Infective Endocarditis and Valvular Heart Disease

Foundations

Clinical Features and Differential Diagnosis

Symptoms of IE are nonspecific and diverse ( Box 69.3 ). Patients often appear relatively well. However, depending on host factors, location of the vegetation, and microbial virulence, some present acutely ill with sepsis and multi-organ failure. The most common symptom is fever (90%). The list of additional possible symptoms includes chills, malaise, weight loss, cough, dyspnea, chest pain, headache, myalgias, arthritis, back or neck pain, altered mental status, or a focal neurologic complaint. A measured fever is present in the ED in about 80% of patients with IE. Since a new murmur, or worsening of a preexisting murmur, is present in only 68% of patients, often no murmur will be heard in the ED. In approximately 30% of cases, the primary presenting syndrome represents a complication of IE, including acute heart failure, stroke, septic pulmonary emboli, and vertebral osteomyelitis.

With such a broad range of possible presentations, IE can easily be mistaken for another infection, such as a viral syndrome, meningitis, or pneumonia, particularly common with right-sided IE and septic pulmonary emboli. It can also present similarly to a non-infectious problem, such as acute coronary syndrome, primary heart failure, or stroke. In these cases, fever may be the key sign prompting consideration of IE.

The most important clue to the diagnosis of IE is the presence of a predisposing condition (see Box 69.1 ). If IE is suspected, a core temperature should be correctly measured to assess for fever, multiple times if necessary, and a particularly careful cardiac auscultatory exam performed. Peripheral embolic and vasculitic stigmata should be sought (see Box 69.2 ), although each is found in only about 5% of cases, with splinter hemorrhages being the most commonly seen ( Fig. 69.1 ).

Diagnostic Testing

Findings on standard laboratory tests in IE are nonspecific. Clinicians must consider IE when faced with a constellation of suggestive findings rather than looking for a single definitive test. Normocytic anemia and hematuria and proteinuria, suggesting glomerulonephritis, are classic findings in indolent infections. An elevated erythrocyte sedimentation rate and C-reactive protein are expected in roughly 60% of cases. A chest x-ray may show signs of heart failure or septic pulmonary emboli, and an electrocardiogram (ECG) may display conduction abnormalities related to a myocardial abscess.

When IE is suspected, it is the responsibility of the emergency clinician to ensure that blood cultures are obtained prior to administering antibiotics. Blood culture results are key to both definitive diagnosis and tailored antimicrobial therapy. At least two sets, each containing 10 cc of blood, should be drawn from separate sites and, if possible, separated in time by at least one hour. Three sets of blood cultures are required in suspected PVE or cardiac device-related infection because one of the most common pathogens in prosthetic device infections, coagulase-negative S. aureus , is also the most common blood culture contaminant.

Echocardiography is the other key diagnostic test in IE. Transthoracic echocardiography (TTE) should be performed as soon as possible whenever IE is suspected. While the diagnostic sensitivity of TTE for one of the definitive endocardial findings of IE (see Box 69.2 ) is no more than 70%, its specificity is very high. Hence, this noninvasive test stands to make the correct diagnosis very rapidly while the patient is still in the ED. More importantly, echocardiography can identify endocardial complications that may require urgent surgery, including acute valvular insufficiency or perforation with heart failure, perivalvular extension, prosthetic valve dehiscence, and vegetation size greater than 10 mm, which presents an elevated embolic risk ( Box 69.4 ). ^, The sensitivity of transesophageal echocardiography (TEE) is significantly higher than that of TTE, both for identifying vegetations and assessing for complications, particularly in PVE.

TEE is now recommended after TTE in all cases, though this invasive modality will usually be performed after hospital admission. The value of point of care TTE, performed immediately by experienced emergency clinicians in the setting of suspected IE, has been demonstrated in numerous case reports, although its role has yet to be evaluated in a large study ( Fig. 69.2 ).

Additional advanced imaging in patients with suspected IE should generally be driven by symptoms. Some advocate routine brain magnetic resonance imaging (MRI) in uncertain cases, even without neurological symptoms, because asymptomatic cerebral emboli are found in up to 60% of those with left-sided infection, and this finding constitutes a Duke minor criteria.

Management

In the sickest subset of IE patients, ED management begins with stabilization, including evidence-based therapy for sepsis, hemodynamic support, and positive pressure ventilation. Patients with suspected IE and acute heart failure require immediate consultation by a cardiothoracic surgeon, and emergency clinicians need to be aware of additional echocardiographic findings that are indications for surgical therapy (see Box 69.4 ). In general, there has been a shift toward earlier surgical treatment in IE, with approximately one-half of patients with left-sided infection undergoing surgery during the index admission. If possible, patients with left-sided IE should be managed by a multidisciplinary team at a center capable of cardiothoracic surgery.

