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PROSTHETIC HEART VAL
HEART VALVES
| Question | Answer |
|---|---|
| EVALUATING PROSTHETIC VALVES Different than evaluating native valves: | 1) several types of prosthetic valves have different fluid dynamics & velocities w/ different sizes 2) mechanisms of dysfunction are different from native valve disease 3) artifacts make diagnostic approach difficult |
| TYPES OF PROSTHETIC VALVES 3 basic types: | .Tissue valves or bioprostheses .Homograft valves .Mechanical valves |
| BIOPROSTHETIC VALVES PART 1 | .AKA tissue valves .3 biologic leaflets .Traditional stented prosthetic valves are called heterograft or xenograft (which is transferred from animal to human |
| BIOPROSTHETIC VALVES PART 2 | Heterograft Leaflets are porcine or bovine Porcine leaflets is transplanted pig valve mounted on sewing ring Bovine valve is usually pericardium shaped to mimic normal leaflets |
| BIOPROSTHETIC VALVES Heterograft's: | .Valve is mounted on a cloth covered ring support that acts like annulus .Raised “stent” at each of 3 commissures .There are many variations |
| FLOW PATTERNS | Trileaflet open to a circular orifice Flow similar to native valve Laminar flow with a blunted flow profile High % of normally functioning bioprosthetic valves have small amount of regurg |
| flow patterns | Prosthesis in mitral position Inflow stream directed anteriorly and medially toward septum (toward apex is normal) |
| PORCINE VALVES | .Pigs aortic valve placed on stents .Attached to sewing ring .Most common brands are: .Hancock I & II .Carpentier-Edwards (standard or supraannular) .Intact (aortic) |
| STENTLESS PORCINE VALVES | .Low pressure intact porcine valve supported by Dacron cloth instead of rigid stents .Tries to optimize valvular hemodynamics and are easier to implant .2 approved valves: .St. Jude Toronto SPV .Carpentier-Edwards freestyle valves |
| BOVINE PERICARDIUM | cow’s pericardium fashioned into trileaflet mounted on stents and sewing ring These valves are more prone to sudden failure from a tear in one of the leaflets compared to other bioprosthetic valves |
| BOVINE PERICARDIUM | .Most common brands are: Carpentier-Edwards Ionescu-Shiley (taken off US market) Mitroflow |
| HOMOGRAFT (ALLOGRAFT) definition: | .Cryopreserved human aortic valve harvested @ autopsy .Usually the AMVL, aortic valve & asc. Ao are taken & trimmed at the time of implantation |
| HOMOGRAFT | .No stents are needed .These valves can be used in the aortic or pulmonic position .Rarely seen in AV valve replacement because more support would be needed .Valve failure is usu because of regurg |
| HOMOGRAFT FLUID DYNAMICS | .Similar to native valve .Flow velocities are slightly higher .Valve areas are slightly smaller .This is because the homograft annulus takes up room in the patient’s outflow tract |
| AUTO-GRAFT (SELF TO SELF | .Excision of aortic valve & placement of pulmonic valve & trunk into aortic position w/ reimplantation of coronaries .Homograft conduit is placed between RV and PA |
| VALVED CONDUIT part 1 | .Used to repair congenital heart disease .May be homograft .May be artificial material .Gore-Tex .Dacron |
| VALVED CONDUIT part 2 | .Conduit may have mechanical or biologic valve .Blood flow through valved conduit is similar to blood flow through a valve implanted in the annulus position |
| AUTOGRAFTS | Those used in mitral position Made from patient’s own tissue Can be made from fascia lata Fibrous membrane that covers and supports the thigh muscle ? Whether these are still in use |
| ADVANTAGES OF BIOPROSTHETIC VALVES | .May avoid antocoagulation .Lower pressure gradients .Central flow dynamics .Failure usually occurs slowly .Valve of choice for TV and PV |
| ANNULOPLASTY RINGS Repair of the native valve is usually preferable to replacement They are flexible rings that: | Are sewn into the annulus position Helps support the native annulus and attached valve leaflets. They restore size and shape of the valves and Help prevent recurrent dilatation Resembles calcified annulus in echo |
| ANNULOPLASTY RINGS | .Resembles calcified annulus in echo .There a number of types but Carpentier-Edwards is the classic type of ring |
| MECHANICAL VALVES All mechanical valves have sewing ring, moving component and a cage strut or frame | .They fall into 4 categories: .Ball and cage valve .Caged disc valves .Tilting disc valve .Bileaflet valve |
