1. DEFINITION Prosthetic heart valve is a device implanted in
the heart of a patient with valvular heart disease. - Brunner &
Suddarths (2012)
2. A surgical implant used to replace an abnormal heart valve.
Most prosthetic valves require open heart surgery. The implanted
valves can be porcine (from a pig) or mechanical (man-made). Also
known as porcine heart valve, heart graft, mechanical heart valve.
- Jose Vega (2010)
3. ANATOMY & PHYSIOLOGY OF HEART
4. HEART VALVES
5. TYPES OF PROSTHETIC VALVES
6. MECHANICAL VALVES CAGED BALL:- The first artificial heart
valve was the caged-ball, which utilizes a metal cage to house a
silicone elastomer ball. When blood pressure in the chamber of the
heart exceeds that of the pressure on the outside of the chamber
the ball is pushed against the cage and allows blood to flow. At
the completion of the heart's contraction, the pressure inside the
chamber drops and is lower than beyond the valve, so the ball moves
back against the base of the valve forming a seal.
7. Advantages Oldest prosthetic valve. Durabilty upto 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% per year.
8. TILTING DISC VALVE Tilting disk valves have a single
circular occluder controlled by a metal strut. They are made of a
metal ring covered by an Eptfe fabric, into which the suture
threads are stitched in order to hold the valve in place. The metal
ring holds, by means of two metal supports, a disc which opens and
closes as the heart pumps blood through the valve. The disc is
usually made of an extremely hard carbon material (pyrolytic
carbon), in order to allow the valve to function for years without
wearing out.
9. Advantages Low profile Good hemodynamics even in small sizes
Excellent durability Permit central laminar flow. Disadvantages
Anticoagulation mandatory Higher risk of thrombosis than cage ball
Sudden catastrophic valve thrombosis.
10. BILEAFLET VALVES They have two semicircular leaflets
retained within the ring by hinges. The potential for impeded
leaflet movement due to interference with cardiac structures is
slim, as the open leaflets are positioned in the middle of the
blood stream and enclosed within the ring in the closed position.
Bileaflet valves are the most protected as the leaflets hardly
protrude from the valve ring, even during maximum opening.
11. Advantages:- 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 lateral, 1 central minor
orifice , no chance of sudden catastro thrombosis. Disadvantages:-
Anticoagulation mandatory risk of thrombosis.
12. TISSUE (BIOLOGICAL) HEART VALVES Tissue valves (also called
biologic or bioprosthetic valves) are made of human or animal
tissue. Some valves may have some artificial parts to help give the
valve support and to aid placement. Once the tissue is removed from
the animal, it is chemically treated to preserve the tissue and
prevent immulogic reactions once it is placed in a patient. There
are three types of tissue valves: pig tissue (porcine), cow tissue
(bovine), and human (allografts or homografts).
13. Porcine Stented valves The porcine stented valve was the
first generation of porcine tissue valves. They have been available
for more than 30 years. The valves are made from natural porcine
aortic valves, but may be used for aortic or mitral valve
replacement. They are trimmed and then fixed in buffered
glutaraldehyde at high pressure.
14. Porcine stentless valve The porcine stentless valve is used
for aortic valve replacement. The valve is made from a natural
porcine aortic valve and is fixed in buffered glutaraldehyde
solution at a low pressure. No stents or synthetic sewing rings are
used. Therefore, these valves are very similar to the homograft
valve (see below). These valves are technically more difficult to
implant but are useful in patients with small hypertrophied
hearts.
15. Pericardial valves The Carpentier-Edwards PERIMOUNT
Pericardial Bioprosthesis Pericardial valves include the Perimount
series valves (Edwards LifeSciences). Ionescu-Shiley pericardial
valves have been discontinued. More recently, stentless porcine
valves have been used. They offer improved hemodynamics with a
decreased transvalvular pressure gradient when compared with older
stented models.
16. Other types of biological valves Xenografts are tissue
valves (eg, bioprostheses, heterografts); most are from pigs
(porcine), but valves from cows (bovine) may also be used. Their
viability is 7 to 10 years. They do not generate thrombi, thereby
eliminating the need for longterm anticoagulation.
17. Homografts, or allografts (ie, human valves), are obtained
from cadaver tissue donations. The aortic valve and a portion of
the aorta or the pulmonic valve and a portion of the pulmonary
artery are harvested and stored cryogenically. Homografts are not
always available and are very expensive.
18. Autografts (ie, autologous valves) are obtained by excising
the p atients own pulmonic valve and a portion of the pulmonary
artery for use as the aortic valve. Anticoagulation is unnecessary
because the valve is the patients own tissue and is not
thrombogenic. The autograft is an alternative for children (it may
grow as the child grows), women of childbearing age, young adults,
patients with a history of peptic ulcer disease, and those who
cannot tolerate anticoagulation.
19. 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
20. Cinefluoroscopy: Structural integrity Motion of the disc or
poppet Excessive tilt ("rocking") of the base ring - partial
dehiscence of the valve Aortic valve prosthesis
21. Fluoroscopy of a normally functioning CarboMedics bileaflet
prosthesis in mitral position A=opening angle B=closing angle
22. MRI: Not useful in assessing prosthetic-valve structure
Used only when prosthetic-valve regurgitation or para valvular
leakage is suspected but not adequately visualized by
echocardiography
23. Cardiac Catheterization: Measure the transvalvular pressure
gradient, from which the EOA can be calculated Can visualize and
quantify valvular or paravalvular regurgitation
24. Echocardiography of Stentless Aortic Homografts Doppler
flow characteristics similar to native valve. Only 2-D evidence:
Increased Echo intensity, and Thickness of aortic annulus.
25. Valve dysfunction complication example Role of echo Primary
mechanical failure Ball variance Strut fracture Visualize
structure, assess gradient & regurgitation Nonstructural
dysfunction Pt- prosthesis mismatch pannus Gradient, visualize
tissue in & around the sewing ring Bleeding event Intracranial
hge Source of embolus, presence & mobility of masses
Endocarditis Vegetation, abcess, dehiscence Visualize area around
the sewing ring, echo dense / lucent area, perivalvular
regurgitation Thrombosis Thrombus impedes opening &closing of
occluder mechanism Localize mass, assess gradient, detect
regurgitation Embolism stroke Identify & characterize the
source of emboli
26. 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 cm /m -- moderate (0.6 -
0.9 cm2/m -- severe (iEOA < 0.6cm/m (Rahimtoola)
27. Three-step algorithm Step 1: Calculation of the patient
BSA. Step 2: Reference to the specific table for identification of
the adequate valvular EOA according to the patient BSA. Step 3:
Selection of the most appropriate type and size of valve prosthesis
according to the target iEOA
28. Valve thrombosis Incidence of 0.1 to 5.7 % per patient/year
10.0 with bleeding)
33. 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