Chapter 15 Congenital Heart Disease
In patients with congenital heart disease, a complete and accurate description of the morphologic abnormalities is crucial for determining appropriate management strategies. Currently, two-dimensional echocardiography (2DE) allows a complete description of the intracardiac anatomy of different congenital lesions. Because of its high spatial and temporal resolution, 2DE is still the mainstay technique for the diagnosis and follow-up of patients with congenital defects. However, the representation of a three-dimensional (3D) structure by a 2D technique has intrinsic limitations, which explains why 3DE, particularly real-time (RT) 3DE, has potential applications in congenital heart disease. The development of RT3DE with matrix transducers and a high-frequency pediatric matrix 3D transducer has especially sparked growth and interest in the congenital field. RT3DE has emerged as a valuable additional tool because it provides a direct representation of morphology and volumetric calculations. The real additional diagnostic value still remains to be proven, but recently published data suggest potential use in the following three areas1:
1. Improved visualization and understanding of the 3D nature of congenital heart defects
Three-Dimensional Visualization of Anatomy
Atrial and Ventricular Septa
Atrial and ventricular septal defects typically are not circular “holes,” but instead are complex structures, often irregularly shaped or fenestrated, that are difficult to visualize in two dimensions. RT3DE enables improved visualization of septal defects using unique en face representations of the interatrial and interventricular septa. The interatrial septum can be represented as viewed from the left or right atrium and the interventricular septum as viewed from the left or right ventricular side. This allows the creation of surgical views of the defects as well as improved understanding of their shape and relationships to surrounding intracardiac structures. These views also allow a more accurate measurement of defect size, including their dynamic shape change during the cardiac cycle.2–4 The importance of viewing the defects from both sides of the septum cannot be overemphasized; this aids in understanding their anatomy and particularly facilitates the determination of both the right and left border edges and shapes.5 These measurements are useful for surgical or interventional planning in the catheterization laboratory (Figures 15-1 and 15-2; Videos 15-1 to 15-3).
Atrioventricular Valves
Transthoracic RT3DE is complementary to 2D transesophageal echocardiography (2DTEE) and 2D transthoracic echocardiography (2DTTE) in detecting anatomic and functional abnormalities of atrioventricular (AV) valves in patients with congenital heart disease.6–8 This is mainly due to the unique 3D visualization and representation of the AV valves. RT3DE facilitates viewing of the mitral valve with its complex annular shape and interactions with the left ventricular shape and function and the subchordal apparatus.7,9 RT3DE also facilitates increased understanding of the maturation of the dynamic function of the mitral valve. The mitral valve is saddle shaped, and its motion and dynamic function during the cardiac cycle are complex. In adults, the mitral valve annulus has its largest dimension at end systole and is smallest at end diastole.10,11 However, RT3DE has demonstrated that in children, the mitral annular motion is somewhat different and that it has its largest area in systole and decreases in diastole.12,13 The main advantage of 3DE is that the individual scallops of the mitral valve can be imaged in the same view, which helps define the surgical anatomy and enhances communication between the echocardiographer and the surgeon.
RT3DE has a clear advantage for imaging the tricuspid valve because the three leaflets are very difficult to view together by cross-sectional imaging. For congenital abnormalities of the tricuspid valve, RT3DE can be useful for a better representation of the valvar anatomy. A typical example is imaging of the tricuspid valve in Ebstein’s anomaly. In this lesion, RT3DE can provide better visualization of the morphology of the tricuspid valve leaflets, their attachments, their degree of coaptation, and the mechanism of regurgitation.14 The multiplanar review mode also facilitates appreciation of the degree of displacement and rotation of the tricuspid valve annulus, which is the key feature of this anomaly.7 Potentially, RT3DE could also help determine the right ventricular stroke volume, although no validation data on right ventricular volumes have been published yet in this disease (Figures 15-2 to 15-5; Videos 15-2 to 15-9).
Atrioventricular Septal Defects
Patients with AV septal defects have a common AV junction with a single AV valve at the entrance of both ventricles. RT3DE can provide clear visualization of the anatomic variability, which is crucial in the preoperative planning. Studies have demonstrated that RT3DE can provide additional anatomic information to cross-sectional imaging in patients before and after surgical repair.15–17 In preoperative assessment, the anatomy of the superior and inferior bridging leaflets, as well as that of the left-sided mural leaflet, provides useful clinical information. In postoperative patients with residual AV valve regurgitation, the mechanisms contributing to the regurgitation can be complex, and RT3DE can be useful in clarifying the origin of the regurgitant jets and in guiding surgical decision making by demonstrating defects such as residual cleft, central regurgitation, leaflet prolapse, dysplasia, annular dilation, and so on (Figures 15-6 and 15-7; Videos 15-10 to 15-12).