Acquired Valvular Heart Disease



Acquired Valvular Heart Disease


Denise Ledoux



DEFINITION, CLASSIFICATION, AND EPIDEMIOLOGY

Valvular heart disease continues to be a common source of cardiac dysfunction and mortality. Competent cardiac valves maintain a unidirectional flow of blood through the heart as well as to the pulmonary and systemic circulations. Diseased cardiac valves that restrict the forward flow of blood because they are unable to open fully are referred to as stenotic. Stenotic valves elevate afterload and cause hypertrophy of the atria or ventricles pumping against the increased pressure. Cardiac valves that close incompetently and permit the backward flow of blood are referred to as regurgitant, incompetent, or insufficient. Regurgitant valves cause an elevated volume load and dilation of the cardiac chambers receiving the blood reflux. Valvular dysfunction may be primarily stenotic or regurgitant, or may be “mixed,” which refers to a valve that neither opens nor closes adequately. Valvular heart disease is usually described by the duration of the dysfunction (acute vs. chronic), the valves involved, and the nature of the valvular dysfunction (stenosis, insufficiency, or a combination of stenosis and insufficiency). The degree of cardiac dysfunction is defined by the New York Heart Association’s (NYHA) Functional and Therapeutic Classification. Acquired valvular heart disease most commonly affects, and is most symptomatic with, the aortic and mitral valves. This chapter focuses on the mitral and aortic valves, with a brief discussion of tricuspid valve disease. Because the cause of pulmonic disease is primarily congenital, it is described in Chapter 31.


CAUSES OF ACQUIRED VALVULAR HEART DISEASE


Rheumatic Heart Disease

Rheumatic fever is an acute autoimmune disorder that results as a complication of streptococcal upper respiratory tract infections. Tissues involved in rheumatic fever include the lining and valves of the heart, skin, and connective tissue (Fig. 29-1). The group A β-hemolytic streptococcal organism is responsible for initial and recurrent attacks of rheumatic fever. Lymphatic channels from the tonsils are thought to transmit group A streptococci to the heart.

The incidence of rheumatic fever has declined to less than 1/100,000 in industrialized nations but remains higher than 100/100,000 in endemic, less developed countries.1 Reasons for the decline in rheumatic fever include the use of antibiotics to treat and prevent streptococcal infections, as well as improved social conditions such as decreased crowding, better housing and sanitation, and access to health care. Rheumatic fever persists in underdeveloped countries in which socioeconomic conditions enable the spread of streptococcal bacteria and limit access to adequate health care. Acute rheumatic fever involves diffuse exudative and proliferative inflammatory reactions in the heart, joints, and skin.

Jones criteria, based on expert opinion rather than clinical trials, were introduced in 1944 for the diagnosis of rheumatic fever. Major diagnostic criteria include carditis, polyarthritis, chorea, erythema marginatum (pink skin rash), and subcutaneous nodules. Minor criteria include arthralgia, fever, and elevated C-reactive protein.1

Carditis is the most important clinical manifestation of acute rheumatic fever, causing inflammation of the endocardium, myocardium, and pericardium. Myocarditis is characterized by interstitial inflammation that may affect cardiac conduction. Endocarditis causes extensive inflammatory changes, resulting in scarring of the heart valves and acute heart failure. Warty lesions of eosinophilic material build-up at the bases and edges of the valves. As the lesions progress, granulation tissue and subsequent vascularization develop, and fibrosis occurs. The annulus, cusps, and chordae tendineae are scarred and, as a result, they thicken and shorten. Acute heart failure develops because of interstitial myocarditis. Fibrinoid degeneration develops, followed by the appearance of Aschoff nodules, the characteristic pathologic lesion of acute rheumatic fever. As Aschoff nodules heal, fibrous scars remain. In severe cases, death from acute heart failure may result. Carditis frequently does not cause any symptoms and is detected only when the patient seeks help because of arthritis or chorea.

Auscultatory signs of aortic and mitral insufficiency are frequently apparent. In more than 90% of patients with carditis, the mitral valve is affected. When the mitral valve is affected, there may be a high-pitched, blowing, pansystolic murmur. A Carey Coombs murmur, a low-pitched, mid-diastolic murmur of short duration, may be noted at the apex. The Carey Coombs murmur may be attributed to swelling and stiffening of mitral valve leaflets, increased flow across the valve, and alteration in left ventricular compliance.

