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Selection Of Prostheses

Selection of Prostheses

1. Mechanical valves

A. Selection
1) <70 yo
2) no h/o bleeding
B. Survival - over ½ of late deaths are related to valve complications
C. Hemodynamics
1) Tilting disc and bileaflet are “low-profile”
a) Tilting disc - 6-7mmHg gradient
2) Caged ball is “high-profile”
D. Thromboembolism
1) Highest risk is in first 14 months
2) Steady level after - 0.5%/pt-yr
3) INR 2.5 = therapeutic
4) Coumadin for all - antiplatelet agent for high-risk (a-fib, h/o embolus, etc.)
5) Thrombolytic therapy - never for patients in a low-output state
E. Hemorrhage
1) Incidence the same for aortic and mitral position
2) Associated w/high anticoagulation levels (INR >4.5)
3) At INR 2.5-3.5, anticoagulation-related death = 0.2%/pt-yr
F. Endocarditis
1) PVE - mortality = 23-69%
2) Most commonly in first several months
3) After initial period = 0.17%/pt-yr
G. Periprosthetic leakage (see Table 122-2)
1) Predisposing factors
a) Annular calcification
b) Infection
c) Annuloprosthetic mismatch
d) Excessive tension on sutures, annulus or both
e) Technique
f) Abnormal annulus tissue
H. Structural valve degeneration
1) Rare
2) Leaflet fracture - may be due to mishandling à scratches
I. Nonstructural valve degeneration
1) Pannus formation

2. Bioprosthetic Cardiac Valves

A. Features
1) No indication for anticoagulation
2) Survival
B. Glutaraldehyde-preserved porcine valves
C. Hemodynamics
1) Central unimpeded flow
2) In aortic position, small (19-21mm) valves are stenotic
3) Supraannular bioprosthesis improves flow
D. Thromboembolism
1) INR 2.0-3.0 for a-fib
E. Hemorrhage-see Table 122-4
F. Structural valve dysfunction
1) Progressive degeneration
2) Reasons
a) Calcification
b) Collagen degeneration-associated cuspal defect
c) Time-dependent - accelerated failure after 8-10 years
d) Valve failure and calcification accelerated in childrenàyoung adults
e) Mitral > aortic failure
G. Endocarditis
H. Periprosthetic leak

3. Pericardial Valves

A. Better flow (than porcine bioprostheses)
B. Newer designs more durable

4. Homograft Valve Prostheses

A. Patient survival 85-90% @ 7.5yr // 71% @ 14yr
B. Durability
1) Early homografts - calcification & cusp rupture
2) Cryopreservation (vs irradiation & chemical processes)
a) 95-98% freedom from structural deterioration (10yr)
C. Thromboembolism
1) ? Role of endothelium
D. Endocarditis
1) S. aureus a major player
2) Many respond to Abx
3) Failure to respond to Abx = surgical indication