Myocardial ischemic injury derived from multiple thromboemboli due to eosinophilic endomyocarditis (Löffler endocarditis) causing right ventricular rupture

Abstract

To the Editor, Eosinophilic endomyocarditis (EEC) is caused by eosinophil infiltration. EEC is induced by multiple causes such as autoimmune diseases, parasitic infections, malignancies, drug hypersensitivity, and genetic aberrations. EEC with an unidentified cause, referred to as idiopathic hypereosinophilic syndrome (HES), frequently involves the heart and typically presents with congestive heart failure. Here we report the first case of an elderly male who suddenly died of cardiac tamponade due to right ventricle (RV) rupture in association with EEC. A 73‐year old male (height 165 cm, weight 54 kg) was found dead in prone position on the floor, with a large amount of vomitus derived from the last evening. He was a habitual smoker and had a history of hypertension. An autopsy revealed approximately 400 mL of pericardial blood, and a peri‐apical epicardial hemorrhage due to RV rupture in the heart (weighed 415 g). The cardiac sections showed transmural hemorrhage, indicating the pathway of rupture in the septal border of the RV posterior wall (Figure 1a, arrows). The epicardial fat was infiltrated with massive hemorrhage, but accompanied neither with macrophage infiltration, hemosiderin deposition, nor findings on vasculitis or oozing from epicardial vessels. Additionally, histology showed pulmonary congestion without hemosiderin‐laden macrophages, indicating acute heart failure. Meanwhile, the vomitus of the last supper indicates well‐being until last evening. These finding support the rapid course from the beginning of the cardiac event to lethal cardiac tamponade. In the left ventricle (LV) anterior wall and the septum, and consequently in the RV wall, we found eosinophil infiltration, and injuries of the endocardium, expanding to the myocardium, as well as overlying thrombi (Figure 1b,c). In the LV endocardial mural thrombi, eosinophils distributed heterogeneously in the background of fibrin fibers and platelets. The lack of organization in the thrombi also support rapid progression of EEC. Eosinophil activation is accompanied with degranulation of major basic protein (MBP). In the LV thrombi, eosinophil degranulation was not evident with hematoxylin–eosin staining, however, immunostaining revealed MBP labeling with intensities varied in each eosinophil (Figure 1d), reflecting different phases of eosinophil degranulation. MBP also labeled endo‐myocardial lining beneath the LV mural thrombus (not shown). These histological findings support diagnosis of EEC in this case. According to histological classification in HES, EEC is classified as the first necrotic stage with eosinophil‐rich myocarditis and endocardial damage, the second thrombotic stage with mural thrombogenesis, and the third fibrotic stage. This case presented the lesions at the first and second stages. Eosinophilic endomyocarditis is caused by diverse etiologies including drug‐allergy, autoimmune disease, neoplasm, parasitic infection, eosinophilic granulomatosis with polyangiitis (EGPA) and genetic aberration. The patient s history presented neither autoimmune disease, neoplasm, drug‐allergy, nor parasite infection. Autopsy identified neither tumors nor pneumonia or other non‐cardiac infections. In addition to findings of EEC, multiple thrombi were found in the small intramural coronary arteries, but not the large epicardial coronary arteries, in the free wall, anterior‐septum, and posterior‐ septum (Figure 1a,e) of the RV, which would have been derived from the LV mural thrombi. We found multiple small foci of myocardial contraction band necrosis around the thrombosed arteries (not shown), possibly due to ischemia(–reperfusion). We did not find low absorption area in the brain CT, but could not exclude small brain infarction, as we did not examine brain histology. Additionally, we cannot exclude the possibility of micro‐emboli in the other organs, though we performed macroscopic and conventional histological examinations, and found no obvious thromboembolism and infarction in the other organs.