41: Infective Endocarditis


CHAPTER 41
Infective Endocarditis


Manfred Otto Vogt1 and Andreas Kühn2


1 Technische Universität München; Special Practice for Pediatric Cardiology and Congenital Heart Defects, Munich, Germany


2 German Heart Center Munich; Special Practice for Pediatric Cardiology and Congenital Heart Defects, Munich, Germany


Definition


Infective endocarditis (IE) is a subacute infectious disease of the heart and its surrounding vessels that carries a very high risk of morbidity and mortality. Unfortunately, a clear‐cut diagnosis of IE is rare in patients with congenital heart disease (CHD) and is reserved for those who fulfill the classic Oslerian manifestations: bacteremia or fungemia, evidence of active vasculitis, and/or peripheral emboli (Figure 41.1) and immunologic vascular phenomena. In most cases the clinical presentation is quite variable and therefore the diagnosis is related to an evidence‐based scoring system that includes clinical, microbiological, and echocardiographic findings (Tables 41.1 and 41.2). The Duke criteria [1] and their modification in 2000 [2] have been validated not only in adults but also in children [3,4]. It should be kept in mind that the Duke criteria were developed primarily to facilitate epidemiologic and clinical research efforts so that data could be compared between different centers and countries. In present clinical practice these criteria serve as a guide for diagnosing IE but can never replace final clinical judgment.


Incidence


The incidence of IE in infancy and childhood is unknown as no data exist from a population‐based cohort. CHD now constitutes the predominant underlying condition for IE in children over the age of 2 years in developed countries [5]. Some of the cases in this age group are due to the complexity of neonatal and pediatric intensive care and may be related to indwelling catheters and instrumentation in this population (Video 41.1).


In pediatric hospitals, IE accounts for about 1 in 1280 pediatric admissions per year [6]. In patients with CHD, ventricular septal defect, patent ductus arteriosus, aortic valve abnormalities (e.g., bicuspid aortic valve), and tetralogy of Fallot are the most common underlying conditions in which IE occurs. IE may afflict such patients before surgical intervention, but an increasing proportion of patients has had previous corrective or palliative surgery [710].


Corrective surgery without residual defects essentially eliminates the increased risk of IE within 6 months of surgery for ventricular and atrial septal defects and/or patent ductus arteriosus. The highest annual risk for IE has been found in children with repaired or palliated cyanotic CHD [10]. Palliative shunt procedures (Video 41.2) or complex intracardiac repairs increase the risk for postoperative IE [8]. The risk is highest among patients who have had prosthetic aortic valve replacement (Figure 41.2, Video 41.3) or operations performed because of reduced pulmonary blood flow. In those patients with prosthetic valves or conduits, the risk for IE is high even in the immediate postoperative period (first 2 weeks after surgery) whereas for all other patients with residual defects the risk increases with time after surgery [11].


Children with congenital or acquired immunodeficiencies but without identifiable risk factors for IE (such as central venous catheters) do not appear to be at increased risk for IE compared with the general population [5]. Intravenous (IV) drug use is infrequent in childhood, but the incidence is rising in adolescence and adulthood. The incidence of IE in IV drug users is unknown [12] but 1.5–3.3 cases per 1000 person‐years [13,14] is a conservative estimate. IE is more frequent in HIV‐seropositive IV drug users than in HIV‐seronegative patients [15]. It may be difficult to diagnose IE correctly in febrile IV drug users because 35% do not present with a heart murmur on admission [16]. The predilective site of infection in this group is typically the tricuspid valve even in those with structurally normal hearts (Figure 41.3, Video 41.4).


In the adult population, the incidence of IE is approximately five episodes/100,000 person‐years if IV drug users are excluded [17]. Apart from pre‐existing structural heart disease, which accounts for three‐quarters of all cases of IE, pacemaker and defibrillator implantations also account for a significant number of episodes of IE (Figure 41.4, Video 41.5) [18]. In a large multicenter study of 2760 patients with proven IE, 6.4% (177) occurred in patients with cardiac devices [19]. IE in patients who have septal defect occluder devices is rare but has been reported [20]. New interventional techniques such as percutaneous pulmonary valve implantation also involve a risk of IE [21]. A new patient group with a risk for IE is growing with the rising numbers of percutaneous implantations of valves (Melody® and Sapien) in the right ventricular outflow tract in repaired tetralogy of Fallot. An annualized risk of 1.9% for IE was found in a single‐center study [22].

