Echocardiography in Pediatric and Adult Congenital Heart Disease, 2nd Ed.

30. Echocardiography in the Diagnosis and Management of Endocarditis

BACKGROUND

The clinical picture of infective endocarditis continues to evolve with changes in the populations at risk, development of new diagnostic tools, improvements in surgical management, and evolution of antibiotic susceptibilities of organisms. The frequency of endocarditis in children appears to be increasing with the current incidence estimated at 0.8 to 3.3 per 1000 pediatric hospitalizations. This increase is often attributed to three major sources: (a) the growing population of individuals with repaired or palliated congenital heart disease, (b) the explosion in the use of indwelling intravenous lines in both neonatal and pediatric intensive care units, and (c) an increase in the use of intracardiac devices and prostheses. A bimodal age distribution for children with endocarditis has been reported, with peaks in infancy (3–11 months) and late teenage years (17–20 years). Although mortality has decreased from 100% in the preantibiotic era to the current rate of 5% to 30% at most pediatric institutions, endocarditis remains a severe disease often accompanied by a high morbidity. At best, endocarditis in children requires prolonged hospitalization and usually 4 to 6 weeks of intravenous antibiotics.

RISK FACTORS

Endocarditis may occur in anyone. However, populations at risk have been defined (Table 30.1), and the index of suspicion should be high in these cases. This is particularly true in the child who has multiple risk factors such as the premature infant with underlying congenital heart disease, an immature immune system, and an indwelling intravenous line for parenteral nutrition. Rheumatic fever, now rare except in specific areas of the United States, has been replaced by indwelling lines, prosthetic valves, intracardiac devices, and congenital heart disease as the highest risk factors for endocarditis in developed countries.

PATHOGENESIS

Bacteria that commonly lead to endocarditis include viridans streptococci, Staphylococcus aureus and S. epidermidis, beta-hemolytic streptococci, and some gram-negative organisms. Polymicrobial endocarditis is uncommon in children, but when it does occur, it is largely limited to intravenous drug users. The most common fungal etiologies of endocarditis are Candida and Aspergillus. Regardless of the organism involved, the pathogenesis is similar. Bacteremia frequently occurs in all individuals in many settings, including postoperatively, with intravenous drug use, or with daily activities such as chewing, tooth brushing, or flossing. Although bacteremia occurs frequently, it rarely leads to endocarditis. Endocarditis only occurs when virulence factors and a unique cytokine milieu allow bacteria to adhere to exposed fibronectin. For example, turbulent blood flow from congenital or acquired heart disease, especially in lesions with high pressure gradients, may traumatize and disrupt endothelium, exposing fibronectin and initiating the clotting cascade and fibrin deposition that leads to clot formation (nonbacterial thrombotic endocarditis). In the setting of bacteremia, bacteria can invade the clot and vegetation growth encases the original nidus of infection. As the infection progresses, it destroys surrounding tissue. The location and amount of tissue destroyed determine the degree of valve regurgitation as well as the presence and size of an abscess cavity.

CLINICAL PRESENTATION

The clinical presentation of the child with endocarditis depends on age, general state of health, and causative organism. Presentations vary widely within age groups and with the causative organism, so the terms “acute” and “subacute” are no longer widely used. Premature or sick neonates requiring central indwelling lines for parenteral nutrition (Fig. 30.1, Video 30.1) are at risk regardless of the presence or absence of a cardiac anomaly. Coagulase-negative staphylococci and enterococci are important pathogens in this age group. The sick neonate may or may not have fever, and other systemic signs may be nonspecific, making the diagnosis of endocarditis difficult. Therefore, the standard of care at many institutions includes a complete echocardiogram in all neonates with indwelling lines who have recurrent or persistent bacteremia to look for vegetations and determine the need for line removal.

The clinical presentation in older children is also variable. Although Osler’s triad of pneumonia, endocarditis, and meningitis is considered the classic finding in adults, it rarely occurs in children. In children, the disease is often indolent and characterized by fever, weight loss, fatigue, and night sweats. Myalgia, arthralgia, headache, and general malaise are common. Nearly all children with endocarditis have a murmur. Some investigators report an average of 35 to 90 days between the first symptom and diagnosis and suggest that the nonspecific and insidious development of symptoms may delay the diagnosis. Viridans group streptococci remain the most frequent cause of endocarditis in children. It commonly presents with an indolent course and rarely leads to complications, especially if diagnosed early and treated with proper antibiotic therapy. Because endocarditis can result in generalized, nonspecific symptoms in children with normal hearts or those with minor unrecognized congenital heart disease, it should be considered in the differential for all children with prolonged, unexplained fever with persistent bacteremia.

Severe infection with valve destruction and significant regurgitation leads to symptoms of congestive heart failure and a severely ill child. In this scenario, a skilled clinician with a high index of suspicion readily makes the diagnosis. The challenge in evaluating a febrile child with less involvement, however, lies in differentiating the innocent murmur associated with the high-output state often associated with fever from the murmur of valve regurgitation. When in doubt, echocardiography should readily resolve the question as to the etiology of the murmur. However, it should be noted that the yield for a positive study indicative of endocarditis is low in the absence of positive blood cultures and appropriate clinical setting.

FIGURE 30.1. Modified subcostal view of a central venous line in the right atrium. The use of B-color allows easy identification of the dense vegetation (arrow), giving a thickened, irregular appearance to the catheter. LV, left ventricle; RV, right ventricle.