| BALL & CAGE VAVLE | .Spherical occluder is in metal cage .In mitral position .During diastole ball moves towards the apex .During systole ball moves towards the LA |
| TYPES OF BALL & CAGE | .Starr Edwards is the most common .Smeloff-Cutter .Braunwald-Cutter .Magovern- surgitool .Magover – Cromie .Harken .DeBakey – surgitool .Hufnagel |
| TILTING DISC VALVE | .A single circular disc opens at an angle to the annulus plane. .It’s motion is controlled be a central strut or slanted slot in the valve ring |
| TYPES OF TILTING DISCS | .Bjork-Shiley and Medtronic Hall are the most common .Bjork-Shiley is no longer in the US because of strut fracture .Lillehei-Kaster .Hall-Kaster .Wada-Cutter .Omniscience .Omnicarbon |
| FLUID DYNAMICS OF TILTING DISC Characteristics | .Two orifices in the open position .Major orifice and minor orifice .Asymmetric flow profile as blood accelerates along the tilted surface of the open disc |
| FLUID DYNAMICS OF TILTING DISC Subtle variations are seen in flow pattern depending on: | .Sewing ring design .Shape of disk .Convex surface .Concave surface |
| BJORK-SHILEY & LILLHEI-KASTER Design: | .No fixed hinges .Disc rotates freely within the housing .Disc pivots on two side struts (u-shaped) |
| BILEAFLET VALVE | .2 semicircular disks hinge open to form 2 large lateral orifices and a smaller central orifice .St. Jude is the most frequently used mechanical valve. It is the least stenotic mechanical prosthetic valve |
| BILEAFLET VALVES Other types: | .Carbomedics .Duromedics (Hemex) .Gott-Daggett |
| FLOW VELOCITY PROFILE | .Three peaks corresponding to three orifices .Higher velocity in the center of each orifice .Pressure gradient from central smaller orifice is usually much higher than the overall valvular pressure gradient |
| BILEAFLET VALVES | .Discs are parallel to annulus plane during systole .Discs perpendicular to annulus plane during diastole .Blood flow through 3 orifices |
| MECHANISM OF PROSTHETIC VALVE DYSFUNCTION Falls into 3 categories: | .Structural failure .Thromboembolic complications .Endocarditis |
| COMPLICATIONS OF BIOPROSTHETIC VALVES | .Calcification/degeneration .Infective endocarditis .Perivalvular leak .Dehiscence .Stenosis .Regurg .Thrombus |
| COMPLICATIONS OF BIOPROSTHETIC VALVES | .Valve bed abnormality (psuedoaneurysm, hematoma) .Ventricular dysfunction .Hemolysis/anemia .Heart valve mismatch .LVOT obstruction *faliure of bioprosthetic valves (to open or close) usu happens 10 yrs + |
| COMPLICATIONS FOR MECHANICAL VALVES | .Thrombus .Stenosis (thrombus, pannus ingrowth) .Dehiscence .Infective endocarditis .Hemolysis .Mechanical failure (ball/disc/cage variance/strut fracture) |
| COMPLICATIONS FOR MECHANICAL VALVES | .Heart-valve mismatch .LVOT obstruction .Valve bed abnormality (pseudoaneurysm, valve ring abscess, fistula, hematoma) .Pannus ingrowth (fibrous ingrowth of tissue can cause regurg or stenosis) .Regurg (central, perivalvular) |
| DISC OR BALL VARIANCE Changes due to abrasion and deposits of lipids Results in: | .Increase in disc size .Distorts contour .Cracking, grooving, or tearing of prosthesis |
| DISC OR BALL VARIANCE | .Decreased disc or ball size .Break loose from cage struts .Severe regurgitation .Increased size or contour distortion .Stick to struts or cage in open position ,Severe regurgitation |
| THROMBOEMBOLIC COMPLICATIONS Causes from flow characteristics | .Blood stagnation Eddies .High shear stress .Usually seen on valve housing not disc, ball, or leaflet |
| THROMBUS Clot from housing can continue to valve surface causing valve thrombosis | .Normal function is altered .May fail to open or stick .Functional obstruction occurs quickly and heart can’t adapt as it does in native stenosis .Severe regurg results |
| PANNUS INGROWTH | .Newly formed vascular tissue around the valve .Problems similar to those with thrombi .Impair excursion and cause .Stenosis .Regurgitation .Both |
| INFECTIVE ENDOCARDITIS | .Foreign bodies make them target form infection .2% of patients with prosthetic valves get endocarditis .High mortality rate if surgery is recent |
| ENDOCARDITIS. In mechanical valves: | .Vegetations may not be seen Infection often paravalvular .Higher incidence of abscess formation .This may cause dehiscence and paravalvular leak |
| VEGETATIONS | .Difficult to see TTE .May prolapse between chambers .May be on stents, sewing ring, or bioprosthetic valve leaflets .TEE is better modality for visualizing |
