Prosthetic Heart Valves from Research Paper

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The past six decades have witnessed significant advancements in patient survival and functional outcomes following heart valve replacement surgery.
Continued refinements in prosthetic valve design and performance, operative techniques, myocardial preservation, systemic perfusion, cerebral
protection, and anesthetic management have enabled the application of surgical and transcatheter valve therapy to an increasingly wider spectrum of
patients. Minimally invasive surgical approaches and the aggressive use of primary valve repair when anatomically appropriate are now routine
practice in the vast majority of high-volume centers. Heart valve teams have been formed to provide multidisciplinary assessment and treatment of
complex patients, including with the use of transcatheter heart valve replacement or repair when appropriate. More than 43,000 aortic or mitral valve
replacement operations (with or without coronary artery bypass) were reported to the Society of Thoracic Surgeons (STS) National Adult Cardiac
Database in 2015. Familiarity with the specific hemodynamic attributes, durability, thrombogenicity, and inherent limitations of currently available
heart valve substitutes, as well as their potential for long-term complications, is critical to appropriate clinical decision making for patients in whom
repair is not appropriate or feasible. The choice of valve prosthesis is inherently a trade-off between durability and risk of thromboembolism, with the
associated hazards and lifestyle limitations of anticoagulation. The ideal heart valve substitute remains an elusive goal.
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TYPES OF PROSTHETIC HEART VALVES
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Mechanical Valves The three basic types of mechanical prosthetic valves are bileaflet, tilting disc, and caged ball. The St. Jude bileaflet valve
was first used in 1977 and is the most frequently implanted mechanical prosthesis worldwide. It consists of two pyrolytic semicircular “leaflets” or
discs with a slitlike central orifice between the two leaflets and two larger semicircular orifices laterally. The opening angle of the leaflets relative to
the annulus plane ranges from 75 to 90 degrees. The CarboMedics valve is a variation of the St. Jude prosthesis that can be rotated to prevent
limitation of leaflet excursion by subvalvular tissue. For a given valve annulus size, effective orifice area (EOA) is generally larger and transprosthetic
pressure gradient lower for the bileaflet mechanical valves compared to the tilting disc valves. Because the central orifice is smaller than the lateral
orifices in bileaflet valves, the blood flow velocity may be locally higher within the inflow aspect of the central orifice; this phenomenon may lead to
overestimation of gradient and underestimation of EOA by transthoracic echocardiography (TTE). Bileaflet valves typically have a small amount of
normal regurgitation (“washing jet”), designed in part to decrease the risk of thrombus formation. A small, central jet and two converging jets
emanating from the hinge points of the discs can be visualized on color Doppler flow imaging.
Tilting disc or monoleaflet valves use a single, circular disc that rotates within a rigid annulus to occlude or open the valve orifice. The disc is secured
by lateral or central metal struts. The opening angle of the disc relative to the valve annulus ranges from 60 to 80 degrees, resulting in two orifices of
different size. The nonperpendicular opening angle of the valve occluder tends to slightly increase the resistance to blood flow, particularly in the
major orifices. Tilting disc valves also have a small amount of regurgitation, arising from small gaps at the perimeter of the valve.

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The bulky Starr-Edwards ball-in-cage valve, the oldest commercially available prosthetic heart valve first used in 1965, is now very rarely implanted.
The ball-cage valve is more thrombogenic and has less favorable hemodynamic performance characteristics than either bileaflet or tilting disc valves.
Currently available mechanical valves have excellent, long-term durability, with up to 45 years for the Starr-Edwards valve and more than 30 years for
the St. Jude valve. Structural deterioration, exemplified by some older-generation Björk-Shiley (strut fracture with disc embolization) and Starr-
Edwards (ball variance) prostheses, is now extremely rare. Ten-year freedom from valve-related death exceeds 90% for both St. Jude and CarboMedics
bileaflet valves. All patients with mechanical valves require lifelong anticoagulation with a vitamin K antagonist (VKA). Long-term issues associated
with mechanical valves include infective endocarditis, paravalvular regurgitation (PVR), hemolytic anemia, thromboembolism/valve thrombosis,
pannus ingrowth, and hemorrhagic complications related to anticoagulation.