Rheumatic fever can be prevented by aggressive treatment of the initial episode of streptococcal pharyngitis: penicillin G, 500 mg as the first dose and then 250 mg four times daily for a duration of 10 days. If the patient is allergic to penicillin, erythromycin or cephalosporins may be used. Effective antibiotic treatment started less than 10 days after the onset of infection almost completely eliminates the risk of rheumatic fever.1


Infective Endocarditis

Infective endocarditis is an endovascular infection that supports continuous bacteremia from the source of the infection, usually a vegetation on a heart valve.2 While endocarditis is uncommon, affecting
only 10,000 to 20,000 people in the United States each year, it may result in serious complications such as stroke, need for surgery, and death.3 Although incidence of infective endocarditis is low, between 1.5 and 6 cases per 100 cases per year, morbidity and mortality are high.4 In intravenous drug users, the risk for endocarditis is 2% to 5% per patient-year.5 Rheumatic heart disease, calcific aortic stenosis, hypertrophic cardiomyopathy, congenital heart disease, and the presence of prosthetic heart valves predispose to endocarditis. Intravenous drug abusers are at risk for infective endocarditis caused by recurrent bacteremias related to injection from contaminated needles and localized infections at injection sites. Patients with long-term intravenous lines or dialysis catheters are also at increased risk. Acute endocarditis can also occur in normal heart valves from infection somewhere else in the body In patients with community-acquired, native valve endocarditis, Staphylococcus aureus exceeds streptococci as the causative pathogen.5 Pathogens that are most commonly responsible for subacute endocarditis include streptococci, enterococci, coagulase-negative staphylococci, and the HACEK group of organisms (Haemophilus species, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella species, and Kingella kingae). Clinical presentations of endocarditis range from fever and malaise to symptoms related to systemic emboli (Table 29-1).






Figure 29-1 Rheumatic mitral valve with leaflet thickening and commissural fusion. (From Alpert, J. S., Sabick, J., & Cosgrove, D. M. [1998]. Mitral valve disease. In E. J. Topol, R. M. Califf, J. M. Isner, et al. [Eds.], Textbook of cardiovascular medicine [p. 511]. Philadelphia: Lippincott-Raven.)

The pathologic process of endocarditis requires that several conditions exist to permit infection to grow in the heart and to promote an environment that supports growth on the endocardial surface. For endocarditis to develop, there is first endocardial injury with thrombus formation at the site. Transient or persistent bacteremia allows bacteria to adhere to the injured surface. Infected vegetations result and may fragment and embolize.5 The complications of infective endocarditis include congestive heart failure (CHF), paravalvular abscess formation, embolic events to the brain or other organs, sepsis, pericarditis, renal failure, and metastatic abscesses.4 The reduction in mortality for infective endocarditis over the past 30 years from 25% to 30% down to 10% to 20% may be largely related to aggressive surgical intervention in cases complicated by CHF, invasive abscesses, and prosthetic valve infections.6








Table 29-1 ▪ CLINICAL MANIFESTATIONS OF INFECTIVE ENDOCARDITIS

































Symptoms


Physical Examination Findings


Fever


Fever


Chills and sweats


Changing or new heart murmur


Malaise


Evidence of systemic emboli


Weight loss


Splenomegaly


Anorexia


Janeway lesions (small hemorrhages on palms or soles of feet)


Stroke symptoms


Myalgias


Splinter hemorrhages (hemorrhagic streaks at finger nail tips)


Arthralgias


Confusion


Osler’s nodules (small, tender nodules on finger or toe pads)


CHF


Blood cultures are an essential diagnostic tool in infective endocarditis. Three separate sets of blood cultures drawn from different venipuncture sites, obtained over 24 hours, usually identify the organism. Patients with infective endocarditis whose cultures remain negative may have fastidious organisms or may have received intravenous antibiotics before blood samples were drawn. In acute endocarditis, antibiotic therapy should be started after blood cultures have been obtained using strict aseptic technique and optimal skin preparation.2 The clinical approach in acute endocarditis includes appropriate antibiotics and monitoring for complications (Display 29-1). The usual course is 6 full weeks of intravenous antibiotics. Patients who do not respond well to standard antibiotic therapy may be referred for surgical valve replacement (Display 29-2).