As stated above, bacteremia is common with daily activities but rarely results in endocarditis. The exception to this rule is when S. aureus is a causative organism. S. aureus causes many pyogenic infections in children and may lead to sepsis. Endocarditis develops in about 20% of cases of staphylococcal sepsis, even in the absence of underlying heart disease. Because the classic findings of endocarditis are seldom present and the clinical picture is often nonspecific, many experts recommend the routine use of echocardiography with all cases of S. aureus sepsis.

Circulating immune complexes and rheumatoid factor occur in 84% to 100% of cases of endocarditis and are deposited in the skin, spleen, synovium of joints, and glomerular basement membrane. These cause the classic noncardiac manifestations associated with endocarditis, including splenomegaly, polyarthritis, glomerulonephritis, splinter hemorrhages, Osler nodes (painful bluish nodules at the fingertips), Janeway lesions (painless hemorrhagic lesions on the palms and soles), and Roth spots (retinal hemorrhages).

Complications of endocarditis may occur early and alter the presentation as described in the next section.

COMPLICATIONS

Complications (Table 30.2) from endocarditis are common and contribute to the morbidity and mortality. Risk factors for complications include prosthetic valves, S. aureus or fungal causative agents, prior episodes of endocarditis, cyanotic heart disease, left-sided involvement, and clinical symptoms for longer than 3 months.

Congestive heart failure is one of the most common complications of endocarditis. Heart failure may occur acutely and abruptly as a result of valvular regurgitation occurring when native valve leaflets or support structures are disrupted (Fig. 30.2) or from dehiscence of a valve prosthesis resulting in a significant paravalvar leak. In other cases, heart failure symptoms may develop more slowly or insidiously. In either case (acute or insidious), heart failure is secondary to valve regurgitation with or without accompanying ventricular dysfunction. Surgical intervention should be considered in patients with endocarditis and heart failure.

Embolization of vegetation fragments complicates endocarditis in 20% to 40% of cases. The risk is highest during the first days after antibiotic therapy is initiated and drops to 9% to 21% after 2 weeks of treatment. Some studies report the most common noncardiac complications involve the brain, occurring in up to 20% of patients. Stroke preceded the diagnosis of infective endocarditis in up to 60% of patients with endocarditis complicated by stroke. The lungs, kidney, and spleen are also commonly affected. Coronary artery embolism is a less common but potentially lethal complication.

Embolism occurs frequently in gram-negative, pneumococcal, or fungal endocarditis. In children, gram-negative endocarditis is most commonly caused by one of the HACEK organisms (HaemophilusActinobacillusCardiobacteriumEikenella, and Kingella spp.) and is associated with embolism in 31% of cases. About one-third of cases of HACEK endocarditis occur in the absence of underlying heart disease. Because these organisms are fastidious and slow growing and require special growth factors and carbon dioxide for isolation, diagnosis and appropriate treatment are typically delayed, allowing the vegetations to become large and friable, increasing the risk of embolization.

There has been a resurgence of pneumococcal endocarditis in parallel with the increase in its antibiotic resistance. Pneumococcal endocarditis is associated with meningitis, pneumonia, otitis media, or mastoiditis in 50% of pediatric cases. The mitral valve is involved (either alone or in association with aortic or tricuspid valve) in 68% of cases, and 80% have large vegetations, predisposed to embolization.

Fungal organisms account for approximately 1.1% of cases of endocarditis in children, occurring most commonly in developing countries where it is often fatal. Candida causes about 63%, and Aspergillus, 26% of cases. Approximately two-thirds of cases involve children younger than 1 year. In developed nations, premature neonates undergoing medical instrumentation and children who have had congenital heart surgery using prosthetic material are at highest risk of developing fungal endocarditis. Diagnosis is often delayed until large, friable vegetations have formed or after embolization has occurred. The major obstacle to diagnosis is the difficulty in reliably growing fungi in automated blood culture systems. Polymerase chain reaction (PCR) has been useful for the detection and identification of fungal organisms.

One of the most severe complications of endocarditis is an abscess. A paravalvular abscess may be seen when the infection extends beyond the valve annulus. Although this is a rare complication, it is strongly associated with a poor outcome. In both children and adults, S. aureus is the most common cause and nearly all abscesses involve the aortic valve. In adults, the incidence of paravalvular abscess is approximately 20% to 40% with native aortic valve endocarditis and 60% in the setting of a prosthetic aortic valve. Similar data are not available for children as only small series or case reports comprise the literature. The literature suggests that the underlying native valve anatomy is normal in 66% of cases of endocarditis complicated by abscess formation in children. Although a paravalvular abscess may have an indolent presentation, the more typical picture is that of acute, severe illness. The child has a new pathologic murmur and may also have a rub indicating pericarditis. The abscess disrupts the aortic annulus, creating severe regurgitation that results in intractable congestive heart failure (Fig. 30.3). The infection may extend into the mitral-aortic fibrosa and involve the anterior mitral leaflet so that the mitral valve becomes regurgitant as well. When the structural integrity of the aortic wall is further weakened, a sinus of Valsalva aneurysm may form and ultimately rupture into the right ventricular outflow tract or either atria, creating a shunt that is poorly tolerated. Fever and bacteremia usually persist despite appropriate antibiotic therapy and recurrent emboli are common. The new development of bundle branch block or complete heart block is highly specific for a paravalvular abscess. Most experts recommend serial echocardiographic evaluations looking for development of paravalvular abscess in the following settings: (a) S. aureus endocarditis regardless of whether a native or prosthetic aortic valve is involved, (b) persistent fever or bacteremia despite appropriate antibiotic therapy, (c) a persistent bundle branch block or complete heart block, especially when there has been a prolonged period of symptoms before diagnosis and treatment, and (d) thickening of the aortic root is visualized by echocardiography in a patient with endocarditis.