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Tissue Valves Tissue or biologic valves include stented and stentless bioprostheses (porcine, bovine), homografts (or allografts) from human
cadaveric sources, and autografts of pericardial or pulmonic valve origin. Tissue valves provide an alternative, less thrombogenic heart valve substitute
that does not require long-term anticoagulation in the absence of additional risk factors for thromboembolism.
Stented Bioprosthetic Valves The traditional design of a heterograft valve consists of three biologic leaflets made from the porcine aortic valve or
bovine pericardium treated with glutaraldehyde to reduce its antigenicity. The leaflets are mounted on a metal or polymeric stented ring; they open to
a circular orifice in systole, resembling the anatomy of the native aortic valve. The vast majority of bioprosthetic valves are treated with anticalcifying
agents or processes. The newer generations of bovine pericardial valves (Carpentier-Edwards Magna or St. Jude Trifecta) offer improved
hemodynamic performance compared with earlier-generation bioprostheses. A small degree of regurgitation can be detected by color Doppler flow
imaging in 10% of normally functioning bioprostheses. One limitation of earlier generations of bioprosthetic valves was their limited durability due to
structural valve deterioration (SVD), typically beginning within 5 to 7 years after implantation, but varying by position and age at implant, with tissue
changes characterized by calcification, fibrosis, tears, and perforations. SVD occurs earlier for mitral than for aortic bioprosthetic valves, perhaps
because of exposure of the mitral prosthesis to relatively higher left ventricular (LV) closing pressures. The process of SVD is accelerated in younger
patients, in those with disordered calcium metabolism (end-stage renal disease), and possibly in pregnant women, independent of younger age. With
newer-generation bioprosthetic pericardial valves, the durability is excellent, with SVD rates of 2% to 10% at 10 years, 10% to 20% at 15 years, and
40% at 20 years.

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Stentless Bioprosthetic Valves The rigid sewing ring and stent-based construction of certain bioprostheses allow for easier implantation and
maintenance of the three-dimensional relationships of the leaflets. However, these features also contribute to impaired hemodynamic performance.
Stentless porcine valves were developed in part to address these issues . Their use has been restricted to the aortic position. Implantation is
technically more challenging, whether deployed in a subcoronary position or as part of a miniroot, and thus these valves are preferred by only a
minority of surgeons. Early postoperative mean gradients can be less than 15 mm Hg, with further improvement in valve performance over time from
aortic root remodeling, lower peak exercise transvalvular gradients, and more rapid reduction in LV mass. Sutureless bioprosthetic valves have also
been developed to decrease the complexity and duration of implantation of bioprosthetic valves.
Homografts Aortic valve homografts are harvested from human cadavers within 24 hours of death and are treated with antibiotics and cryopreserved
at −196°C. They are now usually implanted in the form of a total root replacement with reimplantation of the coronary arteries. Homograft valves
appear resistant to infection and are preferred by some surgeons for management of aortic valve and root endocarditis in the active phase. Neither
immunosuppression nor routine anticoagulation is required. Despite earlier expectations, long-term durability beyond 10 years is not superior to that
for current-generation pericardial valves, and reoperation may be technically more challenging.

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Autografts In the Ross procedure the patient’s own pulmonic valve or autograft is harvested as a small tissue block containing the pulmonic valve,
annulus, and proximal pulmonary artery and is inserted in the aortic position, usually as a complete root replacement with reimplantation of the
coronary arteries. The pulmonic valve and right ventricular outflow tract are then replaced with either an aortic or pulmonic homograft. Thus the
procedure requires two separate valve operations, a longer time on cardiopulmonary bypass, and a steep learning curve. With appropriate selection
of young patients by expert surgeons at experienced centers of excellence, operative mortality rates are less than 1% and 20-year survival rates as
high as 95%, similar to the general population. Advantages of the autograft include the ability to increase in size during childhood growth, excellent
hemodynamic performance characteristics, lack of thrombogenicity, and resistance to infection. The hemodynamic performance characteristics of the
pulmonary autograft are similar to those of a normal, native aortic valve. The procedure is usually reserved for children and young adults, but should
be avoided in patients with dilated aortic roots, given the unacceptably high incidence of accelerated degeneration, pulmonary autograft dilation, and
significant regurgitation.

