Valvular Heart Disease

General Principles

Valvular heart disease (VHD) is characterized by underlying functional or anatomic abnormalities in the cardiac valves that result in regurgitation or stenosis. VHD is common, occurring in approximately 20 million persons in the United States. Although there are congenital forms, VHD is largely age dependent, and 3% to 6% of those aged 65 years and older are affected.

A thorough history and physical examination are essential in evaluating for VHD. Many heart valve lesions are slowly progressive, and patients may unconsciously limit their activity in response to a worsening of underlying VHD. The most common symptom is exertional dyspnea. Other symptoms include angina, syncope, palpitations, lower extremity edema, and ascites, depending on the lesion and severity. Typical physical examination findings for valvular and other cardiac lesions are described in Table 21. Twelve-lead electrocardiography, chest radiography, and transthoracic echocardiography (TTE) with two-dimensional imaging may be performed to evaluate for VHD.

For clinical monitoring and timing of intervention, VHD is classified into four stages (A to D), which consider the presence of symptoms, severity of the lesion, ventricular response to the volume or pressure overload caused by the lesion, effect on the pulmonary or systemic circulation, and heart rhythm changes (Table 22). Surveillance intervals for echocardiographic evaluation based on disease severity are listed in Table 23.

Surgery can be a life-saving intervention in select patients, and surgical risk calculation is a key component of the patient evaluation. Surgical risk is determined through an assessment of the patient's age, morbidities, frailty, and impediments specific to the procedure being considered (for example, prior chest radiation therapy for a sternotomy approach). Risk calculators derived from national databases can assist in estimating risk for morbidity and mortality for various surgical valve procedures. One such calculator, the Society of Thoracic Surgery Adult Cardiac Surgery Risk Calculator, is available at http://riskcalc.sts.org/stswebriskcalc. Although risk calculators contain many data input fields, it is important to note that frailty and some other important patient and procedural characteristics are not part of these online assessment tools. Therefore, a comprehensive, holistic approach is required for determining patient surgical risk and candidacy. Frailty, which is variably defined as a geriatric syndrome characterized by declines in several physiologic systems and processes, portends an increased risk for mortality in patients undergoing surgery and can be measured preoperatively (see MKSAP 18 General Internal Medicine).

For all patients in whom surgical or interventional therapy is being considered, a multidisciplinary approach with a heart team consisting of cardiologists, surgeons, and interventional cardiologists is recommended. Evaluations in centers with specialized expertise in VHD (for example, a Heart Valve Center of Excellence) is also advised for patients in whom intervention is being considered when (1) there are no symptoms; (2) multiple or complex morbidities are present; or (3) surgical valve repair is favored over valve replacement.

Medical therapy, although often effective for symptom palliation, has not been shown to prevent progression of VHD or improve long-term survival in patients with VHD.

Aortic Stenosis

Clinical Presentation and Evaluation

Aortic stenosis may be congenital, such as in persons with a bicuspid aortic valve, or acquired. The most common cause is degeneration of the valve that occurs with aging; severe lesions occur in approximately 3% of persons aged 65 years and older (Figure 20). Other causes include rheumatic disease and chest radiation. Although rheumatic disease of the mitral valve frequently occurs in isolation, rheumatic aortic valve disease almost never occurs without mitral valve involvement. Chest radiation (for example, mantle therapy for non-Hodgkin lymphoma) commonly causes a mixture of both valvular stenosis and regurgitation.

Aortic stenosis results in chronic pressure overload of the left ventricle (LV), leading to concentric LV hypertrophy and myocardial interstitial fibrosis. Diastolic dysfunction follows, with eventual systolic heart failure and pulmonary congestion. Exertional dyspnea, syncope, and angina are the most common presenting symptoms; however, symptoms may not appear until stenosis is severe. The disease typically progresses with a decrease in the aortic valve area of approximately 0.12 cm2 per year, but the rate depends on patient age, underlying severity of the stenosis, and comorbid conditions, such as kidney failure and hypertension. Among asymptomatic patients with severe aortic stenosis, 75% will die or develop symptoms within 5 years. Once symptoms occur in patients with severe aortic stenosis, life expectancy is generally only 1 to 2 years. Thus, serial evaluation every 6 to 12 months is recommended for patients with severe disease (see Table 23).

