Prosthetic valves the past present and future i tammi raju

Prosthetic valves Past,Present & Future

Prosthetic valves the past present and future

Dr . I.Tammi Raju

overview

• Evolution of valves• Present day valves• Evaluation of functioning of valves• Complications• Future of valves

Introduction

• The introduction of valve replacement surgery in the early 1960s has dramatically improved the outcome of patients with valvular heart disease.

• Despite the improvements in prosthetic valve design and surgical procedures , valve replacement does not provide a definitive cure. Instead, native valve disease is traded for “prosthetic valve disease”.


• Although the capacity to surgically correct valvular heart disease through valvuloplasty had been established by the 1920s,

• Initiallly before prosthetic valves-– Volovotomy –Cuttler & Levine 1923 inserting a

volvotome(knife) in to apex –tearing cusps converting MS into MR.

– Finger dilation – Henry souttar & bailey (1948) independently

• The prosthetic heart valve was built on a foundation laid down during the first half of the 20th century with the – Introduction of cardiac

catheterization by André Cournand and Dickinson Richards,

– The development of innovative surgical techniques by Alfred Blalock,

– The invention of the heart–lung machine by John Gibbon, and the

– Heparin by Jay McLean and – Dicumarol by Karl Paul Link.

André Cournand and Dickinson Richards,

Alfred Blalock,

Evolution of Prosthetic Heart Valves

The development of the original ball-and-cage valve design can be attributed to the bottle stopper in 1858

In the early 1950’s, it led to the idea of a prosthetic heart valve consisting of a cage with a mobile spherical poppet

• 1952- The first ever invented artificial heart valve was designed by Charles A. Hufnagel which was the caged-ball design.

Evolution of Prosthetic Heart Valves

This first heart valve was made of a Plexiglass(methyl methacylate)cage surrounding a silicone-coated nylon poppet

First implanted in a human in a closed procedure in September of 1952 (descending thoracic aorta)

• In 1954, Charles Hufnagel and his colleagues described 23 patients with aortic insufficiency who had been treated during the previous 2 years by rapid insertion of an acrylic ball valve into the descending aorta.

• However, since the valve prevented regurgitant flow only from the lower body, cardiac work was only partially relieved and coronary flow was not improved.

• In addition, embolization and thrombosis of the valve occurred frequently, and the noise generated by the valve was disconcerting — reminiscent, according to some, of a ticking time bomb.

Evolution of Prosthetic Heart Valve

• Significant advances were made soon after to help the development of the heart valve:

• In 1953, marked successful use of the heart and lung machine, paving the way for the 1st open heart operations

• The idea of using blood from another patient to oxygenate the blood of the patient was developed

• New methods were came for evacuating air from the heart

• New materials (Plexiglass, Teflon, and Dacron)

Evolution of the Prosthetic Heart Valve

On July 22, 1955, at the City General Hospital in Sheffield, England, Judson Chesterman implanted the first successful heart valve

The patient lived 14 hours after the valve was placed, but died when the poppet twisted out of position

Valve was made of Perspex, an outer cage, a poppet, and 2 buttons to fasten the valve to the outside of the heart

• Edwards proposed that he and Starr collaborate on the invention of a mechanical heart that could replace a failing human heart.

• Starr convinced Edwards to focus on inventing a prosthetic heart valve.

• Edwards would construct the valve prototypes and Starr would insert them into the hearts of dogs.

Evolution of Starr-Edwads valve

Edwards, Starr

Starr sutured the first valve using ring of Teflon cloth attached to the prosthesis. It functioned for several hours before a clot formed and blocked the Silastic

flaps and the animal died. Starr and Edwards developed a method for fabricating a Teflon tube of

cloth material that provided a superior means of suturing the prosthesis into the mitral annulus.

INVENTION OF THE SEWING RING

:BALL-IN-CAGE PROSTHESIS

Starr inserted a ball-in-cage valve prosthesis into the mitral position in the first dog. It was a spectacular success and the dog survived vigorously for months, with normal cardiovascular physiology

• On September 21, 1960, Starr performed the first successful orthotopic valve replacement in the mitral position, which was followed by Harken's implantation of a prosthesis in the aortic position

Patient Philip Admundson: First successful mitral valve replacement


• In 1961, after their success with the mitral valve prosthesis, Edwards and Starr turned their attention to inventing a ball-in-cage prosthesis to replace the aortic valve

• The four struts were replaced by three struts of reduced thickness, made of an exceptionally hard alloy, Stellite . The sewing ring had to be shaped to conform tightly to the high-pressure flows across the aortic valve.

• Importance of hemodynamics in valve design.• The energy required to open the ball valve, as

reflected by the pressure gradient, was substantial.

• An aortic valve that resulted in a large pressure drop with increased resistance to forward flow required greater left ventricular systolic pressure to drive cardiac output, with a commensurate increase in myocardial oxygen consumption.

• Moreover, centrally obstructive flow with large recirculation regions contributed to thrombogenic potential.

HARKEN’S TEN COMMANDMENTS


• Since this time, over 30 mechanical heart designs have been marketed in the U.S. and abroad

• These valves have progressed from the simple caged ball valves, to strut-and-leaflet valves and the modern bileaflet valves, to human and animal tissue

Types of Prosthetic Heart Valves• Mechanical

– Bileaflet (St Jude)(A)– Single tilting disc (Medtronic

Hall)(B)– Caged-ball (Starr-Edwards) (C)

• Biologic– Stented

• Porcine xenograft (Medtronic Mosaic) (D)

• Pericardial xenograft (Carpentier-Edwards Magna) (E)

– Stentless• Porcine xenograft

(Medronic Freestyle) (F)• Pericardial xenograft• Homograft ( allograft)

– Percutaneous – Expanded over a

balloon (Edwards Sapien) (G)

– Self –expandable (CoreValve) (H)

Circulation 2009, 119:1034-1048

Mechanical Valves

• Extremely durable with overall survival rates of 94% at 10 years

• Primary structural abnormalities are rare• Most malfunctions are secondary to perivalvular

leak and thrombosis• Chronic anticoagulation required in all .

