ventriculoarterial connection, or normally related great arteries, is less common (15%) in DILV. This arrangement is called the “Holmes heart.” The bulboventricular foramen is frequently quite stenotic and results in subpulmonary stenosis.

84. ECHOCARDIOGRAPHIC EVALUATION OF DOUBLE-INLET LEFT VENTRICLE SUBCOSTAL FOUR-CHAMBER (CORONAL) VIEW Abdominal and atrial situs should be determined in this view. In DILV, atrial situs is predominantly solitus , followed by right or left isomerism . The four-chamber view reveals the dominant left ventricle with both AV valves entering this chamber; one must angle the transducer anteriorly to see the rudimentary outlet chamber and great arteries. The number, size, and location of defects in the atrial septum should be assessed. Assessment of the atrial septum is particularly important in the setting of a restrictive or atretic AV valve. The origin and orientation of the two great arteries should be assessed. Ventriculoarterial connections are usually discordant with the aorta anterior and to the left of the PA , so that echocardiographic similarities to transposition exist.

85. SUBCOSTAL SHORT-AXIS (SAGITTAL) VIEW The subcostal short-axis view is useful for evaluation of atrial septal anatomy, visualization of the posterior LV receiving two AV valves, examination of the bulboventricular foramen , and confirmation of the arrangement of the great arteries. The two AV valves appear as two circles in the short-axis view; the leaflets touch each other when open in diastole if there is no stenosis. There is an anterior trabecular chamber that is not connected to the atrium. The communication of this anterior chamber with the LV is via the bulboventricular foramen, which is examined in this orthogonal plane to determine its size. In the presence of transposed great arteries, as is most common, the arteries have a parallel course at the base of the heart, with the posterior PA bifurcating. If the great arteries are normally related, the bulboventricular foramen is usually quite restrictive .

86. PARASTERNAL LONG-AXIS VIEW Parasternal long-axis imaging in DILV will demonstrate the posterior LV. With rightward/leftward angling of the transducer, it is seen that both AV valves enter this posterior left ventricular chamber. One must be careful not to confuse this anatomy with a VSD and enlarged LV, as typically only one AV connection is seen at a time. In DILV, one great artery will typically originate from the main ventricular chamber and the other great artery is seen more anteriorly, arising from the rudimentary outlet chamber. The bulboventricular foramen should be evaluated for anatomic size and evidence of restriction, again from multiple imaging planes with 2D/3D, spectral, and color Doppler interrogation. PARASTERNAL SHORT-AXIS VIEW Imaging from the parasternal short axis view shows both AV valves posterior to the trabecular septum which is oriented in a horizontal plane.

87. In DILV, the hypoplastic right ventricular outlet chamber is usually positioned anterosuperior and leftward to the morphologic LV. However, it can occasionally be rightward ; one must angle the transducer toward the base of the heart to visualize this relationship. A Doppler gradient is obtained in a parallel plane to the flow directed anteriorly through the bulboventricular foramen. Typically, the mean gradient will reflect the amount of obstruction more closely than the peak instantaneous gradient. Atrioventricular valves showing classic appearance of both the right (R) and left (L) atrioventricular valves committed to the LV

88. APICAL FOUR-CHAMBER VIEW The apical four-chamber scan plane provides the best view of the crux of the heart . In DILV, the dominant LV has fine apical trabeculations, two main papillary muscle groups, a smooth “septal” surface with no chordal attachments; it receives two AV valves. These two separate AV valves guard the AV junction; both typically have mitral morphology and are in continuity with the posterior great artery Ventricular systolic function and AV valve regurgitation can also be evaluated. The presence of left AV valve stenosis may require atrial septostomy or septectomy to relieve left atrial obstruction Angling anteriorly, the origin, relationship, and size of the great arteries can be evaluated. When the great arteries are transposed, the PA typically originates from the main left ventricular cavity with the anterior (usually leftward) aorta arising from the rudimentary outlet right ventricular chamber. One should also assess the size of the bulboventricular foramen from this plane . The suprasternal long-axis view demonstrates the aortic arch anatomy and the presence/absence of coarctation. If there is significant bulboventricular foramen obstruction, one should suspect arch obstruction—either coarctation or interruption of the aorta.

89. HYPOPLASTIC LEFT HEART SYNDROME (HLHS) Hypoplastic left heart syndrome (HLHS) is the fourth most common congenital cardiac anomaly of infancy,occurs twice as often in boys as in girls HLHS encompasses a heterogeneous group of cardiac malformations characterized by normally related great arteries and varying degrees of underdevelopment of the left heart–aorta complex , resulting in obstruction to systemic cardiac output and the inability of the left heart to support the systemic circulation. In HLHS, the systemic circulation is dependent on the RV and the ductus arteriosus. The aortic arch, ascending aorta, and coronary arteries are perfused by retrograde flow. Coarctation of the aorta is typically present.

90. Systemic and pulmonary flow ratios are dependent on the difference in resistance between the two respective vascular beds. A large, nonrestrictive interatrial communication in the setting of low pulmonary resistance promotes preferential flow into the pulmonary vascular bed at the expense of the systemic circulation. Pulmonary overcirculation and imbalance in the pulmonary/systemic vascular resistance ratio contribute to hemodynamic instability in infants with HLHS. The subcostal four-chamber view typically demonstrates a dilated RA and RV . When angling the transducer posteriorly and imaging toward the base of the LA, the LV either appears very small or is not visualized. It should be immediately apparent when the LV is diminutive or “slit-like” that a significant discrepancy in the size of the RV compared with the LV is present. Once this view is obtained,should evaluate the mitral valve and the great arteries very carefully. Anterior angulation of the transducer typically shows the dilated RVOT and main PA (MPA), but the very tiny aorta may be difficult to visualize in coronal plane imaging.