Echocardiography is frequently used to verify the presence of vegetations on the valves (Fig. 29-2). Transesophageal echocardiography (TEE) provides better resolution and can identify smaller vegetations than transthoracic echocardiography (TTE).5 TEE is also useful to identify paravalvular leaks and annular abscesses seen in prosthetic valve endocarditis. Although TEE is more sensitive, some clinicians recommend to obtain TTE first and to perform TEE only if the TTE images are inadequate or suspicion of infective endocarditis remains high and the initial TTE was negative.7




The American College of Cardiology/American Heart Association (ACC/AHA) guidelines now recommend antibiotic prophylaxis for patients with prosthetic cardiac valves or rings; previous endocarditis; unrepaired cyanotic congenital heart disease; repaired congenital heart disease with prosthetic material or residual defects adjacent to prosthetic device or patch; and cardiac transplant recipients.8


Miscellaneous Causes of Valvular Disease

Degenerative changes of the tissue, such as myxomatous degeneration, calcification, and changes associated with Marfan syndrome, can cause valvular dysfunction. Trauma or infection may affect the supportive or subvalvular apparatus. Dilation of the ventricles caused by chronically elevated preloading may dilate an atrioventricular valve opening to the point that the leaflets no longer approximate and the valve becomes incompetent. Coronary heart disease (CHD) and myocardial infarction can affect the papillary muscles of the right and left ventricles, causing either dysfunction caused by ischemia or frank flail of atrioventricular valve leaflets caused by papillary muscle rupture. Systemic diseases such as lupus erythematosus and scleroderma may also cause valvular dysfunction (see Display 29-3).






Figure 29-2 Two-dimensional echocardiogram view of vegetation on tricuspid valve in 27-year-old woman with endocarditis (arrow).



DIAGNOSTIC TESTING FOR VALVULAR HEART DISEASE

The diagnosis of valvular heart disease is based on patient history, physical assessment, and diagnostic testing. Some tests, such as the electrocardiogram and the chest radiograph, may be relatively insensitive in diagnosing valvular heart disease, even though they are part of the standard screening tests in patients with heart dysfunction. Both TTE and TEE are used to identify and quantify valvular heart disease. Diagnostic findings for specific valvular lesions are noted in the sections discussing each abnormality.


MITRAL STENOSIS


Cause

The predominant cause of mitral stenosis is rheumatic fever. The mitral valve is the valve most often damaged by rheumatic carditis.9 Rheumatic fever causes thickening and decreased mobility of the mitral valve leaflets associated with fusion of the commissures and destruction of normal leaflet structure. Other conditions that simulate the physiology of mitral stenosis include left atrial myxoma, ball-valve left atrial thrombus, large left atrial endocarditis vegetations, or cor triatriatum (three atria).10


Pathology

The rheumatic process causes the mitral valve to become fibrinous, resulting in leaflet thickening, commissural or chordal fusion, and calcification. As a result, the mitral valve apparatus becomes funnel shaped with a narrowed orifice. Fusion of the mitral valve commissures results in narrowing of the principal orifice, whereas interchordal fusion obliterates the secondary orifices.


Pathophysiology

Women have mitral stenosis more frequently than men. The normal mitral valve area is 4 to 6 cm2. Once the cross-sectional area of the mitral valve is reduced to 2 cm2 or less, a pressure gradient between the left atrium and left ventricle occurs. The reduced orifice impedes left atrial emptying. Increased left atrial pressure and dilation occurs along with left atrial hypertrophy in an attempt to maintain normal diastolic flow into the left ventricle. Increased left atrial pressure is transmitted to the pulmonary circuit, resulting
in pulmonary hypertension and pulmonary congestion. Left atrial enlargement may lead to atrial fibrillation and worsening of symptoms related to the loss of atrial kick.10 Patients have left-sided CHF without left ventricular dysfunction. Mitral stenosis has a sparing effect on the left ventricle. Symptoms of mitral stenosis are usually related to obstruction of the mitral valve rather than ventricular dysfunction. As pulmonary pressure increases, rightsided heart failure may occur.


Clinical Manifestations

Mild dyspnea on exertion occurs as the most common symptom of mild mitral stenosis (valve area of 1.6 to 2.0 cm2). As mitral stenosis becomes more severe (valve area of 1 to 1.5 cm2), dyspnea, fatigue, paroxysmal nocturnal dyspnea, and atrial fibrillation may occur. When mitral stenosis becomes severe (valve area of 1 cm2 or less), symptoms include fatigue and dyspnea with mild exertion or rest. With advanced mitral stenosis, pulmonary hypertension and symptoms of right-sided heart failure occur (i.e., edema, hepatomegaly, ascites, elevated jugular venous pressure). Chest pain and hemoptysis may also occur. Increased left atrial pressure, atrial fibrillation, and stagnation of left atrial blood flow can result in the formation of mural thrombi, with resultant embolic events, including cerebral vascular accidents. Women who had previously been asymptomatic with mitral stenosis may become symptomatic and even experience severe hemodynamic decompensation during pregnancy due to increased cardiac output and increased heart rate. Tachycardia reduces diastolic filling time and worsens the mitral valve gradient while atrial fibrillation may precipitate pulmonary edema.11


Physical Assessment

In severe mitral stenosis, on auscultation, there are four typical findings including (1) an accentuated S1; (2) an opening diastolic snap; (3) a middiastolic rumble noted best at the apex (in sinus rhythm), followed by presystolic accentuation; and (4) an increased pulmonic S2 intensity associated with pulmonary hypertension (Table 29-2).