Mechanical Valves:Ball Valves

• This design uses a spherical occluder, or blocking device, held in place by a welded metal cage

Problem and Why failed:– Natural heart valves allow blood to flow

straight through the center of the valve (central flow)

– Caged-ball valves completely blocked central flow and collisions with the occluder ball caused damage to blood cells

– Finally, these valves stimulated thrombosis, or formation of blood clots


Starr-Edwards Ball Valve

Model: Starr-EdwardsType: Aortic Caged BallMaterials: Silicone

Rubber ball with 2% barium sulfate, cage-Stellite alloy No. 21, sewing ring- knitted Teflon and polypropelene cloth

Edwards Lifesciences discontinued production of the Starr-Edwards valve in 2007.


http://en.wikipedia.org/w/index.php?title=Edwards_Lifesciences&action=edit&redlink=1

http://en.wikipedia.org/w/index.php?title=Edwards_Lifesciences&action=edit&redlink=1

Magovern-Cromie Ball Valve

Model: Magovern-Cromie valve

Type:Aortic Caged Ball

Materials: Ball-Silicone rubber with barium, cage-titanium, sewing ring-none, Cage open at top


• Mechanical valves were refashioned in the late 1960s, when a tilting disk was introduced to– minimize resistance to forward flow,– decrease turbulence,– limit regions of stagnation, and– reduce shear stress. – Although thromboembolism was not

eliminated, anticoagulation requirements were reduced.


Single Leaflet Disc Valves

• Uses a tilting occluder disk to better mimic natural flow patterns through the heart

• tilting pattern allow more central flow while still preventing backflow

• Some damage still occurs to blood cells

• Reduces thrombosis and infection, but does not eliminate either problem


Bjork-Shiley Standard Aortic Valve

Model: Bjork-Shiley Standard

Type: Aortic Tilting Disc

Materials: Disk-Pyrolytic Carbon, cage-Haynes 25, sewing ring-Teflon


Bjork-Shiley Valve:Initial Fracture Assessment

• Investigators determined that the floating disc opens and slams shut at least 70 times per minute or 40 million times per year, causing fatigue failure

• Although changes were made, fractures continued to occur

• Finally, in 1984, Shiley discovered the source, known as “Bimodal Closure Phenomenon”

Bjork-Shiley Valve:Role of the FDA

• In 1979, the Bjork-Shiley valve was approved very quickly, only six months after Shiley’s first request

• The main criticism of the FDA was its delay in removing the valve from the market despite knowledge of the outlet struts susceptibility to fracture

• The Bjork-Shiley heart valve failure prompted the FDA to make substantial changes in its policies

Medtronic-Hall Valve

Model: Medtronic-Hall A7700 (aortic), M7700 (mitral)

Type: Aortic and Mitral Tilting Disk

Materials: Cage-titanium, Disk-Pyrolytic carbon, sewing ring-knitted teflon


Other Single Leaflet Disc Valves

• Another similar valve is the caged disc valve

• Examples are Starr-Edward Model 6500 and the Kay-Shiley Model


• In 1977, the ideal of central unimpeded flow was approached with the advent of the bileaflet valve.

• Despite improved hemodynamics and the application of thromboresistant alloys and advanced ceramics, the goal of substituting the use of antiplatelet agents for lifelong anticoagulant therapy remains elusive.


BILEAFLET VALVE.

Bileaflet Disc Heart Valves

• Consists of two semicircular leaflets that pivot on hinges integrated onto the flange

• Carbon leaflets and flange exhibit high strength and excellent biocompatibility

• Largest opening angle-Similar to central flow

• Allows small amount of backflow as leaflets cannot close completely

• Lowest pressure gradients• Low thrombogenisity and

turbulence.


St. Jude Bileaflet Valve

Model: St. Jude Valve Standard

Design :Mitral, Aortic, Tricuspid Bileaflet Valve

Materials-Cage and disk- pyrolytic carbon, sewing ring-double velour knitted polyester


TTK-CHITRAONLY INDIAN-MADE HEART VALVE

• The first implant was December 6, 1990 at Sree Chitra Institute ,Trivandrum.

• TTK Chitra Heart Valve has been in Clinical use for over 14 years.

• More than 55,000 TTK Chitra Heart Valve has been implanted so far in India, Nepal, Sri Lanka, Bangladesh and South Africa(250 CENTERS)

•Complete Structural Integrity•Absence of cavitation related damage•Silent operation•Rotatable within the sewing ring to assure its freedom to rotate if repositioning needed.•Low profile,most price-friendly

Bioprosthetic – Why??

Mechanical valve limitations : No major change in valve design since first

implant. Lifelong Anticoagulation therapy INR Test every 15 days Thrombolysis Treatment of Hemorrhage Hospitalization Congenital Anticoagulation Resistance


Bioprosthetic valve – What??

• Bioprosthetic typically

refers to a xenograft

that is chemically

treated, mounted on

some support structure

(stent), or stentless.

• Term coined by Alan F.

Carpentier.

1960’s

Tissue valves investigated in an attempt to overcome the disadvantages of mechanical valves– 1962: Ross & Boyes performed first successful

allograft replacement from cadaver.

