Endocardial fibroelastosis is characterized by the proliferation of subendocardial elastic and collagen fibers, along with thickening of the ventricular wall and endocardium. Clinically, it manifests as cardiac enlargement and impaired systolic and diastolic ventricular function and is most commonly seen in infants under the age of one.
Pathogenesis
The exact cause remains unclear. Some cases may develop as a progression of viral myocarditis, while insufficient blood supply to the endocardium and intrauterine hypoxia are also likely contributing factors. Certain cases of endocardial fibroelastosis may emerge secondary to obstructive congenital heart diseases of the left heart, such as severe aortic coarctation, hypoplastic left heart syndrome, aortic atresia, or aortic stenosis.
Clinical Manifestations
The primary presentation is congestive heart failure, which can be categorized into three types based on the severity and progression of symptoms:
Fulminant Type
The onset is sudden, with rapid development of symptoms such as respiratory distress, cyanosis of the lips, pallor, irritability, tachycardia, diminished heart sounds, and the presence of a gallop rhythm. Dry or moist rales are often audible in the lungs, and hepatomegaly is common. Some patients may develop cardiogenic shock or succumb to sudden cardiac death within hours. This type is most frequently observed in infants under six months of age.
Acute Type
Symptoms also appear relatively quickly, although heart failure progresses less aggressively compared to the fulminant type. Cerebral embolism may occur in some cases due to detachment of mural thrombi. The age group for this type overlaps with that of the fulminant type. Without timely treatment, most patients die of heart failure.
Chronic Type
Symptoms are similar to those of the acute type but progress more slowly. Affected children often exhibit delayed physical growth and development. With appropriate treatment, symptoms can be alleviated, and survival into adulthood is possible, although recurrent heart failure may still lead to death in some cases.
Auxiliary Examinations
X-ray Examination
Findings typically include marked left ventricular enlargement, reduced pulsations along the left cardiac border, and increased pulmonary markings.
Electrocardiography (ECG)
ECG findings are valuable for diagnosis, commonly showing left ventricular hypertrophy, although a minority of cases may display right ventricular or biventricular hypertrophy. ST segment and T wave changes, as well as atrioventricular conduction block, may also occur.
Echocardiography
Echocardiographic features include enlargement of the left atrium and left ventricle, thickening of the left ventricular posterior wall and interventricular septum, as well as thickening and enhanced reflectivity of the left ventricular endocardium, which are considered characteristic findings.
Cardiac Catheterization
Elevated left ventricular diastolic pressure and its waveform are diagnostically significant. Selective angiography may reveal left ventricular enlargement, thickened ventricular walls, and delayed ventricular emptying.
Cardiac Magnetic Resonance Imaging (MRI)
Delayed gadolinium enhancement of the endocardium aids in identifying endocardial fibroelastosis.
Diagnosis
In addition to characteristic clinical features—such as the predominance of congestive heart failure and the age of onset—auxiliary examinations, particularly echocardiography, have significant diagnostic value.
Treatment
Positive inotropic agents, such as digoxin, are effective in controlling heart failure, generally producing favorable responses. The duration of treatment typically extends to about two years. If no contraindications exist, additional medications such as angiotensin-converting enzyme (ACE) inhibitors and beta-blockers may be used depending on the patient’s condition. However, prolonged use of corticosteroids is not recommended.
Prognosis
Without treatment, most patients die before the age of two. The mortality rate is approximately 50% for individuals who develop the condition before six months of age and about 30% for those diagnosed after six months. Patients who respond well to digoxin and adhere to long-term treatment are associated with better outcomes and a potential for recovery.