Prosthetic Heart Valves
- Author: Eric M Kardon, MD, FACEP; Chief Editor: Richard A Lange, MD, MBA more...
Bioprosthetic valves (see the image below) used in heart valve replacement generally offer functional properties (eg, hemodynamics, resistance to thrombosis) that are more similar to those of native valves. Implantation of prosthetic cardiac valves to treat hemodynamically significant aortic or mitral valve disease has become increasingly common.
Replacement of diseased valves with prosthetic heart valves reduces the morbidity and mortality associated with native valvular disease, but it comes at the expense of risking complications related to the implanted prosthetic device. Emergency medicine physicians must be able to rapidly identify patients at risk and begin appropriate diagnostic testing, stabilization, and treatment. Even when promptly recognized and treated, acute prosthetic valve failure is associated with a high mortality rate.
Essential update: Study finds equivalent patient survival rates for bioprosthetic and mechanical aortic valves
In a retrospective cohort analysis of 4253 patients who underwent primary isolated aortic-valve replacement, 15-year survival and stroke rates were equivalent with bioprosthetic and mechanical valves. For bioprosthetic valves, the risk of repeat surgery was greater but the incidence of major bleeding was lower.[1, 2]
In propensity-matched comparisons, actuarial 15-year mortality rates were 60.6% with the bioprosthetic aortic valve and 62.1% with the mechanical valve. Cumulative 15-year stroke rates were 7.7% and 8.6% in the two groups, respectively. The reoperation rate was 12.1% in the bioprosthetic valve group at 15 years and 6.9% in the mechanical valve group, while major bleeding occurred in 6.6% of bioprosthesis patients and in 13.0% of the mechanical-valve group.
Signs and symptoms
Signs and symptoms of prosthetic heart valve malfunction depend on the type of valve, its location, and the nature of the complication. Presentations may include the following:
Acute prosthetic valve failure: Sudden onset of dyspnea, syncope, or precordial pain
Acute aortic valve failure: Sudden death; survivors have acute severe dyspnea, sometimes accompanied by precordial pain, or syncope
Subacute valvular failure: Symptoms of gradually worsening congestive heart failure; they also may present with unstable angina or, at times, may be entirely asymptomatic
Embolic complications: Symptoms related to the site of embolization (eg, stroke, myocardial infarction [MI], sudden death, or symptoms of visceral or peripheral embolization)
Anticoagulant-related hemorrhage: Symptoms related to the site of hemorrhage
A history of fever should raise the possibility of prosthetic valve endocarditis (PVE).
On physical examination, normal prosthetic heart valve sounds include the following:
Mechanical valves: Loud, high-frequency, metallic closing sound; soft opening sound (tilting disc and bileaflet valves); low-frequency opening and closing sounds of nearly equal intensity (caged ball valves)
Tissue valves: Closing similar to those of native valves, low-frequency early opening sound in the mitral position
Prosthetic heart valve murmurs noted include the following:
Aortic prosthetic valves: Some degree of outflow obstruction with a resultant systolic ejection murmur (loudest in caged ball and small porcine valves); low-intensity diastolic murmur (tilting disc and bileaflet valves)
Mitral prosthetic valves: Low-grade systolic murmur (caged ball valves); short diastolic murmur (bioprostheses and, occasionally, St. Jude bileaflet valves)
Additional findings may include the following:
Acute valvular failure: Evidence of poor tissue perfusion; hyperdynamic precordium and right ventricular impulse (50% of cases); absence of a normal valve closure sound or presence of an abnormal regurgitant murmur
Subacute valvular failure: Rales and jugular venous distention; signs of right-side failure; a new regurgitant murmur or absence of normal closing sounds; a new or worsening hemolytic anemia (may be the only presenting abnormality)
PVE (often obscure): Fever (97% of cases); a new or changing murmur (56% of cases); classic signs of native valve endocarditis; splenomegaly; congestive heart failure, septic shock, or primary valvular failure; systemic emboli
See Clinical Presentation for more detail.
