Abstract
Echocardiography is integral to the diagnosis and management of infective endocarditis (IE) because it can identify vegetations and complications associated with spreading infection, assess the severity of concomitant valve dysfunction, and document the impact of the disease on ventricular function and cardiovascular hemodynamics including pulmonary artery pressure. This chapter focuses on the role of echocardiography in IE with an emphasis on native and prosthetic valves. It discusses the imaging features of vegetations and complications of endocarditis including embolus, abscess, perforation, and other forms of valvular disruption and, in the case of prosthetic valves, variable degrees of dehiscence. It also covers the prognostic role of echocardiography, particularly in the prediction of embolic risk, and emphasizes the important role that echocardiography plays during follow-up treatment, and for intraprocedural guidance during surgical intervention.
Keywords
Endocarditis, echocardiography
Introduction
Infective endocarditis (IE) is a serious infection of the heart that, despite advances in diagnosis and treatment, is associated with in-hospital and 1-year mortalities of approximately 20% and 40%, respectively. IE is also associated with major morbidity with embolic events (stroke in 17% of patients, non-neurologic embolus in 23%), heart failure (32%), abscess (14%), and the need for surgery (48%) being relatively common events. With an overall incidence of 3–10 per 100,000 patient years, in the United States alone there are over 50,000 cases per year, the majority of which affect the left side of the heart. Risk factors for endocarditis include the presence of a valve prosthesis or other implanted device, intravenous drug abuse, diabetes, and immunosuppression.
Echocardiography is integral to the diagnosis and management of this condition because it can identify vegetations and complications associated with spreading infection, assess the severity of concomitant valve dysfunction, and document the impact of the disease on ventricular function and cardiovascular hemodynamics including pulmonary artery pressure. This chapter focuses on the role of echocardiography in IE with an emphasis on native and prosthetic valves. It discusses the imaging features of vegetations and complications of endocarditis including embolus, abscess, perforation, and other forms of valvular disruption, and in the case of prosthetic valves, variable degrees of dehiscence. It also covers the prognostic role of echocardiography, particularly in the prediction of embolic risk, and emphasize the important role that echocardiography plays during follow-up of treatment, and for intraprocedural guidance during surgical intervention. Where specific recommendations for the use of echocardiography are provided, they are consistent with the current American College of Cardiology/American Heart Association (ACC/AHA) Guidelines for the Management of Patients with Valvular Heart Disease, (with the 2017 update including no changes related to echocardiography) European Society of Cardiology (ESC) Guidelines for the Management of Infective Endocarditis, ESC Recommendations for the Practice of Echocardiography in Infective Endocarditis, the AHA Scientific Statement on Infective Endocarditis, and ACCF/ASE/AHA/ASNC/HFSA/HRS/SCAI/SCCM/SCCT/SCMR 2011 Appropriate Use Criteria for Echocardiography.
Although a full discussion of the etiology, pathophysiology, natural history, and optimal approaches to management such as surgical decision making is beyond the scope of this chapter, the reader is referred to the ACC/AHA and ESC Guidelines and AHA Scientific Statement for this information. It is worth noting that echocardiography has served as a research tool in many of the studies that form the basis for these documents. Additionally, the echocardiographic assessment of the hemodynamic severity of valve lesions caused by IE and associated changes in cardiac function are critical to clinical decision making in IE, and the reader is referred to Chapter 8 , Chapter 9 , Chapter 10 , Chapter 28 , Chapter 29 , Chapter 30 , Chapter 31 for a more detailed discussion of the tools that are used to make these assessments.
Diagnosis
Indications for Transthoracic Echocardiography and Transesophageal Echocardiography
Echocardiography is essential for the diagnosis of IE ( Table 40.1 ). Endocarditis may be suspected in a wide variety of situations, most commonly with otherwise unexplained fever lasting at least 48 hours, bacteremia, a new regurgitant heart murmur, new conduction disturbance, and/or embolic events. Although 90% of cases of IE are associated with bacteremia, 10% have culture-negative endocarditis, which may reflect the presence of difficult-to-culture organisms such as the HACEK ( Haemophilus , Aggregatibacter , Cardiobacterium hominis, Eikenella corrodens , and Kingella ) species or the institution of antibiotic therapy before blood cultures are drawn. Although the clinical presentation is most typically subacute, valvular disruption and associated sudden severe valvular regurgitation may be associated with acute heart failure or shock.