– 1964: Duran & Gunning used the first heterograft,

a porcine aortic valve- 1965:Jean-Paul Binet and colleagues five patients with

mercurochrome- and-formalin-preserved heterografts

– 1967: Ross introduced pulmonary autograft for aortic replacement

– 1968: Carpentier showed that glutaraldehyde preservation improved stability of heterografts


• In the late 1960s, Carpentier -tissue stability required the prevention of both immunologic reaction and collagen denaturation.

• Immunologic reaction- – washing a porcine aortic valve in Hanks' solution

and using an oxidizing agent.• Collagen denaturation-

– Further treatment with glutaraldehyde would prevent the denaturation of collagen by creating stable cross-links (promotes calcification).

1968: Glutaraldehyde Fixation Introduced

• Proposed by Carpentier.

• Carpentier in 1968 implanted the first ever

glutaraldehyde treated stent mounted aortic valve.

(C-E valve)

• Glutaraldehyde is chemical used in leather tanning

• All modern xenografts are fixed in glutaraldehyde

1970’s Continued development of

tissue valves including stented products– Early 70’s: Kaiser & Hancock

developed first successful porcine bioprosthesis - metal stent - then plastic

– 1976: Carpentier & Edwards developed porcine valve with an Elgiloy stent

– 1976: Ionescu & Shiley introduced bovine pericardial valve with polyester-covered flexible stent. 43

1980’s and 90’sSTENTLESS tissue valves

introduced

1988: David implanted the first

stentless porcine bioprosthesis

Mitroflow introduced a bovine

bioprosthesis with Delrin stent

1991: Carpentier-Edwards

received FDA approval for a

bovine pericardial bioprosthesis

Bioprosthetic Valve TypesXenografts

Tissue from different species» Porcine valve» Bovine pericardium

Allograft/HomograftTissue from same species

» Human valve

AutograftTissue from same individual

» Pulmonary valve to the aortic position

Types of Stented Tissue Valves Intact porcine valves

• Reduction of muscle shelf bar

Medtronic’s tissue valves Edwards’ porcine tissue

valvesComposite porcine valves

• Three separate leaflets – either the left or the non-coronary cusps

SJM’s Biocor stented tissue valves

Pericardial valvesC-Edwards’ valves

Animal Tissue Valves

• Heterograft or Xenograft Vavles

• Most commonly used tissues are the porcine (pig) valve tissue and Bovine (cow) pericardial tissue

Porcine (pig) Valves

• Two major brands of porcine available today, Hancock and Carpentier-Edwards

• Has good durability and and good hemodynamics

Materials: Porcine valve tissue, stents made of wire, Elgiloy(cobalt-nickel alloy), sewing ring-knitted Teflon

Pericardial (cow) Valves

• Lasts as long as standard porcine valves at 10 years

• The pericardial valve has excellent hemodynamics, even in smaller sizes(19mm to 21mm)and has gained a large market share (about 40% of US tissue valves) in this group of patients

Homografts(Human to Human)

• Homografts are valves transplanted from one human to another

• After donation, valves are cyropreserved until needed

• Since the valve must be thawed overnight, the patient’s size must be known beforehand.

• homograft availability is limited by donor availability

• Advantages: resistance to infection, lack of need for anticoagulation, excellent hemodynamic profile (in smaller aortic root sizes)

• More difficult surgical procedure limits its use.

Autografts (Ross Procedure)• Autografts are valves taken from the same

patient in which the valve is implanted.• Used for patients with diseased aortic valves• Advantages:

– patient receives a living valve in the aortic position - Better durability and hemodynamics

Disadvantages: Difficult procedure for the surgeon and involves

considerable skill Leakage of the valve (aortic regurgitation)

• Stentless Bioprostheses • The first use of a nonallograft stentless valve was

in 1986 by David, at the Toronto General Hospital. • Because these prostheses have no rigid metal

stent, there is little inherent gradient across the valve.

• These valves are supported by the aortic root of the patient when implanted using the subcoronary or inclusion cylinder technique.

Prosthetic heart valves past present,future

• less chance for PPM• Favorable ventricular

remodeling.• Technically demanding

with longer cross-clamp times;

• long-term durability is also a question.

• FDA-approved stentless valves – Toronto Stentless SPV, – the Medtronic Freestyle,

and – the Edwards Prima Plus

Stentless Porcine Valve

Stentless Tissue Valves

• Subcoronary– Medtronic Freestyle– SJM Toronto SPV

• Full Root– Medtronic Freestyle– Edwards Primaplus– SJM Toronto SPV

Desired valves• Mechanical 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


• CLINICAL INFORMATION &CLINICAL EXAMINATION• IMAGING OF THE VALVES

CXR 2D echocardiography TEE 3D echo CineFluoro CT Cardiac catheterisation

Evaluation of prosthetic valves

CLINICAL INFORMATION

• Clinical data including reason for the study and the patient’s symptoms

• Type & size of replacement valve, • Date of surgery• Patient’s height, weight, and BSA should be

recorded to assess whether prosthesis-patient mismatch (PPM) is present

• BP & HR– HR particularly important in mitral and tricuspid

evaluations because the mean gradient is dependent on the diastolic filling period



CXR• Chest x-ray are not performed on a routine basis

in the absence of a specific indication.• It can be helpful in identification of valve type if

information about valve is not available.




• The location of the cardiac valves is best determined on the lateral radiograph.

• A line is drawn on the lateral radiograph from the carina to the cardiac apex.

• The pulmonic and aortic valves generally sit above this line and the tricuspid and mitral valves sit below this line.