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Transcatheter Bioprosthetic Valves Transcatheter aortic valve replacement (TAVR) is a valuable alternative to surgical aortic valve replacement in
patients with symptomatic severe aortic stenosis (AS) considered to be at extreme, high, or intermediate surgical risk. Two main types of
transcatheter aortic valves are currently used: balloon-expandable valves and self-expanding valves.
The Edwards SAPIEN XT and SAPIEN 3 balloon-expandable valves consist of a three-leaflet pericardial bovine valve mounted in a cobalt chromium
frame. These valves are available in 20, 23, 26 and 29 mm sizes. Common access routes for TAVR are transfemoral, transapical, and transaortic.
Approximately 75% to 80% of TAVR procedures are now performed by a transfemoral approach. As catheter sheath sizes decrease (now 14F or 16F for
most valves), the balance is anticipated to shift even more toward the transfemoral approach. The transfemoral approach is associated with lower
mortality and quicker recovery compared to alternative access approaches.
The CoreValve balloon-expandable valve consists of three leaflets of porcine pericardium seated relatively higher in a nitinol frame to provide true
supra-annular placement and is available in 26, 29, and 31 mm sizes. The CoreValve is most frequently implanted using the transfemoral approach.
For a given aortic annulus size, transcatheter valves have larger EOAs and lower gradients compared to surgical bioprosthetic valves. PVR, however,
occurs much more often following TAVR and has adverse long-term consequences. Mild regurgitation occurs in 25% to 60% of patients and moderate
or severe regurgitation in 3% to 20%. Moderate or severe PVR is associated with a 2.0- to 2.5-fold increase in mortality. The most recent transcatheter
balloonexpandable valve (SAPIEN 3) was designed with a skirt to reduce PVR. The rate of moderate or severe regurgitation has dropped to less than
3% with its use. Some studies suggest that self-expanding valves have slightly larger EOAs and lower gradients but somewhat higher rates of PVR than
balloon-expandable valves.

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Dr. Merra Shodwe

CHOICE OF VALVE REPLACEMENT
PROCEDURE AND PROSTHESIS
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Dr. Jonathan Smith
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Once the indication for valve replacement is established, the next step is to select the type of procedure (repair versus replacement) and the type of
prosthetic valve should replacement be necessary. The 2014 American Heart Association and American College of Cardiology (AHA/ACC) guidelines for
the management of patients with valvular heart disease advocate shared (patient-cardiologist–cardiac surgeon) decision making on the choice of
intervention (repair or replacement, transcatheter or surgical) as well as the type of prosthetic valve (mechanical valve or bioprosthesis). This choice is
based on consideration of several factors, including valve durability, expected hemodynamics for a specific valve type and size, surgical or
interventional risk, the potential need for long-term anticoagulation, and patient preferences
Choice of Prosthetic Valve A bioprosthesis is recommended in patients of any age in whom anticoagulant therapy is contraindicated, cannot be
managed appropriately, or is not desired.2,26 A mechanical prosthesis is reasonable for AVR or MVR in patients younger than 50 who do not have a
contraindication to anticoagulation, whereas a bioprosthesis is reasonable in patients older than 70 years.26 Either a bioprosthetic or a mechanical
valve is reasonable in patients between 50 and 70 years old. A bioprosthesis is reasonable for young women contemplating pregnancy to avoid the
hazards of anticoagulation in this setting.