FIGURE 30.2. Aortic valve vegetation. A: Parasternal long-axis view shows a vegetation on the aortic valve (arrow) that prolapses into the left ventricle during diastole. The valve cusps are partially destroyed and prolapsed, resulting in severe aortic regurgitation. Ao, aorta; LA, left atrial. B: Apical four-chamber view demonstrates the extensive involvement of the vegetation (horizontal arrow) on the aortic valve (vertical arrow) that extends along the interventricular septum. Ao, aorta; LV, left ventricle.

DIAGNOSIS

Endocarditis is largely diagnosed by positive blood cultures for a typical organism and the presence of vegetations and/or abscess formation on echocardiography. Systemic, vascular, and/or immunologic findings support the diagnosis. Typical laboratory findings include anemia and elevated white blood count, erythrocyte sedimentation rate, and C-reactive protein. Blood cultures are positive in over 90% of cases but may be negative with prior use of antibiotics, with right-sided endocarditis, or when the pathogen is intracellular or fastidious. Serology may prove useful in these circumstances. Serology is the only method that allows diagnosis of Coxiella burnetii (Q fever), BrucellaBartonella, and chlamydial endocarditis.

Early diagnosis and aggressive treatment are warranted to avoid the serious complications associated with endocarditis. Although infective endocarditis has been diagnosed using bedside, focused ultrasound in the emergency department in isolated instances, more data are needed before this modality can be recommended as an effective and accurate approach to the diagnosis of endocarditis. It is also important to avoid overdiagnosis, as treatment involves weeks or months of intravenous antimicrobial therapy. When the classic noncardiac findings and/or new-onset regurgitant murmurs are present in the febrile child with bacteremia and an echocardiogram shows vegetations and/or abscess, the diagnosis of endocarditis can readily be made. The picture is seldom so clear, however. Fever may be absent if the child is debilitated, immunocompromised, or pretreated with antibiotics. Innocent murmurs are common in children during illness and may be difficult to differentiate from those of valvar regurgitation. Noncardiac manifestations may not be present. In a series of 76 episodes of endocarditis in children, splenomegaly occurred in 5%, splinter hemorrhages in 4%, Roth spots in 4%, and Osler nodes in 3%.

FIGURE 30.3. Paravalvular abscess. A: Parasternal long-axis view of the left ventricular outflow tract shows the shaggy appearance of a hypoechoic space posterior to the aortic outflow tract representing a paravalvular abscess (arrow). Ao, aorta; LV, left ventricle. B:Transesophageal echocardiogram using a longitudinal view of the left ventricular outflow tract in the same patient demonstrates the abscess cavity (arrow). The aortic valve leaflets are thickened and distorted and fail to coapt with significant aortic regurgitation. Ao, aorta; LV, left ventricle.

A team of primary care physicians, infectious disease specialists, cardiologists, and cardiovascular surgeons may be needed for optimal evaluation and management. The modified Duke criteria (Table 30.3) have been validated in children and should be used when the clinical picture is unclear. The Duke criteria function similar to the Jones criteria for rheumatic fever by dividing clinical, microbiological, and echocardiographic findings into major and minor categories. The two major criteria typically include (a) microbiologic evidence and (b) evidence of endocardial involvement (positive echocardiogram or new valvular regurgitation). It is worth noting that three echocardiographic findings qualify as major criteria: (a) discrete, echogenic, oscillating intracardiac mass at the site of endocardial injury, (b) paravalvular abscess, or (c) new dehiscence of a prosthetic valve. The 15 minor criteria include the presence of specific known risk factors, evidence of emboli, classic findings resulting from immunologic phenomena, and laboratory findings. Endocarditis is definitively diagnosed if (a) there is pathologic evidence of an intracardiac or embolized vegetation or intracardiac abscess or (b) fulfillment of clinical criteria, requiring the presence of (i) two major or (ii) one major and three minor or (iii) five minor criteria. Endocarditis is considered possible if one major and one minor or three minor criteria are present. A firm alternative diagnosis, resolution of symptoms within 4 days of antimicrobial therapy, and absence of surgical or autopsy evidence of endocarditis within 4 days of antimicrobial therapy points away from a diagnosis of endocarditis.

Blood cultures are central to the diagnosis and effective treatment of endocarditis. Contrary to what is considered optimal in other settings, it is not necessary to obtain blood sampling at the time of fever, as the bacteremia of endocarditis is continuous. The volume of blood drawn is important, however, and experts recommend 1 to 3 mL in infants and 5 to 7 mL in older children. Three cultures over a minimum time of 1 hour should be drawn before administering empiric antibiotics. Despite numerous cultures with adequate volumes, prolonged culture periods, and examination of surgically excised tissue, about 5–10% of cases of endocarditis are culture-negative. Attempts to obtain an organism through antibody titers and polymerase chain reaction techniques may also fail. Reasons for “culture-negative” endocarditis include inability to grow a fastidious organism, antibiotic use prior to culturing, pulmonary filtering of bacteria for right-sided lesions, and sequestration of the organism within the vegetation.

MANAGEMENT

It is important to note that the Duke criteria provide guidelines for the diagnosis but not the management of endocarditis. Administration of intravenous antibiotics is clearly indicated for those with definite endocarditis, but their use for possible or rejected cases must be considered on an individual basis. The team of experts must weigh the risk factors, evaluate the reliability of the blood cultures, and determine the likelihood that endocarditis best explains the clinical picture.

