The spectrum of macrophage-predominant inflammatory myocardial disease presenting as fulminant heart failure.

BACKGROUND

Endomyocardial biopsy results are integral for diagnosis and management of myocarditis. Current diagnostic classifications of myocarditis are based on the microscopic and immunochemical characterization of inflammation do not include monocyte/macrophage-predominant (i.e. "histiocytic") myocarditis as a histologic subtype.

METHODS

Endomyocardial biopsies from 6 patients with sudden heart failure were reviewed by 3 cardiac pathologists. Routine stains and immunostains to identify T cells and monocytes/macrophages, complement C4d, and endothelium were applied. Electron microscopy was performed in 2 cases.

RESULTS

The 6 patients included 2 with diagnoses of systemic lupus erythematosus (SLE) and 4 without known disease. Microscopy showed space-occupying inflammation in 2 cases and interstitial inflammation in 4. No giant cell myocarditis or eosinophilic myocarditis was found. Immunostains showed infiltration predominantly by macrophages and/or monocytes with markedly fewer T cells. In 4 of 6 cases necrotic cells were immunopositive for complement C4d. Monocytes we identified immunochemically within the microvasculature in 5 cases and by electron microscopy in 2. Patients with SLE had microvascular C4d positivity or interstitial/sarcolemmal staining. Clinical outcomes ranged from spontaneous resolution to persistent heart failure requiring an internal cardioverter/defibrillator.

CONCLUSIONS

(1) Heart failure with CD68 predominant inflammation ("histiocytic" myocardial inflammatory disease, HMID) occurs with variable clinical presentation and outcome; (2) HMID may be primary or secondary; (3) some cases of HMID show features suggestive of antibody and/or complement mediated myocardial injury, and (4) HMID is a diagnosis distinct from those in classification systems currently in use.