Infective Endocarditis – Diagnostic Tools, Signs, Symptoms, and Complications

Overview:

• An infection of the inner lining of the heart, primarily affecting the heart valves.
• Most common bacterial causes:
  • Streptococcus viridans: Usually causes less severe symptoms.
  • Staphylococcus aureus: Typically results in more aggressive infections.

Risk Factors:

• Most individuals are not susceptible to bacteria entering the bloodstream and causing valve infections.
• Risk increases in the presence of valvular abnormalities or compromised immunity.

Major Risk Factors:

1. Valve abnormalities:
   • Congenital valve defects: Structural issues present from birth.
   • History of rheumatic fever: Damage from group A beta-hemolytic Streptococcus in childhood causes valve scarring, making valves vulnerable.
   • Prolapse or damage: Valves that have prolapsed or been replaced (mechanical or biological valves/pigs) are less effective at defending against bacteria.
2. Procedural Sources:
   • Dental procedures:
     • Scaling or cavity cleaning can cause microbleeding and provide portals for bacteria.
     • Common bacteria: Streptococcus viridans, often present in the mouth.
     • Prophylactic antibiotics are given beforehand to prevent bacteria from settling on vulnerable valves.
   • Piercings and tattoos:
     • Risk of bacteria entering through skin breaches.
     • Patients with valve abnormalities are advised to take precautions.
3. Immunosuppression:
   • Reduced immune function increases susceptibility.
   • Common in elderly, cancer patients, those on immunosuppressive medications.
4. IV Drug Use:
   • Use of dirty needles introduces bacteria directly into the bloodstream.
   • High risk of infecting heart valves or other sites.

Additional Risk Considerations:

• Surgical history or prosthetic valves:
  • Artificial or prosthetic valves have less defense, increasing risk.
• History of recent surgery:
  • Provides an entry point for bacteria.

Pathogenesis:

• Infection begins in the bloodstream after a portal of entry such as a wound or other source (perhaps abrasion during dental cleaning).
• Bacteria travel via blood to reach vulnerable sites—mainly heart valves, which are poorly vascularized.
• Valve damage:
  • Bacteria adhering to the valves cause deterioration and growths.
  • The immune response involves white blood cell infiltration but often leads to tissue damage.

Formation of Vegetations:

• Vegetations are large, fragile masses made of:
  • Fibrin
  • Platelets
  • Blood cells
  • Bacteria
• These growths are seen on the cusps of heart valves and can embolize, causing further complications.

Diagnostic Imaging:

1. Transesophageal echocardiogram (TEE):
   • Provides high-resolution images of the valves by inserting a probe into the esophagus.
   • Superior to transthoracic echocardiography (TTE) because of proximity to the heart and less interference from ribs.
   • Helps detect vegetations and valve damage effectively.
     • • Visualizes vegetations (infected growths) on heart valves.
     • Example: Large vegetation on the aortic valve can impair blood flow, reducing stroke volume and cardiac output.
2. 2D echocardiograms can show messy, irregular growths on valves such as the mitral valve.
   • Color Doppler echocardiography helps detect regurgitation (backflow of blood) through diseased valves.

Signs and Symptoms:

• Fever: Common due to bacterial infection.
• Fatigue & Anorexia: Body uses resources for fighting infection, resulting in loss of appetite.
• Murmurs: As valves become leaky or stenotic, abnormal sounds (regurgitation or narrowing) are heard via stethoscope.
• Splenomegaly: Enlargement of the spleen due to immune activity.
• Petechiae and Osler Nodes:
  • Osler Nodes: Tender, painful nodules typically on fingers or toes, caused by septic emboli lodging in dermal capillaries.
  • Petechiae: Small bleeding spots on skin from capillary damage.

Complications:

• Septic Emboli:
  • Clusters of bacteria, white blood cells, fibrin, and blood cells break off vegetations.
  • Emboli can lodge in distant capillaries, causing vascular occlusion or infection.
  • Emboli traveling systemically (from left-sided vegetations) can cause stroke or organ infarctions.
• Vascular occlusion: Can lead to tissue necrosis.
• DIC (Disseminated Intravascular Coagulation): Widespread clotting in the bloodstream, increasing risk of bleeding elsewhere.

Biopsy & Laboratory Tests:

• Biopsy of Osler nodes or other lesions can identify bacteria responsible.
• Blood cultures: Essential for confirming the causative organism (e.g., Streptococcus viridans, Staphylococcus aureus).
• Other causes of similar skin lesions include insect bites; biopsy helps differentiate.

Treatment & Management:

• Antibiotics targeted to the identified bacteria.
• Valve replacement: Often needed if valves are severely damaged or cannot heal.
  • Diseased valves with vegetations or regurgitation are often replaced with mechanical valves or biological (pig) valves.
    • Valve durability:
      • Both last approximately 10-20 years.
      • Mechanical valves are durable but require lifelong anticoagulation.
      • Biological valves last around the same time but usually do not necessitate anticoagulation.

• Managing Heart Failure:
  • If signs of congestive heart failure are present, initiate heart failure medications (e.g., diuretics, ACE inhibitors).
  • Additional interventions like imaging to evaluate valve damage.
  • Possible valve replacement if valves are severely damaged or dysfunctional.

Prevention:

• Dental hygiene:
  • Maintaining good dental health reduces gingivitis and oral infections.
  • Prevention of bacteria from entering the bloodstream during routines like tooth brushing, dental cleaning, or procedures that cause bleeding.
  • Good oral hygiene correlates with overall better health status.
• Other preventive measures:
  • High-risk individuals (e.g., with prosthetic valves) may receive prophylactic antibiotics before dental work.
  • Maintaining overall healthy lifestyle—balanced diet, regular exercise, avoiding smoking.

Summary:

Infective endocarditis results from bacteria traveling through the bloodstream and infecting heart valves. The severity depends on the pathogen, with Staphylococcus aureus typically causing more severe disease. Diagnosis is aided by imaging techniques like transesophageal echocardiography which can reveal vegetations on valves, the hallmark of infection. Prompt treatment is essential to prevent embolic events and valve destruction.

People with pre-existing valvular damage, prosthetic valves, or compromised immune systems are at higher risk for infective endocarditis, especially after procedures like dental work or with intravenous drug use. Prophylactic antibiotics and good hygiene practices are critical for prevention in high-risk individuals.

Infective endocarditis presents with fever, murmurs, and embolic phenomena such as Osler nodes. Diagnosis involves echocardiography, blood cultures, and biopsy. Prompt antibiotic therapy and possible surgical intervention are crucial, especially when vegetations cause significant valvular damage or embolic risks.

Effective treatment of infective endocarditis involves antibiotics tailored to the causative bacteria, addressing heart failure symptoms, and, if necessary, valve repair or replacement. Prevention hinges on good oral hygiene and overall healthy lifestyle choices, including exercise. Advances in prosthetic valves improve outcomes and longevity of valve replacement procedures.