Table 29-2 ▪ DIASTOLIC MURMURS IN ACQUIRED VALVULAR HEART DISEASE






























Origin of Murmur


Auscultatory Location and Radiation


Configuration


Quality and Frequency


Maneuvers That Alter Intensity


Aortic insufficiency


Third and fourth left intercostal spaces


image


Blowing
High pitched


Increases with isometric exercise and squatting
Decreases with amyl nitrate and Valsalva maneuver


Mitral stenosis


Apex


Rumbling
Low pitched


Increases with expiration, squatting, amyl nitrate, and isometric exercise
Decreases with Valsalva maneuver


Pulmonic insufficiency


Second left intercostal space


Blowing
High pitched


Increases with inspiration and amyl nitrate
Decreases with Valsalva maneuver


Tricuspid stenosis


Parasternal at left fourth and fifth intercostal spaces


Rumbling
Low pitched


Increases with inspiration, squatting, and amyl nitrate
Decreases with Valsalva maneuver


Patients with mitral stenosis may exhibit malar blush (pink discoloration of the cheeks). Patients with severe mitral stenosis may have weak pulses secondary to reduced cardiac output. The apical pulse is tapping in quality and is nondisplaced. A lower left parasternal lift or heave caused by right ventricular hypertrophy may be present. Cardiac rhythm is often irregularly irregular, indicating atrial fibrillation.


Diagnostic Tests

Echocardiography is used in the evaluation of mitral stenosis to (1) quantify the valve area and gradient; (2) quantify the degree of mitral insufficiency; (3) define the degree of left atrial enlargement; (4) assess mitral annular calcification; (5) assess pulmonary artery pressures and degree of pulmonary hypertension; and (6) evaluate right- and left-sided ventricular function. A TEE provides better detail of the mitral valve and better visualization of atrial thrombus than does TTE.12

Cardiac catheterization is used less in diagnosis of mitral stenosis as echocardiography techniques improve. Cardiac catheterization does allow for accurate assessment of valve area and can also identify associated mitral regurgitation. For patients with known or suspected CHD, coronary angiography can delineate coronary anatomy. Right heart catheterization can evaluate right heart and pulmonary artery pressures.

Electrocardiography is nonspecific and does not indicate the severity of mitral stenosis. If the patient remains in sinus rhythm and left atrial enlargement has occurred, characteristic P mitrale (broad, bifid P waves in leads II and V1) may be identified. Right axis deviation and right ventricular hypertrophy may be noted in severe mitral stenosis. Atrial fibrillation is common in patients with long-standing mitral stenosis and is usually coarse in appearance.

Chest radiography correlates with the degree of mitral stenosis. As mitral stenosis becomes more severe, the chest radiograph demonstrates straightening of the left heart border caused by left
atrial enlargement, elevation of the left mainstem bronchus caused by distention of the left atrium, and distribution of blood flow from the lower to upper lobes. Although heart size remains normal, central pulmonary arteries become prominent. Kerley B lines and interstitial edema are often present.


Medical Management

Medical therapy for mitral stenosis is aimed at preventing the complications of systemic embolization and bacterial endocarditis as well as atrial fibrillation if it occurs.9 Patients who have asymptomatic mitral stenosis require only antibiotic prophylaxis. Patients with mild pulmonary congestion can be managed with diuretics alone. β-Blockers can be used to reduce heart rate and improve diastolic filling time. When patients have atrial fibrillation, digoxin, β-blockers, or calcium channel blockers can be used for ventricular response rate control. Patients with atrial fibrillation require anticoagulation to prevent thrombus formation in the atrium. Once the patient has symptoms of NYHA functional class III or IV despite adequate medical management, mechanical correction of mitral stenosis by balloon valvuloplasty or surgery should be performed.






