**6. Ecocardiographic anatomy**

The aortic valve leaflet is a three-layered structure (lamina ventricularis, lamina spongiosa and lamina fibrosa) composed of differing amounts of collagen, elastin, and glycosamino‐ glycans, that form a well-defined honeycomb or spongelike structure, suggesting that elastin forms a matrix that surrounds and links the collagen fiber bundles. [35] The leaflets are cov‐ ered by a continuous layer of endothelial cells with a smooth surface on the ventricular side and numerous ridges on the arterial side. The arrangement of the endothelial cells is across,

A thorough knowledge of the anatomy of the aortic valve and its relations to the surround‐ ing cardiac structures is a prerequisite for the successful completion of the repair or replace‐

Surgical descriptions of the aortic root are not always similar with the anatomical descrip‐ tions, leading to a series of confusional data. Also the in vivo measurement of the valve components don't always correspond to the ex vivo measurements, in part due to the move‐

By sequentially following the line of attachment of each leaflet, the relationship of the aortic valve to its surrounding structures can be clearly understood. Beginning posterior‐ ly, the commissure between the noncoronary and left coronary leaflets is positioned along the area of aorto-mitral valvular continuity. The fibrous subaortic curtain is be‐ neath this commissure. To the right of this commissure, the noncoronary leaflet is attach‐ ed above the posterior diverticulum of the left ventricular outflow tract. Here the valve is related to the right atrial wall. As the attachment of the noncoronary leaflet ascends from its nadir toward the commissure between the noncoronary and right coronary leaf‐ lets, the line of attachment is directly above the portion of the atrial septum containing the atrioventricular node. The commissure between the noncoronary and right coronary leaflets is located directly above the penetrating atrioventricular bundle and the membra‐ nous ventricular septum. The attachment of the right coronary leaflet then descends across the central fibrous body before ascending to the commissure between the right and left coronary leaflets. Immediately beneath this commissure, the wall of the aorta forms the uppermost part of the subaortic outflow. An incision through this area passes into the space between the facing surfaces of the aorta and pulmonary trunk. As the fac‐ ing left and right leaflets descend from this commissure, they are attached to the outlet muscular component of the left ventricle. Only a small part of this area in the normal heart is a true outlet septum, since both pulmonary and aortic valves are supported on their own sleeves of myocardium. Thus, although the outlet components of the right and left ventricle face each other, an incision below the aortic valve enters low into the infun‐ dibulum of the right ventricle. As the lateral part of the left coronary leaflet descends

not in line with the direction of flow. [36]

**5. Surgical anatomy**

44 Calcific Aortic Valve Disease

ment performed by the surgeon.

ment of the heart and its structures during the cardiac cycle.

The ability to record high-quality echocardiographic images and obtain accurate Doppler flow recordings are essential determinants of the overall value of the echocardiographic ex‐ amination. As such, echocardiography is highly operator dependent. It is difficult to over‐ emphasize the critical role of the person who performs the imaging. To obtain a comprehensive and accurate echocardiogram, the echocardiographer must understand the anatomy and physiology of the aortic valve and have a thorough knowledge of the ultra‐ sound equipment to optimize the quality of the recording. [38]

#### **6.1. Transthoracic Echocardiography (TTE)**

Anatomic evaluation of the aortic valve is based on a combination of short- and long-axis images to identify the number of leaflets, and to describe leaflet mobility, thickness, and cal‐ cification.

Two-dimensional imaging of the normal aortic valve in the parasternal long axis view dem‐ onstrates two leaflets (right and noncoronary), while the parasternal short axis demonstrates a symmetrical structure with three uniformly thin leaflets that open equally, forming a cir‐ cular orifice during most of systole. During diastole, the normal leaflets form a three pointed star with a slight thickening or prominence at the central closing point formed by the aortic leaflet nodules, known as the nodules of Arantius. The three aortic valve leaflets may also be visualized in a subcostal view.