Photo depicts an Osler node of the first toe as a typical dermatologic sign of bacterial infective endocarditis.

Figure 41.1 An Osler node of the first toe as a typical dermatologic sign of bacterial infective endocarditis.


A particularly vulnerable group at risk for IE is the adult population with CHD. IE accounts for 4% of hospital admissions of adults with CHD in specialized centers [23]. In those with repaired CHD, IE is most commonly seen in those with repaired tetralogy of Fallot and atrioventricular canal defects (Figure 41.5) [24]. In unoperated or palliated CHD, the most common sites of IE are ventricular septal defect, left ventricular outflow tract, and mitral valve. An isolated atrial septal defect (unrepaired or later than 6 months after operation/catheter intervention) has not been associated with an increased risk for IE in any age group.


Etiology and pathogenesis


The pathogenesis of IE is characterized by the triad of endothelial damage, platelet adhesion, and microbial adherence to the vegetation or intact valvar tissue [25]. An intact endothelium within the heart is generally a poor stimulator of blood coagulation and therefore not predestined for bacterial attachment [5]. However, in children with CHD, abnormal high‐velocity jet streams of blood (as seen in such lesions as ventricular septal defect, patent ductus arteriosus, aortic or pulmonary valve stenosis, or regurgitant atrioventricular valves) lead to damage of the endothelium due to shear stress forces and activation of the prothrombotic cascade in the circulating blood. Subsequently, a sterile platelet–fibrin deposition on the endothelial lesion provides a milieu for bacterial colonization. In addition to CHD, the administration of indwelling intravenous catheters into the right side of a structurally normal heart may traumatize the endocardium or valvar endothelium by exposing the subendothelial collagen [26]. This is one of the major mechanisms resulting in IE of the newborn.


Table 41.1 Definition of terms used in the Duke criteria for the diagnosis of infective endocarditis (IE)*


Source: Li JS, Sexton DJ, Mick N, et al. Proposed modifications to the Duke criteria for the diagnosis of infective endocarditis. Clin Infect Dis 2000;30:633–8. © 2000, Oxford University Press.





Major criteria

  1. Positive blood culture for IE


    • Typical microorganism consistent with IE from two separate blood
    • cultures: viridans streptococci, Streptococcus bovis, HACEK group, Staphylococcus aureus, or community‐acquired enterococci in the absence of a primary focus OR
    • Microorganisms consistent with IE from persistently positive blood cultures defined as follows: at least two positive cultures of blood samples drawn >12 hours apart, or all of three or a majority of four or more separate cultures of blood (with first and last samples drawn at least 1 hour apart)
    • Single positive blood culture for Coxiella burnetii or anti‐phase 1 IgG antibody titer >1 : 800

  2. Evidence of endocardial involvement


    • Echocardiogram positive for IE defined as:
      (TEE is recommended for patients with: (i) prosthetic valves; (ii) at least “possible IE” by clinical criteria; or (iii) complicated IE (paravalvular abscess); TTE as first test in other patients)


      • Oscillating intracardiac mass on valve or supporting structures in the path of regurgitant jets, or on implanted material in the absence of an alternative anatomic explanation; OR
      • Presence of an abscess, OR
      • New partial dehiscence of prosthetic valve, OR
      • New valvar regurgitation (worsening or changing or pre‐existing murmur not sufficient)
Minor criteria

  1. Predisposition, predisposing heart condition, or intravenous drug use
  2. Fever, temperature >38 C
  3. Vascular phenomena including major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial hemorrhage, conjunctival hemorrhages, and Janeway lesions
  4. Immunologic phenomena: glomerulonephritis, Osler nodes, Roth spots, and rheumatoid factor
  5. Microbiologic evidence: positive blood culture but does not meet a major criterion as noted above or serologic evidence of active infection with organism consistent with IE
  6. Echocardiographic minor criteria eliminated

* Modifications shown in bold typeface.


Excludes single positive cultures for coagulase‐negative staphylococci and organisms that do not cause endocarditis.


HACEK, Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella; TEE, transesophageal echocardiography; TTE, transthoracic echocardiography.


Once the inciting lesion has been formed, bacteremia must be present to colonize the vegetation. Even in the presence of an endothelial lesion and a sterile thrombus formation, not every bacteremia event leads to IE. Bacteria must be able to survive in the bloodstream in sufficient numbers and adhere to the platelet–fibrin–fibronectin complex on the lesion. Organisms such as Staphylococcus aureus, Streptococcus viridans, Streptococcus pneumoniae, HACEK organisms, and group A, C, and G streptococci as well as Candida albicans are known to have specific surface receptors for fibronectin that promote the adhesion of bacteria to the thrombus formation [27]. After adhesion, the microorganisms are trapped within the vegetation and thus protected from phagocytic cells and other host defense mechanisms [5]. Within the growing vegetation, proliferation is possible up to a maximum bacterial density of 107 to 1010 colony‐forming units per gram of tissue [28,29].


