3.5 Infective Endocarditis, Myocarditis and Rheumatic Heart Disease

Why Inflammatory and Infectious Cardiac Disease Is Tested

Test-plan item I.A.7 covers the conditions where infection or immune activation, not atherosclerosis, is destroying the heart. These patients occupy cardiac step-down and ICU beds for weeks, and the nurse is the person who detects the complication: the new murmur, the PR interval that lengthened overnight, the sudden hemiparesis, the fever that never broke. CMC items reward recognizing the pattern early, because in endocarditis and fulminant myocarditis the window between "stable on antibiotics" and "needs the operating room today" can be a single shift.

Infective Endocarditis: Pathogenesis and Microbiology

Infection requires two things: a damaged or prosthetic endothelial surface where platelets and fibrin deposit as non-bacterial thrombotic vegetation, and bacteremia seeding that nidus. Once organisms embed in the fibrin-platelet matrix they are shielded from phagocytes and from most antibiotic penetration, which is why therapy is intravenous, bactericidal, and measured in weeks rather than days.

Two associations are worth memorizing because they change the workup: Streptococcus gallolyticus (formerly S. bovis) endocarditis mandates colonoscopy to look for colonic neoplasm, and Enterococcus faecalis points toward a genitourinary or gastrointestinal source, classically an older man after a urologic procedure.

Diagnosis: Duke Criteria, Cultures and Echocardiography

The modified Duke criteria remain the framework, updated in 2023 as the Duke-ISCVID criteria to add molecular microbiology, advanced imaging and intraoperative inspection.

Definite endocarditis requires 2 major, or 1 major plus 3 minor, or 5 minor criteria (or pathologic confirmation). Possible endocarditis requires 1 major plus 1 minor, or 3 minor criteria.

The classic peripheral stigmata appear in fewer than a quarter of modern cases, mostly in subacute streptococcal disease, but they are exam favorites: Osler nodes are painful and sit on the finger and toe pads (Osler equals ouch, immune-complex mediated); Janeway lesions are painless macules on palms and soles (septic microemboli); Roth spots are retinal hemorrhages with pale centers; splinter hemorrhages are linear nailbed streaks. Add conjunctival petechiae, palatal petechiae and splenomegaly.

Blood culture and imaging technique the nurse owns

Draw three sets from three separate venipuncture sites, at least 10 mL into each bottle, with the first and last set separated by at least one hour, and before the first antibiotic dose. If the patient is hemodynamically unstable, two sets drawn minutes apart is acceptable so therapy is not delayed. Do not draw sets from an existing catheter unless the question is catheter-related infection and paired differential time to positivity is being assessed. Timing to a fever spike is unnecessary because the bacteremia of endocarditis is continuous, and that continuity is itself part of the major criterion.

Transthoracic echocardiography is the first study but its sensitivity is only about 70% for native valves and roughly 50% or less for prosthetic valves. Transesophageal echocardiography raises sensitivity to roughly 90-96% and is indicated when the transthoracic study is negative but suspicion persists, and always for a prosthetic valve, a CIED, S. aureus bacteremia, or when a complication such as abscess is suspected. A negative TEE early does not close the case; repeat in 3-5 days if the clinical picture holds.

Complications and the nurse's surveillance list

• Heart failure from valve destruction is the most common complication and the leading indication for surgery.
• Systemic embolization occurs in 20-40%, is highest in the first two weeks, and falls sharply once effective antibiotics are running. Large mobile mitral vegetations above 10 mm carry the greatest stroke risk. Perform focused neurologic checks every shift and with any change.
• New AV block on telemetry is an emergency finding. A lengthening PR interval in a patient with aortic valve endocarditis means the infection has burrowed into the aortic root and the perivalvular tissue that houses the conduction system. This is abscess until proven otherwise and warrants urgent TEE and surgical consultation.
• Septic pulmonary emboli in right-sided disease, mycotic aneurysm, splenic and renal infarction, immune complex glomerulonephritis, and persistent bacteremia despite appropriate therapy.

Surgical indications include heart failure from valve dysfunction, uncontrolled infection (abscess, fistula, enlarging vegetation, or fever and bacteremia persisting beyond 5-7 days of appropriate therapy), fungal or highly resistant organisms, prosthetic valve endocarditis with dehiscence, and recurrent embolization with a persistent vegetation despite antibiotics.

Antibiotics, OPAT and prophylaxis

Therapy is intravenous and bactericidal for 4-6 weeks, counted from the first negative blood culture. Representative regimens: penicillin-susceptible viridans streptococci get penicillin G or ceftriaxone 2 g daily; methicillin-susceptible S. aureus gets nafcillin or cefazolin for 6 weeks; MRSA gets vancomycin dosed to an AUC-to-MIC target of 400-600 or daptomycin 8-10 mg/kg; enterococcal endocarditis is treated with ampicillin plus ceftriaxone, a double beta-lactam regimen that avoids gentamicin nephrotoxicity; prosthetic valve staphylococcal disease adds rifampin 300 mg every 8 hours for biofilm penetration plus 2 weeks of gentamicin. Outpatient parenteral antibiotic therapy is reserved for patients who are afebrile and stable for 5-7 days, have reliable vascular access and follow-up, and lack ongoing injection drug use or unstable housing without wraparound support.

