What is the commonest risk factor for infective endocarditis (IE)?

Prosthetic Heart Valve is the Commonest Risk Factor for Infective Endocarditis

Prosthetic heart valves represent the most significant risk factor for developing infective endocarditis (IE), with a higher incidence compared to IV drug use or rheumatic fever without valvular lesions. According to the European Society of Cardiology guidelines, there has been an increasing incidence of IE associated with prosthetic valves in industrialized nations 1.

Epidemiology of Risk Factors for IE

Prosthetic Valve Endocarditis

• Prosthetic valve endocarditis (PVE) has become increasingly common in modern healthcare settings
• A systematic review of 15 population-based investigations accounting for 2371 IE cases from seven developed countries showed an increasing incidence of IE associated with prosthetic valves 1
• Prosthetic valves are classified as high-risk factors for IE according to the European Heart Journal 2
• PVE can occur early (<1 year after surgery) or late (>1 year after surgery) 1
• The risk of IE is particularly high in the immediate postoperative period when prosthetic valves or conduits are used in surgical repairs and hemodynamic problems persist 1

IV Drug Use as a Risk Factor

• IV drug use represents a significant but secondary risk factor for IE
• Injection drug use is the most common risk factor for development of recurrent native valve IE; 43% of 281 patients with this syndrome surveyed from 1975 to 1986 were IDUs 1
• The incidence of IE in IDUs is estimated at 1.5 to 3.3 cases per 1000 person-years 1
• IV drug use-associated IE typically affects the tricuspid valve (right-sided IE), which constitutes only about 10% of total IE cases 3
• Staphylococcus aureus is the most common causative organism in IVDU-related IE 4

Rheumatic Fever Without Valvular Lesion

• Rheumatic fever without valvular lesion carries a significantly lower risk for IE compared to prosthetic valves or IV drug use
• The incidence of IE associated with underlying rheumatic heart disease has decreased in developed countries 1
• In developing countries, rheumatic valve disease remains a significant risk factor for IE 1
• However, it is the valvular damage from rheumatic heart disease, not the rheumatic fever itself without valvular lesion, that increases IE risk

Changing Epidemiology of IE Risk Factors

The epidemiological profile of IE has changed substantially over recent years:

• Traditional risk factors like rheumatic heart disease have decreased in prevalence in developed countries 1
• Newer predisposing factors have emerged—valve prostheses, degenerative valve sclerosis, and intravenous drug abuse 1
• Healthcare-associated procedures now account for up to 30% of all IE cases 2
• The average age of patients with IE has increased, with peak incidence of 14.5 episodes/100,000 person-years in patients between 70-80 years 1

Clinical Implications

Understanding that prosthetic heart valves represent the highest risk for IE has important implications:

• Patients with prosthetic valves require antibiotic prophylaxis before dental procedures with high risk of bleeding 2
• Early recognition of symptoms in prosthetic valve patients is crucial for prompt diagnosis and treatment
• Echocardiographic surveillance is important in prosthetic valve patients to detect early signs of IE
• Blood cultures should be obtained before starting antibiotics in prosthetic valve patients with unexplained fever 2

Conclusion

While all three options presented (IV drug use, rheumatic fever without valvular lesion, and prosthetic heart valve) are associated with IE, the evidence clearly demonstrates that prosthetic heart valves represent the most significant risk factor. The changing epidemiology of IE reflects the increasing prevalence of prosthetic valves and the decreasing incidence of rheumatic heart disease in developed countries, making prosthetic heart valves the commonest risk factor for IE in contemporary practice.