1 / 66

Prosthetic valves

Prosthetic valves. Types Selection Complications . Types . Bioprosthetic valves Heterograft ( xenograft ) Bovine porcine Homograft (allograft) Autograft Pericardial Pulmonary (Ross) Mechanical Caged ball valve Tilting disc valve Bileaflet valve.

dempster
Télécharger la présentation

Prosthetic valves

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Prosthetic valves Types Selection Complications

  2. Types • Bioprosthetic valves • Heterograft (xenograft) • Bovine • porcine • Homograft (allograft) • Autograft • Pericardial • Pulmonary (Ross) • Mechanical • Caged ball valve • Tilting disc valve • Bileaflet valve

  3. Heterografts(xenografts) The Hancock M.O. II aortic bioprosthesis (porcine) • Stentless • Porcine • Toronto SPV valve, medtronicfreestyle valve • Stented - facilitate implant, maintain 3D relationship,more physiological flow • Porcine • Hancock , carpenteiredwards, medtronic • Bovine • Stented bovine p prosthesis Carpentier-Edwards Duralex mitral bioprosthesis

  4. Advantages - No need of anticoagulation after 1st 3 m Little hemolysis Disadvantages Limited ,uncertain durability Cuspal tear Perforation degeneration Rapid deterioration esp children Fibrin depostn Ca++ 10-30% need re op in 10 yr 30-60% need re op in 15 yr Small size have poor hemodynamics Tissue heterograft

  5. Bioprosthetic valve Preferred in • Pregnancy • Bleeding Diathesis • Age> 70 years • Poor compliance

  6. Mechanical valves • Caged ball valve Advantages • Oldest • durabiltyupto 40 yr Disadvantages • high profile • hemolysis • high thrombogenecity • Poor hemodynamics in small sizes Unique features • Occluder travels completely out of the orifice, reduces thrombus & pannus growing from the sewing ring • Continuously changing points of contact of the ball reduces the wear & tear in any one area • Thrombogenic risk 4-6% / year

  7. Starr Edwards Valve • not suitable - for the mitral position in patients with a small left ventricular cavity - for the aortic position in those with a small aortic annulus - those requiring a valve-aortic arch composite graft

  8. Tilting disc valve- monoleaflet • - Medtronic Hall valve - Omnicarbon (Medical CV) - Monostrut (Alliance Medical Technologies) - Bjork-Shiley valves • Adv • low profile • Good hemodynamics even in small sizes • Excellent durability • Permit central laminar flow • Medtronic hall valve • Titanium housing • teflon sewing ring • carbon coated disc • disadv– • Anticoagulation mandatory • higher risk of thrombosis than cage ball v • sudden catastrophic valve thrombosis

  9. St. Jude Medical mechanical heart valve Bileafletvalve Adv – • Low bulk - flat profile • Less thrombogenicy • Central laminar flow • two semicircular discs that pivot between open and closed positions • No need for supporting struts • Good hemodynamics even in small sizes • 2 lat ,1 central minor orifice , no chance of sudden catastro thrombosis Disadv- • Anticoagulation mandatory • risk of thrombosis • Carbomedics • Titanium housing • Pyrolytic carbon

  10. Types of prosthetic valves and thrombogenicity

  11. TTK chitra • tilting disc valve - metallic housing (cobalt based wrought alloy) - circular disc high molecular weight polyethylene - A polyester suture ring • Hemodynamically comparable to other mechanical valves • valve related complications are similar

  12. Characteristics of Various prosthetic valves

  13. Flow Dynamics

  14. Desired valves • Mechanical valves - preferred in young patients who have a life expectancy of more than 10 to 15 years who require long-term anticoagulant therapy for other reasons (e.g., atrial fibrillation) • Bioprostheticvalves preferred in patients who are elderly have a life expectancy of less than 10 to 15 years who cannot take long-term anticoagulant therapy • A bileaflet-tilting-disk or homograft prosthesis is most suitable for a patient with a small valvular annulus in whom a prosthesis with the largest possible effective orifice area is desired.

