From the Guidelines
The most common site of infective endocarditis is the mitral valve, followed by the aortic valve. This is due to the mitral valve's position in the high-pressure left side of the heart and its larger surface area compared to other valves, as discussed in the context of valvular heart disease management 1. The mitral valve is most frequently affected, and pre-existing valvular abnormalities such as mitral valve prolapse, rheumatic heart disease, or degenerative changes increase susceptibility to infection.
Infective endocarditis occurs when microorganisms, typically bacteria, colonize and infect the endocardial surface of the heart, with valvular endocardium being particularly susceptible. The pathophysiology involves initial endothelial damage, followed by platelet and fibrin deposition creating a vegetation where bacteria can adhere and multiply, protected from host defenses. Understanding the common sites of endocarditis helps guide diagnostic imaging and treatment approaches, as outlined in recent guidelines for the management of patients with valvular heart disease 1.
Some key points to consider include:
- The majority of cases of endocarditis are due to streptococcal and staphylococcal organisms 1
- In intravenous drug users, the tricuspid valve becomes a more common site of infection due to the direct path of contaminated material from peripheral veins to the right side of the heart
- Imaging is used to support the diagnosis by demonstrating vegetations of cardiac valves and, in complicated cases, paravalvular abscesses affecting native and prosthetic valves 1
- Blood cultures may be negative in the setting of antibiotic use, and serial blood cultures and transthoracic echocardiography (TTE) are typically included in the workup 1
From the Research
Most Common Site of Infective Endocarditis
- The most common site of infective endocarditis varies depending on the study, but the aortic valve is frequently reported as the most commonly affected valve 2, 3.
- In a systematic review of infective endocarditis by Klebsiella species, the aortic valve was the most commonly infected intracardiac site, followed by the mitral valve 2.
- Another study found that the aortic valve was the most frequently affected valve, as single-valve IE or as multivalve AV-MV, with the predominant causative agents being of the Staphylococcus group 3.
- However, a systematic review of infective endocarditis by Serratia species found that the mitral valve was the most commonly infected site, followed by the aortic valve 4.
- A retrospective study in the Bronx, New York, found that the mitral valve was involved in 32.4% of patients, followed by the aortic valve (19.8%) 5.
Valve Involvement
- The mitral valve is also commonly affected, especially in cases of secondary infection from aortic valve endocarditis 6.
- The tricuspid valve is less commonly affected, but is more frequently seen in younger patients and those with a history of intravenous drug use 3.
- Multivalvular involvement is also possible, with the aortic-mitral valves being the most common combination 3.