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Echocardiography of Prosthetic Valves

Echocardiography of Prosthetic Valves. Dr. Tehrani. Different Types of Valves. Homografts (allograft) Cadaveric human aortic and pulmonary valves Heterograft (Xenograft) Prosthetic Valves Bioprosthetic valves Pig aortic valve Bovine pericardial (other) Mechanical

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Echocardiography of Prosthetic Valves

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  1. Echocardiography of Prosthetic Valves Dr. Tehrani

  2. Different Types of Valves • Homografts (allograft) • Cadaveric human aortic and pulmonary valves • Heterograft (Xenograft) • Prosthetic Valves • Bioprosthetic valves • Pig aortic valve • Bovine pericardial (other) • Mechanical • Urethane ball in a cage • Single or multiple discs

  3. Homografts (allograft)

  4. Homografts • Homograft Valves • Harvested soon after death w/ the endothelium still viable • Preparation for implantation • Storage in ABX • Cryopreservation (more recently) • No anticoagulation • Low incidence of endocarditis • Failure due to gradual aortic incompetence

  5. Homografts • Position • Mitral • Fitted w/ stent, not proved successful (high failure rate at 5 years) • Stentless grafts not an option for MVR • Aortic • Stentless • Subcoronary • Root Replacement

  6. Echocardiography of Stentless Aortic Homografts • Doppler flow characteristics similar to native valve. • Only 2-D evidence: Increased Echo intensity, and Thickness of aortic annulus.

  7. Stentless Heterografts (Xenograft)

  8. Stentless Heterografts (Xenograft) • Same utility as allografts for AVR: • Subcoronary implantation, and • Root replacement • Advantage over allografts is wider availability • Durability is at least as good as allografts

  9. Prosthetic Valves

  10. Prosthetic Valves Bio-Prosthetic and Mechanical Prosthetic • All Prosthetic valves have a sewing ring • anchored to the native tissue with sutures • The occluding portion of the valve: • Tissue leaflets  Bio-Prosthetic • Single or multiple discs/ Urethane ball in a cage  Mechanical Prosthetic

  11. Bio-prosthetic Valves

  12. Bioprosthetic Valves • Two types, of occluding mechanism • Porcine aortic valve (the valve size of the biggest pig is limiting) • Hancock, and • Carpentier-Edwards bioprosthesis Carpentier-Edwards bioprosthesis

  13. Bioprosthetic valves • Bovine Pericadium leaflets are shaped to size. More choices • Echocardiographiaclly these two valves types are indistinguishable. Ionescu-Shiley (1976)

  14. Bioprosthetic valvesMitral Position 2-D ECHOCARDIOGRAPHIC APPEARANCE

  15. Bioprosthetic valvesAortic Position 2-D ECHOCARDIOGRAPHIC APPEARANCE

  16. Bioprosthesis • Used extensively in a variety of sites: • Aortic • Mitral • Tricuspid • Advantage: • Low thrombogenicity => No anticoagulation

  17. Bioprosthesis • Disadvantages: • Less durable than mechanical prosthesis • Mitral position worse • Due to greater backpressure gradient • Dysfunction: • Leaflet thickening, and Ca++ • Fracture, tears, or progressive stenosis • In vivo, roughly 10% of normal bioprosthetic valves have some leakage.

  18. Overview of Various Devices Bio-Prosthetic Valves Mechanical Prosthetic Valves

  19. Mechanical Vlaves • Ball-and-Cage Valves • Tilting disc Prosthesis • Single disk • Bileaflet

  20. Mechanical Prosthesis • The occluding mechanism dictates both: • The echocardiographic appearance of the valve, and • The flow pattern through the valve • To assess performance, the type of valve implanted must be known

  21. Ball-and-Cage Valves • First implanted by starr and Harken in 1960.

  22. Ball-and-Cage Valves Opening and closure of the ball-valve

  23. Ball-and-Cage Valves • Axisymmetric flow around the valve. • Stagnant flow in the shadow of the ball.

  24. Ball-and-Cage Valves Doppler assessment at the margins of the ball

  25. Ball-and-Cage Valves M-Mode assessment of Ball-Cage Valve

  26. Ball-and-Cage Valves • Durable • Mitral position • Satisfactory profile with the largest size (34 or 32 mm diameter devices) • Can affect the interventricular septum • Aortic position • Small prosthesis required, which can be associated with significant gradient • Regurgitation limited to closure backflow.

