I. Overview of Cardiovascular Infections
- Cardiovascular infections are serious and often life-threatening due to the sterile nature of the heart and blood.
- Can affect:
- Heart valves (endocarditis)
- Myocardium (myocarditis)
- Pericardium (pericarditis)
- Bloodstream (bacteremia, septicemia, sepsis)
II. Major Microbiological Conditions
A. Infective Endocarditis (IE)
1. Etiological Agents
Divided by native valve vs prosthetic valve:
- Native Valve IE:
- Streptococcus viridans (oral flora)
- Staphylococcus aureus (esp. IV drug users – tricuspid valve)
- Enterococcus faecalis
- HACEK group (fastidious gram-negative rods: Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella)
- Prosthetic Valve IE:
- Staph. epidermidis, Staph. aureus, Candida
2. Pathogenesis
- Microbes enter bloodstream → adhere to damaged endothelium or valves → form vegetations composed of bacteria, fibrin, and platelets.
- Can lead to septic emboli → stroke, organ infarcts
3. Diagnosis
- Blood cultures (3 sets, before antibiotics)
- Echocardiography (TTE or TEE)
- Duke Criteria (major: positive culture + vegetation)
B. Myocarditis
1. Etiological Agents
- Viruses:
- Coxsackie B virus, Adenovirus, Parvovirus B19
- Bacteria:
- Corynebacterium diphtheriae, Borrelia burgdorferi
- Protozoa:
- Trypanosoma cruzi (Chagas disease)
2. Pathogenesis
- Direct cytolytic effect (e.g., Coxsackie B)
- Autoimmune-mediated damage (post-viral)
- Can result in arrhythmia, heart failure
3. Diagnosis
- Elevated cardiac enzymes
- PCR for viral genomes in biopsy
- ECG changes, cardiac MRI
C. Pericarditis
1. Etiological Agents
- Viruses: Enteroviruses, Coxsackie A/B, Influenza
- Bacteria: TB (Mycobacterium tuberculosis), Strep. pneumoniae, Staph. aureus
- Fungi: Histoplasma (immunocompromised)
2. Clinical signs: Chest pain, pericardial rub, tamponade
- Confirm via pericardial fluid culture, PCR (for TB)