Acute Endocarditis vs. Subacute Endocarditis

What's the Difference?

Acute endocarditis and subacute endocarditis are two different forms of infective endocarditis, a condition characterized by inflammation of the inner lining of the heart. Acute endocarditis typically develops rapidly, with symptoms appearing suddenly and progressing quickly. It is often caused by aggressive bacteria and can lead to severe complications if not treated promptly. On the other hand, subacute endocarditis develops more gradually, with symptoms appearing over weeks or even months. It is usually caused by less aggressive bacteria and tends to have a milder course. However, if left untreated, subacute endocarditis can also lead to serious complications. Both forms of endocarditis require medical intervention, including antibiotics and, in some cases, surgical intervention to repair damaged heart valves.


AttributeAcute EndocarditisSubacute Endocarditis
Causative OrganismsStaphylococcus aureus, Streptococcus pyogenesStreptococcus viridans, Enterococcus faecalis
DurationDays to weeksWeeks to months
Valve AffectedAny valveMitral and aortic valves
PathogenesisDirect invasion of healthy valvesIndolent infection of previously damaged valves
ComplicationsEmbolic events, heart failureValvular regurgitation, heart failure

Further Detail


Endocarditis is a serious infection that affects the inner lining of the heart chambers and heart valves. It can be classified into two main types: acute endocarditis and subacute endocarditis. While both types share similarities in terms of symptoms and complications, they differ in terms of the speed of onset, causative organisms, and risk factors.

Acute Endocarditis

Acute endocarditis is characterized by a rapid onset of symptoms, typically within days to a few weeks. It is often caused by aggressive and highly virulent bacteria, such as Staphylococcus aureus. This type of endocarditis is more commonly seen in individuals with pre-existing heart conditions, intravenous drug users, or those who have undergone invasive medical procedures.

The symptoms of acute endocarditis can include high fever, chills, fatigue, rapid heartbeat, shortness of breath, and joint pain. Patients may also experience symptoms related to the embolization of infected material, such as stroke or organ damage. The rapid progression of acute endocarditis necessitates immediate medical attention and aggressive treatment with intravenous antibiotics.

Diagnosing acute endocarditis involves a thorough evaluation of the patient's medical history, physical examination, blood cultures, and echocardiography. The echocardiogram can reveal abnormalities in the heart valves, such as vegetations or abscesses, which are characteristic of endocarditis.

Treatment for acute endocarditis typically involves a combination of intravenous antibiotics tailored to the specific bacteria causing the infection. In severe cases, surgical intervention may be necessary to repair or replace damaged heart valves. Prompt and appropriate treatment is crucial to prevent life-threatening complications, such as heart failure or septicemia.

Subacute Endocarditis

Subacute endocarditis, as the name suggests, has a more gradual onset of symptoms, often developing over weeks to months. It is commonly caused by less aggressive bacteria, such as Streptococcus viridans or Enterococcus species. Subacute endocarditis is frequently associated with underlying heart conditions, such as congenital heart defects or degenerative valve diseases.

The symptoms of subacute endocarditis are often nonspecific and may include low-grade fever, fatigue, weight loss, night sweats, and aching joints. These symptoms can be easily overlooked or attributed to other causes, leading to delayed diagnosis and treatment. The slower progression of subacute endocarditis allows the bacteria to gradually damage the heart valves, leading to complications like heart murmurs or congestive heart failure.

Diagnosing subacute endocarditis requires a high index of suspicion, especially in individuals with known risk factors. Blood cultures are essential for identifying the causative organism, and echocardiography can reveal characteristic valve abnormalities. The Duke criteria, a set of clinical criteria, are often used to aid in the diagnosis of subacute endocarditis.

Treatment for subacute endocarditis involves a prolonged course of intravenous antibiotics, typically given for 4-6 weeks. In some cases, surgical intervention may be necessary to repair or replace damaged heart valves. Regular follow-up and monitoring are crucial to ensure the eradication of the infection and prevent relapse.


Acute endocarditis and subacute endocarditis are two distinct forms of a serious infection affecting the heart. While acute endocarditis has a rapid onset and is caused by aggressive bacteria, subacute endocarditis develops more gradually and is associated with less virulent organisms. Prompt diagnosis and appropriate treatment are essential for both types to prevent complications and improve outcomes. Understanding the differences between acute and subacute endocarditis can aid in early recognition and management of these potentially life-threatening conditions.

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