Table 41.2 Definition of infective endocarditis (IE) according to modified Duke criteria*


Source: Li JS, Sexton DJ, Mick N, et al. Proposed modifications to the Duke criteria for the diagnosis of infective endocarditis. Clin Infect Dis 2000;30:633–8. © 2000, Oxford University Press.





Definitive IE

  1. Pathological criteria


    • Microorganisms demonstrated by culture or histologic examination of a vegetation, a vegetation that has embolized, or an intracardiac abscess specimen, OR
    • Pathologic lesions: vegetation or intracardiac abscess present, confirmed by histology showing active endocarditis

  2. Clinical criteria


    • Two major criteria, OR
    • One major criterion and three minor criteria, OR
    • Five minor criteria

Possible IE

  1. One major criterion and one minor criterion
  2. Three minor criteria
Rejected

  1. Firm alternative diagnosis explaining evidence of IE, OR
  2. Resolution of IE syndrome with antibiotic therapy for <4 days, OR
  3. No pathologic evidence of IE at surgery or autopsy, with antibiotic therapy for <4 days, OR
  4. Does not meet criteria for possible IE as above

* Modifications shown in bold typeface.

Photo depicts transesophageal echocardiographic view of the left ventricular outflow tract (LVOT) after mechanical valve replacement, showing a subvalvular echogenic mass from the anterior portion of the valve ring indicating infective endocarditis.

Figure 41.2 Transesophageal echocardiographic view of the left ventricular outflow tract (LVOT) after mechanical valve replacement, showing a subvalvular echogenic mass from the anterior portion of the valve ring indicating infective endocarditis.

Photo depicts apical four-chamber view showing a homogenous echogenic mass (arrow) adherent to the septal leaflet of the tricuspid valve.

Figure 41.3 Apical four‐chamber view showing a homogenous echogenic mass (arrow) adherent to the septal leaflet of the tricuspid valve. LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle.

Photo depicts transesophageal echocardiogram in the sagittal plane (90°) of an atrial pacemaker lead with fixation to the anterior wall of the right atrium.

Figure 41.4 Transesophageal echocardiogram in the sagittal plane (90°) of an atrial pacemaker lead with fixation to the anterior wall of the right atrium. Multiple mobile vegetations can be seen adherent to the lead. LA, left atrium; RA, right atrium.

Photo depicts transesophageal echocardiogram in the left ventricular outflow tract (LVOT) plane (120–140°) of a patient after repair of atrioventricular canal defect demonstrating a large echogenic mass adherent to the posterior leaflet of the left atrioventricular valve and another smaller mass fixed to the anterior leaflet.

Figure 41.5 Transesophageal echocardiogram in the left ventricular outflow tract (LVOT) plane (120–140°) of a patient after repair of atrioventricular canal defect demonstrating a large echogenic mass adherent to the “posterior” leaflet of the left atrioventricular valve and another smaller mass fixed to the “anterior” leaflet. LA, left atrium; LV, left ventricle.


Morphology and classification


The morphology of IE vegetations is dependent on the location of the endothelial lesion and typically follows the “pathologic” bloodstream. When IE occurs in association with a ventricular septal defect, the vegetation is typically visualized on the right ventricular aspect of the septum and/or the site where the high‐velocity jet strikes the right ventricular free wall (Figure 41.6). In the case of patent ductus arteriosus, the vegetation may float through the pulmonary opening of the ductus into the main pulmonary artery (Figure 41.7, Video 41.6). With regurgitant atrioventricular valves, the lesion is usually located on the atrial side (Figures 41.8 and 41.9, Videos 41.7 and 41.8). Vegetations on valves may cause perforation (Figure 41.10, Video 41.9), or chordal rupture, but can also extend to the outside of the valve into surrounding structures (Figure 41.11). When semilunar valves are affected, the primary vegetation is typically on the ventricular surface of the valve (Figure 41.12) but may also extend more proximally through the valve into the supravalvar region in systole. When the aortic valve is affected, perforation through the annulus into the myocardium or into either atrium is possible. Newly acquired atrioventricular block (Figure 41.13) together with clinical suspicion of IE may be a strong indicator for the presence of a para‐aortic ring abscess (Figure 41.14, Video 41.10) [30].


