Medicine Marrow Pg No 1045-1054 (Infectious Diseases)

Echocardiography

• Transthoracic echocardiography (TTE) sensitivity: 60-65%
• Transesophageal echocardiography (TEE) Sensitivity: 85-95%
• TTE is used for suspected infective endocarditis (IE) in native valves
• TEE is used for suspected IE in prosthetic valves or when TTE is equivocal or negative
• TEE is used for suspected IE with complications like vegetations < 2mm, myocardial abscess, valve perforation, etc.

Infective Endocarditis

• Risk factors: Congenital heart conditions like MVP, septal defects, IV drug abuse, rheumatic heart disease, degenerative aortic stenosis.
• Types: Left-sided (75%), combined (15%), right-sided (10%).
• Left-sided IE: Common in patients with MVP and mitral regurgitation.
• Right-sided IE: Common in IV drug abusers and patients with IV central lines.
• Complications: Cardiac complications like stroke, heart failure, perivalvular abscess, non-cardiac complications like embolic occlusion, immunological reactions, mycotic aneurysm.

Hepatitis C Virus (HCV)

• Positive-sense RNA virus from the Flaviviridae family.
• 7 genotypes, genotype 1 is most common worldwide, and genotype 3 is most common in India.
• Associated with cirrhosis, hepatocellular carcinoma (HCC).
• Transmission: Percutaneous (IV drug users, CKD patients), transfusion, perinatal, breastfeeding, and sexual modes are negligible.

Membranoproliferative Glomerulonephritis (MPGN)

• Caused by 1C3, 1C4, and HCV.
• Can cause cardiac complications like stroke, ACS, heart failure, and conduction block due to perivalvular abscess.

Salmonellosis

• Incubation period: 5-20 days.
• Infective dose: 105 organisms/mL.
• Complication: Gallstones in chronic carrier state (6%).
• Clinical presentation: Step ladder fever, abdominal pain, GI disturbances, hepatomegaly, splenomegaly, rose spots.
• Investigations: Widal test (low positivity in the 1st and 2nd week, 80-100% positivity in the 3rd week), blood culture (90% positivity in the 1st week).

Modified Duke Criteria for IE Diagnosis

• Major Criteria:
  • Positive blood culture (typical organism, persistently positive culture, HACEK group, single positive culture or antibodies detected)
  • Echocardiographic evidence (oscillating intracardiac mass, abscess, new partial dehiscence, new aortic/mitral regurgitation)
• Minor Criteria: Predisposition to IE, fever, vascular phenomenon (emboli).
• Diagnosis: 2 major criteria, 1 major + 3 minor, or 5 minor criteria.

Pathogenesis of IE

• Valvular endothelial injury leads to platelet fibrin clot formation.
• Bacterial seeding onto the clot.
• Bacterial adherence and proliferation on the clot, forming a vegetation.

Classification of IE

• Native Valve:
  • Most common: Mitral valve (left-sided)
  • Associated valvular heart disease: Mitral regurgitation, congenital heart disease
  • CKD associated IE: Tricuspid
• Prosthetic Valve:
  • < 12 months: CONS > MRSA > Gram-negative bacilli

  • 12 months: Streptococcus viridans > S.aureus > Enterococci

  • IV drug users associated IE: MRSA

Various Endocarditis and Associated Organisms

• Native Valve: S.aureus > Streptococcus viridans > Enterococci
• Prosthetic Valve:
  • < 12 months: CONS > MRSA > Gram-negative bacilli

  • 12 months: Streptococcus viridans > S.aureus > Enterococci

• IV drug users: MRSA

Clinical Presentation of IE

• Acute IE: High mortality (100%), associated with abscess, osteomyelitis, leading to severe sepsis and septic shock.
• Subacute IE: Longer duration (2-8 months), characterized by fever, anorexia, weight loss, fatigue, myalgia, and signs like new onset or worsening cardiac murmur, embolic events, splenomegaly, clubbing, vasculitis.

Subacute IE Features

• Laboratory: Anemia, elevated WBC, ESR, CRP, rheumatoid factor positive, proteinuria and microscopic hematuria.
• Signs: Cardiac murmur changes, macroembolic events (stroke, ACS), microembolic events (petechiae, splinter hemorrhage).
• Vasculitis Manifestations: Osler nodes, Janeway lesions, Roth spots, MPGN.

Treatment of IE

• Streptococcus viridans: Penicillin G IV for 4 weeks.
• Enterococci: Penicillin G IV for 4-6 weeks, plus Gentamicin IV.
• Staphylococcus (MRSA): Vancomycin IV for 4-6 weeks, plus Gentamicin IV for prosthetic valve IE.
• Culture negative: Consider rare conditions, antibiotic treatment based on clinical suspicion.

Surgical Intervention for IE

• Native Valve: Acute valvular regurgitation, fungal endocarditis, perivalvular aortic abscess.

Prophylaxis of IE

• Indications: Prosthetic valve, previous IE episode, post-cardiac transplant, unrepaired CHD, repaired CHD within 6 months.
• Medication: Amoxicillin 2g orally before procedures, alternatives for penicillin allergy, IV options if oral route not possible.
• Pre-procedural prophylaxis: Dental, respiratory tract, or incision/drainage procedures.

HCV Hepatology

• Incubation period: 50 days.
• Chronic hepatitis: 85% over 40 years.
• Anicteric hepatitis: Often undiagnosed.
• Enzyme levels: Variable.
• Fulminant failure: 0.1-1%.
• Anti-HCV testing (EIA): Positive indicates acute/chronic infection, negative indicates no HCV contact.
• Treatment: New DAAs (Direct-Acting Antivirals) are effective for patients > 12 years old with high SVR rates.
• Extrahepatic manifestations: Sjogren's syndrome, lymphoma, cryoglobulinemia, porphyria, lichen planus, MPGN, autoimmune thyroid disease.
• Acute phase: Fever, fatigue, malaise, possible asymptomatic or extrahepatic manifestations.

Tropical Infections

• Fever on Day 1: Paracetamol + decongestants, screen for foci of infection.
• Fever on Day 3:
  • Salmonella: Step-ladder fever pattern.
  • Malaria: Chills and rigors with fatigue.
  • Leptospirosis, scrub typhus: Myalgia, conjunctival suffusion.
  • Dengue: High-grade fever, retro-orbital pain, occipital pain, vomiting.
  • Investigations: CBC, dengue NS-1 antigen, quantitative buffy coat for malaria.
• Fever on Day 4: Doxycycline + Cotrimoxazole DS.
• Fever on Day 5: Blood culture for aerobic, anaerobic, and fungal cultures.
• Typhoid:
  • Isolated from South India, high sensitivity.

Remember that this is just a summary of the text. You should always consult a healthcare professional for any health concerns.

Explore the vital concepts of echocardiography techniques and the intricacies of infective endocarditis. This quiz covers sensitivity comparisons between transthoracic and transesophageal echocardiography, risk factors, types, and complications associated with infective endocarditis. Test your knowledge on how these elements are crucial for diagnosing heart conditions.