| 2014 ACC/AHA Guidelines | 2015 ESC Guidelines | 2011 ASE Appropriate Use Criteria | ||||||
|---|---|---|---|---|---|---|---|---|
| Should Be Performed (Class I) | Reasonable to Perform (Class IIa) | May Be Considered (Class IIb) | Recommended/Indicated (Class I) | Should Be Considered (Class IIa) | May Be Considered (Class IIb) | Appropriate | Rarely Appropriate | |
| TTE |
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| TEE |
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| TTE and/or TEE |
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| Intraoperative TEE |
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| Intracardiac echo |
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The diagnosis of endocarditis is typically based on the Modified Duke criteria ( Tables 40.2 and 40.3 ). In these criteria, echocardiographic evidence of endocarditis, as defined by the presence of vegetation, abscess, or new dehiscence of a prosthetic valve, is one of the major criteria; new valvular regurgitation, which can also be identified by echocardiography, is a second major criterion.
| Definite IE | Possible IE | Rejected IE |
|---|---|---|
| Presence of ANY of the following: Pathologic criteria
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a Modification from the original Duke criteria.
b See Table 40.3 for definitions of major and minor criteria.
| Major Criteria | Minor Criteria |
|---|---|
Blood culture positive for IE
| Predisposition, predisposing heart condition, or injection drug use |
| Evidence of endocardial involvement | Fever, temperature >38°C (100.4°F) |
Echocardiogram positive for IE, defined as follows:
| Vascular phenomena, major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial hemorrhage, conjunctival hemorrhages, and Janeway lesions |
| New valvular regurgitation (worsening or changing of pre-existing murmur not sufficient) | Immunologic phenomena: glomerulonephritis, Osler’s nodes, Roth’s spots, and rheumatoid factor |
| Microbiological evidence: positive blood cultures that do not meet major criteria; or serologic evidence of active infection with organism consistent with IE | |
| Echocardiographic minor criteria eliminated a |
New valvular regurgitation may be on the basis of cusp/leaflet perforation, chordal rupture, or altered cusp/leaflet coaptation caused by bulky vegetations. Valve stenosis is a less common complication but may occur with prosthetic valve IE in which a bulky vegetation obstructs the orifice or a strategically placed smaller vegetation impedes mechanical disk motion. Note that it may be difficult to distinguish superimposed vegetation when there is a flail segment due to chordal rupture. Although transthoracic echocardiography (TTE) is typically the initial study (Class I in ACC/AHA and ESC Guidelines; see Table 40.1 ), there should be a low threshold for transesophageal echocardiography (TEE). Indeed, as listed in Table 40.1 , there are number of scenarios for which TEE has Class I, IIA, and IIB indications for diagnosis. The IIB indication (TEE may be considered) for nosocomial Staphylococcus aureus bacteremia with a portal of entry from a known extracardiac source exists because IE has been reported to occur in approximately 30% of patients with S. aureus bacteremia particularly in patients with osteomyelitis, prolonged bacteremia, or hemodialysis catheters. The European recommendations (see Table 40.1 ) offer expanded recommendations for TEE including its use in patients with a high clinical suspicion of infectious endocarditis but a normal TTE and suggest that TEE should be considered in the majority of adult patients with suspected IE even when the TTE is positive. TEE should not be performed in patients with a negative TTE of excellent quality when there is a low clinical suspicion of IE.
TTE has a reported sensitivity of 62%–82% and a specificity of 91%–100% for native valve endocarditis and is most likely to detect vegetations larger than 3 mm in size. For prosthetic valve endocarditis, the sensitivity is only 36%–69%. TEE with spatial resolution of 1–2 mm has a reported sensitivity of 87%–100% and specificity of 91%–100% for native valve endocarditis. Notably, although the sensitivity of TEE for prosthetic valve endocarditis is significantly higher than that of TTE, it is still somewhat lower than that for native valve endocarditis, but can increase with follow-up studies when the initial study is negative but the clinical suspicion of IE is high. TEE has a specificity of over 90% for prosthetic valve endocarditis.
As discussed later, there are a number of reasons for which echocardiography, even TEE, may be negative in cases of IE. Therefore, if the clinical suspicion of endocarditis remains high, it is reasonable to repeat echocardiography, typically after 7–10 days. A similar approach is reasonable in cases of suspected abscess, but a shorter interval between initial and subsequent echoes is probably warranted because there can be dramatic changes in the appearance of an abscess over the course of even several hours. Additional indications for repeat echocardiographic evaluation include a clinical change in a patient with established endocarditis and surveillance without clinical change in patients at high risk for complications based on the extent of infection or organism ( Staphylococcus , Enterococcus or fungus [AHA/ACC Class I]). Conversely, there is no indication for TEE or follow-up TTE when the initial transthoracic echo is of high quality and there is a low clinical suspicion of endocarditis.
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