| ABSCESS FORMATION | .Along sewing ring .Dehiscence of implant is common with abscess .Echo appearance: .Localized area of US density different from surrounding tissue |
| DEHISCENCE | .Rupture of one or more sutures that anchor the sewing ring .Complication post surgery from endocarditis and resulting abscess Causes perivalvular regurg .Must be repaired |
| DEHISCENCE. Echo features: | .Exaggerated motion of valve relative to annulus .Rocking motion as sewing ring prolapses outside plane of valve annulus (only in extreme cases) |
| CALCIFIC CHANGGES | .Can weaken bioprosthetic valve leaflets or annulus tissue .Reduces leaflet mobility .Obstructs flow .Regurgitation can develop |
| SIGNS OF PROSTHETIC DYSFUNCTION | Reduced CO Increased velocity across valve Decreased valve area Increased regurg Increased CW doppler intensity Increased chamber size Persistent LVH Recurrent pulmonary HTN |
| PSEUDO-PROSTHETIC DYSFUNCTION Cardiac dysfunction due to: | .Implant too small for pt .Implant too large and prosthesis obstructs outflow .Ball and cage mitral can obstruct LVOT if too large |
| PSEUDO-PROSTHETIC DYSFUNCTION | .Poor cardiac output .Abnormal EKG can mimic dysfunction .A-fib |
| INCIDENTAL FINDINGS Spontaneous contrast | .Not from slow flow .Clot formation incidence does not increase .Flow seen from microcavitation downstream from impact of occluder to sewing ring |
| INCIDENTAL FINDINGS Abnormal position | .Poses no problem .Flow patterns will be different .Doppler may be more difficult to obtain |
| ECHO EVALUATION Can use TEE or TTE Obtains information about: | .Spatial info .Structural info .Quantitative flow characteristics |
| Spatial info Structural info Quantitative flow characteristics To properly evaluate must have: | .Valve type .Valve size .Date of implantation .Patient body habitus .Ventricular function .Blood pressure |
| ECHO EVALUATION | .ECHO EVALUATIONThrombus .Vegetations .Pannus ingrowth of tissue .Calcific changes in leaflet tissue or native annulus |
| TEE Because TEE views structures from behind the heart; | .No shadowing in LA .Mode of choice for thrombus, vegetations, abscess or flail leaflets .Perivalvular leaks .Not as good w/ aortic valve because of LVOT shadowing |
| ECHO CALCULATIONS For MVR use: | .Peak velocity .peak gradient .Mean gradient .PHT .Continuity equation .PISA for MR |
| ECHO CALUCLATIONS For AVR use: | .Contiuity equation .Peak velocity & peak instantaneous pressure gradient .Mean gradient .Velocity ratio .Look for AI |
| VELOCITY RATIO | .Measure the “step-up” in velocity across the valve .LVOT velocity/aortic jet velocity .Ratio close to 1 = no obstruction .increases .Prosthetic valve normally .35-.50 .Normal ao valve .75-.90 |
| NORMAL PROSTHETIC REGURG | .MR jet area of <2cm2 .MR jet length <2.5cm .AI jet area < 1cm2 .AI jet length <1.5cm |
| SEVERE MV PROSTHETIC REGURG | .Increased mitral inflow peak velocity .Normal mitral inflow PHT .Dense MR CW signal .Regurgitant fraction of 55% or higher |
| SEVERE AO PROSTHETIC REGURG | .PHT of regurg 250m/sec or lower .Restrictive mitral inflow pattern .Holodiastolic reversals in the descending thoracic aorta .Regurgitant fraction of 55% or higher |
| CAGED BALL EVALUATION Can be in mitral or aortic position M-mode for both valves: | .Can be difficult especially on aortic because valve is usually smaller .Done from apical .M-mode will resemble normal m-mode of aortic valve |
| TILTING DISC EVALUTAION | .Bjork-Shiley tilting disc is the most common ..Parasternal long-axis and apical views are best for visualizing .Parasternal is used for m-mode |
| BIOPROSTHETIC VALVES | .Trileaflet valve that attaches to a sewing ring .Appears similar to Ao valve except: .Increased thickness in LVOT and ascending ao @ suture site |
| PROSTHETIC VALVE DOPPLER | PROSTHETIC VALVE .DOPPLERObstruction to flow is always present .Slightly higher forward flow velocities are recorded |
| ASSOCIATED ECHO FINDINGS | .Changes caused by diseased valves and hemodynamic overload will improve after valve replacement .Improvement depends on heart function prior to surgery |
| OBSERVED CHANGES | .Aortic stenosis .LVH from increased afterload improves .Contractility can improve .Mitral stenosis .Gradual decrease in LA size .LA will always remain larger than normal |
| ASSOCIATED ECHO FINDINGS | .Post surgery (open heart) .Paradoxical or atypical septal motion .Related to postoperative adhesions along the anterior border of the chest wall .Also seen post CABG |
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