In patients with severe aortic stenosis, the characteristic physical findings include a late-peaking systolic murmur, a diminished or absent aortic component of the S2, and a delay in the carotid upstroke (pulsus tardus) that may be accompanied by a decreased pulse amplitude due to low cardiac output (pulsus parvus). Physical findings that suggest severe aortic stenosis should be promptly evaluated (see Table 21).

The primary imaging modality for the evaluation of aortic stenosis is TTE (Figure 21). Echocardiography can determine the cause and severity of aortic stenosis (such as the gradient and valve area) as well as LV function and wall thickness. In some patients, echocardiography may underestimate the severity of aortic stenosis. Further evaluation with cardiac catheterization, during which the cardiac output and the gradient across the aortic valve can be measured, is required when there are discrepancies between the findings on physical examination and the echocardiographic results in symptomatic patients being considered for surgery.

Severe aortic stenosis is typically defined by a small valve area (≤1.0 cm2) and either high peak velocity (>4 m/s) or high mean gradient (>40 mm Hg). There are two patient subsets in which severe aortic stenosis may be present with a small valve area and either low velocity or low gradient: patients with severe LV dysfunction and low cardiac output and patients with preserved LV function and paradoxical low-flow, low-gradient aortic stenosis. In the former group, dobutamine echocardiography or an invasive hemodynamic study is needed to distinguish true aortic stenosis from pseudostenosis. With pseudostenosis, dobutamine increases cardiac output and the opening forces on the aortic valve, causing the valve area to increase out of the severe range. With true aortic stenosis, the calculated valve area remains in the severe range with dobutamine administration, and the aortic valve gradient and velocity increase with increased stroke volume. In patients with paradoxical low-flow, low-gradient aortic stenosis, low stroke volume (<35 mL/m2) results from a combination of small LV size and high aortic impedance to flow (hypertension). Determination of lesion severity in paradoxical aortic stenosis requires consideration of the hemodynamics, valve morphology (such as degree of degeneration), presence of LV hypertrophy, and clinical presentation of the patient. In patients with either low-flow, low-gradient severe aortic stenosis or paradoxical low-flow, low-gradient severe aortic stenosis, observational studies have shown improved survival with aortic valve replacement compared with medical therapy.

Management

Aortic valve replacement is a life-prolonging procedure in patients with severe aortic stenosis. The indications for aortic valve replacement in severe aortic stenosis are (1) the presence of symptoms (such as dyspnea, angina, presyncope, or syncope), (2) LV systolic dysfunction (ejection fraction <50%) in an asymptomatic patient, or (3) a concomitant cardiac surgical procedure for another indication (such as simultaneous coronary artery bypass grafting or ascending aorta surgery). Aortic valve replacement may be considered in asymptomatic patients with abnormal results on supervised exercise testing, such as those with poor exercise tolerance, abnormal electrocardiographic changes, or hypotension during testing.

Aortic valve replacement can be performed with open cardiac surgery (surgical aortic valve replacement [SAVR]) or via transcatheter approach (transcatheter aortic valve replacement [TAVR]) (Figure 22). SAVR and TAVR have similar procedural and long-term survival rates, with expected operative mortality rates of 1% to 3%. The choice between surgical and transcatheter interventions is based on the presence of symptoms and the patient's surgical risk, as determined through comprehensive assessment by a multidisciplinary heart team. TAVR is currently indicated for symptomatic patients with trileaflet aortic stenosis who are at intermediate or high surgical risk and who do not have concomitant severe aortic regurgitation. Randomized trials comparing TAVR with SAVR in low-risk patients are ongoing.

Although the pathophysiology of aortic stenosis is known to be inflammatory, randomized trials of medical therapy, specifically statins, have not found this therapy to be effective in slowing disease progression. For patients with coexistent hypertension or heart failure, guideline-directed medical therapy is recommended. Vasodilators should be used with caution in patients with aortic stenosis and heart failure symptoms. In select cases, balloon valvuloplasty may be used to bridge patients to therapy with TAVR or SAVR.

Aortic Regurgitation

Clinical Presentation and Evaluation

Aortic regurgitation may be caused by aortic root pathology or intrinsic valve disease and can manifest acutely or chronically. Causes of chronic aortic regurgitation include ascending aortic dilatation and valve abnormalities due to bicuspid disease, calcific degeneration, rheumatic involvement, or chest radiation. Causes of acute aortic regurgitation are endocarditis, blunt chest trauma, iatrogenic causes (such as complications of balloon aortic valvuloplasty), and aortic dissection.

