Endomyocardial Fibrosis

Endomyocardial fibrosis is a genuinely distinct route into restrictive cardiomyopathy — not myocardial infiltration, not intracellular storage, but disease of the endocardium itself. Recognizing it as mechanistically separate matters practically, since the diagnostic pattern, the natural history, and — in its eosinophilic form — the treatment window are all genuinely different from the other RCM causes covered elsewhere in this section.

Where EMF Sits in the Classification

The current ESC framework organizes restrictive heart disease into three mechanistic categories: intrinsic myocyte dysfunction (genetic sarcomeric, cytoskeletal, and storage disease), myocardial extracellular matrix disorders (amyloidosis, sarcoidosis, hyperoxaluria), and endomyocardial disorders — the category EMF belongs to, alongside Löffler endocarditis, carcinoid heart disease, endocardial fibroelastosis, endocardial neoplasms, and iatrogenic or drug-related toxicity. This third category is defined by disease of the endocardium specifically — the innermost layer lining the ventricular cavity — rather than the myocardium or its interstitium, and this distinction is exactly why EMF’s echocardiographic signature (thickened, obliterated endocardial surfaces with preserved underlying systolic function) looks genuinely different from amyloid’s diffuse interstitial infiltration or HCM’s true myocyte hypertrophy.

Two Genuinely Different Diseases, One Shared Endpoint

EMF isn’t a single entity — it splits into two forms with different epidemiology, different associated findings, and a different relationship to eosinophils, even though both converge on a similar restrictive, endocardially mediated phenotype.

Endomyocardial Fibrosis Without Hypereosinophilia

Endemic in tropical and subtropical regions — Africa, India, Asia, and South and Central America — and rare outside them. Typically affects adolescents and young adults, with an insidious onset progressing to biventricular heart failure and a historically high mortality rate. It remains a significant cause of cardiovascular death in the second and third decades of life in endemic regions. Acquired forms outside the classic tropical pattern have also been linked to parasitic infection, certain drugs, inflammatory conditions, and nutritional factors.

Löffler Endocarditis (Eosinophilic Endomyocardial Disease)

Occurs in the setting of hypereosinophilic syndrome — an elevated eosinophil count (conventionally over 1,500 cells/µL) without another explanation, with multi-organ involvement including the heart. In its earlier stages this overlaps with eosinophilic myocarditis, which shares the same LV hypokinesis-with-apical-thrombus pattern before progressing to the fibrotic, restrictive phenotype described here. Unlike classic tropical EMF, this form occurs worldwide and is directly tied to the underlying eosinophilic disorder, which genuinely changes management: early disease may respond to corticosteroids, with chemotherapy and the tyrosine kinase inhibitor imatinib as further options, while surgical removal of fibrotic plaques is reserved for late, established cases.

Disease Progression: Three Stages Worth Knowing Explicitly

The pathophysiology unfolds in a recognizable sequence, and understanding it explains why the echocardiographic appearance — and the treatment window — genuinely changes over the course of disease rather than simply worsening in severity:

1. Early stage: eosinophil degranulation causes direct endocardial necrosis.
2. Intermediate stage: thrombus forms over the damaged, necrotic endocardial surface.
3. Late stage: progressive fibrotic replacement of the endocardium produces the restrictive physiology and ventricular dysfunction that define the established disease.

This sequence matters clinically: the early, necrotic and thrombotic phase is where corticosteroid therapy has the most to offer in the eosinophilic form, while the late, fibrotic phase is largely fixed and mechanical, better addressed (if at all) surgically.

Echocardiographic Features

2D Imaging

• Apical obliteration: endocardial thickening involving the inflow and apical portions of both ventricles — genuinely bilateral in classic disease, not confined to one chamber. The apex can appear foreshortened or entirely filled in, rather than tapering normally to a point.
• Postero-basal LV thickening, a specific pattern worth looking for deliberately, since it directly limits posterior mitral leaflet motion — producing regurgitation through restriction and tethering of an otherwise structurally intact leaflet, not primary valve disease.
• Layered (laminated) thrombus frequently fills the obliterated apices of one or both ventricles — a genuinely characteristic finding, worth specifically describing as laminated rather than simply “thrombus present,” since the layered appearance reflects the staged, progressive nature of the underlying disease.
• Systolic function is usually preserved, even as the endocardial process severely restricts diastolic filling — a genuine point of contrast with amyloidosis, where longitudinal systolic dysfunction is typically present early. In EMF, it’s specifically the restrictive filling, not contractile failure, that dominates the clinical and echocardiographic picture through most of the disease course.
• Biatrial enlargement, reflecting chronically elevated filling pressure from the restrictive endocardial process — see Evaluation of the Left Atrium for the broader atrial assessment framework this builds on.

Valve Involvement

Fibrous endocardial lesions in the RV and/or LV inflow tract commonly produce atrioventricular valve regurgitation as a direct mechanical consequence — not from primary leaflet pathology, but from the subvalvular apparatus and leaflet mobility being physically restricted by the underlying fibrotic process. See Mitral Regurgitation for the general severity-grading approach, which still applies once this mechanism is recognized. The degree of regurgitation can be genuinely severe and is itself a significant contributor to the clinical heart failure picture, independent of the restrictive filling itself.