The aortic valve leaflets appear thin and delicate and may be difficult to visualize. In the long-axis view, the leaflets open rapidly in systole and appear as linear parallel lines close to the walls of the aorta. With the onset of diastole, they come together and are recorded as a faint linear density within the plane of the aortic annulus. Because the velocity of valve mo‐ tion during opening and closing is high relative to the frame rate of most echocardiographic systems, the normal aortic valve is usually visualized either fully opened or closed but rare‐ ly in any intermediate position. In the basal short-axis view, the three aortic leaflets can be visualized within the annulus during diastole. The three lines of coaptation can be recorded, normally forming a Y (sometimes referred to as an inverted Mercedes-Benz sign). With the onset of systole, the leaflets open out of the imaging plane, providing a view of the aortic annulus. The short-axis perspective is most helpful to determine the number of leaflets and whether fusion of one or more commissures is present. In patients who are difficult to im‐ age, normal leaflets are so delicate that they are hard to visualize, generally an indication that they are morphologically normal. [38]

**Figure 8.** Transthoracic echocardiogram, parasternal long axis view. Aortic valve is open (author's collection).

**Figure 10.** Transthoracic echocardiogram, suprasternal view. Aortic valve is open (author's collection).

Anatomy and Function of Normal Aortic Valvular Complex

http://dx.doi.org/10.5772/53403

47

**Figure 11.** Transthoracic echocardiogram, suprasternal view. Aortic valve is closed (author's collection).

**Figure 9.** Transthoracic echocardiogram, parasternal long axis view. Aortic valve is closed (author's collection).

**Figure 10.** Transthoracic echocardiogram, suprasternal view. Aortic valve is open (author's collection).

**Figure 8.** Transthoracic echocardiogram, parasternal long axis view. Aortic valve is open (author's collection).

46 Calcific Aortic Valve Disease

**Figure 9.** Transthoracic echocardiogram, parasternal long axis view. Aortic valve is closed (author's collection).

**Figure 11.** Transthoracic echocardiogram, suprasternal view. Aortic valve is closed (author's collection).

### **6.2. Transesophageal Echocardiography (TEE)**

Transthoracic imaging usually is adequate, although TEE may be helpful when image quali‐ ty is suboptimal.

**6.3. Three-Dimensional Echocardiography (3DE)**

structures from any spatial point of view.

(zoomed or full-volume acquisition).

que plane.

3DE represents a major innovation in cardiovascular ultrasound. Advancements in comput‐ er and transducer technologies permit real-time 3DE acquisition and presentation of cardiac

Anatomy and Function of Normal Aortic Valvular Complex

http://dx.doi.org/10.5772/53403

49

A complete 3D TTE exam requires multiple acquisitions from the parasternal, apical, sub‐ costal, and suprasternal transducer positions. Because the volume-rendered 3D data set can be cropped to display a variety of intracardiac structures by choosing different cut planes as an alternative to ''view'' (referred to heart's orientation to the body axis), ''anatomic planes''

For the visualization of the aortic valve the 3DE TTE protocol is the parasternal long-axis view with and without color (narrow angle and zoomed acquisitions) and the 3DE TEE pro‐ tocol is the 60º mid-esophageal, short-axis view with and without color (zoomed or full-vol‐ ume acquisition) and the 120º mid-esophageal, long-axis view with and without color

The common approaches for imaging the aortic valve by 3D TTE are from the parasternal and apical views. Three-dimensional data sets including the aortic root can be cropped and rotated for a dynamic 3D rendering of the aortic valve, which can be visualized from both the aortic and ventricular perspectives, as well as sliced in any desired longitudinal or obli‐

**Figure 12.** Three-dimensional TEE data set cropped to demonstrate the aorta in long axis (A, top). Using this image, in face views of the sinotubular junction (A, bottom left), sinus of Valsalva (A, bottom middle), and aortic annulus (A, bottom right) can be obtained for assessment. Dynamic, automatic tracking of the aortic valve leaflets (B, top left) and annulus (B, top right) can be performed, providing aortic valve area throughout the cardiac cycle (B, middle left and

bottom strip). A model derived from the automated tracking is also produced (middle right). [41]

(referred to the heart itself) can be used to describe image orientation. [40]

To characterize the aortic valve using TEE, the valve should be imaged in short-axis view (the aortic valve can generally be visualized in a plane between 30 to 60º from the transverse 0º) and long-axis view (typically at 120 to 160° from transverse 0º).

The short-axis view is the only view that provides a simultaneous image of all three leaflets. The leaflet adjacent to the atrial septum is the noncoronary leaflet, the most an‐ terior is the right coronary leaflet, and the other is the left coronary leaflet. The probe is withdrawn or anteflexed slightly to move the imaging plane superiorly through the sinuses of Valsalva to bring the right and left coronary ostia and then the sinotubular junction into view. The probe is then advanced to move the imaging plane through and then proximal to the AV annulus to produce a short axis view of the left ventricular outflow tract. The mid esophageal short-axis view at the level of the leaflets is used to measure the length of the free edges of the leaflets and the area of the aortic valve ori‐ fice by planimetry.

