AORTIC VALVE AORTIC VALVE PROSTHESISPROSTHESIS

Basic Types of Artificial Heart Valves

Mechanical – made of synthetic material

Tissue valve – made from animal tissues called xenograft or taken from the human tissue of a donated heart (called allograft or homograft).

2D: May identify leaflet thickness,

calcification, leaflet motion, thrombus, dehiscence, vegetation.

Evaluated left ventricular function.

Assessment of APV in Echo

2D Echo

Helpful in evaluating for the complications of mechanical valve although reverberations make the diagnosis difficult.

Can identify gross structural abnormalities of a prosthesis such as dehiscence, vegetations, thrombus or degeneration.

Difficulties in 2D Echo

Echo reflectance of the prosthetic material attenuation of the ultrasound beam and multiple ultrasound reverberations from the prosthesis result in difficulties in interpretation.

TEE may be able to visualize normal and abnormal prosthetic valve motion.

Doppler: Determine the peak velocity. Determine the maximum pressure gradient

> 45MmmHg may be abnormal. Determine the mean pressure gradient

> 25mmHg may be abnormal. Determine the AV area using CE. Presence and severity of aortic

regurgitation. A paravalvular leak is abnormal.

Assessment of AVP in Echo

Calculation of EOA

AParea = LVOT area x LVOT VTI X AP VTI

= SRODdiam.2 x 0.785 x LVOT VTI/AP VTI

(may not be used if significant regurgitation

of aortic or mitral valve is present)

0.785 X (LVOTdiam.)2 . X LVOT VTI

AV VTI

Continuity Equation

Aortic ValveAortic Valve AbnormalAbnormal

Peak pressure gradient > 45mmHgPeak pressure gradient > 45mmHg

Mean pressure gradient > 25mmHgMean pressure gradient > 25mmHg

Aortic valve area < 1.0cm2 Aortic valve area < 1.0cm2

Velocity ratio < 0.35Velocity ratio < 0.35

Aortic regurgitation > mildAortic regurgitation > mild

Normal Doppler Data for Prosthetic Aortic Valves

Mean Gradient

Valve Type Size (mm) Vmax (m/s) (mmHg) AVA (cm2)

Mechanical valves

Bileaflet (St. Jude) 19 3.0(2.0-4.5) 20 (10-30) 1.0

21 2.7 (2.5-3.5) 14 (10-30) 1.3

23 2.5 (2.0-3.5) 12 (10-30) 1.3

25 2.4 (2.0-3.5) 12 (5-30) 1.8

Tilting disk (bjork-Shiley, 19 21 ± 7

Medtronic Hall 21 2.8 ± 0.9 16

23 2.6 ± 0.4 14 ± 5

25 2.1 ± 0.3 13 ± 3

Ball-cage (Starr-Edwards) 3.1 ± 0.5 24 ± 4

Tissue Valves

Stented porcine tissue 19 2.8 ± 0.7 16 ± 2 1.5 ± 0.1

(Handcock or 21 2.6 ± 0.4 15 ± 6 1.8 ± 0.2

Carpentier -Edwards) 23 2.6 ± 0.4 13 ± 6 2.1 ± 0.2

25 2.5 ± 0.4 11 ± 2

Pericardial Valve (CEPerimount) 1.5 ± 0.9 4.4 ± 1.8 2.5 ± 0.6

Mosaic valve (Medtronic) 2.3 ± 1.2 12 ± 3

23 mm

Nonstended tissue valves

SPV-Toronto (St. Jude) 2.2 ± 0.4 3 (2-20) 1.8-2.3

Ao-homograft 1.8 ± 0.4 7± 3 2.2 (1.7-3.1)

TEE may be visualize normal and abnormal motion of a prosthetic valve.

The most accurate method for detecting and quantifying the degree of prosthetic obstruction is doppler Echo.

Increased flow velocity does not always indicate prosthetic obstruction. Can be increased without stenosis in high-output state and in the presence of severe prosthetic regurgitation.

Complications

Calcifications Infective endocarditis Paravalvular leak Dehiscence Thrombus Stenosis Regurgitation

Case of DVR

AV – well seated metallic prosthesis with residual moderate AS and mild AR.

Continuity Equation

0.785 X (1.8)2 X 30 =

0.94

81

Advantage of Mechanical Prosthesis

Excellent durability.Disadvantage Tendency for blood to clot.

Advantage of Tissue Valve Prosthesis Do not require the use of anticoagulant drugs due to the improved blood flow

dynamics resulting in less red cell clot formation.

Disadvantage Limited lifespan.

Obstruction The obstruction of an aortic mechanical

prosthesis is caused more frequently by pannus formation (fibrous ingrowth tissue which may lead to regurgitation or stenosis).

When a prosthetic valve becomes obstructed, the motion of the disk, ball or leaflets decreased.

However, it is difficult to visualize & more difficult to quantify the restriction of excursion with 2D.

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