Infectious endocarditis: Clinical sciences

Infective endocarditis, or IE for short, refers to the inflammation of the endocardium due to a pathogenic infection. As microorganisms spread through the blood, they can attach to the intracardiac surface, forming vegetations on the endocardium, most commonly on the heart valves. Vegetations can also form on the septa, mural endocardium, and even implantable electronic devices. To diagnose infective endocarditis, you need to identify the Modified Duke Criteria using blood cultures, echocardiogram, and history and physical exam findings.

Now, here’s a high-yield fact to remember! There are several common pathogens involved in infective endocarditis. For example, the viridans group streptococci are most commonly associated with native valve infective endocarditis. Staphylococci are most commonly associated with intravenous substance use or patients with health care contact; they tend to affect the right sided heart valves, like the tricuspid valve. Next up is enterococcal endocarditis, which can be seen in both community- and hospital-acquired infective endocarditis.

You should also be aware of a group of gram-negative organisms commonly found in the human oropharynx known as the HACEK organisms, which include the species Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, and Kingella. Finally, if you have a patient with recent cardiac valve surgery, prolonged use of an indwelling vascular catheter, or immunodeficiency, you should keep in mind fungal causes, like Aspergillus and Candida species. This is especially applicable if your patient is on empiric antibiotics and worsening.

Now, if you have a patient presenting with signs and symptoms of infective endocarditis, first, you should perform an ABCDE assessment to determine if your patient is unstable or stable. If the patient is unstable, stabilize their airway, breathing, and circulation. Next, obtain IV access, start IV fluids, and begin continuous vital sign monitoring including blood pressure, heart rate, and pulse oximetry. If needed, provide supplemental oxygen, and don’t forget to start broad spectrum IV antibiotics.

Okay, now let’s go back to the ABCDE assessment and take a look at stable patients. If your patient is stable, first obtain a focused history and physical exam. Next draw blood cultures and order an ECG.

History typically reveals fever, night sweats, fatigue, as well as palpitations. Additionally, there might be a predisposing heart condition, such as a prosthetic valve; or a history of intravenous substance use. On the other hand, physical exam typically reveals a heart murmur, dyspnea on exertion, pallor, and peripheral pitting edema. You may also observe specific skin findings, like Osler nodes, which are small and painful nodules on the palmar surfaces of fingers and toes, you can remember this by thinking O for “ouch!” when you prick your finger; you may also observe Janeway lesions, which are hemorrhagic but non-painful macules on the palms and soles; and splinter hemorrhages, which refer to non-blanching, linear brownish-red lesions that are found in the nail bed. Finally, a fundoscopic exam may reveal Roth spots, which are retinal hemorrhages due to septic emboli.

Okay now, let’s look at the blood culture and ECG results. Blood cultures may or may not be positive for an infectious pathogen. Finally, ECG results can be variable, showing normal sinus rhythm or an arrhythmia, like AV block.

At this point, you should suspect infective endocarditis, so your next step is to admit them and start empiric IV antibiotics. Do not delay this while waiting for culture results, because they may take a while, and we want to prevent further damage to the cardiac valves. In general, initial empiric therapy should involve vancomycin to cover staphylococci like methicillin-sensitive and methicillin-resistant Staphylococcus aureus, or MSSA and MRSA respectively; Streptococci; and Enterococci. If history is concerning for HACEK organisms, be sure you include anaerobic coverage by adding ceftriaxone or ampicillin-sulbactam to that vancomycin.

Next, you’ll want to obtain an echocardiogram. There are two types, a transesophageal echocardiogram or TEE, and a transthoracic echocardiogram or TTE. In most patients, you’d obtain a TTE first, but there are specific cases where you should obtain a TEE first. These include if your patient has a prosthetic valve that could be infected, if there is concern for complicated infective endocarditis like paravalvular abscess, or if your clinical suspicion suggests infective endocarditis is a likely possibility. Regardless of the one you choose, these imaging methods will help you detect an intracardiac vegetation on a valve or implanted material such as an intracardiac device, or new valvular regurgitation.

Your next step is to assess for Modified Duke Criteria to determine if the clinical scenario fits infective endocarditis or not. The Modified Duke Criteria consists of major and minor criteria. Major criteria include a blood culture that is either positive for a typical organism associated with infective endocarditis or persistent bacteremia, as well as an echocardiogram positive for endocardial involvement. On the other hand, minor criteria include a predisposing heart condition, history of intravenous substance use, and fever greater than 38oC.