Prosthetic valves

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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. - PowerPoint PPT Presentation

Transcript of Prosthetic valves

Prosthetic valves

Prosthetic valvesTypesSelectionComplications

1Types Bioprosthetic valvesHeterograft (xenograft)BovineporcineHomograft (allograft)AutograftPericardialPulmonary (Ross)

MechanicalCaged ball valveTilting disc valveBileaflet valve

Heterografts(xenografts)StentlessPorcine Toronto SPV valve, medtronic freestyle valve

Stented - facilitate implant, maintain 3D relationship,more physiological flow

PorcineHancock , carpenteir edward s, medtronic BovineStented bovine p prosthesis

The Hancock M.O. II aortic bioprosthesis (porcine)Carpentier-Edwards Duralex mitral bioprosthesis Tissue heterograftAdvantages

- No need of anticoagulation after 1st 3 m

Little hemolysis

Disadvantages

Limited ,uncertain durabilityCuspal tearPerforationdegeneration

Rapid deterioration esp childrenFibrin depostnCa++10-30% need re op in 10 yr30-60% need re op in 15 yr

Small size have poor hemodynamicsBioprosthetic valve Preferred in PregnancyBleeding DiathesisAge> 70 yearsPoor complianceMechanical valvesCaged ball valveAdvantagesOldest durabilty upto 40 yrDisadvantages high profilehemolysis high thrombogenecityPoor hemodynamics in small sizes

Unique features

Occluder travels completely out of the orifice, reduces thrombus & pannus growing from the sewing ringContinuously changing points of contact of the ball reduces the wear & tear in any one areaThrombogenic risk 4-6% / year

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 Tilting disc valve- monoleaflet - Medtronic Hall valve - Omnicarbon (Medical CV) - Monostrut (Alliance Medical Technologies) - Bjork-Shiley valves

Adv low profileGood hemodynamics even in small sizesExcellent durabilityPermit central laminar flow

Medtronic hall valveTitanium housing teflon sewing ring carbon coated disc

disadv Anticoagulation mandatory higher risk of thrombosis than cage ball vsudden catastrophic valve thrombosis

Bileaflet valveAdv Low bulk - flat profile Less thrombogenicy Central laminar flow two semicircular discs that pivot between open and closed positionsNo need for supporting strutsGood hemodynamics even in small sizes2 lat ,1 central minor orifice , no chance of sudden catastro thrombosis Disadv-Anticoagulation mandatoryrisk of thrombosis

St. Jude Medical mechanical heart valve

CarbomedicsTitanium housing Pyrolytic carbon

Types of prosthetic valves and thrombogenicity

Type of valveModelThrombogenicityMechanicalCaged ballStarr-Edwards++++Single tilting discBjork-Shiley,Medtronic Hall+++BileafletSt Jude Medical,Sorin Bicarbon,Carbomedics++BioprostheticHeterograftsCarpentier-Edwards,Tissue Med (Aspire), Hancock II+ to ++Homografts+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 valvesvalve related complications are similar

Characteristics of Various prosthetic valves

Flow Dynamics

Desired valvesMechanical 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)

Bioprosthetic valves 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. algorithm for choice of prosthetic heart valve

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)

TTE stenosis Valve area calculationsContinuity equation Area Ao prosthesis = (diameter sewing ring) x 0.785xLVOT VTI/ Ao prosthesis VTI Area mitral prosthesis= (diameter LVOT)x 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

Prosthetic Valve regugitation

Mitral velocity2.5m/sec - jet area 2cm Aortic -- aortic PHT 250m/sec -- flow reversal in aorta

Normal Doppler Values of Prosthetic ValvesAortic Position Velocity Mean Gr Starr Edward 3.10.5 244 St Jude 3.00.8 116Medtronic Hall 2.60.3 123Aortic Homograft 0.80.4 73Hancock 2.40.4 112Carpentiers 2.40.5 146Mitral Position Velocity MeanGrStarr Edward 1.80.5 72 St Jude 1.50.3 52 Medtronic Hall 1.60.3 52Aortic Homograft 1.50.4 42Hancock 1.50.3 52Carpentiers 1.50.3 52

Importance of TEEhigher-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

Mitral Bileaflet

CinefluoroscopyStructural integrity Motion of the disc or poppetexcessive tilt ("rocking") of the base ring - partial dehiscence of the valveAortic valve prosthesis - RAO caudal - LAO cranial Mitral -- RAO cranial

Fluoroscopy of a normally functioning CarboMedics bileaflet prosthesis in mitral position A=opening angle B=closing angle

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

MRINot useful in assessing prosthetic-valve structure

used only when prosthetic-valve regurgitation or para valvular leakage is suspected but not adequately visualized by echocardiography

Cardiac Catheterization measure the transvalvular pressure gradient, from which the EOA can be calculated

can visualize and quantify valvular or paravalvular regurgitation

Valve dysfunction complicationexampleRole of echoPrimary mechanical failureBall varianceStrut fractureVisualize structure, assess gradient & regurgitationNonstructural dysfunctionPt- prosthesis mismatchpannusGradient, visualize tissue in & around the sewing ringBleeding eventIntracranial hgeSource of embolus, presence & mobility of massesEndocarditisVegetation, abcess, dehiscenceVisualize area around the sewing ring, echo dense / lucent area, perivalvular regurgitationThrombosis Thrombus impedes opening &closing of occluder mechanismLocalize mass, assess gradient, detect regurgitation

Embolism strokeIdentify & characterize the source of emboli 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/m2EOA (echo) differs from geometric orifice area (measured directly)EOA for each prostheses type & size obtained in literature from pts normally functioning prosthesesAverage if > 1 value

-- mild (0.9 - 1 cm /m -- moderate (0.6 - 0.9 cm2/m -- severe (iEOA < 0.6cm/m (Rahimtoola)

in-vitro area of the majority of valve prostheses ( int diameter