91. A large patent ductus arteriosus (PDA) may be seen, essentially representing a continuation of the MPA as the ductal arch, but this is better visualized in subcostal short-axis views . In the setting of cardiovascular collapse, right ventricular function may also be reduced, sometimes significantly so. Tricuspid regurgitation is usually present in this clinical setting. The atrial septum should be carefully evaluated from the subcostal windows. The size, number, and location of communications from LA to RA should be assessed. Bulging of the atrial septum from the LA into the RA is suggestive of restriction to egress from the LA. Bidirectional shunting is very unusual but may be seen in the presence of severe tricuspid regurgitation or anomalous venous connections.Should be alert to the possibility of anomalous connection and drainage of the pulmonary veins Subcostal short-axis views are excellent for interrogation of the atrial septum . The relative size of the very hypoplastic aorta posteriorly and dilated PA anteriorly is evaluated.

92. By angling the transducer rightward, the continuation of the dilated MPA as the ductal arch is easily demonstrated. Color Doppler interrogation may show bidirectional PDA shunting (typically right-to-left in systole with left-to-right shunting in diastole depending on pulmonary resistance characteristics). The entire aortic arch visualized in this view (with definitive imaging obtained from suprasternal imaging). Scanning toward the midventricular level shows the enlarged anterior RV and hypoplastic, posterior LV. Right ventricular function and tricuspid regurgitation should be assessed Parasternal long-axis views confirm the s ize discrepancy between the large RV anteriorly and the diminutive or small LV posteriorly. Careful examination for the slit-like, muscle-bound LV confirms that the anterior ventricle is the RV. The ventricular septum is most often intact. Right ventricular systolic function can be evaluated from the long-axis view.

93. Mitral and aortic valve leaflets should be examined for mobility or patency. The mitral annulus is characteristically hypoplastic with the mitral valve and its subvalvular apparatus appearing abnormal. If patent, the valve may be thickened and doming , with shortened chordae. A supravalvar mitral ring may also be present. The aortic valve is usually completely atretic but may be thickened and doming. Subaortic obstruction may be present. The size of the hypoplastic aortic annulus and ascending aorta (usually an internal diameter of less than 5 mm) is more easily measured in the parasternal long-axis view. The transducer is angled anteriorly and superiorly to evaluate the RVOT, the dilated MPA, and the ductal arch . Typically, the ductus is very large. Moving the transducer to a high left parasternal window may bring the large ductus/ductal arch into view more easily. Pulsed-wave Doppler is used to evaluate a ductal gradient in the setting of early ductal constriction as typically indicated by an increased systolic Doppler flow velocity through the PDA (> 2.5 m/s).

94. PARASTERNAL SHORT-AXIS VIEW In the parasternal short-axis view, there is a large anterior RV and small posterior LV. This view is also useful in the assessment of ventricular function, mitral valve size and morphology, and mitral papillary apparatus number and position . The mitral valve may be “parachutelike” in nature with a single papillary muscle group. Short-axis scans at the base of the heart allow assessment of the ascending aortic size in cross section and further evaluation of aortic valve morphology . The great arteries are normally related with the severely hypoplastic aorta in the center. The MPA is usually much dilated and the PDA is prominent. The branch PAs should be assessed in this view.

95. An apical four-chamber view provides comparison of the relative sizes of the ventricles. The RV is typically dilated and hypertrophied. The LV is small, muscle bound, and non-apex forming. The mitral valve annulus is usually hypoplastic with either an atretic opening or severely stenotic leaflets. If flow is present, one should assess the degree of stenosis from this view (taking into account that a larger interatrial communication may reduce the measured gradient). Furthermore, the mitral leaflet excursion may be limited in the presence of critical aortic stenosis or atresia, secondary to severely elevated left ventricular end-diastolic pressure. The transmitral gradient may also be artificially reduced in this setting. Short-axis view - D iminutive ascending Ao (arrow) and dilated pulmonary artery (PA) with trifurcation of branches into the right (R) and left (L) branch pulmonary arteries and large ductus arteriosus (D) .

96. ROLE OF 3-DIMENSIONAL ECHOCARDIOGRAPHY IN HYPOPLASTIC LEFT HEART SYNDROME Suprasternal long-axis scans provide an excellent view of the ascending aorta, aortic arch, and upper descending aorta. The ascending aortic size may range from mild to severely hypoplastic; however, the caliber of the aorta is much larger at the level of the innominate artery and beyond. Coarctation of the aorta is usually present . In the presence of a severe coarctation, there is a juxtaductal posterior ledge and increased distance between left common carotid and subclavian artery The presence of coarctation may be difficult to assess due to a severely dilated ductus arteriosus. An anterior ledge is common where the dilated ductus enters the descending aorta. Using color Doppler, the flow in the transverse aortic arch and ascending aorta is retrograde in the presence of critical aortic stenosis or atresia. A transient forward flow in the aortic arch in systole may be secondary to movement of the atretic aortic valve during systole