Introduction

Endomyocardial fibrosis (EMF) is the most common type of restrictive cardiomyopathies. These are conditions in which the walls of the heart become too stiff to expand and fill with enough blood. In endomyocardial fibrosis, the inner linings of the heart (endocardium) and the heart muscle (myocardium) have scar-like tissue buildups. The buildup thickens the heart and makes it less flexible.^1,2,3 

Depending on which part of the world you live in and the country's socio-economic framework, endomyocardial fibrosis can be either one of the rarest or most common forms of heart disease. There is an obvious geographic divide in the prevalence of endomyocardial fibrosis with clusters of cases in poor tropical and sub-tropical regions of Asia, Latin America and Africa, primarily affecting children and adolescents. It is rarely observed in areas outside these endemic zones.^1,2,4 

What causes endomyocardial fibrosis?

The exact cause of EMF is unknown and is a major area of research. However, several risk factors and hypotheses are available to guide our overall understanding.⁵

Risk factors^1,2

• Age: Endomyocardial fibrosis mostly affects children and adolescents
• Gender: More common in boys than girls
• Ethnicity: More common in certain ethnic groups in tropical and subtropical regions
• Low socioeconomic status: Poor nutrition and parasitic infections might initiate the disease process
• Genetic predisposition: A cluster of cases in families is observed, although it is not fully understood
• Autoimmune or inflammatory responses

Proposed causes 

Infectious agents and hypereosinophilia/eosinophil toxins

Parasites, like Schistosoma, Trypanosoma, Wuchereria and Toxocara, release larvae into the bloodstream during infection, or the transmission stage of the parasite's life cycle. The larvae migrate to organs through the bloodstream, triggering the immune system, especially eosinophils, which causes allergic-like responses in the heart. Eosinophils accumulate around the heart and release toxic chemicals like major basic protein and eosinophil cationic protein. These toxins damage the inner lining of the heart and the heart muscles. To heal the damaged lining, specialised cells get recruited to the heart. Instead of regenerating normal heart tissue, these cells lay down dense fibrous tissue that is primarily made from collagen. Fibrous tissues are less flexible and non-contractile, making the lining and muscles of the heart stiff, especially when injuries occur chronically and repeatedly.^5,6,7,8,9 

Other than parasitic infections, hypereosinophilia, an overload of eosinophils, can happen secondary to allergic conditions, inflammatory diseases, medications, cancer, genetic mutations and even without any identifiable cause.^10,11 

Nutritional Factors 

Established low-protein staple foods, like cassava, cause protein deficiency, leading to cardiac cell death and fibrosis. Deficiencies of trace metals and excess radioactive elements in food are also possible factors behind EMF.^1,2  

Autoimmune Reaction

An autoimmune reaction happens when our immune system fails to distinguish between foreign invaders and our own cells. The immune system identifies proteins of the heart as intruders and produces antibodies against them. The caused damage is repaired with fibrous tissue formation.¹

How does it start and progress?

Endomyocardial fibrosis starts with repeated infections, eosinophilia or other environmental triggers that lead to endomyocardial inflammation and damage, particularly in the chambers of the heart. The body tries to patch up the damaged area with fibrous tissue. Symptoms in this stage can be unnoticeable or mimic other heart problems. As inflammation and damage continue or happen repeatedly, fibrous tissue gradually lines the inner walls of the chambers, starting from the bottom tip (apex). More build-up thickens the tissue, leaving less space for blood. Fibrous tissue build-up will also stiffen the heart chambers. These stiff chambers don't expand well enough to fill with blood, and the thickened bottom tip becomes a dead end zone, causing stagnation in the blood flow. The heart chambers’ ability to fill with blood and pump it out is impaired.^5,12,13

What are the symptoms of endomyocardial fibrosis?

Early endomyocardial fibrosis is characterised by subtle, progressive symptoms that often go unrecognised until advanced stages. Key early symptoms include:^2,14

• Shortness of breath during activities (most frequent)
• Cough
• Recurrent fever
• Distended abdomen, stomach pain or discomfort
• Loss of appetite
• Weight loss
• Blueish or dark lips
• Fatigue, low energy, and listlessness

The key signs of advanced heart failure include:^2,14

• Massive abdominal swelling that looks disproportionate to the rest of the child’s body
• Wasting or thinning of muscles
• Swelling in the face and neck
• Severe weight loss of both fat and muscle in the arms and legs, even with a swollen belly
• Stunted growth
• Small testes and a lack of male traits
• Bulging eyes
• Bluish discolouration of lips, tongue and nail beds
• Swelling in different parts of the body 

These advanced symptoms require immediate medical attention.