CXREvaluation of prosthetic valves

• For further localization prosthetic valves involves drawing a second line which is perpendicular to the patient's upright position which bisects the cardiac silouette.

• The aortic valve projects in the upper quadrant, the mitral valve in the lower quadrant ,the tricuspid valve in the anterior quadrant and pulmonary valve in the superior portion of the posterior quadrant


CXREvaluation of prosthetic valves

• On the frontal chest radiograph ( AP or PA ) - longitudinal line through the mid sternal body. draw a perpendicular line dividing the heart horizontally.

• The aortic valve - intersection of these two lines.

• The mitral valve - lower left quadrant (patient’s left).

• The tricuspid valve - lower right corner (the patient's right)

• The pulmonic valve- upper left corner (the patient's left).

This method is less reproducible


Some bioprosthetic valves have components that determine the direction of flow which helps localize the valve prosthesis.

If the direction of flow is from inferior to superior – likely aortic valve. superior to inferior- likely a mitral valve.


2D ECHO Valves should be imaged from multiple views, with

attention to determine the specific type of prosthesis, confirm the opening and closing motion confirm stability of the sewing ring(abnormal rocking

motion ) Presence of leaflet calcification or abnormal echo density -

vegetations and thrombi Calculate valve gradient Calculate effective orifice area Confirm normal blood flow patterns Detection of pathologic transvalvular and paravalvular

regurgitation.Prosthetic valves

Past,Present & Future


TIMING OF ECHO CARDIOGRAPHIC FOLLOW-UP

• Ideally, a baseline postoperative transthoracic echocardiography(TTE) study should be

performed 3-12weeks after surgery, when the chest wound has healed, ventricular function has improved, and anaemia with its associated hyperdynamic state has

resolved.• Bioprosthetic valves Annual echocardiography is

recommended after the first 5years, • Mechanical valves, routine annual

echocardiography is not indicated in the absence of a change in clinical status.


Evaluation of prosthetic valves-2D ECHO

The high reflectance leads to • shadowing • Reverberations• multiple echocardiographic windows must be

used• TEE is necessary to provide a thorough

examination.• For stented valves-ultrasound beam aligned

parallel to flow to avoid the shadowing effects of the stents and sewing ring.



For bioprostheses, evidence of leaflet degeneration can be recognized

leaflet thickening (cusps >3 mm in thickness)-earliest sign

calcification (bright echoes of the cusps), tear (flail cusp).

Prosthetic valve dehiscence is characterized by a rocking motion of the entire prosthesis.

An annular abscess may be recognized as an echolucent, irregularly shaped area adjacent to the sewing ring of the prosthetic valve.


PRIMARY GOALS OF DOPPLER INTERROGATION

• Assesment of obstruction of prosthetic valve

• Detection and quantification of prosthetic valve regurgitation


Doppler Assessment of Obstruction of Prosthetic Valves

• Quantitative parameters of prosthetic valve functionTrans prosthetic flow velocity & pressure

gradients, valve EOA, Doppler velocity index(DVI).


Effective orifice area(EOA)

• Continuity equation EOA PrAV = (CSA LVO x VTI LVO) / VTI PrAV

However, this method cannot be applied when there is more than mild concomitant mitral or aortic regurgitation.

Better for bioprosthetic valves and single tilting disc mechanical valves.

Underestimation of EOA in case bileaflet valves.


EOA of mitral prostheses:Pressure half time may be useful if it is significantly

delayed or shows significant lengthening from one follow-up visit to the other despite similar heart rates.


PPM PPM occurs when the EOA of the prosthesis is

too small in relation to the patient’sbody size, resulting in abnormally high postoperative gradients. (Rahimtoola in 1978)

EOA indexed to the patient’s body surface area

.

PPM AORTIC MITRAL

Insignificant >0.85 cm2/m2. >1.20 cm²/m²

moderate 0.65and0.85cm2/m2. 0.9-1.20 cm²/m²

severe <0.65 cm2/m2. <0.90 cm²/m²


• Clinical implication of PPM• Impaired exercise capacity,• less regression of LV hypertrophy,• less improvement in coronary flow reserve• adverse cardiac events.• Moreover, PPM has a significant impact on both

short-term and long-term mortality• young patients than in older patients


• Prevention of PPM• Avoid moderate PPM in AVR;

– preexisting LV dysfunction and/or– severe LV hypertrophy, – age 65 to 70 years, and – regular and/or intense physical activity.

• Avoided by systematically – Calculating the projected indexed EOA of the

prosthesis– Model with better hemodynamic performance– Aortic root enlargement to accommodate a larger

size of the same prosthesis model.


• The prevention of PPM in the mitral position represents a much greater challenge than in the aortic position because valve annulus enlargement or stentless valve implantation is not an option in this situation.

Magne J, Mathieu P, Dumesnil JG, Tanné D, Dagenais F, Doyle D,

Pibarot P. Impact of prosthesis-patient mismatch on survival after mitral

valve replacement. Circulation. 2007;115:1417–1425.


Transprosthetic jet contour and acceleration time


DOPPLER VELOCITY INDEX

• Dimensionless ratio of the proximal flow velocity in the LVOT to the flow velocity through the aortic prosthesis

DVI=VLVOT/VPrAv

• Time velocity time integrals may also be used in Place of peak velocities

DVI= TVILVOT /TVIPrAv

• Prosthetic mitral valves, the DVI is calculated by DVI=TVIPrMv/TVILVOT


• IMPORTANCE

• DVI can be helpful to screen for valve dysfunction,

particularly when the

– Crosssectional area of the LVO tract cannot be obtained

– Valve size is not known.

• DVI is always less than unity, because velocity will always

accelerate through the prosthesis.