In chronic aortic regurgitation, volume overload causes progressive LV dilatation and eccentric hypertrophy. Chronic aortic regurgitation may be tolerated for many years but can eventually lead to symptoms, including shortness of breath, fatigue, or angina. Physical findings result from the large stroke volume and LV dilatation and include bounding peripheral pulses, displacement of the LV apex, and a diastolic decrescendo murmur heard either along the right sternal border (suggesting root pathology) or left sternal border (suggesting valve pathology) (see Table 21). The large forward stroke volume can also result in an early-peaking systolic ejection murmur. In patients with acute regurgitation, the abrupt onset of volume overload may not be well tolerated, and these patients can present with acute heart failure or even cardiogenic shock. Additionally, patients with acute regurgitation may not have bounding pulses because stroke volume has not markedly increased, and murmurs may be softer or shorter in duration, owing to the rapid equalization of pressures between the aorta and LV.

TTE is recommended for the evaluation of aortic regurgitation and LV function. When endocarditis is suspected and transthoracic imaging is suboptimal, transesophageal echocardiography (TEE) is advised. As an alternative, cardiac magnetic resonance (CMR) imaging and invasive angiography also can be used to determine the severity of regurgitation. Criteria for severe aortic regurgitation include a jet width that occupies 65% of the LV outflow tract or more, vena contracta greater than 0.6 cm, holodiastolic flow in the descending aorta, regurgitation volume of 60 mL or more, and effective regurgitant orifice area of 0.3 cm2 or greater. The LV is also typically dilated in chronic aortic regurgitation. For patients suspected of having an aortic root abnormality, an evaluation with CMR imaging, CT, or TEE is recommended.

Management

Acute aortic regurgitation due to aortic dissection is a surgical emergency. For other acute causes, the indications for surgery depend on severity, presence of symptoms, and the hemodynamic stability of the patient. In cases of chronic aortic regurgitation, surgery with traditional open aortic valve replacement is advised for patients with symptoms (typically, dyspnea or angina), those with LV dysfunction (ejection fraction <50%), or patients undergoing other cardiac surgery. Surgical treatment of aortic regurgitation is reasonable in cases of significant LV dilatation (end-systolic diameter >50 mm or indexed end-systolic dimension >25 mm/m2). Aortic valve repair without valve replacement may be performed in centers of expertise. Follow-up of asymptomatic patients is based on severity of regurgitation and other factors (see Table 23).

Medical therapy, preferably with dihydropyridine calcium channel blockers (nifedipine, isradipine, felodipine, nicardipine, nisoldipine, lacidipine, and amlodipine), ACE inhibitors, or angiotensin receptor blockers, is recommended in patients with chronic aortic regurgitation in the setting of hypertension. In the absence of hypertension, medical therapy is appropriate for symptomatic patients who are not surgical candidates.

Bicuspid Aortic Valve Disease

Bicuspid aortic valve disease affects approximately 1% to 2% of the general population. Bicuspid morphology leads to abnormal shear forces and predisposes to early degeneration of the valve, resulting in stenosis in most patients (up to 75%) (see Figure 20) and pure regurgitation in a small minority of patients (2%-10%). Patients with a bicuspid aortic valve typically present with an incidental systolic ejection murmur in adolescence or young adulthood and gradually progress to severe disease in the fifth or sixth decade of life. More than one third of those older than 70 years with severe aortic stenosis have an underlying bicuspid valve.

A bicuspid aortic valve is often accompanied by abnormalities in the aortic arch, independent of the severity of aortic stenosis or regurgitation, and may be associated with aneurysms, dissection, or coarctation. Therefore, in patients with a bicuspid aortic valve, the aortic arch should be examined for aortopathy with CMR imaging, echocardiography, or cardiac CT; serial imaging is indicated if abnormalities are detected. The imaging modality and frequency depend on several factors, including the location and severity of the abnormalities, age of the patient, family history, and candidacy for surgery (see Diseases of the Aorta). Importantly, bicuspid aortic valve disease is heritable, and first-degree relatives should be screened for its presence with echocardiography.

