Three-Dimensional Visualization of Anatomy

Instead of 2D tomographic images, current 3D techniques allow real-time representation of intracardiac structures, which aids in the understanding of cardiac morphology even in simple heart defects. By combining cropping and the multiplanar review modes, the operator can “slice” the heart in an anatomically appropriate plane to view the structures of interest in an appropriate orientation. Views that help in surgical understanding and planning can be created.

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).

Figure 15-1 A, Atrial septal defect viewed from the right atrium. Three-dimensional echocardiography more clearly demonstrates the defect’s margins and shape. The asterisk notes the septal defect. B, Atrial septal defect in a 4-year-old girl. The defect is viewed en face from the left atrial side, demonstrating its irregular margins. Both patients presented with incidental findings of murmurs and were asymptomatic but had significant right ventricular dilation. Both proceeded to elective closure of the defect via cardiac catheterization (see Video 15-1). IVC, inferior vena cava; LV: left ventricle; LVOT: left ventricular outflow tract; SVC, superior vena cava.

Figure 15-2 A, Perimembranous ventricular septal defect (VSD; asterisk) viewed from the left ventricle. This image is from a 6-month-old infant who had a routine echocardiogram performed as part of an investigation for dysmorphism with a possible genetic cause. This defect is small and does not cause symptoms or heart failure; a conservative management approach was therefore taken (see Video 15-2). B, Perimembranous VSD (asterisk) from a 2-year-old boy born prematurely at 34 weeks’ gestation who had a murmur detected while in the neonatal unit. This image demonstrates the relationship of the VSD to the tricuspid valve, by which it is partially shrouded (arrow, tricuspid valve tissue). The patient was asymptomatic and the VSD restrictive. Surgery is currently not planned (see Video 15-3). C, Subcostal view of a VSD (asterisk) with partial override of the aortic valve (AV) in a 4-month-old infant with tetralogy of Fallot diagnosed after birth. The dotted line marks the plane of the ventricular septum. This patient had elective surgical repair at the age of 5 months without complications (see Video 15-4). LA, left atrium; LV, left ventricle; LVOT, left ventricular outflow tract; RV, right ventricle.

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.