• Similar to EOA, DVI is not affected by high flow conditions

through the valve, including AR, whereas blood velocity and

gradient across the valve are.


DVI had a sensitivity, specificity, positive and negative predictive values, and accuracy of 59%, 100%, 100%, 88%, and 90%, respectively.


Transprosthetic velocity and gradient

• The flow is eccentric - monoleaflet valves three separate jets - bileaflet valvesmulti-windows

examination

Localised high velocity may be recorded by continuous wave(CW) DopplerInterrogation through the smaller central orifice of the bileaflet mechanical prostheses

overestimation of gradient


• Highvelocity or gradient alone is not proof of intrinsic prosthetic obstruction and may be secondary to

prosthesis patient mismatch (PPM), high flow conditions, prosthetic valve regurgitation, or localised high central jet velocity in bileaflet

mechanical valves. Increased heart rate.


Algorithm for interpreting abnormally high transprosthetic pressure gradients


DETECTION AND QUANTIFICATION OFPROSTHETIC VALVE REGURGITATION

• Physiologic Regurgitation. closure backflow (necessary to close the

valve) leakage backflow (after valve closure)-

washing jetsshort in durationnarrowsymmetricalhomogenous

• Pathologic Prosthetic Regurgitation.

Abnormal echoes

• Abnormal echoes that may be found in patients with prosthetic valves are spontaneous echo contrast (SEC), microbubbles or cavitations, strands,sutures, vegetations, thrombus.


Importance of TEE• Higher-resolution image than TTE • Proximity of the esophagus to the heart .• Size of vegetation defined more precisely• atrial side of the mitral valve prosthesis and

especially the posterior part of the aortic prosthesis.

• Peri annular complications indicating a locally uncontrolled infection (abscesses, dehiscence, fistulas) detected earlier.

Evaluation of prosthetic valves-

TEE evaluation immediately after valve replacement

1. Verify that all leaflets or occluders move normally.

2. Verify the absence of paravalvular regurgitation.3. Verify that there is no left ventricular outflow

tract obstruction by struts or subvalvular apparatus.

TEE diagnosis of prosthetic valve dysfunction1. Identification of prosthetic valve type.4. Detection and quantification of transvalvular or

paravalvular regurgitation.3. Detection of annular dehiscence.4. Detection of vegetations consistent with

endocarditis.5. Detection of thrombosis or pannus formation on

the valve.6. Detection and quantification of valve stenosis.7. Detection of tissue degeneration or calcification.

Evaluation of prosthetic valves-

Stress Echocardiography• Stress echocardiography should be considered

in patients with exertional symptoms for which the diagnosis is not clear.

• Dobutamine and supine bicycle exercise are most commonly used.

• Treadmill exercise provides additional information about exercise capacity but is less frequently used because the recording of the valve hemodynamics is after completion of exercise, when the hemodynamics may rapidly return to baseline.


Stress Echocardiography(cont)

Prosthetic Aortic Valves• Guide to significant obstruction would be similar

to that for native valves, such as a rise in mean gradient >15 mm Hg with stress.

Prosthetic Mitral Valves• Obstruction or PPM is likely if the mean gradient rises

> 18 mm Hg after exercise, even when the resting mean gradient is normal.


RT-3D TEE

• Excellent spacial imaging• Ease of use• Enables enface viewing(surgical

view)• adds to the available information

provided by traditional imaging modalities.

Cinefluoroscopy• Structural integrity • Motion of the disc or poppet• Excessive tilt ("rocking") of the base ring - partial

dehiscence of the valve• Aortic valve prosthesis - RAO caudal - LAO cranial Mitral valve prosthesis - RAO cranial .


Fluoroscopy of a normally functioning CarboMedics bileaflet prosthesis in mitral position

A=opening angle B=closing angle

Evaluation of prosthetic valves-Cinefluoroscopy

http://circ.ahajournals.org/content/vol108/issue90101/images/large/15FF1.jpeg

• St. Jude medical bileaflet valve – Mildly radiopaque

leaflets are best seen when viewed on end

– Seen as radiopaque lines when the leaflets are fully open

– Base ring is not visualized on most models

Evaluation of prosthetic valves-Cinefluoroscopy

Cardiac Catheterization

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

• can visualize and quantify valvular or paravalvular regurgitation

PREGNANCY AND PROSTHETIC VALVES

COMPLICATIONS

• Structural deterioration, particularly with bioprosthetic

• Valve obstruction due to thrombosis or pannus• Systemic embolization• Bleeding• Endocarditis and other infections• Left ventricular systolic dysfunction• Hemolytic anemia


• FREQUENCY OF COMPLICATIONS —• The frequency of serious complications depends

upon the valve type and position, and multiple clinical risk factors.

• The overall incidence of complications in appropriately managed patients is approximately 3 percent per year .

COMPLICATIONS

• Paravalvular Regurgitation• Paravalvular regurgitation typically is due

to– infection,– suture dehiscence, or– fibrosis and calcification of the native annulus,

leading to inadequate contact between the sewing ring and annulus.

COMPLICATIONS

• STRUCTURAL FAILURE —• Paravalvular leaks early after surgery are

common. • Incidence ranges from 18 to 48 percent of

patients with a mitral or aortic prosthesis; the majority of leaks are trivial or mild and do not progress over a two to five year follow-up.

• severe regurgitation results from prosthetic valve endocarditis or structural failure valve implantation.

Rallidis LS, Moyssakis IE, Ikonomidis I, Nihoyannopoulos P. Natural history of early aortic paraprosthetic regurgitation: a five-year follow-up. Am Heart J 1999; 138:351.