Management of bicuspid aortic valve disease depends on the predominant lesion type (aortic stenosis or regurgitation) and its severity. In patients with a bicuspid valve who are undergoing surgery for severe aortic stenosis or regurgitation, surgical repair of the ascending aorta is advised when the aortic diameter is greater than 4.5 cm. In the absence of surgical indications for a stenotic or regurgitant aortic valve, surgical repair of the ascending aorta or aortic sinuses is advised when the aortic diameter is greater than 5.5 cm or when the diameter is greater than 5.0 cm with additional risk factors for dissection (family history, rate of progression ≥0.5 cm/year).

No medical therapies slow aortic dilatation in patients with aortopathy and a bicuspid aortic valve. Blood pressure should be controlled in patients with concomitant hypertension.

Mitral Stenosis

Clinical Presentation and Evaluation

The leading cause of mitral stenosis is rheumatic heart disease, which has a higher predilection for women than men (female-to-male ratio of 4:1). Although relatively uncommon in the United States, rheumatic heart disease is frequent in populations with limited access to treatment for streptococcal pharyngitis. Rheumatic heart disease results in fusion of the mitral commissures and, in more advanced forms, calcification of the valve and abnormalities in the subvalvular apparatus (Figure 23). Other causes of mitral stenosis are parachute mitral valve, chest radiation, and severe mitral annular calcification. Mitral annular calcification is more common in the elderly and is associated with inflammatory disorders, peripheral artery disease, and chronic kidney disease.

The natural history of mitral stenosis is characterized by a slow progression over decades, with gradual enlargement of the left atrium (LA) and preservation of LV function. Symptoms of mitral stenosis may arise from low cardiac output (fatigue), pulmonary congestion (dyspnea), and pulmonary hypertension with right-sided heart failure (lower extremity edema). Symptoms typically occur with exertion because exercise shortens diastolic filling time and increases the transvalvular flow and diastolic mitral gradient, leading to worsening of LA hypertension. Symptoms may first occur during pregnancy owing to increased blood volume and cardiac output. Patients can also present with systemic embolization, atrial fibrillation, or, in severe cases, hemoptysis. Heart failure is the cause of death in approximately 60% of patients with mitral stenosis, and thromboembolism is the cause in most others.

On physical examination, the findings of mitral stenosis when the valve is pliable include a tapping LV impulse in the precordium, a loud S1, an increased pulmonic component of S2, a diastolic opening snap, and a diastolic rumble or low-pitched murmur at the apex (see Table 21). Signs of pulmonary or systemic congestion may be present depending on the severity of the lesion and the patient's volume status.

TTE is highly accurate for assessing mitral stenosis severity, pulmonary pressures, and right ventricular function (see Table 23). Additional imaging or cardiac catheterization is rarely required. Severe mitral stenosis is defined by a mitral valve area of 1.5 cm2 or less, which usually corresponds to a mean mitral gradient of more than 5 to 10 mm Hg at a normal heart rate. In patients with a discrepancy between the clinical findings and the echocardiographic findings, stress echocardiography with pharmacologic or physical stressors should be pursued to assess the response of the mitral gradient and pulmonary pressures.

Management

The procedure of choice for patients with significant rheumatic mitral stenosis and a pliable mitral valve is percutaneous balloon mitral commissurotomy (PBMC). PBMC is indicated for symptomatic patients with severe mitral stenosis and favorable valve morphology. PBMC may be considered in asymptomatic patients with critical mitral stenosis when the valve area is less than 1.0 cm2. In patients with LA thrombus, moderate mitral regurgitation, or a severely calcified valve, PBMC should not be performed. In appropriately selected patients, success rates with PBMC are 95%, and complications occur in less than 5% of patients. Surgery for mitral stenosis should be performed in patients with severe symptoms (New York Heart Association functional class III or IV) and a nonpliable valve or concomitantly in patients undergoing other cardiac surgical procedures.