Laboratory studies that may be useful include the following:
Complete blood count
Blood urea nitrogen (BUN) and creatinine levels
Prothrombin time (PT) or international normalized ratio (INR)
Imaging studies that may be helpful include the following:
Chest radiography: This can help in delineating the valvular morphology and determining whether the valve and occluder are intact; each of the most commonly used valve types has its own characteristic radiographic appearance
Echocardiography (2-dimensional, Doppler, transesophageal [the study of choice for a suspected prosthetic valve complication], transthoracic)
Cinefluorography: This may detect impaired occluder movement but often cannot readily determine the etiology
Computed tomography: A consensus statement from the Society of Cardiovascular Computed Tomography (SCCT) states that CT should be performed as part of the evaluation of all patients being considered for transcatheter aortic valve implantation (TAVI)/transcatheter aortic valve replacement (TAVR), except those in whom CT is contraindicated, [3, 4] and that the CT images should be interpreted with a member of the TAVI/TAVR team or reviewed with the operator before the procedure
See Workup for more detail.
In patients with acute valvular failure, diagnostic studies must be performed simultaneously with resuscitative efforts.
Treatment approaches to primary valve failure include the following:
Emergency valve replacement
Concomitant adjunctive therapy
Afterload reduction and inotropic support
In selected cases, intra-aortic balloon counterpulsation
Treatment approaches to PVE include the following:
Intravenous antibiotics administered as soon as 2 sets of blood cultures are drawn
Cessation of warfarin until central nervous system involvement is ruled out and invasive procedures are determined to be unnecessary 
Consideration of anticoagulation
Consideration of emergency surgery in patients with moderate to severe heart failure or with an unstable prosthesis noted on echocardiography or fluoroscopy
Treatment approaches to thromboembolic complications include the following:
Anticoagulation (if it has not already been initiated or if the patient has a subtherapeutic INR)
Assessment of valve function
Note: US dabigatran prescribing information now includes a contraindication in patients with mechanical prosthetic valves 
Treatment approaches to prosthetic valve thrombosis include the following:
Surgery (historically the mainstay of treatment but associated with a high mortality)
Thrombolytic therapy (appropriate for selected patients with thrombosed prosthetic valves): Should always be performed in conjunction with cardiovascular surgical consultation
In cases of major anticoagulant-related hemorrhage, reversal of anticoagulation
Implantation of prosthetic cardiac valves to treat hemodynamically significant valvular disease has become an increasingly common procedure. It is estimated that 60,000-95,000 patients per year are undergoing heart valve replacement in the United States.
Bioprosthetic valves used in heart valve replacement generally offer functional properties (eg, hemodynamics, resistance to thrombosis) that are more similar to those of native valves. Implantation of prosthetic cardiac valves to treat hemodynamically significant aortic or mitral valve disease has become increasingly common.
Replacement of diseased valves reduces the morbidity and mortality associated with native valvular disease but comes at the expense of risking complications related to the implanted prosthetic device. These complications include primary valve failure, prosthetic valve endocarditis (PVE), prosthetic valve thrombosis (PVT), thromboembolism, and mechanical hemolytic anemia. In addition, because many of these patients require long-term anticoagulation, anticoagulant-related hemorrhage may occur.
Transcatheter approaches to aortic valve implantation have allowed patients previously felt to be poor operative risks to undergo valve replacement.
Emergency medicine physicians must be able to rapidly identify patients at risk and begin appropriate diagnostic testing, stabilization, and treatment. Even when promptly recognized and treated, acute prosthetic valve failure is associated with a high mortality rate.
More than 80 models of artificial valves have been introduced since 1950. In day-to-day emergency practice, however, it is necessary to be familiar with a few basic types. Prosthetic valves are either created from synthetic material (mechanical prosthesis) or fashioned from biological tissue (bioprosthesis). The choice of prosthesis is determined by the anticipated longevity of the patient and his/her ability to tolerate anticoagulation.
Three main designs of mechanical valves exist: the caged ball valve, the tilting disc (single leaflet) valve, and the bileaflet valve. The only Food and Drug Administration (FDA)–approved caged ball valve is the Starr-Edwards valve, shown in the image below.
Tilting disc valve models include the Medtronic Hall valve, shown in the image below, Omnicarbon (Medical CV) valves, Monostrut (Alliance Medical Technologies), and the discontinued Bjork-Shiley valves.