COMPLICATIONS

• Long-term outcomes —• The incidence of late structural failure varies with

the type of valve and with valve position.• The risk with current mechanical valves is

extremely low.• Most mechanical valves can be expected to last

20 to 30 years with the exception of the Bjork-Shiley convexoconcave (BSCC) valveHammermeister KE, Sethi GK, Henderson WG, et al.. Veterans

Affairs Cooperative Study on Valvular Heart Disease. N Engl J Med 1993; 328:1289.

COMPLICATIONS

• In contrast, 10 to 20 percent of human aortic homograft prostheses, and 30 to 35 percent of porcine heterograft prostheses fail within 10 to 15 years of implantation.– O'Brien MF, Stafford EG, Gardner MA, et al. Allograft

aortic valve replacement: long-term follow-up. Ann Thorac Surg 1995; 60:S65.

• Pericardial prostheses may be more durable than porcine valves . – Poirer NC, Pelletier LC, Pellerin M, Carrier M. 15-year

experience with the Carpentier-Edwards pericardial bioprosthesis. Ann Thorac Surg 1998; 66:S57.

• The failure rate with porcine valves is higher with valves in the mitral position (eg, 44 versus 26 percent in the aortic position at 15 years in the Veterans Administration trial) .

COMPLICATIONS


COMPLICATIONS

• 2.VALVE OBSTRUCTION — • Unexpected rise in transprosthetic gradient &

new symptomats dyspnea, heart failure, systemic embolization .

• Causes of obstruction include – thrombus, – pannus, and – vegetation.

• study of 112 obstructed mechanical valves, – thrombus alone -77%– pannus -11 %,– pannus with thrombus -12 % .

Deviri E, Sareli P, Wisenbaugh T, Cronje SL. Obstruction of mechanical heart valve prostheses: clinical aspects and surgical management. J Am Coll Cardiol 1991; 17:646.

COMPLICATIONS

Dürrleman N, Pellerin M, Bouchard D, et al. Prosthetic valve thrombosis: twenty-year experience at the Montreal Heart Institute. J Thorac Cardiovasc Surg 2004; 127:1388.

COMPLICATIONS

• Valve thrombosis —• Equal frequency in bioprosthetic valves and

mechanical valves.• The reported annual incidence of PVT ranges from

0.03 to 5.7%; higher rates with mitral prostheses (in some reports) and/or subtherapeutic anticoagulation.

Types of prosthetic valves and thrombogenicity

Type of valve Model Thrombogenicity

Mechanical

Caged ball Starr-Edwards ++++

Single tilting disc Bjork-Shiley,Medtronic Hall

+++

Bileaflet St Jude Medical,Sorin Bicarbon,Carbomedics

++

Bioprosthetic

Heterografts Carpentier-Edwards,Tissue Med (Aspire), Hancock II

+ to ++

Homografts +

• Diagnosis —• The gold standard for the diagnosis of PVT is

transesophageal echocardiography (TEE) and/or cine-fluoroscopy to assess both valve motion and clot burden .

• However, transthoracic Doppler echocardiography can establish the diagnosis in many patients and is also indicated to assess hemodynamic severity.

COMPLICATIONS

• Treatment — • Surgery and thrombolytic therapy, but neither is

ideal. • With surgery, there is a high operative mortality

that is largely related to clinical functional class (17.5% in patients in NYHA class IV compared to 4.7 % with less severe disease in a review of 106 patients) . – Deviri E, Sareli P, Wisenbaugh T, Cronje SL. Obstruction of

mechanical heart valve prostheses: clinical aspects and surgical management. J Am Coll Cardiol 1991; 17:646.

COMPLICATIONS

• As a result, thrombolytic therapy has evolved as an alternative to surgery.

• The largest study consisted of 127 episodes of obstructive PVT (almost all left-sided) in 110 patients with mechanical valves who were treated with various thrombolytic agents: streptokinase and urokinase initially and recombinant tissue-type plasminogen activator (alteplase)

COMPLICATIONS

Alpert JS. The thrombosed prosthetic valve: current recommendations based on evidence from the literature. J Am Coll Cardiol 2003; 41:659.

• The following findings were noted:• Complete hemodynamic resolution in 71 %, partial

resolution in 17%, and no resolution in 12 %. Surgery was performed in 23 percent.

• There was a trend toward greater efficacy in aortic valve prostheses (80 versus 65 percent in mitral valve prostheses).

• A 2nd dose -in 30 % and a 3rd - 9 percent. • Complications occurred in 25 % of patients.

– Major bleeding - 4.7 % (including two intracranial hemorrhages),

– systemic embolization in 15 percent, and – death in 11.8 percent due to complications or primary failure of

therapy.

• Recurrent PVT developed in 24 patients (19 %) at a mean interval of 2.1 years.

COMPLICATIONS

• Thrombolytic regimens include • alteplase (100 mg given as a 10 mg bolus

followed by 90 mg as an infusion over 90 minutes) or

• streptokinase (500,000 IU over 20 minutes followed by 1.5 million IU over 10 hours).

• Intravenous heparin is typically given concurrently to achieve an activated partial thromboplastin time 1.5 to 2.0 times control.

COMPLICATIONS

• We agree with the 2006 ACC/AHA guideline -• For left-sided PVT with

– NYHA class III to IV symptoms OR large clot burden, emergency operation is suggested.

– NYHA class III to IV symptoms(NYHA class II with large clot). with small or large clot burden, fibrinolytic therapy may be considered if surgery is high risk or not available.

– NYHA class II to IV symptoms and a large clot burden, fibrinolytic therapy may be considered if emergency surgery is high risk or not available.