Nearly 50% of patients with mitral stenosis have atrial fibrillation, and without anticoagulation therapy, these patients have a risk for thromboembolism of 20% to 25%. Patients with moderate to severe mitral stenosis and atrial fibrillation should receive warfarin, with a goal INR of 2.0 to 3.0. Non–vitamin K antagonist oral anticoagulants (NOACs), including dabigatran, rivaroxaban, apixaban, and edoxaban, are recommended in preference to warfarin in eligible patients with mild mitral stenosis and atrial fibrillation. NOACs are noninferior and possibly superior to warfarin for preventing stroke and systemic embolism and are associated with lower risk for serious bleeding. Other indications for anticoagulation are a history of LA thrombus or systemic embolization. Notably, clinical trials of NOACs in atrial fibrillation excluded patients with moderate to severe mitral stenosis; therefore, the efficacy and safety of these agents in this population have not been demonstrated.

Because the mitral gradient is heavily dependent on transvalvular flow, medical therapy with negative chronotropic agents, diuretics, and long-acting nitrates can be effective for symptom palliation in patients who are not candidates for interventional or surgical therapy.

Mitral Regurgitation

Clinical Presentation and Evaluation

Mitral regurgitation may arise from any portion of the complex valve apparatus (such as the leaflets, annulus, chordae, papillary muscles, or LV free walls) and may present acutely or chronically. Causes of acute mitral regurgitation are infective endocarditis, papillary muscle ischemia or rupture, trauma (for example, injury from PBMC), or degenerative disease with chordal rupture and flail leaflet. Chronic mitral regurgitation is classified as primary or secondary. Chronic primary mitral regurgitation relates to processes involving any portion of the mitral annulus. Common causes of primary mitral regurgitation are mitral valve prolapse (also known as myxomatous or degenerative mitral valve disease), radiation therapy, rheumatic disease, and cleft mitral valve. Chronic secondary mitral regurgitation involves causes other than the annulus, such as ventricular dysfunction.

Mitral regurgitation results in volume overload with LV dilatation and LA hypertension, which may progress and cause pulmonary hypertension and right ventricular failure. In acute mitral regurgitation, heart failure symptoms often occur abruptly because there has not been time for adaptive chamber dilatation, and patients may present with cardiogenic shock. The systolic murmur in acute mitral regurgitation may be brief because of the rapid equalization of LA and LV pressures. Echocardiography with color flow imaging can underestimate the severity of the regurgitation. Thus, when acute mitral regurgitation is suspected, comprehensive assessment to identify the potential causes should be pursued, and additional imaging with TEE should be considered. Aggressive evaluation and accurate diagnosis are crucial for patients with acute mitral regurgitation.

Chronic primary mitral regurgitation is predominantly caused by mitral valve prolapse, which affects approximately 2% of the general population or roughly 500,000 persons in the United States. Echocardiography in patients with chronic primary mitral regurgitation may show a range of abnormalities, including prolapse, gross degeneration of one or both leaflets (Barlow syndrome), or chordal rupture with flail leaflet (Figure 24). Barlow syndrome is more common in young adult patients. In patients who are relatively older, fibroelastic deficiency predominates and frequently results in chordal rupture. The mitral valve apparatus is normal in patients with chronic secondary mitral regurgitation (Figure 25). In these patients, ventricular dysfunction causes mitral regurgitation through papillary muscle displacement and tethering of the mitral leaflets, which impairs coaptation.

The physical examination in patients with chronic mitral regurgitation is notable for a blowing holosystolic murmur at the apex. In patients with mitral valve prolapse, one or more systolic clicks may precede the murmur, and variation in severity, preload, and afterload can lead to differences in murmur onset (holosystolic, midsystolic, or late systolic). In patients with LV dilatation, the apical impulse may be displaced laterally, and an S3 may be audible, especially in patients with secondary mitral regurgitation due to LV dysfunction.

TTE readily assesses the severity of primary mitral regurgitation, with a high degree of accuracy and precision. Severe primary mitral regurgitation is defined by using several parameters; the most common is an effective regurgitant orifice area of 0.4 cm2 or larger, regurgitant volume of 60 mL or more, or vena contracta of 0.7 cm or larger. In some instances, TEE may be required to further elucidate the mechanism of the mitral regurgitation, particularly when surgical or interventional therapy is planned. TEE may be especially useful in evaluating for acute mitral regurgitation, in which rapid systolic equalization of LV and LA pressures can pose challenges for both the bedside examination and TTE imaging.

Appropriate follow-up of asymptomatic patients with mitral regurgitation is outlined in Table 23.

