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.