– NYHA class I to II and small clot burden, fibrinolytic therapy may be considered as a first-line therapy. Alternatively, intravenous unfractionated heparin may be considered.

• For right-sided PVT with NYHA functional class III to IV OR large clot burden, fibrinolytic therapy is suggested.

ACC/AHA 2006 guidelines for the management of patients with valvular heart disease Circulation 2008; 118:e523.

COMPLICATIONS

• A size threshold for clot burden -– 2006 ACC/AHA - differing thresholds ranging from 5 to 8 mm. – 2008 ACCP guidelines a small area -<80 mm2 and a large

defined as ≥80 mm2.• For patients who have had successful resolution of PVT,

initiation of IV UFH and warfarin (or other vitamin K antagonist) therapy is suggested .

• Continuation of IV UFH -until a therapeutic INR is achieved.• For a mechanical valve in the aortic position, a goal INR of

3.5 (range 3.0 to 4.0) plus aspirin (50 to 100 mg/d) is suggested.

• For a mechanical valve in the mitral position, a goal INR of 4.0 (range 3.5 to 4.5) plus aspirin (50 to 100 mg/d) is suggested.

COMPLICATIONS

• Pannus formation —• Pannus formation due to fibrous tissue ingrowth

is a less common cause of valve obstruction .• Since thrombolytic therapy is an alternative to

surgery only for thrombosis, distinction between these two causes is important; echocardiography and clinical features are helpful in distinguishing between these

COMPLICATIONS

THROMBUS PANNUS

Shorter time from valve insertion to valve

dysfunction(62 days versus)

Longer(178 days)

Shorter duration of symptoms before reoperation (9days)

Longer ( 305 days)

Lower rate of adequate anticoagulation (21%)INR<2.5

Higher(versus 89 %)

Greater total mass length (2.8cm), primarily due to

extension into the left atrium,mobile

Smaller -1.2 cmfirmly fixed (minimal mobility)

to the valve apparatus

less echo-dense highly echogenic, (fibrous composition)

associated with spontaneous contrast,

common in aortic position Para valve jet suggests pannus

• SYSTEMIC EMBOLIZATION —• Systemic embolization can result from valve

thrombosis (even when nonobstructed), vegetations, or left atrial thrombus, particularly in patients with atrial fibrillation.

• Transesophageal echocardiography may be the preferred method for evaluating these patients

COMPLICATIONS

• The frequency of systemic embolization, predominantly cerebrovascular events, is approximately 0.7 to 1.0 percent per patient-year in patients with mechanical valves who are treated with warfarin .

• In comparison, the risk is 2.2 percent per patient-year with aspirin and 4.0 percent with no anticoagulation; patients with mitral valve prostheses are at twice the risk of those with aortic valve prostheses

COMPLICATIONS

If embolic event occurs while the patient is on adequate antithrombotic therapy

• If on warfarin with INR of 2.0 to 3.0: increase dose to achieve INR of 2.5 to 3.5

• If on warfarin with INR of 2.5 to 3.5: add aspirin 50 to 100 mg/d

• If on warfarin with INR of 2.5 to 3.5, plus aspirin 80 to 100 mg/d: aspirin dose may also need to be increased to 325 mg/d

• If on aspirin 325 mg/d: switch to warfarin with goal INR of 2.0 to 3.0

• BLEEDING —• Bleeding is a not infrequent problem in patients

with prosthetic heart valves .• The risk is greater with mechanical valves which,

because they are thrombogenic, require chronic anticoagulation.

• In contrast, most patients who receive a bioprosthetic valve are given only short-term anticoagulation unless there is an additional risk factor such as atrial fibrillationVongpatanasin W, Hillis LD, Lange RA. Prosthetic heart valves. N Engl J Med 1996; 335:407.

COMPLICATIONS

• ENDOCARDITIS —• Infective endocarditis and other infections such

as valve abscess can occur with prosthetic valves. • Transesophageal echocardiography is superior to

standard transthoracic echocardiography for the detection of valvular vegetation, ring abscesses, and other complications, particularly with mitral prostheses.

COMPLICATIONS

• Early endocarditis < 60 days P.O.D- perioperative bacteremia from skin/wound infections/contaminated intravascular devices.

• Staphylococcus epidermidis, S. aureus, gram-negative bacteria, diphtheroids, and fungi.

• Late prosthetic-valve endocarditis (>60 days POD) is usually caused by the organisms responsible for native-valve endocarditis, most often streptococci.

• However,S. epidermidis is a common causative organism up to 12 months after surgery.

Mechanical = Bioprosthetic valves

COMPLICATIONS

• Endocarditis Prophylaxis• Patients with prosthetic valves are at high risk for

endocarditis because of the foreign valve surface and sewing ring.

• Therefore, a lifelong requirement exists for antibiotic prophylaxis for dental, endoscopic, and surgical procedures in patients with a prosthetic valve.

• LEFT VENTRICULAR SYSTOLIC DYSFUNCTION —• Patients with prosthetic heart valves may

develop left ventricular systolic dysfunction with or without heart failure– Preoperative left ventricular dysfunction that

persists.– Perioperative myocardial infarction– Progression of other valve disease– Complications of the prosthetic valve– An unrelated disorder such as CAD or

hypertension

COMPLICATIONS

• HEMOLYTIC ANEMIA —• Hemolysis is associated with rapid regurgitant jet

and/or high peak shear rates.• Mild and subclinical, but is severe in up to 15

percent (ball-cage and bileaflet valves, or those with paravalvular regurgitation.)

• It is uncommon with tissue valves (except porcine valve failure).

• Presenting features may be subtle and include anemia, heart failure, jaundice, dark urine, increasing serum lactate dehydrogenase, and a new or changed regurgitant murmur .