Management

Medical therapy and surgical intervention can be life-saving in patients with acute severe mitral regurgitation. Vasodilator therapy with a titratable drug, such as nitroprusside, decreases aortic impedance and mitral regurgitation, thereby improving forward cardiac output. An intra-aortic balloon pump can be used to decrease afterload and augment systemic and coronary perfusion pressures. Prompt surgical correction should be considered for all patients with acute severe mitral regurgitation.

Patients with chronic severe primary mitral regurgitation generally do poorly without surgery, particularly when there are significant symptoms, flail leaflet, or LV dilatation. In one study of 458 patients with asymptomatic severe primary mitral regurgitation, the 5-year survival rate was only 58%. Surgical treatment with repair of the mitral valve is indicated for chronic severe primary mitral regurgitation in (1) symptomatic patients with left ventricular ejection fraction (LVEF) greater than 30%, (2) asymptomatic patients with LV dysfunction (LVEF of 30%-60% and/or LV end-systolic diameter ≥40 mm), or (3) patients undergoing another cardiac surgical procedure. Surgical repair is reasonable in asymptomatic patients with preserved LV function when the expected repair success rate is greater than 95% and the operative risk is less than 1% or when serial imaging studies have demonstrated a progressive increase in LV size or decrease in LVEF. Mitral valve repair should also be considered in asymptomatic patients with chronic severe primary mitral regurgitation who have new-onset atrial fibrillation or pulmonary hypertension (pulmonary artery systolic pressure >50 mm Hg). Surgical repair is preferred over replacement in all patients, and patients should be referred to a surgical center with expertise in valve repair. Medical therapy with vasodilators in patients with primary mitral regurgitation is not beneficial in the absence of symptoms or LV dysfunction.

For patients who are not surgical candidates, mitral valve repair with a catheter-based clip device was approved by the FDA in 2013. The percutaneously delivered clip improves coaptation of the mitral valve leaflets, leading to increased valve closure and a reduction in regurgitation. In selected patients with primary mitral regurgitation, success rates with implantation of the device are approximately 90%, with a procedural mortality of approximately 2%.

In patients with chronic secondary mitral regurgitation, the primary goal of therapy is to address the underlying ventricular dysfunction with guideline-directed medical therapy and, if indicated, cardiac resynchronization therapy (see Heart Failure). Guideline-directed medical therapy for ventricular dysfunction includes ACE inhibitors, angiotensin receptor blockers, an angiotensin receptor–neprilysin inhibitor, β-blockers, diuretics, and/or aldosterone antagonists. Benefits of valve repair or replacement in patients with secondary mitral regurgitation are less certain, although studies have demonstrated favorable LV remodeling after surgery. Surgery for secondary mitral regurgitation is generally advised for those undergoing concomitant cardiac surgical procedures (for example, coronary artery bypass grafting), but mitral regurgitation may recur after repair because of primary LV dysfunction. Trials of transcatheter mitral valve replacement for patients with secondary mitral regurgitation and high surgical risk are ongoing.

Tricuspid Valve Disease

Tricuspid regurgitation, the most common form of tricuspid valve disease, is frequently functional and clinically asymptomatic. Causes of tricuspid regurgitation include cor pulmonale (or pulmonary hypertension) with right ventricular failure, pacemaker or defibrillator lead placement, trauma, congenital abnormalities, and infective endocarditis. When symptomatic, patients can present with fatigue from low cardiac output and symptoms and signs of right-sided failure, such as elevated jugular venous pulse (a large c-v wave), a palpable right ventricular lift, hepatic congestion with pulsatile liver, and peripheral edema. The murmur of tricuspid regurgitation is typically a holosystolic murmur heard along the left sternal border that increases during inspiration due to increased venous return.

Tricuspid regurgitation should be evaluated by TTE, which also allows assessment of right ventricular function and estimation of pulmonary pressures. In patients with tricuspid regurgitation due to pacemaker or defibrillator lead placement, TEE may be required to more clearly evaluate the regurgitant murmur.

Medical therapy with loop diuretics and aldosterone antagonists is effective in improving symptoms of right-sided congestion; however, caution should be exercised to minimize the potential for creating a low-flow state with impaired cardiac output. Surgery is recommended for patients with severe tricuspid regurgitation who are undergoing left-sided valve surgery. Additionally, surgery may be considered in patients with symptomatic tricuspid regurgitation who are unresponsive to medical therapy or have right-sided heart failure.