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Dr. Jonathan Smith
Dr. Merra Shodwe
Choice of Procedure In patients with severe AS having an indication for AVR (see Chapter 68), the choice between surgical AVR versus TAVR is based
on the predicted surgical risk, which is assessed by combining the STS-PROM estimate, patient frailty, major organ system dysfunction, and procedure-
specific impediments. TAVR is recommended in patients who meet an indication for AVR for severe AS and who have a prohibitive surgical risk and a
predicted post-AVR survival longer than 1 year. Surgical AVR or TAVR is recommended for patients with high surgical risk, depending on patient-
specific procedural risks and preferences. TAVR is a reasonable alternative to surgical AVR for intermediate-risk patients, whereas surgical AVR is
recommended for patients with low surgical risk. In patients with chronic severe primary mitral regurgitation (MR) who meet an indication for mitral
valve surgery (see Chapter 69), mitral valve repair is recommended over MVR when a successful and durable repair can be accomplished. In patients
with chronic secondary MR, MVR may actually be superior to mitral valve repair because it is associated with lower rates of recurrent MR. Tricuspid
valve annuloplasty repair is frequently performed at leftsided valve surgery when tricuspid regurgitation (TR) is severe or when there is significant
tricuspid annular dilation (>40 mm) despite only mild or moderate degrees of TR. Tricuspid valve replacement is undertaken for severe disease that
cannot be repaired, such as with advanced rheumatic disease, carcinoid, or destructive endocarditis. Surgical or transcatheter pulmonic valve
replacement in the adult is rare.

MEDICAL MANAGEMENT AND
SURVEILLANCE AFTER VALVE
REPLACEMENT
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Dr. Jonathan Smith
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Antithrombotic Therapy
General Principles
Table 71.1 presents the antithrombotic regimen that is recommended in the 2014 AHA/ACC guideline for the different types of procedures and
prosthetic valves. All patients with mechanical heart valves require lifelong anticoagulation with a VKA, the intensity of which varies as a function of
valve type or thrombogenicity, valve position and number, and the presence of additional risk factors for thromboembolism, such as atrial fibrillation,
LV systolic dysfunction, a history of thromboembolism, and hypercoagulable state. Anticoagulant therapy with oral direct thrombin inhibitors or anti-
Xa agents should not be used in patients with mechanical prostheses. Although there is no clear consensus, a VKA may be used even in the absence of
risk factors for thromboembolism for the first 3 to 6 months after bioprosthetic AVR or MVR. Longer-term treatment of low-risk bioprosthetic AVR and
MVR patients consists of low-dose aspirin, although there are no data to support this practice.

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Interruption of Antithrombotic Therapy In the planned interruption of VKA therapy for noncardiac surgery, the following
must be taken into account: the nature of the procedure; the magnitude of risk of thromboembolism based on valve type, position, and number;
underlying patient risk factors; and the competing risk of periprocedural hemorrhage. Low-risk patients with low-profile bileaflet or tilting disc valves
in the aortic position can usually stop VKA therapy 3 to 5 days before noncardiac surgery and then resume it postoperatively as soon as considered
safe, without the need for a heparin “bridge.” In all other patients, either low-molecular-weight heparin (LMWH) or intravenous unfractionated
heparin (UFH) should be given both before and after surgery, as directed by the surgeon. The use of LMWH avoids the need for preoperative
hospitalization. Randomized trial data are sparse and institutional/operator variability is great regarding the use of bridging strategies for noncardiac
surgery in such patients.

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Dr. Jonathan Smith
Dr. Merra Shodwe
PregnancyPregnant patients with prosthetic valves should be followed carefully because of the increased hemodynamic burden that can cause
or worsen heart failure if there is prosthetic valve dysfunction or if the hypercoagulable state related to pregnancy increases the risk of valve
thrombosis. All antithrombotic regimens carry an increased risk to the fetus, an increased risk of miscarriage, and hemorrhagic complications for the
mother. Therefore, patients require appropriate counseling, close monitoring, and adjustment of anticoagulation therapy. In pregnant patients with
mechanical valves, warfarin is reasonable (class IIa) in the first trimester if the dose is 5 mg/day or less and is recommended (class I) to achieve a
therapeutic international normalized ratio (INR) target in the second and third trimesters. Discontinuation of warfarin with initiation of intravenous
UFH is recommended before planned vaginal delivery in pregnant patients with a mechanical valve.
Infective Endocarditis ProphylaxisPatients with prosthetic valves are at increased risk for infective endocarditis because of the
foreign valve surface and sewing ring. Antibiotic prophylaxis is only indicated (class IIa) for patients with prosthetic valves who undergo dental
procedures that involve manipulation of gingival tissue, the periapical region of teeth, or perforation of the oral mucosa. Prophylaxis is no longer
recommended for nondental procedures such as transesophageal echocardiography (TEE), esophagogastroduodenoscopy, colonoscopy, or cystoscopy
(unless there is active infection in these areas).