Once diagnosed, the patient’s condition and causative organism dictate the course and length of treatment. All patients require medical therapy and some will require surgery. If antibiotics are started before culture results become available, treatment is usually directed toward the most common bacteria—streptococci and staphylococci. Once the organism is isolated, susceptibilities are determined and antibiotics adjusted accordingly. Antibiotics may be combined to provide synergy and must be given intravenously to achieve concentrations sufficiently high to treat infection in the poorly vascularized valve leaflets as well as penetrate infected vegetations. Treatment is typically for 4 to 6 weeks but may be longer in those patients with prosthetic valves or those who are immunocompromised or have other extenuating circumstances. Anticoagulation is not indicated (unless given for a reason other than endocarditis) and is actually contraindicated with severe cerebral complications or mycotic aneurysms. Afterload reduction in the setting of significant acute aortic or mitral regurgitation is limited to stabilization of the patient before surgical intervention.

While surgery is indicated in patients with cardiogenic shock or life-threatening congestive heart failure due to valve disease from endocarditis, the indications for surgical intervention in the hemodynamically stable patient are not as clear. Those indications with the strongest evidence include abscess formation, severe valvular regurgitation with intractable congestive heart failure, recurrent arterial emboli, fungal infection, and persistent bacteremia after 1 week of appropriate antibiotic therapy (Table 30.4).Typically, patients with infected pacing systems (Fig. 30.4, Video 30.2), intracardiac devices (Fig. 30.5), and prosthetic valves are managed surgically. Some experts recommend surgery for left-sided vegetations ≥1 cm in size, for right-sided vegetations ≥2 cm in size, with increasing vegetation size while on appropriate antibiotics, or marked mobility of the vegetation, but data are conflicting and these indications remain controversial.

Some studies in adults suggest earlier surgical intervention may be warranted in specific situations. For example, some investigators report that adult patients with vegetations >1 cm and severe valve regurgitation in the absence of heart failure who had surgery within 48 hours of diagnosis of infective endocarditis had better outcomes than those treated with conventional medical therapy and surgical indications. While the study was randomized, the numbers were small and more data are needed to determine the appropriate extrapolation of this information to the pediatric population. Also, closure of a hemodynamically insignificant ventricular septal defect is warranted after successful treatment of endocarditis to decrease the risk of recurrence.

PROGNOSIS

Prognosis depends on several factors. Patients with a more severe course leading to hospitalization within 1 week of onset of the first symptom have higher mortality rates. The prognosis is worse for younger children (younger than 3 years) compared with older children, even when the time to diagnosis is similar. In terms of bacterial etiology, S. aureus infection carries the highest mortality rates in most published series. In contrast to adults, left-sided and right-sided vegetations appear to carry a similar mortality in children. The primary causes of death include congestive heart failure, renal failure, rupture of a mycotic aneurysm, or consequences of emboli.

FIGURE 30.4. Endocarditis with involvement of the pacemaker lead. The midesophageal four-chamber echocardiographic view shows a pacemaker lead with a vegetation (arrow) in this patient with endocarditis and a past history of repaired complete atrioventricular septal defect. RA, right atrium; RV, right ventricle.

FIGURE 30.5. ASD device endocarditis. A: Parasternal long-axis view of a patient after device closure of an atrial septal defect shows an arm of the device in the mitral valve funnel. A vegetation (arrow) is seen attached to this arm. Ao, aorta; LA, left atrium. B: Off-axis apical four-chamber view demonstrating the device (horizontal arrow) and the thickened irregular vegetation (vertical arrow) attached to it. LV, left ventricle. C: Transesophageal echocardiogram at the level of the mitral valve and left ventricular outflow tract demonstrates an additional vegetation (arrow) on the posterior leaflet of the mitral valve. LA, left atrium; LV, left ventricle.

PROPHYLAXIS

The American Heart Association guidelines regarding antibiotic prophylaxis for endocarditis have evolved over the past 50 years. The latest revision, published in 2007, substantially revised the indications for antibiotics in at-risk groups. Prophylaxis is no longer recommended for genitourinary or gastrointestinal tract procedures. Prophylaxis for dental procedures is recommended only for cardiac conditions associated with the highest risk of adverse outcome from infective endocarditis: (a) prosthetic valve, (b) history of endocarditis, (c) unrepaired cyanotic congenital heart disease (including after palliation with shunts and conduits), (d) for 6 months after completely repaired heart defects using prosthetic materials, (e) repaired defects with residual lesions at, or adjacent to, the site of prosthetic material or device, and (f) cardiac transplant patients with valvulopathy. In contrast to previous guidelines, antibiotic prophylaxis is not recommended for any other congenital heart defect. Good oral hygiene to decrease the incidence of bacteremia is probably the best way of reducing the risk of endocarditis.

The impact of the changes from the 2007 guidelines for endocarditis prophylaxis is not yet clear. One study showed a significant change in practice among pediatric cardiologists in the United States, Canada, Australia, and New Zealand; however, the study also showed significant practice variation. To date, studies regarding the clinical impact of the newest guidelines have not shown an increase or change in the incidence of endocarditis, including endocarditis from viridans streptococci, in either pediatric or adult populations.