Tricuspid stenosis is nearly always caused by rheumatic disease. Other causes include radiation therapy, carcinoid syndrome, and medication use (for example, the ergot agents pergolide or cabergoline). Symptoms of tricuspid stenosis (fatigue, cold skin) are typically overshadowed by those caused by the left-sided abnormalities of coexistent rheumatic mitral disease. Findings on physical examination include those of right-sided congestion (elevated jugular venous pulse, hepatic congestion, peripheral edema) and a diastolic rumble. Surgery for tricuspid stenosis is typically performed in concert with therapy for rheumatic mitral disease.

Prosthetic Valves

The choice of prosthesis for a patient undergoing surgical valve replacement is complex. Factors to consider are the patient's age, the expected durability of the prosthesis, the surgical risk for reoperation in the event of degeneration, and the ability and willingness of the patient to take warfarin for anticoagulation. The American College of Cardiology/American Heart Association VHD guideline recommends a mechanical valve prosthesis in patients younger than 50 years, bioprosthesis in patients older than 70 years, and either a bioprosthesis or mechanical valve prosthesis in those age 50 to 70 years. However, the final decision on valve type should be reached through a shared decision-making process between the care provider and patient. The patient should thoroughly understand the risks and benefits as well as have decision-making capacity. Additional considerations include the expected durability of bioprostheses (15 years) and that structural deterioration of the valve is more common in younger patients. In those younger than 60 years, approximately 40% of valves have evidence of clinically severe deterioration by 15 years.

Immediately after implantation, all patients should undergo echocardiography to document the baseline hemodynamic performance of the valve, and repeat evaluations should be performed for signs or symptoms of prosthetic dysfunction. Annual evaluation is recommended for all patients with a bioprosthesis beginning at 10 years after surgery. Data on long-term durability of TAVR prostheses are currently limited to a follow-up of 5 years; however, thus far, valve durability is not different from surgical prostheses.

Lifelong warfarin anticoagulation is indicated in all patients with a mechanical valve prosthesis. In recent VHD guidelines, the goal INR for warfarin anticoagulation in patients with a mechanical prosthesis has shifted from a range to a single value. This change was made to minimize the time the patient spends at the low and high ends of a target range because drifting above and below the range can be deleterious. The use of a single-value INR target can pose logistic challenges for testing and warfarin adjustments, and in those instances, recommendations to improve processes and enhance patient understanding and motivation should be considered.

In patients with a mechanical aortic valve prosthesis (bileaflet or current-generation single-tilting disc) with no additional risk factors for thromboembolism (history of embolization, hypercoagulable disorder, LV dysfunction, atrial fibrillation), the goal INR for warfarin anticoagulation is 2.5. In patients with a mechanical aortic valve prosthesis with risk factors for thromboembolism, an older-generation aortic valve prosthesis (ball-in-cage), or any mitral prosthesis, the target INR is 3.0. Because of the risk for valve thrombosis, direct thrombin inhibitors and factor Xa inhibitors should not be used for anticoagulation therapy in patients with a mechanical valve prosthesis. Oral anticoagulation with warfarin should be considered for at least 3 months and as long as 6 months after implantation of a mitral or aortic bioprosthesis. An INR of 2.5 should be targeted in these patients.

Aspirin (75-100 mg/d) is highly recommended in addition to warfarin therapy for patients with a mechanical prosthesis based on the results of randomized trials, which showed reduction in the risk for embolic events, including stroke (1.3% per year versus 4.2% per year; P < 0.027) and death (2.8% per year versus 7.4% per year; P < 0.01). For all patients with a bioprosthesis, low-dose aspirin is generally recommended.

Infective Endocarditis

Diagnosis and Management

Infective endocarditis is a life-threatening disorder that involves native valvular structures or implanted cardiovascular devices. Such devices include cardiac valve prostheses, permanent pacemakers, implanted cardioverter-defibrillators, and occluders for repair of congenital lesions (such as atrial septal defect and ventricular septal defect occluders). Risk factors for infective endocarditis include advanced age, diabetes mellitus, immunosuppression, injection drug use, congenital heart disease, cardiac transplantation with valvulopathy, and an implanted cardiovascular device. Early diagnosis, targeted antimicrobial therapy, and consideration of early surgical intervention are paramount to the evaluation and treatment of infective endocarditis.