EVALUATION AND TREATMENT OF
PROSTHETIC VALVE DYSFUNCTION AND
COMPLICATIONS
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Dr. Jonathan Smith
Dr. Merra Shodwe
The suspicion of prosthetic valve dysfunction may be the appearance of a new murmur or symptom in a patient with a
prosthetic valve or the incidental finding of abnormally high flow velocities and gradients detected during a routine
echocardiography. Doppler-echocardiography is the method of choice to evaluate prosthetic valve function, identify and
quantitate prosthetic valve stenosis or regurgitation, and identify patient-prosthesis mismatch. Cinefluoroscopy and
multidetector computed tomography (MDCT) may also be very helpful to evaluate leaflet mobility in mechanical and
bioprosthetic valves, respectively. Prosthetic valve stenosis may be caused by thrombus formation, pannus ingrowth (or a
combination of both), leaflet calcification in the case of bioprosthetic valves, and vegetations related to PVE. Prosthetic valve
regurgitation may be caused by thrombus formation (mechanical valves), leaflet tear (bioprostheses), vegetations, or PVR.

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Prosthesis-Patient Mismatch Patient-prosthesis mismatch (PPM) occurs when the size of a normally functioning prosthetic valve is too
small in relation to the patient’s body size, and thus to the patient’s cardiac output requirements, resulting in abnormally high postoperative
gradients. PPM is defined as an indexed EOA less than 0.85 cm2 (severe, <0.65 cm2 ) for aortic prosthetic valves and less than 1.2 cm2 (severe, <0.9
cm2 ) for mitral prosthetic valves. The prevalence of moderate PPM ranges from 20% to 70% and severe PPM from 2% to 10% after AVR or MVR.
Patients with aortic PPM have worse functional class and exercise capacity, reduced regression of LV hypertrophy, more adverse cardiac events, and
increased risk of both perioperative and late mortality after AVR compared with patients who do not have PPM. Patients with mitral PPM have
persisting pulmonary hypertension and increased incidence of heart failure and death. A greater clinical impact of aortic PPM is also observed in
specific groups of patients such as those with preexisting LV dysfunction or severe LV hypertrophy, and/or concomitant MR, as well as in those
younger than 65 to 70 years. PPM is less common with TAVR compared to surgical AVR, particularly in the subset of patients with a small aortic
annulus. Figs. 71.2 and 71.3 provide algorithms for differentiating between normal prosthetic valve function, PPM, and intrinsic valve dysfunction
caused by SVD, thrombus, or pannus.

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Dr. Jonathan Smith
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Structural Valve Deterioration Mechanical prostheses have an excellent durability, and SVD is extremely rare with contemporary valves,
although mechanical failure (e.g., strut fracture, leaflet escape, occluder dysfunction caused by lipid adsorption) occurred with some models in the
past. On the other hand, SVD from leaflet calcification or collagen fiber disruption is the major cause of bioprosthetic valve failure. SVD may lead to
leaflet stiffening and progressive stenosis or leaflet tear with ensuing transvalvular regurgitation. Although SVD of bioprostheses has long been
considered a purely passive degenerative process, more recent studies suggest that active and potentially modifiable processes may be involved,
including lipid infiltration, inflammation, immune rejection, and active mineralization. Transcatheter valve-in-valve implantation offers a valuable
alternative to surgery for patients with failed bioprosthetic valves who are at high or extreme surgical risk for reoperation.

