Infective Endocarditis

Endocarditis is a common cardiology consult that hides behind nonspecific symptoms. The two habits that make you good at it: think of it in the right patient (fever + a reason), and get blood cultures BEFORE antibiotics so the diagnosis isn’t lost.

• •Fever PLUS a new or changing murmur — the classic pairing.
• •Risk factors: prosthetic valve, prior endocarditis, injection drug use, structural/congenital heart disease, indwelling lines/devices, recent invasive procedure.
• •Constitutional symptoms (fevers, sweats, weight loss, fatigue) and embolic/immune signs: Janeway lesions, Osler nodes, Roth spots, splinter hemorrhages, splenic or cerebral emboli.

• •Obtain multiple sets of blood cultures from separate sites BEFORE starting antibiotics (unless the patient is septic/unstable — then don’t delay needed therapy).
• •Persistently positive cultures (≥2 separate draws growing a typical organism) carry diagnostic weight.
• •Echocardiography: TTE first; TEE when TTE is non-diagnostic, the suspicion is high, or there’s a prosthetic valve/device.

• •Definite IE = 2 major, OR 1 major + 3 minor, OR 5 minor (or pathologic confirmation of a vegetation/abscess).
• •MAJOR: (1) typical organisms from 2 separate blood cultures (or persistently positive cultures); (2) endocardial involvement — a vegetation, abscess, or new valvular regurgitation on echo/imaging.
• •MINOR: a predisposing heart condition or injection drug use; fever ≥38 °C; vascular phenomena (arterial emboli, Janeway lesions, mycotic aneurysm); immunologic phenomena (Osler nodes, Roth spots, glomerulonephritis); microbiologic evidence not meeting a major.
• •The 2023 Duke-ISCVID update adds imaging (e.g., cardiac CT, and PET-CT for prosthetic valves) and expands the microbiology — but the 2-major / 1-major-plus-3-minor / 5-minor scoring is the core to remember.

Antibiotic choice is ID/protocol-directed and tailored to cultures; the principles below are the framework, not a prescription.

• •Common organisms: Staphylococcus aureus (acute, injection drug use, prosthetic valves), viridans streptococci (subacute native valve), enterococci, coagulase-negative staph (prosthetic), and the HACEK group.
• •Native-valve, acutely ill: empiric cover for staph (including MRSA) and strep — commonly vancomycin plus an anti-staph β-lactam/ceftriaxone per local protocol — then narrow to cultures.
• •Prosthetic-valve staph IE: typically vancomycin + gentamicin + RIFAMPIN (rifampin penetrates the prosthetic biofilm) — ID-directed.
• •Therapy is prolonged IV (often 4–6 weeks), dosed to the organism and susceptibilities. Don’t start before cultures unless the patient is unstable.
• •Manage anticoagulation cautiously and per specialist input (intracranial hemorrhage risk with septic emboli).

• •Heart failure from valve destruction — the leading and most urgent indication for surgery.
• •Uncontrolled infection: perivalvular abscess, fistula, a NEW conduction block (lengthening PR / new AV block suggests a root abscess), or persistent bacteremia despite appropriate antibiotics.
• •Prevention of embolism: a large vegetation (>10 mm) with an embolic event — or very large/mobile vegetations — may prompt earlier surgery.
• •Prosthetic-valve IE and certain resistant or fungal organisms often require surgery — a Heart Team decision (cardiology + ID + cardiac surgery).

• •Injection drug use classically causes TRICUSPID-valve IE (often S. aureus).
• •It seeds septic PULMONARY emboli — fever, cough, pleuritic pain, and nodular/cavitary lung infiltrates — rather than systemic (left-sided) emboli.
• •Right-sided IE is more often managed medically, but recurrent/persistent disease, large vegetations, or right heart failure still drive surgery.

• •Antibiotic prophylaxis before high-risk DENTAL procedures (manipulating the gingiva/periapical region or perforating the oral mucosa) is reserved for the HIGHEST-risk patients only.
• •That high-risk group: prosthetic valves/prosthetic material used for repair, prior IE, specific unrepaired/recently-repaired congenital heart disease, and cardiac-transplant recipients with valvulopathy.
• •Standard regimen: amoxicillin 2 g PO ~30–60 min before the procedure (alternatives if penicillin-allergic).
• •Most patients do NOT need prophylaxis anymore — routine prophylaxis for everyone is outdated.

• •Starting antibiotics before drawing blood cultures (loses the diagnosis).
• •Stopping at a normal TTE when suspicion is high or there’s a prosthetic valve (get a TEE).
• •Missing it in the febrile injection-drug-use or prosthetic-valve patient — and forgetting right-sided IE presents with pulmonary, not systemic, emboli.
• •Giving endocarditis prophylaxis to everyone instead of just the highest-risk group.
• •Overlooking a new AV block as a sign of a root abscess.