Infective endocarditis is diagnosed with the modified Duke criteria. Definite infective endocarditis requires either pathological confirmation (microorganisms demonstrated by culture or histologic examination of a vegetation, a vegetation that has embolized, or an intracardiac abscess specimen; or a vegetation or intracardiac abscess confirmed by histological examination showing active endocarditis) or clinical criteria consisting of two major criteria, one major criterion plus three minor criteria, or five minor criteria (Table 24). Possible infective endocarditis requires one major criterion and one minor criterion, or three minor criteria. Infective endocarditis is excluded when there is a firm alternate diagnosis, resolution of infective endocarditis syndrome with antibiotic therapy for 4 days or less, or no pathological evidence of infective endocarditis at surgery or autopsy with antibiotic therapy for 4 days or less.

Blood cultures are positive in 90% of infective endocarditis cases. In the remaining cases (that is, culture-negative infective endocarditis), serologic testing is required to identify the causative microorganism. For patients with infective endocarditis with a prosthetic valve, the syndrome is classified according to the time from surgery as early (within 60 days), intermediate (60-365 days), and late (>365 days). Early prosthetic valve endocarditis (PVE) is characterized by infection with hospital-acquired microbes, such as Staphylococcus aureus. Coagulase-negative staphylococci are the most common microbes in intermediate PVE. Although both S. aureus and coagulase-negative staphylococci remain important causes of late PVE, the microbes in late PVE more typically resemble those of native valve endocarditis.

TTE is recommended to identify vegetations and associated hemodynamic derangements (for example, changes in LV function or pulmonary pressures). TEE is recommended in patients with intermediate or high suspicion for infective endocarditis when TTE is not diagnostic (such as with a prosthetic valve), intracardiac device leads are present, or complications such as abscess have developed or are suspected (conduction abnormalities on electrocardiogram or persistent bacteremia despite antibiotic therapy).

Appropriate antimicrobial therapy should be initiated once cultures have been obtained and guidance from sensitivity data and infectious disease consultants has been made available. Empiric antimicrobial therapy may be initiated in high-risk patients (such as those with septic shock) on the basis of patient characteristics, predisposing factors, and epidemiologic factors. For patients with VHD and unexplained fever, antimicrobials should not be administered before several blood cultures are drawn, and all efforts should be made to use targeted therapy when microbiologic results are available.

The decision to pursue surgery for treatment of infective endocarditis is complex and requires a multidisciplinary approach. Early surgery (during hospitalization and before completion of an antimicrobial course) is recommended for patients with (1) symptomatic heart failure and valvular dysfunction; (2) left-sided infective endocarditis caused by fungal infections or highly-resistant organisms; (3) associated complications, such as annular or aortic abscess, destructive penetrating lesions, or heart block; or (4) persistent bacteremia or fevers lasting more than 5 to 7 days despite appropriate antimicrobial therapy. Early surgery is reasonable in patients with recurrent emboli and persistent valve vegetations and may be considered in the presence of a large (>10-mm), left-sided vegetation. When infective endocarditis is associated with a pacemaker or defibrillator, the entire system (generator and leads) must be removed.

Infective endocarditis carries significant risk for morbidity and mortality, with high rates of in-hospital mortality (20%), 1-year mortality (40%), peripheral embolization (23%), stroke (17%), and need for cardiac surgery (48%).

Prophylaxis

Endocarditis prophylaxis is recommended in a specific group of patients before dental procedures that involve manipulation of gingival tissue or the periapical region of the teeth, or perforation of the oral mucosa (Table 25). Although endocarditis prophylaxis was previously advised for a broad population, current guidelines now recommend its use only for patients with (1) a history of endocarditis; (2) cardiac transplantation with valve regurgitation due to a structurally abnormal valve; (3) a prosthetic valve; (4) prosthetic material used for cardiac valve repair, including annuloplasty rings and chords; or (5) congenital heart disease, including unrepaired cyanotic disease, repaired lesions with residual defects at the site or adjacent to the site of a prosthetic patch or prosthetic device, or disease that has been repaired with prosthetic material (surgical or catheter-based) within the previous 6 months.