IMPORTANT ECHOCARDIOGRAPHIC CONSIDERATIONS

Echocardiography should be performed in any child suspected of having endocarditis to allow earlier diagnosis and prevent complications. That being said, not all masses seen on an echocardiogram are vegetations (Fig. 30.6). The echocardiographic appearance of vegetations, noninfectious thrombi, and other intracardiac masses may be indistinguishable. In the absence of microbiological, serologic, or physical evidence to support the diagnosis, the positive predictive value of echocardiography is poor. Therefore, the incidental echocardiographic finding of a mass in a child who has no associated clinical suspicion of endocarditis likely warrants further investigation and follow-up but should not be considered a vegetation without supporting clinical features (see modified Duke criteria, Table 30.3).

Vegetations

Echocardiographic findings typical of endocarditis are present in more than 90% of cases. False negative examinations may occur when preexisting pathology obscures the vegetations or when the vegetations are too small to be seen with the ultrasound equipment or imaging approach used (including when imaging is suboptimal). Detection rates may improve with the transesophageal approach, especially in older children and adolescents, allowing visualization of vegetations as small as 1 mm. Vegetations large enough to be visualized by current ultrasound machines appear as echogenic masses attached to a cardiac valve, papillary muscle, chordae, endocardium, prosthetic patch, or indwelling line or device. The typical vegetation forms downstream from the turbulent flow—on the right ventricular side of a ventricular septal defect, the ventricular side of the regurgitant, infected semilunar valve, or the atrial side of a regurgitant, infected atrioventricular valve (Fig. 30.7, Video 30.3). When vegetations are seen on one valve, care should be taken to determine if other cardiac valves are also involved or if abscesses are present. This is particularly true with intravenous drug abuse, where multivalvular involvement is common. In some cases, the vegetations themselves may disrupt valve function and cause varying degrees of regurgitation. More frequently, however, infection destroys the leaflets or supporting apparatus resulting in significant regurgitation. Chordae may rupture resulting in a flail leaflet and significant regurgitation, but this must also be considered in the clinical setting where it occurs. The flail leaflet as a result of infection may appear identical to the flail leaflet resulting from trauma or bioprosthesis degeneration. Color Doppler echocardiography is useful for differentiating transvalvular and paravalvular jets when a prosthesis is involved.

FIGURE 30.6. Example of a cardiac mass not related to endocarditis. A: This patient presented with the new onset of a cardiac murmur. He had no associated fever, bacteremia, or other systemic or laboratory findings. A large mass (arrow) is demonstrated attached to the ventricular side of the mitral valve that moves into and partially obstructs the left ventricular outflow tract during systole. Although endocarditis was considered, neither the clinical picture nor the location of the mass supported the diagnosis. B: Apical four-chamber view demonstrates the attachments of the mass (arrow) to the ventricular side of the anterior mitral valve leaflet. The mass was excised and pathology demonstrated a ventricular myxoma. Ao, aorta; LV, left ventricle.

Attempts have been made to determine echocardiographic predictors of complications. Patients with larger vegetations have a higher incidence of embolization, abscess formation, heart failure, failure of medical therapy, and death. The echogenicity of the vegetation appears to have no relationship to the risk of embolization. Spontaneous echocardiographic contrast is thought to imply increased platelet aggregation involved in the formation and growth of vegetations. In one series, the dynamic clouds of slowly curling or spiraling echoes characteristic of spontaneous contrast were seen within the left ventricular cavity in 26% of patients with endocarditis. These investigators found spontaneous contrast had a specificity of 83% and a sensitivity of 38% for predicting an embolic event. The presence of spontaneous contrast was also associated with an increased risk for valve replacement, prolonged healing, and death. Although controversial, size and mobility of vegetations are frequently considered risk factors. Vegetation size greater than 1 cm and marked mobility predict embolization with odds ratios of 9 and 2.4, respectively. Vegetations greater than 1.5 cm have the worst prognosis.

FIGURE 30.7. Mitral valve vegetation. A: Parasternal long-axis view with B-color shows a vegetation on the left atrial side of the mitral valve (arrow) due to Haemophilus endocarditis. B: Parasternal short-axis view with the mitral valve en face, showing the vegetation (arrow). LA, left atrium; LV, left ventricle.

Valve regurgitation is an important finding in endocarditis, and while its presence does not prove endocarditis, its absence makes the diagnosis extremely unlikely. Echocardiography may allow determination of the mechanism of regurgitation, such as visualization of leaflet perforation, loss of leaflet coaptation, chordal rupture, or disruption of the annular support.

Abscesses and Fistulae

With careful attention to imaging detail, echocardiography allows detection of more than 90% of paravalvular abscesses; other imaging modalities are rarely needed. Vegetations involving the right coronary cusp of the aortic valve have the highest association with abscess formation. The abscess cavity appears as marked thickening or enlargement of the aortic wall or sinuses of Valsalva (anteriorly or posteriorly), frequently associated with a hypoechoic space or a spontaneous contrast appearance (Fig. 30.8). Similar densities may extend to the interventricular septum or the ventricular wall adjacent to the native or prosthetic valve annulus. Significant regurgitation and the formation of fistulae into the pulmonary artery or cardiac chambers are common. In the setting of an infected prosthetic valve, there may be a rocking or asynchronous movement of the valve between the annulus and the sewing ring. If the transthoracic examination is equivocal and the index of suspicion for endocarditis is high, the transesophageal approach should be used. The long- and short-axis views with the transducer at the level of the aortic valve allow visualization of the abscess cavity as a circumscribed pocket with reduced echo density. The total extent of involvement can usually be defined but often requires nonstandard, off-axis views. Color Doppler aids in detecting fistulae draining to other vessels and/or cardiac chambers.