How can doctors diagnose endomyocardial fibrosis?

Echocardiography (Echo)

The ultrasound of the heart gives a moving image of the heart's structure and function. Doctors can see if the heart has thickened or changed shape, if valves are dysfunctional and if there is fibrous scarring, stiffening and a restrictive filling pattern in the ventricles.^2,15 

Electrocardiogram (ECG/EKG)

It is a simple and painless procedure that measures the electrical activity of the heart. It gives information about the heartbeat rhythm and rate.^1,2 

Heart MRI

It provides a very detailed picture of the heart. It is the best way to visualise the extent of scarring and to see if there is a blood clot and calcium deposition in the heart.^1,2,16 

Chest X-ray

A chest X-ray can show the enlarged heart, fluid accumulation around the heart and lungs, and poor blood flow to the lungs.^1,2 

Blood tests

Blood work checks for general heart failure markers in moderate to advanced stages and looks for high levels of eosinophils in the early stages of EMF.^1,2

Biopsy

In some cases, a small sample of the heart lining may be taken to confirm the presence of fibrosis and inflammation.¹⁷

Treatment options 

Medical Management 

Medical management can temporarily relieve symptoms but doesn’t cure or reverse scarring.¹⁸ 

• In the early inflammatory stage, before the heart is severely scarred, anti-inflammatory (immunosuppressive) therapy can help calm eosinophils¹⁹ 
• Scarring of the heart’s inner lining and slow blood flow can make blood in the heart clot; blood thinners (anticoagulants) help prevent and treat tiny clots entering the blood and block thin blood vessels²⁰ 
• Water pills (diuretics) can remove the excess fluid from the legs and abdomen through urine caused by the leakage of blood vessels¹ 
• Angiotensin-converting enzyme inhibitors are useful to relax the blood vessels and make them wider, so it is easier for the strained heart to push blood through¹ 
• Beta-blockers can correct the strained heart’s fast heart rate and irregular rhythm¹

Surgery 

Surgery is the main treatment for scarring. Surgical treatment primarily involves endocardiectomy combined with atrioventricular valve replacement or repair. Endocardiectomy removes the thick, scarred inner lining of the heart (endocardium) that has become stiff due to fibrosis. Heart valves might be repaired or replaced if damaged. This restores space in the heart and improves blood filling and flow. These corrections relieve symptoms and improve the patient’s quality of life. Unfortunately, it is a high-risk surgery, especially in advanced cases and does not provide a cure beyond symptomatic relief.^2,19,21,22 

Challenges of living with endomyocardial fibrosis

A child with endomyocardial fibrosis needs continuous care and close follow-up. Medications have to be adjusted, and outcomes should be monitored to prevent or treat complications. Such care is often unavailable or inaccessible in rural areas.² Children often arrive at clinics with end-stage disease, when the heart is already severely scarred. By then, medication won’t help much, and surgery becomes risky. At this stage, the chances of death during or after surgery increase, especially in children who are malnourished, cachectic, or in advanced heart failure.¹²

Other challenges include:

• Unknown disease origin - has multiple potential triggers⁵
• Late diagnosis - due to limited access to healthcare, low level of awareness and misdiagnosis due to similar symptoms to other heart conditions²³
• Limited treatment options - no definitive effective therapy available²⁴
• Open-heart surgery - it is the last resort, but it requires highly skilled teams, intensive care units, and long-term follow-up, which are rarely available in endemic regions^1,25

Summary

Endomyocardial fibrosis is a rare heart condition mostly reported from low-income tropical and subtropical regions of Asia, Africa and South America. In this disease, scar tissue builds up on the inner lining of the heart and heart muscle, reducing the heart’s flexibility. It is the most common type of restrictive cardiomyopathies. Surgical intervention appears to be the most promising treatment, potentially increasing survival, especially in advanced heart failure cases, but it also carries a high risk.