6: Cardiac valvular structure and function

Published on 02/03/2015 by admin

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Last modified 22/04/2025

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TOPIC 6 Cardiac valvular structure and function

Unidirectional flow of blood through the cardiac chambers is ensured by the presence of four cardiac valves which prevent backflow. Normal structure and function of the aortic, mitral, pulmonary and tricuspid valves is described, followed by normal values for the common prosthetic valves.

Table 6.1 Normal values for mean and peak gradients and valve area for the four heart valves

Aortic valve disease

Aortic stenosis

It is important to remember that these peak gradients/velocities depend upon preserved left ventricular systolic function. In the setting of impaired left ventricular function, acceleration of ejected blood from the LVOT (subvalvular) to AV by greater than four times (the dimensionless

Table 6.2 Echocardiographic parameters for grading the severity of aortic stenosis

index) is suggestive of significant aortic stenosis, and dobutamine stress echocardiography is indicated.

Figure 6.1 Example of severe aortic stenosis demonstrated using transaortic continuous wave Doppler

Aortic regurgitation

Table 6.3 Echocardiographic parameters for grading severity of aortic valve regurgitation

Figure 6.2 Example of moderate–severe aortic regurgitation. (A) Continuous wave Doppler tracing demonstrating pressure half time. (B) Colour Doppler and (C) colour M-mode demonstrating the size of the regurgitant jet relative to the aortic valve orifice and left ventricular outflow tract.

Mitral stenosis

Table 6.4 Echocardiographic parameters for grading severity of mitral valve stenosis

Figure 6.3 Pulse wave Doppler images demonstrating transmitral diastolic flow in patients with severe mitral stenosis. (A) Example in sinus rhythm. (B) Example in atrial fibrillation, when the mean pressure gradient from several cardiac cycles is required.

Figure 6.4 Schematic demonstrating (A) left atrial and left ventricular pressure tracings during normal, mild, moderate and severe mitral stenosis; and (B) heart sounds and murmurs heard on auscultation of the normal heart, and hearts with mild and severe mitral stenosis.

Mitral regurgitation

Table 6.5 Echocardiographic parameters for grading severity of mitral valve regurgitation

Figure 6.5 Severe mitral regurgitation. (A) Continuous wave Doppler tracing of MR jet with measurement of the velocity time integral (VTI). (B, C) Examples of PISA measurement using colour Doppler at the mitral valve regurgitant orifice.

Pulmonary stenosis

PS is diagnosed when peak jet velocity is >3 m/s, corresponding to a peak PV gradient of 36 mmHg.

Moderate PS peak gradient 40–74 mmHg

Severe PS peak gradient >75 mmHg

Pulmonary regurgitation

Treatment of PR is currently based on symptoms rather than severity scales, although other factors including RV function and QRSD are important variables in timing replacement.

Table 6.6 Echocardiographic parameters for grading severity of pulmonary valve regurgitation

Tricuspid stenosis

Normal TV area is ~7.0 cm².

Severe tricuspid stenosis is rare, and is diagnosed when the TV area is less than 1 cm², resulting in a pressure drop of >5 mmHg.

Tricuspid regurgitation

Tricuspid regurgitation is relatively common, reflecting tricuspid annular dilatation secondary to right ventricular dilatation as a result of pulmonary hypertension.

The peak velocity of the TR jet can be used as an indirect measure of PA pressure, as it reflects the pressure difference between the RV and RA.

Table 6.7 Echocardiographic parameters for grading severity of tricuspid valve regurgitation

Prosthetic heart valves

Mechanical – caged ball, monoleaflet, bileaflet

Biological – stented, stentless, percutaneous

Size chosen to provide the largest effective orifice area (EOA) in relation to the patient’s valve annulus size.

Normal reference values of EOAs are presented in Table 6.8 for aortic valve prostheses, and in Table 6.9 for mitral valve prostheses. Threshold for prosthetic valve ? patient mismatched sizing are presented in Table 6.10.

Table 6.8 Effective orifice area values for the different sizes of commonly used aortic valve prostheses

Table 6.9 Effective orifice area values for the different sizes of commonly used mitral valve prostheses

Table 6.10 Threshold values of body surface area-indexed prosthetic valve EOA for diagnosis of prosthesis–patient mismatch (PPM)

Percutaneous aortic valve bioprostheses

Edwards-Sapien – 23 mm and 26 mm

CoreValve bioprostheses exists in two sizes according to the ascending aortic diameter (<35 mm or <45 mm) and one size for the aortic annulus (23 mm).

Figure 6.6 Edwards-Sapien Transcatheter Percutaneous Aortic Valves: 26 mm (left) and 23 mm (right).

Courtesy of Edwards-Sapien.

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