FIGURE 30.8. Parasternal short-axis view just below the level of the aortic valve demonstrates the left ventricular outflow tract (LVOT) in cross section. An abscess cavity is imaged posterior to it (vertical arrow), creating a double-circle appearance. RV, right ventricle.

Embolism, Ventricular Dysfunction, and Pericarditis

Embolism is a relatively common complication of endocarditis and should be considered when symptoms develop or when there is a sudden decrease in the size of the vegetation. Embolism may occur to any organ system, most commonly, the lungs, brain, kidney, or spleen. Left ventricular dysfunction is unusual but may occur in the setting of acute volume overload secondary to valvular regurgitation or a sizeable fistulous connection, after coronary embolism, or when myocarditis complicates the clinical picture. Coronary embolism will be accompanied by typical electrocardiographic changes as well as new regional wall motion abnormalities or global impairment of ventricular function on echocardiography.

A pericardial effusion may result from inflammation or direct extension of the infection into the adjacent pericardium, mycotic aneurysm of the proximal aorta, septic coronary embolus, or myocardial abscess (Fig. 30.9).Although reported in only 6% of patients with endocarditis without abscess, 52% of patients with a paravalvular abscess have a pericardial effusion. Purulent pericarditis is associated with an extremely high mortality.

Prosthetic Valves and Conduits

Prosthetic valves are associated with a significantly increased risk of endocarditis in children and adults. Because the prosthesis produces reverberation artifact and acoustic shadowing, it may be difficult to differentiate postoperative from inflammatory changes. It may be useful to note that isolated mild paravalvular regurgitation does not predict endocarditis and should not be considered as an echocardiographic finding suggestive of endocarditis. In contrast, vegetations, paravalvular abscesses, valve dehiscence, pseudoaneurysms, fistulae, or moderate or greater regurgitation is useful for making the diagnosis with a positive and negative predictive value of 94% and 96%, respectively, for any of these findings.

Even stentless aortic tissue valves present diagnostic challenges. The postoperative echocardiographic appearance varies with the implantation technique. Most surgical implantation methods retain part of the native aortic root, resulting in a double-lumen appearance that may be mistaken for a paravalvular abscess in the postoperative patient with a fever. The development of paravalvular thickening, diffuse leaflet thickening, or new valvular regurgitation or the presence of vegetation or fistula is indicative of endocarditis. In addition, because the typical postoperative double-lumen densities resolve within the first few months after surgery, an interval increase in the size of the densities on serial examinations suggests endocarditis.

FIGURE 30.9. Tricuspid valve vegetation. A: Apical four-chamber view shows a vegetation on the tricuspid valve (arrow). Note the small pericardial effusion adjacent to the right atrial wall. RA, right atrium; LV, left ventricle. B: Transesophageal imaging and B-color allow better visualization of this large vegetation (arrow) associated with the tricuspid valve. RA, right atrium; RV, right ventricle

Valved conduits are often used to establish continuity between the ventricles and the pulmonary arteries in many types of congenital heart disease. In such cases, echocardiographic evaluation should focus not only on the valve within the conduit but also on the proximal and distal anastomoses.

Role of Transesophageal and Intracardiac Echocardiography

It is clear that the transesophageal approach is superior to the transthoracic approach in adults, but such evidence is lacking in children. Transesophageal echocardiography is not as widely used because of the need for sedation or general anesthesia and intubation in children, who often have favorable transthoracic acoustic windows. When the two approaches were systematically studied in a pediatric population (ages 0.3 to 17.5 years), the transesophageal approach added little when a vegetation was imaged transthoracically. Therefore, most pediatric cardiologists reserve transesophageal echocardiography for special circumstances: (a) poor transthoracic acoustic windows, (b) prosthetic valves that may obscure vegetations by acoustic shadowing, (c) persistent clinical and microbial evidence of endocarditis but a normal transthoracic study, or (d) older children and adolescents who are closer to adult size, a scenario where the sensitivity of transthoracic echocardiography decreases from 97% to 70% in patients ≥60 kg. Similar to the adult practice, most pediatric cardiologists adhere to the principle that transesophageal echocardiography should be performed if the transthoracic examination is negative when there is strong clinical evidence of endocarditis.

Intracardiac echocardiography has been used in adults to diagnose infective endocarditis in the setting of cardiovascular implantable electronic devices. This practice is not widely used in children. Similar to transesophageal echocardiography, the use of intracardiac echocardiography must be weighed against the risks of sedation or general anesthesia and intubation in children. However, when imaging of the right ventricle is challenging with transthoracic and transesophageal echocardiography (in part due to acoustic shadowing from a pacemaker lead), intracardiac echocardiography may prove diagnostic.

IMPORTANT ECHOCARDIOGRAPHIC SUGGESTIONS

Careful attention to both machine and examination settings is important (Table 30.5). The highest-frequency transducer that allows adequate penetration to image cardiac structures should be used both to optimize detection as well as to resolve the edges of a vegetation and/or delineate abscess cavities. Gains must be set high enough to detect small, subtle vegetations and clearly visualize the blood-endocardium interface but not so high that low attenuation creates artifacts. All acoustic windows (both standard and nonstandard) should be used to image cardiac structures, detect vegetations and abscesses, and to differentiate subtle positive findings from artifacts. In contrast to artifacts that cannot consistently be seen in multiple planes, true abnormalities can be confirmed by imaging them from orthogonal and off-axis views. Color-encoded tissue processing (B-color), where real-time images are displayed with a dynamic compression of varying colors, should routinely be used. Compared with gray-scale imaging, B-color allows better differentiation of the extent of the mass and increases the user’s ability to detect small vegetation.