In a series of 153 patients [31], the major underlying cardiac lesion associated with IE in childhood was the unoperated ventricular septal defect (30%) followed by mitral regurgitation (15%) and bicuspid aortic valve (9%) (Figure 41.15). In patients who undergo palliative surgery, infected aortopulmonary shunts (80%) predominate. In those who have corrective surgery, the most common sites for development of IE include right ventricle‐to‐pulmonary artery valved conduits (27%) (Figure 41.16), prosthetic valves (22%), and ventricular septal defect patch (22%) (Table 41.3) [31,32]. Endocarditis on prosthetic valves usually initiates on the valvar cuff (Figure 41.2, Video 41.3) and often extends outside the annulus, causing dehiscence (Figure 41.17) and myocardial involvement [25]. Mechanical prosthetic valves appear to have higher risk for IE in the early period after surgery whereas the risk with bioprosthetic valves appears to be higher later on [33,34]. Bovine jugular vein grafts appear to be at higher risk for IE [35], whereas implantable rings appear to have the lowest risk [36].

Photo depicts transesophageal echocardiogram in the sagittal plane (90°) of a patient with a small restrictive ventricular septal defect (VSD) under the aortic valve.

Figure 41.6 Transesophageal echocardiogram in the sagittal plane (90°) of a patient with a small restrictive ventricular septal defect (VSD) under the aortic valve. A large vegetation is seen at the site of the jet lesion on the anterior right ventricular wall just below the pulmonary artery (PA). Ao, aorta.

Photo depicts parasternal short-axis view demonstrates a thin vegetation originating from a small persistent ductus arteriosus.

Figure 41.7 Parasternal short‐axis view demonstrates a thin vegetation originating from a small persistent ductus arteriosus. The mass is directed toward the main pulmonary artery (MPA) similar to the direction of blood flow. LPA, left pulmonary artery; RPA, right pulmonary artery.

Photo depicts transesophageal echocardiogram in the left ventricular outflow plane (120–140°) demonstrates multiple echogenic masses attached to the atrial side of the mitral valve leaflets.

Figure 41.8 Transesophageal echocardiogram in the left ventricular outflow plane (120–140°) demonstrates multiple echogenic masses attached to the atrial side of the mitral valve leaflets. Ao, aorta; LA, left atrium; LV, left ventricle; MV, mitral valve.

Photo depicts transesophageal horizontal view (0°) oriented to the left ventricle (LV). There are two echogenic masses (arrows) on the atrial side of the anterior and posterior mitral leaflets.

Figure 41.9 Transesophageal horizontal view (0°) oriented to the left ventricle (LV). There are two echogenic masses (arrows) on the atrial side of the anterior and posterior mitral leaflets. LA, left atrium; RV, right ventricle.

Photo depicts transesophageal echocardiogram of the same patient as in Figure 41.8.

Figure 41.10 Transesophageal echocardiogram of the same patient as in Figure 41.8. Color Doppler shows newly acquired mitral regurgitation through a perforation in the posterior leaflet of the mitral valve. Ao, aorta.

Photo depicts transesophageal echocardiogram in the sagittal plane (90°) demonstrates an aortic ring abscess with perforation into the left atrium (LA).

Figure 41.11 Transesophageal echocardiogram in the sagittal plane (90°) demonstrates an aortic ring abscess with perforation into the left atrium (LA). The underlying heart disease was a calcified stenotic aortic valve. Ao, aorta; LV, left ventricle.

Photo depicts this transesophageal echocardiogram in the left ventricular outflow tract plane (120–140°) demonstrates native aortic valve endocarditis with a large globular vegetation on the ventricular side of the semilunar valve.

Figure 41.12 This transesophageal echocardiogram in the left ventricular outflow tract plane (120–140°) demonstrates native aortic valve endocarditis with a large globular vegetation on the ventricular side of the semilunar valve. Ao, aorta; LA, left atrium; LV, left ventricle.

Schematic illustration of an electrocardiogram demonstrating newly acquired atrioventricular block in a patient with aortic valve replacement who developed a paravalvular abscess.

Figure 41.13 Electrocardiogram demonstrating newly acquired atrioventricular block in a patient with aortic valve replacement who developed a paravalvular abscess. A transesophageal echocardiogram of this patient is shown in Figure 41.14 and Video 41.10.

