In a male patient with a one‑month fever, a new apical murmur, and signs of congestive heart failure, what is the most likely diagnosis?

Diagnosis: Infective Endocarditis

The most likely diagnosis is infective endocarditis (IE), given the classic triad of prolonged fever (one month), new apical murmur, and signs of congestive heart failure. 1, 2

Clinical Reasoning

This patient presents with the cardinal features of IE:

• Fever for one month represents the hallmark symptom, occurring in up to 90% of IE cases 1, 2, 3
• New murmur at the apex indicates mitral valve involvement with regurgitation, found in up to 85% of IE patients 1, 2
• Heart failure is the most common and serious complication of IE, typically resulting from acute valve destruction causing severe regurgitation 1, 4

The apical location specifically suggests mitral valve endocarditis with acute mitral regurgitation, which can develop from vegetation formation, chordal rupture, or papillary muscle dysfunction 5. The combination of new mitral regurgitation with heart failure indicates hemodynamically significant valve damage 6.

Immediate Diagnostic Workup

Obtain at least 3 sets of blood cultures from separate venipuncture sites before starting antibiotics, with the first and last samples drawn at least 1 hour apart 5, 1, 2. This is critical—starting antibiotics before blood cultures may render cultures negative and obscure the diagnosis 1.

Perform transthoracic echocardiography (TTE) immediately, followed by transesophageal echocardiography (TEE) if TTE is negative but clinical suspicion remains high 5, 1, 2. TEE has >95% sensitivity for detecting vegetations versus 60-75% for TTE 1. Look specifically for:

• Oscillating intracardiac mass or vegetation on the mitral valve 5
• Valvular regurgitation severity 5
• Perivalvular abscess formation 5
• Ventricular function and chamber dimensions 5

Key Echocardiographic Findings to Expect

The echocardiogram will likely demonstrate:

• Mobile vegetation on the mitral valve (anterior or posterior leaflet) 6, 7
• Severe mitral regurgitation with an eccentric jet directed away from the affected leaflet 5
• Possible flail leaflet if chordal rupture has occurred, appearing as a triangular mobile structure prolapsing into the left atrium during systole 5
• Left ventricular dysfunction secondary to acute volume overload 5
• Elevated left ventricular filling pressures with pulmonary congestion 5

Critical Diagnostic Caveats

A negative TTE does not rule out IE—if clinical suspicion remains high (which it should given this presentation), proceed immediately to TEE 5, 3. Both TTE and TEE can produce false-negative results, particularly in early disease 5, 3.

Do not delay echocardiography or blood cultures—these should be obtained expeditiously as they directly impact the duration and type of therapy 5.

Most Likely Causative Organisms

Expect blood cultures to grow:

• Staphylococcus aureus (most common overall cause of IE) 6, 4
• Viridans streptococci (if there is history of dental procedures) 1, 7
• Streptococcus species (cultured in 75% of mitral valve prolapse-associated IE) 8

Indications for Urgent Surgical Consultation

Congestive heart failure from acute severe mitral regurgitation is the most important indication for urgent cardiac surgery 9, 4. This patient already has heart failure, which carries the greatest impact on prognosis 4.

Additional surgical indications to monitor for include:

• Perivalvular abscess (occurs in 42-85% of IE cases and significantly increases mortality) 4
• Uncontrolled infection despite appropriate antibiotics 6
• Recurrent embolic events 4
• Hemodynamic instability requiring vasopressor support 6

Involve cardiology and cardiac surgery immediately—patients with heart failure from valve dysfunction require urgent multidisciplinary evaluation 5, 1, 3. The decision for surgery timing should not be delayed, as early surgical intervention improves outcomes in complicated IE 4.

Common Pitfalls to Avoid

Do not attribute the fever to another source without ruling out IE first—the combination of prolonged fever, new murmur, and heart failure is IE until proven otherwise 1, 3.

Do not start empiric antibiotics before obtaining blood cultures—this is a critical error that can prevent pathogen identification 1.

Do not rely solely on clinical examination to assess valve function—echocardiography is essential for quantifying regurgitation severity and detecting complications 5.