What is the best approach for diagnosing Hypertrophic Obstructive Cardiomyopathy (HOCM) and Infective Endocarditis?

Diagnostic Approach for HOCM and Infective Endocarditis

Infective Endocarditis Diagnosis

For suspected infective endocarditis, obtain at least 3 sets of blood cultures from separate venipuncture sites before antibiotics, then perform transthoracic echocardiography (TTE) immediately, followed by transesophageal echocardiography (TEE) if TTE is nondiagnostic, prosthetic material is present, or intracardiac device leads are present. 1, 2

Initial Diagnostic Steps

• Blood cultures are the cornerstone: Obtain at least 3 sets from separate venipuncture sites before initiating antibiotics, as they are positive in 90% of IE cases when properly obtained 2, 3
• Start with TTE in all suspected cases as the initial imaging modality due to its safety, wide availability, rapid results, and ability to assess both structural abnormalities (vegetations, abscesses) and functional consequences (valve regurgitation, ventricular function) 1, 2

When to Proceed to TEE (Class I Recommendation)

TEE should be performed immediately in the following situations 1, 2:

• TTE is nondiagnostic and clinical suspicion remains high
• Prosthetic valves or prosthetic material is present (TTE sensitivity only ~50% for prosthetic valve vegetations)
• Intracardiac device leads are present (TTE sensitivity only 25-40% for CIED lead infections)
• Complications are suspected (paravalvular abscess, perforation, pseudoaneurysm)
• High-risk infections: S. aureus, enterococci, or fungal infections
• Clinical deterioration occurs with change in signs or symptoms

Diagnostic Framework: Modified Duke Criteria

Apply the Modified Duke Criteria which integrates clinical, microbiological, and imaging findings 1, 2:

Major Criteria:

• Positive blood cultures: Typical microorganisms (Viridans streptococci, S. gallolyticus, HACEK group, S. aureus, community-acquired enterococci) from 2 separate cultures 1, 2
• Echocardiographic findings: Vegetation, abscess, pseudoaneurysm, intracardiac valvular perforation, new partial dehiscence of prosthetic valve, or new valvular regurgitation 1, 2
• Imaging positive for IE: Abnormal activity around prosthetic valve site on ¹⁸F-FDG PET/CT (if prosthesis implanted >3 months) or paravalvular lesions on cardiac CT 1, 2
• Coxiella burnetii: Single positive blood culture or anti-phase I IgG antibody titer ≥1:800 1

Definite IE Diagnosis:

• 2 major criteria, OR
• 1 major + 3 minor criteria, OR
• 5 minor criteria 1, 2

Advanced Imaging When Echocardiography is Inconclusive

When TTE and TEE remain negative or inconclusive despite high clinical suspicion 1:

• Cardiac CT angiography (Class 2a): Superior for detecting paravalvular abscesses, pseudoaneurysms, and myocardial abscesses; 100% sensitivity/specificity for vegetations >1 cm 1
• ¹⁸F-FDG PET/CT (Class 2a): Particularly valuable for prosthetic valve endocarditis (>3 months post-implant) and cardiac device infections; provides whole-body assessment for septic emboli 1
• Repeat TEE within one week if initial TEE is negative but suspicion remains high 1

Critical Pitfalls to Avoid

• Do not delay TEE in prosthetic valve or device-related cases—TTE sensitivity is inadequate (only 25-50%) 1
• Obtain blood cultures BEFORE antibiotics—antibiotic pretreatment is a major cause of culture-negative endocarditis 2, 3
• Recognize atypical presentations in elderly patients: Non-specific symptoms (digestive complaints, urinary symptoms, anemia, cognitive changes) are more common than classic peripheral stigmata 2
• Early perivalvular abscesses may appear only as nonspecific thickening—repeat imaging if clinical deterioration occurs 1

---

HOCM Diagnosis

Echocardiography is the gold standard for diagnosing hypertrophic obstructive cardiomyopathy (HOCM), demonstrating asymmetric septal hypertrophy (≥15 mm), systolic anterior motion of the mitral valve, and left ventricular outflow tract obstruction.

Key Diagnostic Features on Echocardiography

• Asymmetric septal hypertrophy: Wall thickness ≥15 mm (or ≥13 mm with positive family history)
• Systolic anterior motion (SAM) of the anterior mitral leaflet causing dynamic left ventricular outflow tract (LVOT) obstruction
• LVOT gradient: Resting gradient ≥30 mmHg or provoked gradient ≥50 mmHg defines obstruction
• Mitral regurgitation: Often present due to SAM and altered mitral valve geometry

Special Consideration: HOCM and Infective Endocarditis

The anterior mitral leaflet is the most frequent site of vegetative lesions in HOCM patients due to chronic endocardial trauma from systolic anterior motion 4. When IE is suspected in HOCM patients:

• TEE is particularly important as the combination of SAM, mitral valve abnormalities, and potential vegetations creates diagnostic complexity 4
• Severe valvular damage combined with HOCM hemodynamics portends adverse clinical outcomes and may require urgent surgical intervention 4
• Both aortic and mitral valves should be carefully evaluated, as both can be affected by IE in HOCM patients 4

Multidisciplinary Team Approach

Early involvement of an "Endocarditis Team" including cardiologist, infectious disease specialist, cardiac surgeon, and microbiologist is highly recommended for complicated IE cases, particularly in HOCM patients where hemodynamics are already compromised 2.