Bileaflet valves include the St. Jude (St. Jude Medical), shown in the image below, which is the most commonly implanted valve in the United States; CarboMedics valves (Sulzer CarboMedics); ATS Open Pivot valves (ATS Medical); and On-X and Conform-X valves (MCRI).
Bioprosthetic (xenograft) valves are made from porcine valves or bovine pericardium. Porcine models include the Carpentier-Edwards valves (Edwards Lifesciences) and Hancock II and Mosaic valves (Medtronic); both valves are shown in the images below.
Pericardial valves include the Perimount series valves (Edwards LifeSciences). Ionescu-Shiley pericardial valves have been discontinued. Stentless porcine valves have also come into use. They offer improved hemodynamics with a decreased transvalvular pressure gradient when compared with older stented models. These models include the Edwards Prima Plus, Medtronic Freestyle, and Toronto SPV valve (St. Jude Medical).
Homografts or preserved human aortic valves are used in a minority of patients.
Two devices have been approved for transcatheter aortic valve implantation (TAVI): the SAPIEN XT valve (Edwards LifeSciences), made of bovine pericardium, and the CoreValve (Medtronic), made of porcine pericardium.
Indications for Bioprosthetic Valves
The American College of Cardiology/American Heart Association (ACC/AHA) recommendations for aortic valve replacement in patients with valvular aortic stenosis (AS) are summarized in the list below. In most adults with symptomatic severe AS, aortic valve replacement (AVR) is the surgical treatment of choice. If concomitant coronary disease is present, AVR and coronary artery bypass graft (CABG) surgery should be performed simultaneously.
Successful AVR produces substantial clinical and hemodynamic improvement in patients with AS, including octogenarians. AVR should be performed in all symptomatic patients with severe AS regardless of left ventricular (LV) function, as survival is better with surgical treatment than with medical treatment.
ACC/AHA recommendations for AVR in AS are as follows (indication; class):
Symptomatic patients with severe AS; Class I
Patients with severe AS undergoing CABG surgery; Class I
Patients with severe AS undergoing surgery on the aorta or other heart valves; Class I
Patients with moderate AS undergoing CABG surgery or surgery on the aorta or other heart valves; Class IIa
Prevention of sudden death in asymptomatic patients with none of the findings listed under asymptomatic patients with severe AS; Class III
AVR is also recommended in asymptomatic patients with severe AS and the following:
LV systolic dysfunction; Class IIa
Abnormal response to exercise (eg, hypotension); Class IIa
Ventricular tachycardia; Class IIb
Marked or excessive left ventricular hypertrophy (LVH) (>15 mm); Class IIb
Valve area less than 0.6 cm 2; Class II
The classes referred to above are defined as follows:
Class I - Conditions for which there is evidence and/or general agreement that the procedure or treatment is beneficial, useful, and effective
Class II - Conditions for which there is conflicting evidence and/or a divergence of opinion about the usefulness/efficacy of a procedure or treatment
Class IIa - Weight of evidence/opinion is in favor of usefulness/efficacy
Class IIb - Usefulness/efficacy is less well established by evidence/opinion
Class III - Conditions for which there is evidence and/or general agreement that the procedure/treatment is not useful/effective and in some cases may be harmful
Candidates for percutaneous aortic valve placement must have severe, symptomatic aortic stenosis with formal contraindications for conventional aortic valve surgery or other characteristics that would limit the patient's surgical candidacy because of excessive morbidity or mortality. The procedure should be offered to patients who would gain functional improvement from the procedure and not because they refuse conventional operation.
Under current ACC/AHA guidelines, aortic valve surgery is recommended for patients with chronic, severe aortic regurgitation (AR) when the patient is symptomatic. It is also recommended in the asymptomatic patient with chronic, severe AR who has a resting ejection fraction (EF) of 50% or less or left ventricular dilatation. Additional circumstances in which aortic valve surgery may be reasonable are listed below. Surgical treatment of AR usually requires replacement of the diseased valve with a prosthetic valve, although valve-sparing repair is increasingly possible with advances in surgical technique and technology.
