Chief's Corner: Infective Endocarditis

Background:

Image courtesy of Wikimedia Commons [3]

Infective endocarditis is a common diagnosis we see at University Hospital. Across the US, it has increased in incidence to about 15 in 100,000 patients. The diagnosis, treatment, and surgical management are important to know in internal medicine. The IDSA has some detailed recommendations that I encourage you to peruse here. JAMA recently (July 2018) published a review article on infective endocarditis, I’d like to take some time to review some of the interesting aspects from the review.

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Some Interesting Things to Know:

Who’s getting it?

It’s interesting, all throughout residency it felt like my exposure to infective endocarditis was predominantly associated with IVDU. I was surprised to read that a recent large multicenter study showed that health care-associated infective endocarditis accounted for 34% of cases of infective endocarditis. These included those associated with hemodialysis, intravascular catheters, and invasive procedures – noting that cases related to prosthetic valves and implantable cardiac devices is also on the rise. That being said, infective endocarditis related to IVDU is certainly on the rise with one hospital reporting it being the cause of 56% of its infective endocarditis hospitalizations.

Some interesting factoids related to its diagnosis:

We learn of all these clinical findings in medical school and frequently go looking for Janeway lesions, Osler nodes, and splinter hemorrhages when we are concerned for endocarditis. But just how often are these signs present? In JAMA’s review article, they looked at the percentage of patients with infective endocarditis who presented with these clinical findings. Interestingly splinter hemorrhages, Osler nodes, and/or Janeway lesions all occurred in < 10% of patients. The most common signs were fever (86-96%), new murmur (48%), worsening old murmur (20%), and hematuria (26%).

The most commonly learned imaging for endocarditis is echocardiogram, including TTE and TEE, as it should be since these are the first-line and gold standards for diagnosis. However, there is also a role for more nuanced imaging including radiolabeled leukocyte scintigraphy (tagged-WBC scan), FDG-PET/CT and cardiac CT angiography. These imaging modalities are recommended when there is suspected prosthetic device infection with a nondiagnostic TEE. It should also be considered if there is concern for complications of infective endocarditis including abscess, assuming echocardiographic imaging is nondiagnostic.

Video: Bedside ultrasound images showing tricuspid valve endocarditis [4]

The bugs:

We can’t talk about infective endocarditis and not talk about what bugs are involved. Staph aureus is the most common cause of native and prosthetic valve infection in high-income countries including the US. The next most common bacteria depend on the valve. For native valves, viridans strep and enterococci the 2nd and 3rd most common bacteria respectively. However, for prosthetic valves and cardiac devices, coagulase-negative staphylococci is more common. Specifically with transcatheter aortic valve replacements (TAVR), the most common organism to cause endocarditis is Enterococcus. It has been suggested that this may be due to the transfemoral access used in the procedure, since enterococcus is a frequent groin contaminant. The “blood culture-negative infective endocarditis” cases can be due to coxiella burnetii, Bartonella species, and Chlamydophilia species. Pathogen diagnosis in these cases relies on serology, PCR, and/or histopathology of resected cardiac valve tissue.

Treatment and Prognosis:

The treatment of infective endocarditis is multifaceted and depends on the nature of the valve infected, the bacteria isolated, and the absence or presence of complications. Again, please refer to the IDSA guidelines for specifics. In general, management includes antibiotics, infectious disease consult, and the consideration of cardiac surgery. However, the prognosis of infectious endocarditis should be noted which was touched on in this review article. The in-hospital mortality for infective endocarditis is 20% and the 6-month morality is 30%. Expectedly, poor prognostic factors include advanced age, hemodialysis, and the presence of complications including severe heart failure, stroke, or abscess. I found these prognosis statistics to be a little jarring and perhaps a useful tidbit of knowledge to have for patient counseling in the future.

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Learning Points:

• While infective endocarditis related to IVDU is becoming more common, health care-associated IE still make up roughly 1/3 of cases
• The most common clinical signs of IE include fever and a new murmur while classically taught signs of Janeway lesions, Osler nodes, and splinter hemorrhages happen in <10% of patients
• There is a role for imaging beyond TTE and TEE including PET scans, WBC scans, and cardiac CT angiography in specific indications
• TAVR-associated endocarditis is most commonly due to Enterococcus

References:

1. Wang, A. et al. “Management Considerations in Infective Endocarditis: A Review.” JAMA, vol. 320, no. 1, 3 July 2018, pp. 72-83
2. Hartman, L. et al. “Opiate Injection-Associated Infective Endocarditis in the Southern United States.” AM J Med Sci, vole. 352, no. 6, 23 Aug 2016, pp. 603-8
3. <https://commons.wikimedia.org/wiki/File:Endocarditis.png>
4. Seif D, Meeks A, Mailhot T, Perera P (2013). "Emergency department diagnosis of infective endocarditis using bedside emergency ultrasound". Critical Ultrasound Journal. DOI:10.1186/2036-7902-5-1. PMID 23399454. PMC: 3740785.

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Authored by: GREGORY WIGGER, MD