Photo depicts transesophageal echocardiogram at 42° demonstrating a large paravalvular ring abscess years after aortic valve replacement with a mechanical St. Jude Medical valve.

Figure 41.14 Transesophageal echocardiogram at 42° demonstrating a large paravalvular ring abscess years after aortic valve replacement with a mechanical St. Jude Medical valve.

Photo depicts transesophageal echocardiogram at 114° demonstrates a bicuspid aortic valve with a mobile vegetative mass on the posterior cusp and an immobile lesion on the anterior cusp such that the leaflets have a significant coaptation gap when closed.

Figure 41.15 Transesophageal echocardiogram at 114° demonstrates a bicuspid aortic valve with a mobile vegetative mass on the posterior cusp and an immobile lesion on the anterior cusp such that the leaflets have a significant coaptation gap when closed. Ao, aorta; LV, left ventricle.

Photo depicts transesophageal echocardiogram at 60° in a patient after the Ross operation with right ventricle (RV) to pulmonary artery (PA) conduit using a valved pulmonary homograft.

Figure 41.16 Transesophageal echocardiogram at 60° in a patient after the Ross operation with right ventricle (RV) to pulmonary artery (PA) conduit using a valved pulmonary homograft. There is a large vegetation attached to the homograft valve. Ao, aorta.


Table 41.3 Patients with congenital heart disease (CHD) at risk for infective endocarditis





Patients without surgery
Ventricular septal defect, patent ductus arteriosus, atrioventricular canal defect, tetralogy of Fallot, mitral valve prolapse, bicuspid aortic valve, aortic valve stenosis, mitral valve regurgitation, pulmonary valve stenosis, complex CHD
Patients with previous palliation
Aortopulmonary shunt, pulmonary banding, aortic/pulmonary conduit
Patients with corrective surgery – increasing risk with residual lesion
Ventricular septal defect patch (simple and complex), tetralogy of Fallot repair, prosthetic valve implantation, atrioventricular canal repair, aortic/mitral valve surgery, coarctectomy, complex CHD, pacemaker implantation
Photo depicts transesophageal echocardiogram in the left ventricular outflow tract plane just prior to surgery for infective endocarditis of a mechanical valve prosthesis with aortic ring abscess and incomplete dissection of the valve. Intraoperatively, the valve was noted to be held in place by only two stitches.

Figure 41.17 Transesophageal echocardiogram in the left ventricular outflow tract plane just prior to surgery for infective endocarditis of a mechanical valve prosthesis with aortic ring abscess and incomplete dissection of the valve. Intraoperatively, the valve was noted to be held in place by only two stitches. Ao, aorta.


Pathophysiology


The pathophysiologic consequences of IE are primarily defined by the underlying CHD and the complications that arise from the insult, such as valvar obstruction, regurgitation and/or perforation, ventricular dysfunction, embolic phenomena, and conduction disturbances. Age at presentation and location of IE (right‐sided versus left‐sided) also play a pivotal role. In newborns, symptoms are generally related to septicemia rather than cardiac failure [37,38]. In children with systemic–pulmonary artery shunts, increasing cyanosis may be the primary symptom together with pulmonary findings related to septic pulmonary embolization [39].

Photo depicts transesophageal echocardiogram in the left ventricular outflow tract plane showing a large dehiscence between the native mitral and aortic valves in 2D (a) and color (b) Doppler.

Figure 41.18 Transesophageal echocardiogram in the left ventricular outflow tract plane showing a large dehiscence between the native mitral and aortic valves in 2D (a) and color (b) Doppler.


In adult patients with left‐sided IE, congestive heart failure is one of the complications with the greatest impact on prognosis [4042]. Moderate to severe heart failure is identified as one of the independent risk factors for 6‐month mortality along with abnormal mental status, bacterial etiology other than viridans streptococci, and medical therapy without valve surgery [40]. The severity of symptoms is often not influenced by appropriate antibiotic therapy. Compensation of heart failure is dependent on the valve affected, with acute aortic regurgitation being tolerated the least and acute tricuspid regurgitation being tolerated the best. Congestive heart failure will develop acutely when there is perforation of a native or bioprosthetic valve leaflet, acute valve dehiscence (Figure 41.18, Video 41.11), rupture of an infected mitral chord, obstruction to outflow from a bulky vegetation, or sudden intracardiac shunt from a fistulous tract [12].


Imaging

Oct 30, 2022 | Posted by in EQUINE MEDICINE | Comments Off on 41: Infective Endocarditis

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