Etiology of Infective Endocarditis

Introduction

Infective endocarditis (IE) is a serious infection of the endocardium, the inner lining of the heart. It is primarily caused by microbial colonization of heart valves, leading to severe complications if untreated.

Etiology

The development of IE is influenced by various microbial and host factors. The major causes include:

Microbial Agents

• Staphylococcus aureus: Most common pathogen, particularly in healthcare-associated cases.
• Streptococcus viridans: Frequently seen in native valve endocarditis, especially after dental procedures.
• Enterococcus species: Commonly associated with urinary tract infections.
• HACEK organisms: Rare causes, often implicated in subacute presentations.
• Fungal pathogens: Candida species and Aspergillus can lead to severe complications in immunocompromised patients.

Predisposing Conditions

• Rheumatic heart disease: Damaged valves increase susceptibility.
• Congenital heart defects: Structural anomalies promote bacterial adherence.
• Prosthetic heart valves: Higher risk, especially in early postoperative stages.
• Intravenous drug use (IVDU): Direct introduction of pathogens into the bloodstream.
• Immunosuppression: Increased susceptibility in conditions like HIV or post-transplant states.

Pathophysiology

IE begins with endothelial damage, leading to fibrin deposition and bacterial colonization. This results in vegetation formation, which can embolize and cause systemic complications.

Diagnosis and Clinical Features

Diagnosis is based on clinical symptoms, echocardiographic findings, and positive blood cultures. Major criteria include persistent bacteremia and evidence of endocardial involvement.

Complications

Complications include valvular destruction, embolic events, heart failure, and systemic infection.

Conclusion

Understanding the etiology of infective endocarditis is essential for early diagnosis and effective management. Preventive strategies, including prophylactic antibiotics, play a crucial role in reducing morbidity and mortality.