Figure 29-3 Mitral valvuloplasty: Inoue’s technique. (A) Inflation of distal portion of balloon, which is then pulled back and anchored at the mitral valve. (B) Inflation of proximal and middle portions of balloon. At full inflation, the narrowed “waist” of the balloon has disappeared. (From Vahanian, A. S. [1998]. Valvuloplasty. In E. J. Topol, R. M. Califf, J. M. Isner, et al. [Eds.], Textbook of cardiovascular medicine [p. 2157]. Philadelphia: Lippincott-Raven.)


Interventional and Surgical Management


Percutaneous Mitral Catheter Balloon Valvuloplasty

Percutaneous mitral catheter balloon valvuloplasty is an alternative, less invasive procedure than surgical treatment for mitral stenosis. Balloon valvuloplasty is performed in the cardiac catheterization laboratory by a cardiologist experienced with invasive techniques. A small balloon valvuloplasty catheter is introduced percutaneously at the femoral vein and passed into the right atrium. The catheter is then directed transseptally and positioned across the mitral valve. Mitral balloon valvuloplasty is recommended in patients with moderate-to-severe mitral stenosis that is symptomatic with favorable valve morphology.10

Inflation of either one large balloon (23 to 25 mm) or two smaller balloons (12 to 18 mm) stretches the valve leaflets (Fig. 29-3). Inflation of the balloon separates the fused commissures thus improving valve mobility. The best results from this technique to date have been in patients with rheumatic mitral stenosis with commissural fusion. An echocardiographic scoring system rates leaflet thickening, leaflet mobility, calcification, and
subvalvular deformity, with a maximum score of 4 in each division. Patients with a total echo score of ≤8 respond most favorably.13 Balloon valvuloplasty has been associated with complications including systemic embolization (1% to 3%), severe mitral regurgitation (3% to 5%), and death (0% to 1%).14 An atrial septal defect also may occur in as many as 10% of patients undergoing balloon valvuloplasty as a result of the transseptal approach, but the defect closes or decreases in most patients.15 Results have been promising, with the average gradient reduction being approximately 18 to 6 mm Hg and, on the average, an increase in calculated valve area of 50% to 100%. Mitral balloon valvuloplasty is reserved for patients who continue to be symptomatic despite adequate medical therapy. Mitral balloon valvuloplasty may be used in women who experience hemodynamic decompensation during pregnancy due to mitral stenosis as it offers less risk to the fetus than mitral valve replacement and cardiopulmonary bypass.


Surgical Treatment

Surgical replacement of the mitral valve is required when there is severe mitral regurgitation coexisting with mitral stenosis or if the mitral stenosis is not amenable to percutaneous balloon valvuloplasty. Although some valves with mitral stenosis may be repaired by open commissurotomy and reconstruction, heavily calcified rheumatic mitral valves are often beyond the point of repair. For patients with coexistent tricuspid regurgitation, combined mitral valve surgery with tricuspid repair is related to better clinical outcomes than mitral balloon valvuloplasty alone.16 The usual prosthetic valve of choice in mitral stenosis is a mechanical prosthesis, because patients already require life-long anticoagulation because of atrial fibrillation. For young women who wish to become pregnant, a bioprosthesis may be recommended.








Table 29-3 ▪ SYSTOLIC MURMURS RELATED TO ACQUIRED VALVULAR HEART DISEASE



































Origin of Murmur


Auscultatory Location and Radiation


Configuration


Quality and Frequency


Maneuvers That Alter Intensity


Aortic stenosis


Right second intercostal space
Radiates to carotid arteries and apex


image


Harsh
High pitched


Increases with squatting, amyl nitrate
Decreases with standing, Valsalva maneuver, and isometric exercise


Mitral regurgitation


Apex
Radiates to axilla and back


Harsh or blowing
High pitched


Increases with expiration, squatting, and isometric exercise
Decreases with Valsalva maneuver, standing, and amyl nitrate


Mitral valve prolapse


Apex
Radiates to axilla and back


Harsh
High pitched


Increases with Valsalva maneuver, amyl nitrate, and inspiration
Decreases with squatting, standing, and isometric exercise


Tricuspid regurgitation


Fourth and fifth left intercostal spaces
Radiates to right parasternal border


Harsh
High pitched


Increases with amyl nitrate and inspiration
Decreases with Valsalva maneuver and standing


Pulmonic stenosis


Second left intercostal space
Radiates to back


Harsh
High pitched


Increases with amyl nitrate, squatting, and inspiration
Decreases with Valsalva maneuver and standing

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Jan 10, 2021 | Posted by in NURSING | Comments Off on Acquired Valvular Heart Disease
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