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Dr. Jonathan Smith
Paravalvular Regurgitation Paravalvular regurgitation (PVR) occurs external to the prosthetic valve at the interface between the sewing ring
and the native valve annulus . It can occur as a result of inadequate technique, suture dehiscence, compromised native tissue integrity (dense
calcification, extensive myxomatous degeneration), infection, or chronic abrasion of the sewing ring against a calcified or rigid annulus. The magnitude
of the regurgitant volume will depend on the size of the orifice. A small, hemodynamically inconsequential paravalvular leak is usually discovered
incidentally during routine TTE with color Doppler flow imaging, with no change in management indicated. However, small paravalvular leaks may be
associated with significant intravascular hemolysis and anemia as red blood cells are forced through a narrow orifice at high velocity. Despite a high
clinical index of suspicion in this circumstance, a new, regurgitant murmur may not be audible. TEE may be necessary to differentiate PVR from
transvalvular regurgitation and to visualize the defect appropriately, especially with mitral prostheses. Larger paravalvular leaks may result in
significant volume overload and heart failure, to an extent that reoperation might be indicated. Significant PVR may develop during the late
postoperative period and is often the result of endocarditis. Experience with transcatheter closure devices in patients with clinically important PVR
has increased, but results to date have been mixed. Management can prove challenging, and a conservative approach with medical therapy is often
chosen, in part related to the risks associated with reoperation in some patients

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Dr. Jonathan Smith
PVR occurs more frequently after transcatheter than surgical AVR; its incidence is significantly lower with newer-generation TAVR prostheses. Because
PVR jets after transcatheter AVR are often multiple, irregular, and eccentric, the imaging and grading of PVR can be challenging. A multiwindow,
multiparametric, integrative approach is essential to assess the severity of PVR by Doppler echocardiography. Other imaging modalities, such as
cineangiography, cardiac CT, and cardiac magnetic resonance imaging, as well as serum biomarkers, may also be useful to complement or corroborate
the findings on echocardiography. Corrective procedures such as repeat balloon dilation, valve-in-valve implantation, and transcatheter leak closure
may be considered depending on the severity of PVR and the risk of procedural complications.

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Dr. Jonathan Smith
Thromboembolism and Bleeding Thromboemboli are a major source of morbidity in patients with prosthetic heart valves. The incidence
of clinically recognizable events ranges from 0.6% to 2.3% per patient-year, an estimate that does not account for any subclinical episodes that might
be detected with sensitive imaging techniques. Thromboembolic incidence rates are similar for non-anticoagulated patients with bioprostheses and
appropriately anticoagulated patients with mechanical valves. Risk factors for thromboembolism include the inherent thrombogenicity of the
prosthesis, valve position (mitral > aortic), valve number, time spent out of the therapeutic range of anticoagulation, a history of thromboembolism,
hypercoagulable state, atrial fibrillation, left atrial enlargement, and LV systolic dysfunction. The risk of bleeding, estimated at 1% per patient-year,
increases with age and the intensity of anticoagulation. In patients with uncontrollable bleeding who require reversal of anticoagulation,
administration of fresh-frozen plasma or prothrombin-complex concentrate is reasonable.
Management of a thromboembolic event in patients with mechanical valves generally proceeds as follows :
• For patients whose INR is subtherapeutic, the dose of the VKA is advanced to achieve the intended INR range.
• For patients whose INR is in the therapeutic range, the dose of the VKA is advanced to achieve a higher INR range, and/or low-dose aspirin is
provided if not already used.
• The patient and family are informed about the increased risks of bleeding.
• The potential for drug interactions is reviewed.
Reoperation to implant a less thrombogenic valve is rarely undertaken for patients with recurrent thromboemboli despite aggressive antithrombotic
therapy.

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Dr. Jonathan Smith
Prosthetic Valve Thrombosis The incidence of mechanical valve thrombosis is estimated at 0.3% to 1.3% per patient-year in developed
countries, but as high as 6% per patient-year in developing countries.2 Thrombosis of a mechanical heart valve can have devastating consequences.
Bioprosthetic (surgical or transcatheter) valve thrombosis is less common, with a reported incidence of 0.03% to 0.5% per patient-year. However,
recent studies suggest that subclinical thrombosis may occur in 5% to 15% of patients within the first 2 years after TAVR.
Clinical suspicion of prosthetic valve thrombosis should be raised by symptoms of heart failure, thromboembolism, or low cardiac output, coupled
with a decrease in the intensity of the valve closure sounds (mechanical valves), new and pathologic murmurs, or documentation of inadequate
anticoagulation. Thrombosis is more common in the mitral and tricuspid positions than in the aortic position. Although differentiation from pannus
formation can be difficult, the clinical context usually allows accurate diagnosis. Evaluation with TTE/TEE can help guide management decisions. In
patients with mechanical valves, confirmation of abnormal leaflet or disc excursion in the presence of an occluding thrombus can also be obtained
with cinefluoroscopy. MDCT can be useful to identify leaflet thickening and reduced mobility after valve replacement with a bioprosthesis.