• The peripheral smear -schistocytes and smaller red cell fragments

Maraj R, Jacobs LE, Ioli A, Kotler MN. Evaluation of hemolysis in patients with prosthetic heart valves. Clin Cardiol 1998; 21:387.

COMPLICATIONS

• Oral iron replacement is effective in the majority of patients, although transfusion may be required; in occasional patients, the administration of recombinant human erythropoietin may eliminate the need for transfusion .

• Reoperation may be required, especially if hemolysis is due to regurgitation from a paravalvular leak or valve failure.

COMPLICATIONS

• Mortality and morbidity — • The overall perioperative mortality following nonemergent

replacement of prosthetic heart valves is approximately 10 percent .

• In a review of 2246 consecutive procedures in 1984 patients between 1963 and 1992, the in-hospital mortality rates in patients with New York Heart Association class I, II, III, and IV were 2.3, 5.7, 9.1, and 21.0 percent, respectively.

• In-hospital mortality was lowest (1.3 percent) in the healthiest patients undergoing a first elective reoperation. Similar findings have been noted in other series.

• Age is another important determinant. It has been estimated that the perioperative mortality increases about three-fold from age 35 to age 75.Piehler JM, Blackstone EH, Bailey KR, et al. Reoperation on prosthetic

heart values. Patient-specific estimates of in-hospital events. J Thorac Cardiovasc Surg 1995; 109:30.

• Limitations of the current technology will continue to drive the field toward new, minimally invasive and endovascular approaches for valve delivery.

• Valves that have the capacity for growth and self-repair, especially suited to the treatment of congenital heart disease, may be within reach through the application of tissue-engineering strategies.

future

Transcatheter Aortic Valve Implantation (TAVI)

• 1993: Andersen– First description of valve

sutured in stent– Animal model– Encountered major limitations

• Obstruction of coronary ostia

Cribier- edward valve

first generation : Cribier-Edwards valve

Second generation Edwards SAPIEN

THV bovine pericardium that is firmly mounted within a tubular, slotted, stainless steel balloon-expandable stent

CoreValve Revalving device first implantation in 2005 - Grube et al• first-generation : bovine pericardial tissue and

was constrained with 25F delivery catheter. • second-generation : porcine pericardial tissue

within a 21 F catheter .

FUTURE.

Stentless pericardial valves. Sorin pericarbon Freedom (Aortic and

mitral)3F pericardial equine (aortic)SJM Quattro (mitral)

- Glutaraldehyde fixed at low concentrations.

- Three commissures created by suturing 3 flaps of pericardium.

FUTURE..

Autologous pericardial aortic valve.CardioMedspecial instrumentation (sizer,

tissue tester, cutting tool and formers to hold the tissue in the anatomical position) to construct the tissue.

tissue treated with 0.6% glutaraldehyde

animal studies.

FUTURE…Tissue engineered valves (microfabrication

techniques.) scaffolds either synthetic or natural.allograft valve decellularised and

repopulated in vitro with the host cells.endothelial cells from patient harvested,

cultured and incorporated in the scaffold.living valve then implanted.Tissue engineered heart valves: better

biocompatibility, less infection, life expectancy of valve increase,

To make artificial heart valves compatible for children.

FUTURE….

Polymers- durability superior to biological

valves. - haemocompatible.- polyurethane possess high tensile

strength and resistant to cyclic fatigue.

- surface modification to prevent thrombosis.

FUTURE…..

Flexible tube as heart valve.- James L Cox propounded that since the CV system begins in utero as a simple tube,

on attaining maturity all four heart valve

function as a simple tubes.

- Hence came into existence the concept of heart

valve replacement using flexible tubes.

Heart valve replacement using flexible tubes

US 5480424 A• Replacement of AV valves (mitral or tricuspid)-

the tube inlet is sutured to a valve annulus from which the native leaflets have been removed, and the tube outlet is sutured to papillary muscles in the ventricle.

• To create a semilunar (aortic or pulmonary) valve, the tube inlet is sutured to an annulus from which the native cusps have been removed, and the tube is either "tacked" at three points distally inside the artery; this allows the flaps of tissue between the three fixation points to function as movable cusps.

• These approaches generate flow patterns that closely duplicate the flow patterns of native valves.

• Preferred tubular material comprises submucosal tissue from the small intestine of the same patient.

• By using tissue from the same patient, the risk of immune rejection and the need to treat the tissue to reduce antigenicity are eliminated.

FUTURE…..

• The main characteristics of the tri-leaflet valve

• when completely open (65degrees) present a large central area for flow and therefore present a configuration with small resistance for blood flow.

• This large opening is the results of the location of the pivots which are the closest possible to the ring and the flow avoid the overgrow of natural tissue which way immobilize the leaves.

• permits a flow which is more similar to the natural valve.

• The main advantage of the present design is not only– central flow– velocity gradient in any radial direction is small

compared to the bi-leaflet valve. • In the case of the tri-leaflet valve, most of the

central region has a high range of velocities between 2.6 -2.0m/s , while in the bi-leaflet valve the velocity gradient is high.

• In such case the effect of any local disturbance in the flow has a much larger impact than in the tri-leaflet valve design.

SUMMARY

For the moment it seems that designing the ideal prosthetic valve is likely to occupy the visionary for many years to come. If human efforts is ever able to achieve absolute perfection in this matter, it would be the greatest breakthrough in valve replacement surgery.

The valve which lasts permanently without anticoagulation and without structural degeneration is still a distant reality at present, but surely not an impossible one.

Prosthetic valves the past present and future i tammi raju

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