Prophylaxis under current AHA guidance is limited to four highest-risk cardiac conditions: a prosthetic valve or prosthetic material used in valve repair (including transcatheter valves, annuloplasty rings and clips); previous infective endocarditis; specific congenital heart disease (unrepaired cyanotic disease, repaired disease with prosthetic material during the first 6 months, or repaired disease with a residual defect adjacent to prosthetic material); and cardiac transplant recipients with valvulopathy. Prophylaxis covers dental procedures that manipulate gingival tissue or the periapical region of teeth or perforate the oral mucosa, invasive respiratory procedures involving incision or biopsy, and procedures on infected skin or musculoskeletal tissue. It is not indicated for routine gastrointestinal or genitourinary procedures such as colonoscopy or cystoscopy in the absence of active infection. The regimen is amoxicillin 2 g orally 30-60 minutes before the procedure (ampicillin 2 g IM/IV, or cefazolin or ceftriaxone 1 g, if oral intake is not possible). For penicillin allergy use cephalexin 2 g, azithromycin or clarithromycin 500 mg, or doxycycline 100 mg; the 2021 AHA statement removed clindamycin because of Clostridioides difficile and other adverse reactions.

Myocarditis

Myocarditis is inflammatory injury of the myocardium, most often viral (parvovirus B19, human herpesvirus 6, coxsackie B and other enteroviruses, adenovirus, influenza, SARS-CoV-2) or immune-mediated (giant cell myocarditis, eosinophilic and hypersensitivity myocarditis, cardiac sarcoidosis).

Immune checkpoint inhibitor myocarditis deserves separate attention because oncology patients now populate cardiac units. It complicates roughly 1% of treatment courses with agents such as ipilimumab, nivolumab and pembrolizumab, usually within the first 6 weeks or first one to two doses, but carries a mortality of 25-50% and a striking tendency toward high-grade conduction disease and ventricular arrhythmia. Management is permanent discontinuation of the checkpoint inhibitor plus high-dose IV methylprednisolone (roughly 500-1,000 mg daily), escalating to agents such as mycophenolate, abatacept or antithymocyte globulin if troponin does not fall, with continuous telemetry throughout.

The presentation classically mimics acute coronary syndrome: chest pain, elevated troponin, and ST-segment changes that are often diffuse and concave rather than territorial, with angiographically unobstructed coronary arteries - a MINOCA workup. Cardiac magnetic resonance imaging is the non-invasive standard, using the updated Lake Louise criteria: one T2-based marker of edema plus one T1-based marker (native T1, extracellular volume, or late gadolinium enhancement in a non-ischemic subepicardial or mid-wall distribution, classically inferolateral). Endomyocardial biopsy is reserved for suspected giant cell, eosinophilic or infiltrative disease and for fulminant presentations, because those diagnoses change therapy.

Fulminant myocarditis presents as cardiogenic shock days after a viral prodrome, often with ventricular arrhythmia or complete heart block. The key teaching point is that if the patient is supported through the acute phase with temporary mechanical circulatory support - intra-aortic balloon pump, percutaneous ventricular assist device, or venoarterial ECMO - ventricular recovery is common. The nursing mindset is bridge, not futility.

Additional practice points: continuous telemetry is mandatory because ventricular tachycardia and high-grade AV block are the proximate causes of death; Lyme carditis AV block usually reverses with ceftriaxone and rarely needs a permanent pacemaker; NSAIDs are avoided in acute myocarditis although colchicine is used when pericarditis coexists (myopericarditis); and patients must abstain from competitive or high-intensity exercise for 3-6 months, resuming only after ejection fraction, troponin and inflammatory markers normalize and ambulatory monitoring plus exercise testing show no arrhythmia.

Acute Rheumatic Fever and Rheumatic Heart Disease

Acute rheumatic fever is a delayed immune response to group A streptococcal pharyngitis, appearing 2-4 weeks after infection when antibodies against streptococcal M protein cross-react with cardiac myosin and valve tissue (molecular mimicry). Diagnosis uses the revised Jones criteria, which stratify by population risk.

Diagnosis requires evidence of preceding streptococcal infection (positive rapid antigen test or throat culture, or rising antistreptolysin O or anti-DNase B titers) plus 2 major or 1 major and 2 minor criteria; a recurrent episode may be diagnosed with 3 minor criteria.

Carditis in rheumatic fever is a valvulitis. Acute disease produces mitral regurgitation, but the classic long-term sequela is mitral stenosis, appearing 10-20 years later with a loud S1, an opening snap, a low-pitched diastolic rumble, atrial fibrillation from left atrial enlargement, and hemoptysis. Severe mitral stenosis is a valve area of 1.5 cm2 or less; percutaneous mitral balloon commissurotomy is the treatment of choice when valve morphology is favorable and there is neither left atrial thrombus nor moderate-to-severe mitral regurgitation.

Secondary prophylaxis is benzathine penicillin G 1.2 million units IM every 4 weeks (600,000 units if under 27 kg, and every 3 weeks in high-risk or recurrent cases). Duration depends on cardiac involvement: rheumatic fever without carditis, 5 years or until age 21, whichever is longer; carditis without residual valve disease, 10 years or until age 21; carditis with residual valve disease, 10 years or until age 40, and sometimes lifelong.

Nursing Priorities Across All Three

Track the fever curve and blood culture clearance as the primary markers of treatment response; persistent fever beyond 5-7 days on appropriate therapy is a surgical trigger, not a reason to wait. Monitor vancomycin AUC or trough levels with renal function and daily weights, and watch for aminoglycoside ototoxicity and rifampin drug interactions and orange body fluids. Perform neurologic checks every shift for embolic stroke and review telemetry deliberately for a lengthening PR interval. For patients going home on parenteral therapy, teach line care, the signs of line infection, and the appointment schedule. For injection-drug-use-associated endocarditis, engage addiction medicine early, use harm-reduction language, and treat the substance use disorder as part of the cardiac plan, because untreated it is the strongest predictor of reinfection. For patients with a high-risk cardiac condition, provide a written prophylaxis card and reinforce dental hygiene, which prevents far more endocarditis than pre-procedure antibiotics do.