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Dr. Jonathan Smith
Emergency surgery is reasonable for patients with left-sided prosthetic valve thrombosis and shock or New York Heart Association (NYHA) Functional
Class III or IV symptoms and for patients with a large thrombus burden (≥0.8 cm2 on TEE). Fibrinolytic therapy is reasonable for patients with recent-
onset (<2 weeks) NYHA Class I or II symptoms and small thrombus burden (<0.8 cm2 ) and for sicker patients with larger thrombi when surgery is
either not available or inadvisable. Fibrinolytic therapy is generally recommended for patients with rightsided prosthetic valve thrombosis. Some
patients with no or minimal symptoms and small thrombi can often be managed with intravenous UFH alone and then converted to fibrinolytic
therapy if unsuccessful. An encouraging report of the efficacy of low-dose, slow-infusion tissue plasminogen activator in pregnant women with
prosthetic valve thrombosis should prompt investigation of this approach in other patient subsets. Any course of fibrinolytic therapy is followed at the
appropriate interval by a continuous infusion of UFH during the transition to VKA therapy targeted to a higher INR, with or without low-dose aspirin.
Serial TTE studies are useful to assess the response to treatment. In patients with suspected or confirmed bioprosthetic valve thrombosis who are
hemodynamically stable and have no contraindications to anticoagulation, initial treatment with a VKA is reasonable.

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Dr. Jonathan Smith
Infective Endocarditis Prosthetic valve endocarditis is the most severe form of infective endocarditis (IE) and occurs in 1% to 6% of patients
with valve prostheses, accounting for 10% to 30% of all IE cases. PVE is an extremely serious condition with high mortality (30% to 50%). The
diagnosis, based on the Modified Duke Criteria, relies predominantly on the combination of positive blood cultures and echocardiographic evidence of
prosthetic valve infection, including vegetations, paravalvular abscess, or a new PVR. TEE is essential in patients with prosthetic valves because of its
greater sensitivity in detecting these abnormalities. Recent studies suggest that increased uptake of F-fluorodeoxyglucose measured by positron
emission tomography combined with computed tomography (PET-CT) may improve the early diagnosis of PVE. Despite prompt and appropriate
antibiotic treatment, many patients with PVE will eventually require surgery. Medical treatment alone is more likely to succeed in late PVE (>6 months
after surgery) and in nonstaphylococcal infections. Surgery should be considered in patients with heart failure; failure of antibiotic treatment;
hemodynamically significant prosthetic valve regurgitation, especially if associated with deterioration of LV function; large vegetations (>10 mm);
persistently positive blood cultures on therapy; recurrent emboli with persistent vegetations; and intracardiac fistula formation2. PVE after TAVR
occurs predominantly within the first year after the procedure; its incidence is low (1%/patient-year), but in-hospital (approximately 35%) and 2-year
(67%) mortality rates are high, likely reflective of patient age and comorbidities.

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Hemolytic Anemia The development of a nonimmune hemolytic anemia after valve replacement or repair is usually attributable to PVR with
intravascular red blood cell destruction. Diagnosis is based on a high index of suspicion, coupled with laboratory evidence of hemolysis, including the
characteristic changes in red blood cell morphology (schistocytes), elevated indirect bilirubin and LDH, a high reticulocyte count, and depressed serum
haptoglobin. Reoperative surgery or catheter closure of the defect is indicated when heart failure, a persistent transfusion requirement, or poor
quality of life intervenes. Empiric medical measures include iron and folic acid replacement therapy and betaadrenoreceptor blockers. It is important
to exclude PVE as a cause.

Prosthetic Heart Valves from Research Paper

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