The etiology of an intracardiac mass can seldom be determined by echocardiography alone. Both the sonographer performing the examination and the physician interpreting the study require extensive knowledge of normal and congenitally abnormal structures of the heart including the Eustachian valve, dilated coronary sinus, Chiari network, and atrial or ventricular septal aneurysms that may appear as masses or abscesses. All abnormalities seen by echocardiography must be considered in the setting in which they occur. Vegetations cannot be distinguished from other intracardiac masses solely by echocardiography. The positive predictive value of echocardiography for endocarditis is low in the absence of microbiologic, serologic, and/or clinical evidence for systemic infection.

Serial echocardiograms are important during the course of the illness. Vegetations too small to be imaged on the initial study may subsequently be seen as they grow in size. Large vegetations may show a sudden decrease in size or disappear completely if embolization occurs. Valvular regurgitation may progress and volume overload may ultimately impair ventricular function. Complications such as abscesses or fistulae may not be present until later in the course of the disease. With appropriate therapy, the vegetations slowly decrease in size as the mass organizes, but serial exams have shown that they may persist for months or even years after the acute episode. These “healed vegetations” have no distinguishing echocardiographic features from the masses that present during the acute phase of the disease. Therefore, it is important to obtain an echocardiogram at the end of medical therapy when blood cultures are negative after completion of antibiotics. This end-of-therapy “baseline study” can then serve as a comparison should the patient develop clinical findings suggesting persistent or recurrent infection.

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Questions

1.Of the following, which is the most frequent risk factor for the development of endocarditis in children in the United States?

A.Congenital heart disease

B.Rheumatic heart disease

C.Staphylococcus epidermidis sepsis

D.Systemic hypertension

E.Immunocompromised state

2.Routine echocardiography is recommended to evaluate for endocarditis in all cases of sepsis from which organism?

A.Streptococcus viridans

B.Streptococcus pneumoniae

C.Staphylococcus epidermidis

D.Staphylococcus aureus

E.Streptococcus agalactiae

3.Antibiotic resistance has led to a resurgence of endocarditis from which of the following organisms?

A.Staphylococcus aureus

B.Streptococcus pneumoniae

C.Streptococcus viridans

D.Aspergillus

E.Staphylococcus epidermidis

4.A 12-year-old female with a structurally normal heart is hospitalized with Staphylococcus aureus bacteremia and endocarditis involving the aortic valve. She then develops bradycardia and is found to have complete heart block. You suspect this is secondary to which of the following complications?

A.Severe heart failure from mitral valve regurgitation

B.Stroke and increased intracranial pressure

C.Embolism to the right coronary artery

D.Hypertension from a renal infarct

E.Perivalvar abscess

5.Which of the following findings qualifies as a major criterion in the diagnosis of endocarditis using the modified Duke criteria?

A.Loss of atrioventricular capture in a child with a pacemaker

B.Dehiscence of a prosthetic mitral valve in a child with Shone’s complex

C.Murmur in a child with an unexplained fever

D.New onset of hematuria

E.Night sweats in a child with poor weight gain

6.The 2007 American Heart Association guidelines for endocarditis prophylaxis recommend antibiotic prophylaxis to which of the following children?

A.Six-year-old girl with mild recoarctation after repair during infancy.

B.Fifteen-year-old boy with an indwelling line for chemotherapy who has cardiomyopathy.

C.Ten-year-old girl with Trisomy 21 and successful repair of an atrioventricular septal defect.

D.Sixteen-year-old football player with a bicuspid aortic valve and aortic dilation.

E.A seven year old with a hemodynamically insignificant ventricular septal defect who recovered from endocarditis last year without sequelae.

7.Vegetations involving which of the following structures have the highest association with abscess formation?

A.Anterior leaflet of the mitral valve

B.Posterior leaflet of the mitral valve

C.Left coronary cusp of the aortic valve

D.Right coronary cusp of the aortic valve

E.Noncoronary cusp of the aortic valve

8.A four-year-old boy was admitted for fever of unknown origin. He had nearly completed a 10-day course of antibiotics for otitis media at the time of admission, yet remained febrile throughout his antibiotic course. A murmur was noted at the time of admission, which his parents report is new. An echocardiogram was performed to evaluate the new murmur, and a mobile mass was noted on the atrial side of the mitral valve with moderate mitral regurgitation. Neither of his two blood cultures that were obtained on the two days prior to admission had grown an organism. In your consult, you suspect that

A.the mass is a myxoma, and the fevers are likely due to an oncologic process.

B.this is likely endocarditis, and prior antibiotic treatment has resulted in negative blood cultures.

C.the patient has Kawasaki Disease.

D.the patient has rheumatic fever.

E.the patient has a viral endocarditis.

9.Which of the following is no longer considered an indication for endocarditis prophylaxis?

A.Systemic to arterial shunt

B.Mitral regurgitation after cardiac transplantation

C.Prosthetic valve in the aortic position

D.Rheumatic mitral regurgitation

E.Repaired ventricular septal defect with residual shunt adjacent to the patch

10.The risk of transesophageal echocardiography outweighs the benefits when evaluating a child for suspected endocarditis in which of the following scenarios?

A.Prosthetic valve obscures images due to acoustic shadowing on transthoracic echocardiography.

B.The transthoracic acoustic windows are poor.

C.The child is older and closer to adult size.

D.Persistent clinical and microbial evidence of endocarditis exists in the setting of a normal transthoracic echocardiogram.

