Subacute Infective Endocarditis: Understanding Its Most Common Complications

Subacute infective endocarditis (SIE) is a serious infection that affects the inner lining of the heart chambers and valves. If left untreated, it can lead to a range of life-threatening complications. Among these, certain complications are more prevalent and significantly impact patient outcomes.

Cardiac Complications

Heart Failure

Heart failure is the most frequent and clinically significant complication associated with subacute infective endocarditis. It typically results from valve damage, particularly involving the aortic or mitral valves, which can lead to regurgitation and impaired cardiac function. Early detection and treatment are crucial to prevent irreversible heart damage.

Myocardial Abscess

A myocardial abscess can develop when the infection spreads into the heart muscle. This condition may interfere with the heart's electrical conduction system and lead to arrhythmias or more severe structural damage.

Myocardial Infarction

Although less common, myocardial infarction can occur due to embolization of infected material or inflammation of the coronary arteries. This complication is particularly dangerous and requires immediate intervention.

Suppurative Pericarditis

Suppurative pericarditis is a rare but severe complication where the infection spreads to the pericardium, causing inflammation and pus formation. It can lead to cardiac tamponade and requires urgent drainage.

Myocarditis

In some cases, the infection can cause myocarditis, an inflammation of the heart muscle that weakens the heart's ability to pump effectively.

Systemic Complications

Arterial Embolism

While arterial embolism occurs more frequently in acute cases, it can still be a significant issue in subacute infective endocarditis. These embolic events can affect the brain, kidneys, spleen, or limbs, potentially causing stroke, organ dysfunction, or limb ischemia.

Bacterial Aneurysm

Bacterial aneurysms are more commonly seen in subacute cases. They result from infection weakening the arterial wall, leading to localized dilation. These aneurysms can rupture, causing internal bleeding and requiring surgical intervention.

Metastatic Abscesses

Although metastatic abscesses are more typical in acute infective endocarditis, they can occasionally occur in subacute cases. These abscesses form when bacteria spread to distant organs such as the liver, spleen, or brain.

Neurological Involvement

Approximately one-third of patients with subacute infective endocarditis experience some form of neurological involvement. This can include stroke, meningitis, brain abscess, or encephalopathy, often due to embolic events or direct infection spread.

Renal Complications

Kidney damage is common in patients with subacute infective endocarditis. The most frequent renal complication is immune complex-mediated glomerulonephritis, which can lead to proteinuria, hematuria, and in severe cases, renal failure. Prompt diagnosis and treatment are essential to preserve kidney function.