  15. algorithm for choice of prosthetic heart valve

  16. Radiologic Identification Starr-Edwards caged ball valve Radiopaque base ring Radiopaque cage Three struts for the aortic valve; 4 struts for the mitral or tricuspid valve Silastic ball impregnated with barium that is mildly radiopaque (but not in all models)

  17. TTE – stenosis Valve area calculations • Continuity equation Area Ao prosthesis = (diameter sewing ring)² x 0.785xLVOT VTI/ Ao prosthesis VTI Area mitral prosthesis= (diameter LVOT)²x 0.785xLVOT VTI/ VTI mitral prosthesis • Pressure Half time ( mitral valve prosthesis) • Dimensionless index- LVOT velocity/ aortic prosthesis velocity < 0.23 indicates prosthetic valve stenosis

  18. Prosthetic Valve regugitation • Mitral – velocity2.5m/sec - jet area 2cm² • Aortic -- aortic PHT≤ 250m/sec -- flow reversal in aorta

  19. Normal Doppler Values of Prosthetic Valves Aortic Position Mitral Position Velocity MeanGr Starr Edward 1.8±0.5 7±2 St Jude 1.5±0.3 5±2 Medtronic Hall 1.6±0.3 5±2 Aortic Homograft 1.5±0.4 4±2 Hancock 1.5±0.3 5±2 Carpentier’s 1.5±0.3 5±2 Velocity Mean Gr Starr Edward 3.1±0.5 24±4 St Jude 3.0±0.8 11±6 Medtronic Hall 2.6±0.3 12±3 Aortic Homograft 0.8±0.4 7±3 Hancock 2.4±0.4 11±2 Carpentier’s 2.4±0.5 14±6

  20. Importance of TEE • higher-resolution image than TTE • size of vegetation defined more precisely • peri annular complications indicating a locally uncontrolled infection (abscesses, dehiscence, fistulas) detected earlier • limitation -inability to detect aortic prosthetic-valve obstruction or regurgitation, especially when a mitral prosthesis is present

  21. Mitral Bileaflet

  22. Cinefluoroscopy • Structural integrity • Motion of the disc or poppet • excessive tilt ("rocking") of the base ring - partial dehiscence of the valve • Aortic valve prosthesis - RAO caudal - LAO cranial Mitral -- RAO cranial

  23. Fluoroscopy of a normally functioning CarboMedicsbileaflet prosthesis in mitral position A=opening angle B=closing angle

  24. St. Jude medical bileaflet valve • Mildly radiopaque leaflets are best seen when viewed on end • Seen as radiopaque lines when the leaflets are fully open • Base ring is not visualized on most models

  25. MRI • Not useful in assessing prosthetic-valve structure • used only when prosthetic-valve regurgitation or paravalvular leakage is suspected but not adequately visualized by echocardiography

  26. Cardiac Catheterization • measure the transvalvular pressure gradient, from which the EOA can be calculated • can visualize and quantify valvular or paravalvularregurgitation

  27. Valve dysfunction

  28. patient-prosthesis mismatch • When the effective prosthetic valve area, after insertion into the patient less than that of a normal valve (Rahimtoola in 1978) • EOA indexed to BSA is less than 0.85 cm2/m2 • EOA (echo) differs from geometric orifice area (measured directly) • EOA for each prostheses type & size obtained in literature from pts normally functioning prostheses • Average if > 1 value -- mild (0.9 - 1 cm² /m² -- moderate (0.6 - 0.9 cm2/m² -- severe (iEOA < 0.6cm²/m² (Rahimtoola)

  29. in-vitro area of the majority of valve prostheses ( int diameter <23 mm) < that of the normal human valve area • the in-vivo prosthetic area further reduced by IVS hypertrophy, progressive endothelialization and tissue ingrowth (Aortic prosthetic devices may be functionally stenotic)

  30. three-step algorithm • Step 1: Calculation of the patientBSA. Step 2: Reference to the specific table for identification of the adequate valvular EOA according to the patientBSA. Step 3: Selection of the most appropriate type and size of valve prosthesis according to the target iEOA

  31. Valve Thrombosis Incidence of 0.1 to 5.7 % per patient-year <0.2% per year for mech valves <0.1% bioprosthetic valves • small thrombus, at the hinge portion of a bileaflet valve obstruct the mechanism • tilting disk -- a much larger thrombus to prevent function • Ball and cage valves – less susceptible  occluder has no contact at all with the valve housing for a portion of every cycle Clinical • Non obstructive- incidental/embolic phenomenon • Partial obstruction- dyspnea,systemic embolism , fever • Severe obstruction- overt heart failure

