13. Prosthetic Valves

Question 0

Mechanical Valves vs Biological

Answer 0

• more durable
• more thrombogenic and require anticoagulation
• mechanical chosen in:
  
  • young patients due to long life expectancy
  • someone who cannot have a reoperation in future
  • someone anticoagulated for other reasons

Question 1

Bernoulli equation can assess flow through which types of prosthetic valves?

Answer 1

• bileaflet
• tilting disc
• biological

NOT

• caged ball
• caged disc
• mechanism alters blood flow

Question 2

Mechanical valves, types

Answer 2

1. Bileaflet
   - two semicircular hinged leaflets in a circular ring open almost perpendicular to form three orifices
2. Caged ball
   - circular sewing ring with two u-shaped arches containing a silastic ball
3. Caged disc
   - circular sewing ring with short cage containing a light weight silastic central occluding disc
4. Tilting disc
   - eccentrically hinged single tilting disc in circular ring that opens to form two orifices
   - provide large orifice size to stent size

Question 3

Evaluating for stenosis after mechanical valve

Answer 3

• Bernoulli equation is only that truly applies, but may overestimate true gradients since prosthetic valves are normally mildly obstructive +/- inotropes causing increase CO

Aortic valve: LVOT VTI/aortic VTI (using double envelope)
2.2 - prosthetic valve stenosis

Question 4

Biological tissue valves

Answer 4

• last 12-15 years

1. Stented porcine heterografts
2. Stunted bovine pericardial
   - lower profile than porcine valves
3. Stentless
   - porcine heterografts without stent used in aortic position only
   - allow for increased orifice to graft size (Esp if native annulus
   diameter <20mm)
   - WILL dilate if root dilates over time
   - proper sizing: annulus diameter must be within 10% of STJ
   diameter
4. Allograft
   - preserved human root
   - stentless

Question 5

Prosthesis-patient mismatch

Answer 5

EOAI = EOA/BSA

Aortic valve mismatch:
Severe - EOAI 0.85

Mitral valve mismatch:
Significant - EOAI < 1.2

Question 6

Panned vs thrombus

Answer 6

Pannus: composed of fibrous tissue
- echodense, firmly adhered to valve

Thrombus: blood clot
- larger, mobile, associated with spontaneous echo contrast