Which of the following patients does NOT usually require endocarditis prophylaxis?

In the context of endocarditis prophylaxis, patients with arrhythmias typically do not require this type of preventive treatment. Endocarditis prophylaxis is generally recommended for individuals with specific high-risk conditions, primarily to prevent the potential for a bacterial infection of the heart valves during invasive procedures.

Patients with prosthetic valves are at a significantly elevated risk for developing infective endocarditis, so they require prophylaxis. Similarly, individuals with a prior history of infective endocarditis are also considered at higher risk for recurrence and thus need prophylactic measures. Patients with certain congenital heart diseases, particularly those with unrepaired cyanotic heart disease or those who have undergone certain repairs, also fall into the category of needing prophylaxis due to their increased risk of endocarditis.

On the other hand, patients with arrhythmias, unless associated with other risk factors, such as structural heart anomalies or history of endocarditis, do not have a direct indication for endocarditis prophylaxis when undergoing dental or other procedures. This aligns with current guidelines that focus on specific high-risk groups, which do not routinely include asymptomatic patients with arrhythmia.