Presentation on theme: "AORTIC VALVE PROSTHESIS. Basic Types of Artificial Heart Valves Mechanical – made of synthetic material Tissue valve – made from animal tissues called."— Presentation transcript:
AORTIC VALVE PROSTHESIS
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 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 Valve Abnormal Aortic Valve Abnormal Peak pressure gradient > 45mmHg Peak pressure gradient > 45mmHg Mean pressure gradient > 25mmHg Mean pressure gradient > 25mmHg Aortic valve area < 1.0cm2 Aortic valve area < 1.0cm2 Velocity ratio < 0.35 Velocity ratio < 0.35 Aortic regurgitation > mild Aortic regurgitation > mild
Normal Doppler Data for Prosthetic Aortic Valves Mean Gradient Valve TypeSize (mm)Vmax (m/s)(mmHg)AVA (cm2) Mechanical valves Bileaflet (St. Jude)193.0( )20 (10-30) ( )14 (10-30) ( )12 (10-30) ( )12 (5-30)1.8 Tilting disk (bjork-Shiley,1921 ± 7 Medtronic Hall212.8 ± ± ± ± ± 3 Ball-cage (Starr-Edwards)3.1 ± ± 4
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.
Case of DVR AV – well seated metallic prosthesis with residual moderate AS and mild AR.
Continuity Equation X (1.8) 2 X 30 =
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.