In the ED, initial antimicrobial treatment of IE is almost always empiric. Occasionally, patients present because previously drawn blood cultures have returned positive; in such cases, isolate susceptibility-directed antibiotics should be selected in consultation with an infectious disease specialist. Consensus guidelines on IE treatment tend to focus on pathogen-specific therapy, with limited discussion or recommendations regarding empiric treatment. ^, Patient characteristics to consider in choosing the empiric regimen include whether there is a prosthetic valve, history of IDU, or recent health care exposure, as well as disease severity. If available, hospital-specific empiric treatment recommendations, which account for local susceptibility patterns and are updated regularly, supersede published guidelines, which are updated infrequently.

In most cases, empiric therapy in the ED should include vancomycin (20 to 35 mg/kg actual body weight loading dose, then 15 to 20 mg/kg every 8 to 12 hours not to exceed 3000 mg). Vancomycin alone for one or two doses is a reasonable approach for native valve and prosthetic valve infection and in IDUs. Addition of ceftriaxone (2 g/day) can be considered to cover HACEK and other gram-negative organisms, responsible for less than 6% of infections. ^, As soon as blood culture results return, pathogen and susceptibility-directed therapy is selected by an infectious disease specialist. Because of the complex pathology of bacterial growth within vegetations, 4 to 6 weeks of parenteral antibiotic therapy is generally required to eliminate infection. For selected stable patients who respond well to initial therapy in the hospital, IV treatment can be completed as an outpatient. Protocols that include partial oral therapy have recently proven effective and safe.

Disposition

All patients with suspected IE, in whom blood culture results are pending, should be hospitalized. Increasingly, for selected stable patients who respond well to initial treatment in the hospital, IV antibiotic therapy can be completed at home.

Prophylaxis

The American Heart Association and European Society of Cardiology recommend antibiotic prophylaxis to prevent IE for individuals with very high-risk predisposing conditions before undergoing procedures that produce heavy bacteremia with potential IE pathogens. These primarily consist of dental procedures. High-risk predisposing conditions include a prior history of IE, certain forms of congenital heart disease (see previous) and the presence of a prosthetic valve. This issue is of limited relevance to emergency practice, since most commonly performed ED procedures do not produce the kind of bacteremia that requires prophylaxis—including local anesthesia injection into uninfected tissue, laceration repair, endotracheal intubation, and foley catheter placement in the absence of infection. Prophylaxis should be administered prior to cutaneous abscess drainage, however. A reasonable approach is to administer IV vancomycin (15 mg/kg) one hour before incision and drainage.

Foundations

Clinical Features and Differential Diagnosis

ARF occurs 1 to 5 weeks after the initial bout of pharyngitis. Up to one-third of patients with documented ARF do not remember having had pharyngitis in the preceding month. Fever is generally present during the acute phase of rheumatic fever, rarely lasting more than 2 weeks. Additional manifestations include arthritis, carditis, chorea, subcutaneous nodules, and erythema marginatum (see Box 69.4 ).

A syndrome of mono- or poly-articular arthralgias and arthritis is the most common finding in ARF. Arthritis tends to occur early in the course of ARF and often coincides with a rising titer of streptococcal antibodies. It classically affects large joints, such as the knee, ankle, elbow, and wrist. The pain may be more severe than physical findings suggest (severe arthralgias). Synovial fluid analysis generally reveals a sterile inflammatory fluid.

Cardiac manifestations of ARF may be subtle and can include symptoms and signs of pericarditis, myocarditis, and endocarditis. The mitral valve is the most commonly affected, causing acute mitral regurgitation (MR). Inflammation of the valvular endocardium may result in permanent deformity and impairment of one or more valves over the course of decades. Stenotic lesions of the mitral and/or aortic valve are common late manifestations of RHD ( Fig. 69.3 ).

Chorea is a random, rapid, purposeless movement, usually of the upper extremities and face. Chorea is a relatively rare manifestation of ARF that tends to emerge after a long latency period. Subcutaneous nodules and erythema marginatum are found in fewer than 10% of cases of ARF. Their presence, however, should suggest the diagnosis. Subcutaneous nodules are pea-sized and nontender. They typically appear over the extensor surfaces of the wrists, elbows, knees and, occasionally, the spine. Erythema marginatum is a nonpruritic, painless, evanescent ring of erythema that commonly appears on the trunk and proximal extremities (see Fig. 69.3 ).