Introduction

Endomyocardial Fibrosis (EMF) is a disease with unclear causes (also known as idiopathic), often found in economically disadvantaged tropical and subtropical areas.¹ In simple terms, this occurs when the endocardium (innermost layer of the heart) and myocardium (middle muscular layer of the heart) thicken, creating fibrotic tissue in one or both ventricles.¹ This scarring prevents the ventricles from filling up, meaning sufficient blood cannot be pumped to the rest of the body- as a result, EMF is considered an important cause of heart failure in low-income and resource-poor countries, and accounts for up to 20% of heart failure cases in endemic areas of Africa.^1,2 Research demonstrates that the condition’s distribution is most concentrated in low-lying, humid parts of tropical countries, with a poor prognosis.² Unfortunately, detailed cardiovascular research is difficult to carry out in these settings due to a lack of available resources, and therefore, although there are several theories, it is not yet fully understood how EMF happens in the body, or what causes it.²

Epidemiology and Prognosis

EMF is a condition rarely seen outside of tropical areas, mostly affecting impoverished children and young adults in sub-Saharan Africa, equatorial Asia and South America.² There are large clusters seen in Uganda, coastal Mozambique and West Africa, along with widespread occurrences across Congo and Malawi. India’s rainy state of Kerala also has a high prevalence of EMF cases (mostly in coastal areas), as well as the Chinese province of Guangxi. In South America, reports mostly come from Brazil and Colombia. In such areas, the burden of this disease is considerably higher than the global average, with almost 20% of the general population in a rural Mozambique community reported to have EMF. Given that no genetic cause has yet been identified, and the condition is not contagious, such a statistic seems to tie EMF to socioeconomic and environmental factors.³ Despite being a leading cause of cardiomyopathy in the young in these regions, restricted access to quality medical services means that the global burden of EMF is likely to be significantly underreported, with many patients not realising they have it in earlier stages. Advanced stages are mostly identified by specialists in tertiary or referral hospitals, when patients show quite severe structural and haemodynamic complications.⁴ By the time of diagnosis, the average mortality rate after two years is 75%, representing the second leading cause of paediatric admission for acquired heart disease (after rheumatic heart disease).³ EMF prevalence (specifically in Uganda) has a bimodal peak at the ages of 10 and 30, affecting boys and girls equally in childhood; by adulthood, women are affected twice as much as men.

Aetiology, Risk Factors and Burden of Disease

The pathogenesis of EMF is yet to be determined, and greater research is required. Despite this, a number of potential causes have been identified; these include poverty, malnutrition, parasitic infestation, genetics and cluster ethnicity. Due to widespread parasitic infections in endemic countries, it has been suggested that EMF could be linked to an excessive immune response to environmental triggers. This is further supported by increased levels of malaria parasites among a Rwandan community heavily impacted by EMF. However, it is critical to note that correlation does not necessarily lead to causation, and malaria specifically has never had proven links to either myocardial or endocardial damage. Similarly, no concrete evidence attributes environmental or dietary factors to the prevalence of EMF. Despite this, long-term dietary imbalances and poor protein intake are commonly seen in EMF patients.³ Cassava has also been linked to EMF diagnosis rates due to its molecular makeup. This is once again supported by research; improved socioeconomic status and a drop in cassava consumption occurred at a similar time to a decline in EMF rates in Kerala.

As previously outlined, diagnosis is often delayed for EMF patients- this means that complications progress fast after diagnosis, and healthcare systems are often not equipped to treat these. Due to this, rates of EMF are highest in places where resources for cardiac surgery are not readily available.² In Mozambique, for example, roughly 70% of the population lives below the poverty line, and healthcare systems only cover approximately 40% of the population.⁵ This is most likely due to a lack of staff and diagnostic resources (limited echocardiography leads to frequent misdiagnosis)- the social repercussions also lead to a decrease in productivity, and a large economic toll on economically disadvantaged families and fragile health systems. Poor prognosis means that treatment options are mostly palliative, further contributing to the pressure on fragile economic systems.⁵

Neglected Tropical Disease Criteria

Technically, EMF is not classified as a Neglected Tropical Disease (NTD), as it is not caused by a specific pathogen, as far as we know. However, it fulfils many other criteria listed by the WHO, and therefore presents very similarly to an NTD- this criteria involves:⁶

• Prevalence in impoverished, tropical communities
• Large geographical distribution
• Frequently linked to environmental conditions
• Challenging public health control
• Devastating health, social and economic consequences

Summary

Overall, EMF is an idiopathic condition highly prevalent in low-income, tropical regions - most commonly across Africa, Asia and South America. There are numerous theories about what causes it, and research on this gives no definitive answer so far, but contributing factors are likely to be multifactorial and ultimately linked to the socioeconomic background of most patients with the condition. There are severe clinical, economic and health system burdens of EMF on affected regions, and more research and awareness are needed for vulnerable populations to reduce mortality rates, particularly in young people.