ACC/AHA recommendations for AVR in AR are as follows (indication; class):
Symptomatic patients with severe AR, irrespective of LV systolic function; Class I
Asymptomatic patients with chronic, severe AR and LV systolic dysfunction (EF < 0.50) at rest; Class I
Patients with chronic, severe AR while undergoing CABG or surgery on the aorta or other heart valves; Class I
Asymptomatic patients with severe AR with normal LV systolic function (EF >0.50) but with severe LV dilatation (end-diastolic dimension >75 mm or end-systolic dimension >55 mm); Class IIa
Patients with moderate AR while undergoing surgery on the ascending aorta; Class IIb
Patients with moderate AR while undergoing CABG; Class IIb
Asymptomatic patients with severe AR and normal LV systolic function at rest (EF >0.50) when the degree of LV dilatation exceeds an end-diastolic dimension of 70 mm or end-systolic dimension of 50 mm, when there is evidence of progressive LV dilatation, declining exercise tolerance, or abnormal hemodynamic responses to exercise; Class IIb
Asymptomatic patients with mild, moderate, or severe AR and normal LV systolic function at rest (EF >0.50) when degree of dilatation is not moderate or severe (end-diastolic dimension < 70 mm, end-systolic dimension < 50 mm); Class III
Valve replacement for mitral stenosis (MS) may be considered in patients who are candidates for surgical therapy when the valve is not suitable for valvotomy (either surgical or percutaneous). The recommendations for surgery in patients with mitral stenosis, according to the current ACC/AHA guidelines, are described below.
Mitral valve surgery (repair if possible) is indicated in patients with symptomatic (New York Heart Association [NYHA] functional Class III–IV) moderate or severe MS under any of the following circumstances:
Percutaneous mitral balloon valvotomy is unavailable
Percutaneous mitral balloon valvotomy is contraindicated because of left atrial thrombus despite anticoagulation or because concomitant moderate to severe mitral regurgitation (MR) is present
The valve morphology is not favorable for percutaneous mitral balloon valvotomy in a patient with acceptable operative risk (Class I)
Symptomatic patients with moderate to severe MS who also have moderate to severe MR should receive mitral valve replacement (MVR) unless valve repair is possible at the time of surgery (Class I).
Mitral valve replacement is reasonable in patients with severe MS and severe pulmonary hypertension (pulmonary artery systolic pressure >60 mm Hg) who have NYHA functional Class I–II symptoms and who are not considered candidates for percutaneous mitral balloon valvotomy or surgical mitral valve repair (Class IIa).
Although more technically demanding, mitral valve repair is recommended over MVR in most patients with severe, chronic mitral regurgitation (MR) who require surgery. Patients should be referred to surgical centers experienced with mitral valve repair. If mitral valve repair is not feasible, MVR with preservation of the chordal apparatus is preferred, as this preserves LV function and enhances postoperative survival.
Clinical Implementation of Bioprosthetic Valves
The ACC/AHA recommendations for selection of a prosthetic aortic valve include the following :
A mechanical prosthesis is recommended for AVR in patients with a mechanical valve in the mitral or tricuspid position (Class I)
A bioprosthesis is recommended for AVR in patients of any age who will not take warfarin or who have major medical contraindications to warfarin therapy (Class I)
A bioprosthesis is reasonable for AVR in patients aged 65 years or older without risk factors for thromboembolism (Class IIa)
Aortic valve re-replacement with a homograft is reasonable for patients with active prosthetic valve endocarditis (Class IIa)
A bioprosthesis might be considered for AVR in a woman of childbearing age (Class IIb)
In addition, according to the recommendations, patient preference is a reasonable consideration in the selection of aortic valve operation and valve prosthesis. A mechanical prosthesis is reasonable for AVR in patients younger than age 65 years who do not have a contraindication to anticoagulation. A bioprosthesis is reasonable for AVR in patients younger than 65 years who elect to receive this valve for lifestyle considerations after detailed discussions of the risks of anticoagulation versus the likelihood that a second AVR may be necessary in the future (Class IIa).