In the long axis view, the left ventricular outflow tract appears toward the left of the display and the proximal ascending aorta toward the right. The leaflet that appears an‐ teriorly or toward the bottom of the display is always the right coronary, but the leaflet that appears posteriorly in this cross-section may be the left or the noncoronary, de‐ pending on the exact location of the imaging plane as it passes through the valve. The mid esophageal long-axis view is the best cross-section for assessing the size of the aortic root by measuring the diameters of the annulus, sinuses of Valsalva, sinotubular junction and proximal ascending aorta, adjusting the probe to maximize the internal di‐ ameter of these structures. The diameter of the annulus is measured during systole at the points of attachment of the aortic valve leaflets to the annulus and is normally be‐ tween 1.8 and 2.5 cm.

The deep transgastric view is obtained by advancing the probe deep into the stomach and positioning the probe adjacent to the left ventricular apex. The exact position of the probe and transducer is more difficult to determine and control deep in the stomach, but some tri‐ al and error flexing, turning, advancing, withdrawing, and rotating of the probe develops this view in most patients. In the deep transgastric long-axis view, the aortic valve is located in the far field at the bottom of the display with the left ventricular outflow tract directed away from the transducer. Detailed assessment of valve anatomy is difficult in this view be‐ cause the left ventricular outflow tract and aortic valve are so far from the transducer, but Doppler quantification of flow velocities through these structures is usually possible. [39]

The TEE examination is also performed intraoperative to refine and confirm preoperative diagnosis, to assess the etiology and severity of aortic valve disease, to measure the annulus and to prepare the surgeon for other alternatives.

#### **6.3. Three-Dimensional Echocardiography (3DE)**

**6.2. Transesophageal Echocardiography (TEE)**

0º) and long-axis view (typically at 120 to 160° from transverse 0º).

ty is suboptimal.

48 Calcific Aortic Valve Disease

fice by planimetry.

tween 1.8 and 2.5 cm.

and to prepare the surgeon for other alternatives.

Transthoracic imaging usually is adequate, although TEE may be helpful when image quali‐

To characterize the aortic valve using TEE, the valve should be imaged in short-axis view (the aortic valve can generally be visualized in a plane between 30 to 60º from the transverse

The short-axis view is the only view that provides a simultaneous image of all three leaflets. The leaflet adjacent to the atrial septum is the noncoronary leaflet, the most an‐ terior is the right coronary leaflet, and the other is the left coronary leaflet. The probe is withdrawn or anteflexed slightly to move the imaging plane superiorly through the sinuses of Valsalva to bring the right and left coronary ostia and then the sinotubular junction into view. The probe is then advanced to move the imaging plane through and then proximal to the AV annulus to produce a short axis view of the left ventricular outflow tract. The mid esophageal short-axis view at the level of the leaflets is used to measure the length of the free edges of the leaflets and the area of the aortic valve ori‐

In the long axis view, the left ventricular outflow tract appears toward the left of the display and the proximal ascending aorta toward the right. The leaflet that appears an‐ teriorly or toward the bottom of the display is always the right coronary, but the leaflet that appears posteriorly in this cross-section may be the left or the noncoronary, de‐ pending on the exact location of the imaging plane as it passes through the valve. The mid esophageal long-axis view is the best cross-section for assessing the size of the aortic root by measuring the diameters of the annulus, sinuses of Valsalva, sinotubular junction and proximal ascending aorta, adjusting the probe to maximize the internal di‐ ameter of these structures. The diameter of the annulus is measured during systole at the points of attachment of the aortic valve leaflets to the annulus and is normally be‐

The deep transgastric view is obtained by advancing the probe deep into the stomach and positioning the probe adjacent to the left ventricular apex. The exact position of the probe and transducer is more difficult to determine and control deep in the stomach, but some tri‐ al and error flexing, turning, advancing, withdrawing, and rotating of the probe develops this view in most patients. In the deep transgastric long-axis view, the aortic valve is located in the far field at the bottom of the display with the left ventricular outflow tract directed away from the transducer. Detailed assessment of valve anatomy is difficult in this view be‐ cause the left ventricular outflow tract and aortic valve are so far from the transducer, but Doppler quantification of flow velocities through these structures is usually possible. [39]

The TEE examination is also performed intraoperative to refine and confirm preoperative diagnosis, to assess the etiology and severity of aortic valve disease, to measure the annulus

3DE represents a major innovation in cardiovascular ultrasound. Advancements in comput‐ er and transducer technologies permit real-time 3DE acquisition and presentation of cardiac structures from any spatial point of view.

