Differences and Similarities Between Acute and Subacute Infective Endocarditis

Infective endocarditis is a serious infection that affects the inner lining of the heart chambers and valves. It is broadly categorized into two types: acute and subacute. Understanding the differences and similarities between these two forms is crucial for accurate diagnosis and effective treatment.

Primary Causes

One of the key differences lies in the causative organisms. Acute infective endocarditis is most commonly caused by Staphylococcus aureus, a highly virulent bacteria known for its aggressive nature. On the other hand, subacute infective endocarditis is typically associated with Streptococcus viridans, a less aggressive organism that often affects individuals with pre-existing heart conditions.

Pathogenesis and Affected Areas

The pathogenesis of acute endocarditis is not entirely understood, but it tends to affect previously normal heart valves, with the aortic valve being the most commonly involved. In contrast, subacute endocarditis usually develops in individuals with underlying structural heart disease, particularly involving damaged or abnormal heart valves.

Clinical Course and Prognosis

Acute endocarditis progresses rapidly and can be life-threatening within a short period, often leading to severe complications within weeks if left untreated. Subacute cases, however, have a more gradual onset and may take months—often six months or more—to lead to significant complications such as heart failure.

Common Symptoms and Complications

Despite their differences, both acute and subacute forms share several clinical features. Common symptoms include persistent fever, heart murmurs, and peripheral signs such as petechiae, splinter hemorrhages, and Osler's nodes. Both types are also associated with a high risk of embolic events, which can lead to stroke or organ damage. Heart failure is another serious complication seen in both conditions.

Diagnosis and Treatment

Accurate diagnosis is primarily based on blood cultures, which help identify the causative organism and guide antibiotic therapy. Echocardiography is also essential for detecting vegetations on the heart valves. Treatment typically involves long-term intravenous antibiotics, and in many cases, surgical intervention may be necessary to repair or replace damaged valves.