Endocardite à éosinophiles de Löffler

What is Löffler's eosinophilic endocarditis?

Also known as eosinophilic endomyocardial fibrosis, Löffler's eosinophilic endocarditis involves eosinophilic myocarditis, endomyocardial fibrosis, thromboembolism, and acute heart failure.

It was first described in 1936 when Löffler reported a very rare syndrome of eosinophilia, active carditis and multi-organ involvement.¹

Löffler's eosinophilic endocarditis is a rare manifestation of prolonged hypereosinophilia. There are three stages:²

• Acute necrotic stage: eosinophilic infiltration into cardiac tissues leads to endomyocardial inflammation and necrosis (occurring in the first 4-8 weeks).

• Thrombotic stage: endothelial damage leads to mural thrombi formation, often involving both ventricles, the ventricular outflow tracts, and the subvalvular regions (occurring after about 10 months).

• Fibrotic stage: thrombi are replaced by fibrosis, leading to a restrictive cardiomyopathy and sometimes valvular incompetence (occurring after 1 to 2 years).

NB: Löffler's syndrome is different. It is a transient respiratory illness with eosinophilia and shadowing on chest X-ray, usually due to parasitic infestation.

Causes of Löffler's eosinophilic endocarditis (aetiology)³

Löffler's eosinophilic endocarditis is caused by eosinophilic infiltration of cardiac tissues, itself occurring due to a hypereosinophilic state. This is commonly idiopathic (idiopathic hypereosinophilic syndrome).

Parmi les autres causes, on peut citer

• Primary hypereosinophilic syndrome (due to a myeloproliferative cause, such as leukaemias and lymphomas).

• Secondary hypereosinophilias, such as those caused by:

  • Allergie.

  • Parasitic infections.

  • Fungal infections.

  • Other malignancies.

Symptoms of Löffler's eosinophilic endocarditis (presentation)²

• Löffler's eosinophilic endocarditis may present with signs and symptoms of heart failure, intracardiac thrombi, myocardial ischaemia, arrhythmias, and, rarely, pericarditis.

• Symptoms may include dyspnoea, chest pain, cough, and palpitations.

• The physical findings are those of heart failure:
  

  • Peripheral oedema and elevated jugular venous pressure

  • Tachycardie

  • Cardiomegaly may precede signs of heart failure

  • There may be a murmur of mitral regurgitation as described in mitral valve disease

  • The gallop of a 3rd heart sound may be heard and possibly even a 4th heart sound.

• Systemic emboli may cause renal or neurological problems.

• Signs of a restrictive cardiomyopathy may be very similar to those of constrictive pericarditis but the presence of a palpable apex beat and mitral regurgitation suggest cardiomyopathy.

Diagnostic différentiel⁴

Differentials include:

• Syndrome de Churg et Strauss.

• Giant cell myocarditis.

• Medication-induced hypersensitivity reactions.

• Tropical endomyocardial fibrosis.

Diagnosing Löffler's eosinophilic endocarditis (investigations) ^{2 4}

• Full blood count will show marked eosinophilia - at least 0.44 x 10⁹/l.

• Electrocardiographic (ECG) findings are typically non-specific, such as T wave inversions, left atrial enlargement, left ventricular hypertrophy, incomplete right bundle branch block, and left axis deviation.

• Echocardiography may show left ventricular hypertrophy, endomyocardial thickening, bilateral ventricular apical thrombi, and posterior mitral valve cusp involvement.

• Cardiac MRI is a very useful non-invasive test. It may demonstrate ventricular thrombi and myocardial fibrosis and inflammation.

• An endomyocardial biopsy remains the gold standard diagnostic test, but non-invasive tests (such as cardiac MRI) are generally preferred.

Management of Löffler's eosinophilic endocarditis²

• The underlying hypereosinophilic syndrome should be treated as soon as possible.

  • Steroid treatment is usually first-line with hydroxycarbamide used as a second-line agent.

  • Treatment is also guided by the specific aetiology of the hypereosinophilia. For example, myeloproliferative hypereosinophilic syndrome with a FIP1L1-PDGFRA mutation can be treated with imatinib.

• Congestive failure is treated in the usual way with diuretics, digoxin, beta blockers, ACE inhibitors, aldosterone antagonists, and other drugs to reduce afterload.

• Anticoagulation should be started if there is evidence of a mural thrombus.

• Once fibrosis has occurred, surgery may be of benefit:
  

  • Removing fibrosed endocardium may improve elasticity.

  • Mitral valve replacement is the most common surgery performed. Mechanical valve replacements appear to have a high risk of thrombosis, despite anticoagulation; bioprosthetic valves are usually advocated as a result.

• A heart transplant may be considered if there is progressive restrictive cardiomyopathy and/or recurrent valve thrombosis.

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Pronostic^{5 6}

• Prognosis depends on the aetiology of the hypereosinophilia and the severity of the cardiac involvement.

• Generally, though, cardiac involvement in hypereosinophilic syndromes has a poor prognosis, and is associated with high rates of morbidity and mortality.