The ACC/AHA recommendations for selection of a prosthetic mitral valve include the following :
A mechanical prosthesis is recommended for MVR in patients with a mechanical valve in the mitral or tricuspid position (Class I)
A mechanical prosthesis is reasonable for MVR in patients younger than age 65 years with long-standing atrial fibrillation (Class IIa)
A bioprosthesis is reasonable for MVR in patients aged 65 years or older (Class IIa)
A bioprosthesis is reasonable for MVR in patients younger than age 65 years in sinus rhythm who elect to receive this valve for lifestyle considerations after detailed discussions of the risks of anticoagulation versus the likelihood that a second MVR may be necessary in the future (Class IIa).
Clinical Trial Evidence for Bioprosthetic Valves
In a Veterans Affairs study comparing bioprosthetic valves with mechanical valves, at 15 years, all-cause mortality after AVR was lower in patients who received a mechanical valve than in those who received a bioprosthetic valve (66% vs 79%, respectively). In the study, 575 patients at 13 VA medical centers undergoing single AVR (n = 394) or single MVR (n = 181) were randomized at the time of surgery to receive a Hancock porcine valve or a Bjork-Shiley spherical disc valve. Long-term survival and valve-related complications were compared. No significant difference in all-cause mortality was seen between the two MVR groups.
Reoperation rate after AVR was higher with the bioprosthetic valve than with the mechanical valve (29 ± 5% vs 10 ± 3%). Valve-related deaths after AVR accounted for 41% of all deaths in the bioprosthetic group and 37% in the mechanical valve group; valve-related deaths after MVR were 57% and 44% of all deaths, respectively. Primary valve failure was significantly greater with bioprosthetic valves for AVR (bioprosthetic vs mechanical, 23 ± 5% vs 0 ± 0%) and for MVR (44 ± 8% vs 5 ± 4%).
Almost all the primary valve failures were in patients younger than age 65 years (18 of 20 patients in the AVR group and 20 of 21 patients in the MVR group). Bleeding occurred more frequently in patients with a mechanical valve than in those with a bioprosthesis (AVR, 51 ± 4% vs 30 ± 4%; MVR, 53 ± 7% vs 31 ± 6%). No statistically significant differences were seen between the two valve groups for systemic embolism, infective endocarditis, or valve thrombosis.
Similar results were seen in the Edinburgh heart valve trial, in which 533 patients (AVR, n = 211; MVR, n = 261; double valve replacement, n = 61) were randomized at the time of surgery to receive a Bjork-Shiley 60° spherical tilting disc valve (n = 267) or a porcine bioprosthesis (Hancock, n = 107; Carpentier-Edwards, n = 159). Long-term survival rates at 20 years were not significantly different between the 2 valve groups (mechanical 25.0 ± 2.7%, porcine 22.6 ± 2.7%). Major bleeding was more common in Bjork-Shiley patients than in bioprosthesis patients (40.7 ± 5.4% vs 27.9 ± 8.4%, respectively). No significant differences were seen in major embolism or endocarditis.
Primary valve failure may occur abruptly from the tearing or breakage of components or from a thrombus suddenly impinging on leaflet mobility. More commonly, valve failure presents gradually from calcifications or thrombus formation. Bioprostheses are less thrombogenic than mechanical valves, but this advantage is balanced by their diminished durability when compared with mechanical valves. Although 30-35% of bioprostheses will fail within 10-15 years, it can be anticipated that most mechanical valves will remain functional for 20-30 years.
Stenosis or incompetence of prosthetic valves occurs and may be due to a tear or perforation of the valve cusp, valvular thrombosis, pannus formation, valve calcification, or stiffening of the leaflets.
Primary failure of mechanical valves may be caused by suture line dehiscence, thrombus formation, or breakage or separation of the valve components. Acute valvular regurgitation or embolization of the valve fragments may result.
When the mitral valve acutely fails, rapid left atrial volume overload causes increased left atrial pressure. Pulmonary venous congestion and, ultimately, pulmonary edema occur. Cardiac output is decreased because a portion of the left ventricular output is being regurgitated into the left atrium. The compensatory mechanism of increased sympathetic tone increases the heart rate and the systemic vascular resistance (SVR). This may worsen the situation by decreasing diastolic filling time and impeding left ventricular outflow, thereby increasing the regurgitation.