  32. Fibrinolytic therapy - Rt sided thrombosis 80-100% success rate • Surgery for fibrinolysis failure/symptoms > 3 wk • Surgery – Lt sided thrombosis, large clot burden

  33. FIBRINOLYTIC PROTOCOLheart 2007;93:137-142 • 2 types of protocol -rescue fibrinolysis (short protocol for unstable pt) - long protocol for stable pt • Short protocol - r tPA 10 mg bolus + 90 mg in 90 min or - SK 15lac in 60 min • Long protocol -- SK- 5lac u in 20 min f/b 15lac u for 10 hr -- rtPA -- 10 mgbolus f/b 90mg/hr for 9 hrs • Urokinase • High dose: 4,500 IU/kg/h for 12 h without heparin • Low dose: 2,000 IU/kg/h with heparin for 24 h

  34. Embolisation • cerebral embolization CT normal/infarctwarf & heparin – 72 hrs APTT lower therapeutic level till the desired INR • anticoagulantion delayed for at least 7 to 14 days - ICH, extensive cerebral infarction  OAC

  35. If embolic event occurs while the patient is on adequate antithrombotic therapy • If on warfarin with INR of 2.0 to 3.0: increase dose to achieve INR of 2.5 to 3.5 • If on warfarin with INR of 2.5 to 3.5: add aspirin 50 to 100 mg/d • If on warfarin with INR of 2.5 to 3.5, plus aspirin 80 to 100 mg/d: aspirin dose may also need to be increased to 325 mg/d • If on aspirin 325 mg/d: switch to warfarin with goal INR of 2.0 to 3.0

  36. Excessive Anticoagulation • vit K 2.5 mg daily until the INR is acceptable • fresh frozen plasma • Human recombinant factor VIIa, 15 to 19 g/kg (INR >10.0 with bleeding)

  37. Structural Failure of Bioprosthetic Valves • About 30 % of heterograft bioprosthetic valves and 10 to 20 % of homograft valves require replacement within 10 to 15 years because of structural failure • severe regurgitation due to a tear or rupture of one or more of the valve cusps • calcified and rigid valves • Rarely severe valvularstenosis

  38. Structural deterioration • Higher incidence patients <40 years & with mitral prostheses • gradual onset of dyspnea and other symptoms of heart failure • Bioprosthetic-valve regurgitation or stenosis can be detected by auscultation • valve dysfunction assessed by echocardiography or catheterization

  39. Failure of Bio prosthetic Valves

  40. Hemolysis • Incidence - 6% • Subclinical intravascular hemolysis • severe hemolytic anemia uncommon & suggests paravalvular leakage due to partial dehiscence of the valve or infection • Patients with a caged-ball valve / multiple prosthetic valves have an increased incidence & severity of hemolysis.

  41. Hemolysis • Pts with hemolytic anemia treated with iron & folate supplements or blood transfusion - decreased blood viscosity & increased COP a/w anemia increase the hemolysis • Paravalvular leakage & severe hemolysis – valve replacement or repair

  42. Para valvular leak • improper implantation of a valve • A heavily calcified annulus is a risk factor for paravalvular leaks -- incomplete debridement of calcium compromises both suture placement and valve seating • Active endocarditis is also a risk factor • Late paravalvular leaks are suggestive of prosthetic valve endocarditis • generally result in hemolysis • In the absence of a paravalvular leak, a normally functioning modern valve should not result in hemolysis

  43. Paravalvular Regurgitation • mild or moderate paravalvular leakage - asymptomatic , may have only a mild hemolytic anemia - can be observed carefully with serial echo • severe paravalvular leakage - usually have symptoms of heart failure or severe anemia - should be treated with surgical repair or replacement of the valve

  44. PVE (2-6%) salient features • Endovascular, microbial infection occurring on parts of a valve prosthesis or on reconstructed native heart valves , with or without implantation of an annular ring • early PVE is 5% higher in surgery during active IE • Diagnostic approach, surgical indications same

More Related