Aortic Valve Anatomy
The recent revolution in the field of interventional cardiology, particularly percutaneous transcatheter aortic valve interventions (TAVR) has led to better understanding of the complex anatomy of aortic valve apparatus. The aortic valve is composed of three semilunar cusps attached to the aortic root. It is important to understand that the function of the aortic valve depends on the integrity of the aortic root, which refers to the region between the aortic valve junction at the left ventricular outflow tract (LVOT), known as the ventriculo-arterial junction, to the sinotubular junction at the origin of the proximal ascending thoracic aorta. Any anatomical changes of the aortic root can adversely affect the function of the aortic valve. For instance, dilatation of the aortic root and ascending aorta can lead to aortic regurgitation despite intact aortic valve leaflets.
The main advantage of 3D echocardiography over conventional 2D modality, its ability to acquire the entire aortic valve and surrounding structures in 3D dataset, which allows visualization of the aortic valve in en face view from different perspectives and facilitates cropping in multiplanar reconstruction mode. The use of 3D echocardiography can provide accurate assessment of the aortic valve morphology and eliminates any geometric assumptions of the LVOT, aortic annulus and root measurements. In general, transthoracic 3D imaging of the aortic valve remains challenging in many cases, yet is feasible and the image quality has improved dramatically with newer 3D echocardiography machines. Using transthoracic 3D matrix-array transducer, the aortic valve can be imaged from both parasternal and apical views. For anatomic assessment of the aortic valve, live 3D or 3D zoom acquisition modes are the preferred imaging modes. Adding 3D color Doppler is used to assess for aortic regurgitation and cusp integrity. Suboptimal 3D transthoracic echocardiography (TTE) images usually occur in patients with poor acoustic windows or heavily calcified aortic valve. In these cases, the use of 3D transesophageal echocardiography (TEE) can provide better image quality with superior spatial resolution and the first report describing its utility in planimetry of the aortic valve orifice area in a patient with aortic stenosis was published as early as 1994 (Figure 1).6 Clinical live/real time 3DTEE was first introduced several years later in 2007.7 Transthoracic and transesophageal 3D dataset of the aortic valve can be processed and displayed from both aortic and ventricular perspectives, which improves the diagnostic accuracy and helps guide interventional procedures. The use of multiplanar reconstruction mode is very useful in obtaining accurate measurements of the aortic valve area, aortic annulus dimensions, and aortic root size when planning for TAVI or other interventional procedures.