Acute failure of a prosthetic aortic valve causes a rapidly progressive left ventricular volume overload. Increased left ventricular diastolic pressure results in pulmonary congestion and edema. The cardiac output is reduced substantially. The compensatory mechanism of an increased heart rate and a positive inotropic state, mediated by increased sympathetic tone, partly helps to maintain output. However, this is hampered by an increase in SVR, which impedes forward flow. Increased systolic wall tension causes a rise in myocardial oxygen consumption. Myocardial ischemia in acute aortic regurgitation may occur, even in the absence of coronary artery disease.
Biological prosthetic valves often slowly degenerate over time, become calcified, or suffer from thrombus formation. These events result in the slowly progressive failure of the valve. The presentation is usually that of gradually worsening congestive heart failure, with increasing dyspnea. Alternatively, patients may present with unstable angina or systemic embolization, or they may be entirely asymptomatic.
The first TAVI device for use in the United States was approved in November 2011. Subsequently, not enough time has passed to gather data concerning longevity and use. Vascular complications and strokes related to the procedure are decreasing with improved delivery techniques and equipment. Complications related to the conduction system requiring permanent pacemaker implantation occur in 14% of patients. This risk is increased with the use of the CoreValve prosthesis.
Prosthetic valve endocarditis
PVE occurring within 1 year of implantation (early PVE) usually is due to perioperative contamination or hematogenous spread. PVE occurring after 1 year (late PVE) is usually caused by hematogenous spread.
The pathologic hallmark of PVE in mechanical valves is ring abscesses. Ring abscess may lead to valve dehiscence and perivalvular leakage. Local extension results in the formation of myocardial abscesses. Further extension to the conduction system often results in a new atrioventricular block. Valve stenosis and purulent pericarditis occur less frequently.
Bioprosthetic valve PVE usually causes leaflet tears or perforations. Valve stenosis is more common with bioprosthetic valves than with mechanical valves. Ring abscess, purulent pericarditis, and myocardial abscesses are much less frequent in bioprosthetic valve PVE.
Finally, glomerulonephritis, mycotic aneurysms, systemic embolization, and metastatic abscesses also may complicate PVE.
Prosthetic valve thrombosis is more common in mechanical valves. With proper anticoagulation, the rate of thrombosis in all valves is within the range of 0.1-5.7% per patient-year. Caged ball valves have the highest rate of thromboembolic complications, and bileaflet valves have the lowest. Valve thrombosis is increased with valves in the mitral position and in patients with subtherapeutic anticoagulation.
Anticoagulant-related hemorrhagic complications of mechanical valves include major hemorrhage in 1-3% of patients per year and minor hemorrhage in 4-8% of patients per year.
Low-grade hemolytic anemia occurs in 70% of prosthetic heart valve recipients, and severe hemolytic anemia occurs in 3%. The incidence is increased with caged ball valves and in those with perivalvular leaks.
Primary valve failure occurs in 3-4% of patients with bioprostheses within 5 years of implantation and in up to 35% of patients within 15 years. Mechanical valves have a much lower incidence of primary failure.
PVE occurs in 2-4% of patients. The incidence is 3% in the first postoperative year, then 0.5% for subsequent years. The incidence is higher when valve surgery is performed in patients with active native valve endocarditis. The incidence is higher in mitral valves. Mechanical and biological valves are equally susceptible to early PVE, but the incidence of late PVE is higher for bioprostheses. Despite improvements in surgical techniques, no appreciable change in the incidence has been observed.
Acute failure of a prosthetic aortic valve usually leads to sudden or near-sudden death. Prompt recognition and treatment of acute prosthetic mitral valve failure can be lifesaving.
PVE has an overall mortality rate of 50%. In early PVE, the mortality rate is 74%. In late PVE, the mortality rate is 43%. The mortality rate with a fungal etiology is 93%. The mortality rate for staphylococcal infections is 86%. PVE due to Staphylococcus has a mortality rate of 25-40%.[13, 14]
Fatal anticoagulant-induced hemorrhage occurs in 0.5% of patients per year.
In children, bioprostheses rapidly calcify and, therefore, undergo rapid degeneration and valve dysfunction. Incidence of bioprosthetic failure is much higher in patients younger than 40 years. The incidence of having any prosthetic valve complication decreases with age.
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