Doppler Findings

The expected pattern reflects severe restrictive physiology from endocardial — rather than myocardial — disease:

• Restrictive mitral inflow, with a markedly E-dominant pattern (predominant early filling, reduced atrial contribution), shortened deceleration time, and an elevated E/e′ ratio indicating high filling pressure.
• A representative illustrative pattern in Löffler endocarditis specifically: predominant early (E-dominant) mitral filling; reduced tissue Doppler annular velocities in both systole and diastole — genuinely useful, since reduced systolic (not just diastolic) tissue velocity is a less commonly emphasized but real finding here; diastolic-only forward hepatic vein flow; and a dilated IVC without respiratory variation — together reflecting markedly elevated right atrial pressure from truly biventricular diastolic dysfunction, not an isolated left- or right-sided process.

Clinical Picture by Ventricular Predominance

The symptom pattern follows directly from which ventricle’s inflow and apex are most affected, though biventricular involvement — with mixed pulmonary and systemic congestive symptoms — is common in established disease:

• Left-sided predominance: symptoms of pulmonary congestion dominate.
• Right-sided predominance: systemic venous congestion — hepatomegaly, ascites, and peripheral edema — dominates, and this pattern is classically emphasized in tropical EMF specifically. See Evaluation of the Right Ventricle for the standard assessment approach this builds on.
• Biventricular involvement: a mixed picture of both pulmonary and systemic congestive symptoms, reflecting the genuinely bilateral endocardial process described above.

Endocardial Fibroelastosis: A Distinct Entity Worth Naming Separately

Though related in mechanism (both are endomyocardial disorders producing a restrictive phenotype), endocardial fibroelastosis is not simply a synonym for classic tropical EMF and deserves its own recognition. It’s an important cause of heart failure specifically in tropical Africa, with fibrosis characteristically involving the LV and RV apices and extending to the chordae tendineae, the posterior mitral leaflet, and the tricuspid valve. Surgical removal of the fibrotic lesions, with valve repair where needed, is technically possible, but outcomes remain poor — worth setting realistic expectations around, in contrast to the more genuinely treatable early, eosinophilic form of EMF above.

Complications

• Severe atrioventricular valve regurgitation, from the mechanical tethering described above, often requiring its own independent management consideration.
• Thromboembolism, systemic or pulmonary, from the laminated apical thrombus characteristic of this disease — a genuine, active risk given how commonly thrombus accumulates in the obliterated apices.
• Progressive heart failure, predominantly diastolic through much of the disease course, though systolic involvement can emerge in advanced, fibrotic-stage disease.
• Atrial fibrillation, from the biatrial enlargement that accompanies chronically elevated filling pressure.

How to Diagnose It: A Practical Sequence

1. Consider the epidemiologic and clinical context first — tropical or subtropical residence or origin, young age, and an insidious course point toward classic EMF; an elevated eosinophil count and multi-organ involvement point toward Löffler endocarditis specifically, and should prompt a hematology workup alongside the echo.
2. Look specifically at the ventricular apices and inflow tracts in multiple views, assessing for obliteration, thickening, and — characteristically — laminated thrombus, rather than relying on a single standard apical window alone, since apical pathology is easy to underappreciate without deliberate attention.
3. Assess the posterior mitral leaflet and subvalvular apparatus specifically for restriction from postero-basal thickening, and grade any resulting regurgitation.
4. Confirm the restrictive Doppler pattern — markedly E-dominant inflow, shortened deceleration time, elevated E/e′ — and, where feasible, the hepatic vein and IVC findings described above for a fuller hemodynamic picture.
5. Confirm systolic function is preserved — a genuine point of distinction from more advanced amyloidosis and from most other causes of a severely restrictive picture, and worth stating explicitly in the report rather than assuming reduced EF given the severity of diastolic findings.
6. Assess both atria for the degree of enlargement, and screen for atrial fibrillation given how commonly it accompanies this degree of atrial remodeling.
7. If hypereosinophilic syndrome is suspected, recognize that the disease stage (necrotic/thrombotic versus fibrotic) genuinely affects treatment options — early recognition matters more here than in the classic tropical form, since it’s the one setting where medical therapy can meaningfully alter the disease course before fibrosis becomes fixed.

Clinical Importance

EMF’s real diagnostic value lies in recognizing it as a genuinely distinct mechanism — endocardial, not myocardial or interstitial — which explains almost everything else about how it looks and behaves on echo: preserved systolic function despite severe restriction, laminated apical thrombus rather than diffuse wall thickening, and valve regurgitation from mechanical tethering rather than primary leaflet disease. Within that mechanism, the further split between the tropical, non-eosinophilic form and Löffler endocarditis is what actually determines whether a patient has a genuinely treatable early disease or an established, largely mechanical process — a distinction worth making explicitly rather than treating “endomyocardial fibrosis” as a single endpoint.