A complete 3D TTE exam requires multiple acquisitions from the parasternal, apical, sub‐ costal, and suprasternal transducer positions. Because the volume-rendered 3D data set can be cropped to display a variety of intracardiac structures by choosing different cut planes as an alternative to ''view'' (referred to heart's orientation to the body axis), ''anatomic planes'' (referred to the heart itself) can be used to describe image orientation. [40]

For the visualization of the aortic valve the 3DE TTE protocol is the parasternal long-axis view with and without color (narrow angle and zoomed acquisitions) and the 3DE TEE pro‐ tocol is the 60º mid-esophageal, short-axis view with and without color (zoomed or full-vol‐ ume acquisition) and the 120º mid-esophageal, long-axis view with and without color (zoomed or full-volume acquisition).

The common approaches for imaging the aortic valve by 3D TTE are from the parasternal and apical views. Three-dimensional data sets including the aortic root can be cropped and rotated for a dynamic 3D rendering of the aortic valve, which can be visualized from both the aortic and ventricular perspectives, as well as sliced in any desired longitudinal or obli‐ que plane.

**Figure 12.** Three-dimensional TEE data set cropped to demonstrate the aorta in long axis (A, top). Using this image, in face views of the sinotubular junction (A, bottom left), sinus of Valsalva (A, bottom middle), and aortic annulus (A, bottom right) can be obtained for assessment. Dynamic, automatic tracking of the aortic valve leaflets (B, top left) and annulus (B, top right) can be performed, providing aortic valve area throughout the cardiac cycle (B, middle left and bottom strip). A model derived from the automated tracking is also produced (middle right). [41]

Real-Time 3D can be realized by obtaining a TEE 2D image of the aortic valve at either the 60º midesophageal, short-axis view or the 120º midesophageal, long-axis view. After the 2D image is optimized, narrow-angled acquisitions can be used to optimize the 3D image and to examine aortic valve and root anatomy. After acquisition, the aortic valve should be ori‐ ented with the right coronary cusp located inferiorly, regardless of whether the aortic or the left ventricular outflow tract perspective is presented.

A study of 100 formalin-fixed hearts from adult patients with normally functioning aortic valves found that the luminal area of the aorta at the sinotubular junction increased with age and with heart weight, where increased heart weight was attributed to systemic hyperten‐ sion. [45] Volume-wise, the sinuses are largest when the valve closes, serving as reservoirs

Anatomy and Function of Normal Aortic Valvular Complex

http://dx.doi.org/10.5772/53403

51

When left ventricular pressure exceeds that in the aortic root, the valvular leaflets are pushed apart and fall back into their respective sinuses, allowing unimpeded ejection of blood. The orifices of the coronary arteries are commonly found close to the level of

In the new era of cardiac surgery, now more then ever, the need to further study the aortic

A thorough knowledge of the anatomy of the aortic valve and its relationships is essen‐ tial to understanding aortic valve pathology and many congenital cardiac malforma‐ tions. Also it is crucial for the diagnosis and treatment (both surgical and conservatory)

Accurate understanding of the anatomy of interest is of cardinal importance for the develop‐ ment of devices and treatment protocols. We emphasize the importance of considering ana‐ tomic variations in the development of treatments, an understanding of the intraindividual and interindividual variations that may exist can lead to refinements in current designs of

Although the aortic valve is the most intensely studied cardiac valve, there is still no consen‐ sus on how to describe its components and a universal terminology is yet to be found. The multidisciplinary approach will continue to be crucial in working through these challenges.

1 Internal Medicine Clinic, Division of Cardiology, University of Medicine and Pharmacy

2 Infectious Disease Clinic, University of Medicine and Pharmacy Tirgu Mures, Romania

3 Cardiology Clinic, Emergency Clinical County Hospital Tirgu Mures, Romania

, Cristina Maria Tatar1

, Mihaela Ispas3

and

during ventricular diastole and allow filling of the coronary arteries.

the sinotubular junction. [25]

of aortic valve pathology.

valvular prostheses.

**Author details**

, Horatiu Suciu3

Razvan Constantin Serban3

Tirgu Mures, Romania

, Brindusa Tilea2

Ioan Tilea1

valve complex anatomy and function is greater.

**8. Conclusion**

Color Doppler 3D TEE imaging should also be performed to detect the initial appearance of flow at the onset of systole. [41]