E.A mobile mass is seen on the mitral valve by transthoracic echocardiography in a febrile child with bacteremia.

Answers

1.Answer: A. As the prevalence of children with congenital heart disease has increased with improved survival, congenital heart disease is one of the most frequent risk factors for the development of endocarditis in the United States, along with indwelling lines, prosthetic valves, and intracardiac devices. Although rheumatic heart disease was historically a frequent risk factor for the development of endocarditis, the incidence of rheumatic fever has decreased in the United States significantly over the past few decades. Rheumatic heart disease continues to be a common risk factor for infective endocarditis in developing countries. An immunocompromised state and bacteremia from Staphylococcus epidermidis are risk factors for the development of endocarditis in some settings, but they are not the most frequently occurring risk factors. There is no known association between systemic hypertension and infective endocarditis.

2.Answer: D. Staphylococcus aureus sepsis leads to endocarditis in about 20% of cases, and the clinical presentation may not include the classic findings of endocarditis. Furthermore, studies have shown that endocarditis from S. aureus has a shorter duration of symptoms before diagnosis, and is associated with more severe comorbidity and mortality in comparison with other pathogens. Therefore, experts recommend an echocardiogram routinely in all cases of S. aureus bacteremia.

3.Answer: B. About half of pediatric cases of infective endocarditis from Streptococcus pneumoniae are associated with common pediatric infections such as otitis media, pneumonia, meningitis, or mastoiditis. Streptococcus pneumoniae with intermediate or high penicillin resistance is being seen increasingly in these patients. Therefore, penicillin susceptibility should be tested in cases of pneumococcal infective endocarditis.

4.Answer: E. Infection involving the valve annulus can spread to contiguous tissues and create perivalvar cavities. These cavities typically occur at the weakest portion of the annulus. In the case of infective endocarditis involving a native aortic valve, the weakest part of the annulus is near the membranous septum and atrioventricular node. Therefore, heart block is a significant consequence in native aortic valve endocarditis and patients with native aortic valve endocarditis should be monitored closely for this. In addition, for the patient with sudden onset of heart block in the setting of fever, endocarditis involving the aortic valve should be strongly considered.

5.Answer: B. Due to the clinical variability of the presentation of infective endocarditis, a diagnostic tool was developed in 1994 by researchers at Duke University Medical Center (and modified in 2000) to aid in the diagnosis of infective endocarditis. Termed the Duke criteria, this tool has demonstrated a high sensitivity and specificity, and has been validated in children. Along with microbiologic evidence of infective endocarditis, echocardiographic evidence of infective endocarditis is included as a major criterion. Echocardiographic evidence of infective endocarditis has been defined as any one of the following:

1) oscillating mass on a valve or endocardium.

2) perivalvar abscess.

3) dehiscence of a prosthetic valve.

6.Answer: E. The updated 2007 American Heart Association guidelines for the prevention of infective endocarditis were changed to recommend antibiotic prophylaxis prior to dental procedures for cardiac conditions associated with the highest risk of adverse outcome from infective endocarditis, rather than those at highest risk for development of infective endocarditis. The groups at highest risk of adverse outcome include those with:

1) prosthetic valve

2) history of endocarditis

3) unrepaired cyanotic congenital heart disease

4) repaired heart defects using prosthetic materials, but only for 6 months post-op

5) repaired defects with residual lesions at, or adjacent to, the site of prosthetic material or device

6) cardiac transplant with valvulopathy

Based on these most recent guidelines, the majority of patients with congenital heart defects do not require antibiotic prophylaxis.

7.Answer: D. Previous studies have shown that vegetations involving the right coronary cusp of the aortic valve were associated with increased occurrence of abscess formation compared to the other cusps of the aortic valve. Abscess involving only the mitral valve is rare.

8.Answer: B. Antibiotic therapy prior to drawing blood cultures can lead to negative blood cultures. Culture negative endocarditis occurs in 5-10% of cases of infective endocarditis. Given the clinical scenario of a febrile patient, echocardiographic evidence of an oscillating mass, as well as newly diagnosed mitral valve regurgitation, the clinical index of suspicion for infective endocarditis is high despite failure to fulfill modified Duke criteria for a definitive diagnosis. Myxomas are not typically associated with fevers or an oncologic process. Intracardiac masses are not typical of Kawasaki Disease or rheumatic carditis, though involvement of the mitral valve with regurgitation may occur.

9.Answer: D. Similar to Question 6, the 2007 guidelines for the prevention of infective endocarditis from the American Heart Association recommend that antibiotic prophylaxis prior to dental procedures be administered to patients at highest risk for adverse outcome if they develop infective endocarditis. Of these possible answers, those with rheumatic fever are not at highest risk for an adverse outcome.

10.Answer: E. Because acoustic windows in children are typically good, transthoracic imaging is often sufficient to diagnose infective endocarditis. In studies comparing transthoracic to transesophageal echocardiography, transesophageal imaging added little in the pediatric population. In the case of a bacteremic, febrile child with a mobile mass seen on transthoracic echocardiogram, the diagnosis of infective endocarditis can be made and no transesophageal imaging is needed. However, in older children, in children who are as big as adults, or in those with poor transthoracic images (i.e., from significant lung artifact or acoustic shadowing from a cardiac pacing wire) transesophageal echo can provide diagnostic imaging. When the clinical suspicion for infective endocarditis is high, the added value of transesophageal echo can outweigh the risks of sedation or general anesthesia for the procedure, because the sequelae of a missed diagnosis of infective endocarditis can be significant and include death.