  27. Tilting Disc Prosthesis • All essentially similar consisting of • Circular prosthetic material, and • One or two hinged and mobile disc(s) • Disc attachment to the ring is eccentric Closure occurs by backpressure on the largest portion of the disk

  28. Single Disc Prosthesis • Single Disc devices: • Hall-Medtronics monostrut • Bjork-Shiley • Opening arch is 55-70 degrees • Flow orifice: • Major and minor flow orifices • Streamlines of flow passing through the sewing ring and then laterally out and around the prosthetic disc

  29. Single Disc Prosthesis • Bjork-Shiley • Standard • Convex-concave • Many other variations in the market • All of these devices have a zone of stagnation behind the disc  thrombus formation

  30. Single Disc Prosthesis Bjork-Shiley in the Mitral position

  31. Single Disc Prosthesis • Leak around: • Central strut • Dominant jet • Between the occluding disc and sewing ring. • Two smaller peripheral jets • Normal hemodynamics • Reg.Frac. approx. 12% • Tachycardia, and low output • Reg.Frac. upto 37%

  32. Single Disc Prosthesis

  33. Single Disc Prosthesis • Dysfunction • Gradual ingrowth of fibrous tissue (panus) • Flow obstruction • Intermittent sticking of the valve with associated flash pulmonary edema

  34. Bileaflet Mechanical Prosthesis • St. Jude prosthesis • The most commonly used. • Two equal sized semi-circular leaflets attached by a midline hinge. • Discs can tilt in excess of 80 degrees, resulting in larger: Orifice area

  35. Bileaflet Mechanical Prosthesis • St. Jude prosthesis • The most commonly used. • Two equal sized semi-circular leaflets attached by a midline hinge. • Discs can tilt in excess of 80 degrees, resulting in larger: Orifice area Regurgitant back flow

  36. Bileaflet Mechanical Prosthesis • Regurgitation occurs at the disc margins • The regurgitant jets converge toward the center of the valve

  37. Bileaflet Mechanical Prosthesis St. Jude valve in the mitral position.

  38. Imaging of Prosthetic Valves

  39. Special Problems of 2-D Imaging Artificial Valves • Echocardiographs are calibrated to measure distance based on the speed of sound in tissue. • Prosthetic valves have different acoustic properties than tissue. Hence, distortion of: • Size • Location, and • Appearance, of the prosthesis.

  40. Special problems of artificial valves • Intense reverberation, and • Shadowing • Less gain leads to less: • Reverberation, and • Shadowing, as well as • Better visualization of non-biologic components of the valve • HOWEVER  Decreased definition of cardiac structures

  41. Special problems of artificial valves • First image at normal settings, then • Reduce the gainto interrogate the leaflets of Bio-prosthetic valves. • Utilize multiple views.

  42. Prosthetic Valve Pathology • Prosthetic Valve Stenosis • Aortic • Mitral • Prosthetic Valve Regurgitation • Aortic • Mitral

  43. G E N E R A L L Y Prosthetic Stenosis (and Regurgitation) is: • A question of degree, • Not a question of whether.

  44. Prosthetic Valve Stenosis • Determinants of gradients across normal prosthetic valves include: • Valve type, i.e., Manufacturer • Valve size • Flow through the valve Wide range of “Normals”

  45. Aortic Prosthesis Gradients as a Function of ValveTYPE and SIZE • Dependence on: • Valve type, and • Size No.21 No.27

  46. Gradient as a Function of Valve Type Normal Dopplar data in patients with various types of prosthetic valves in the Aortic Position

  47. Gradient as a Function of Valve Size • Valve specifications and doppler echocardiographic data in 67 St. Jude medical valves in the Aortic position Chafizadeh ER, Circ. 83:213, 1991

  48. Gradient as a Function of Flow Valve type, i.e., Manufacturer Valve size No.21 Flow through the valve

  49. Indicies of Valve Stenosis which are LessFlow Depenent • Contour of jet velocity • Doppler velocity index • Effective orifice area • Valve resistance

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