**9. Endomyocardial biopsy**

Myocarditis may be focal or diffuse affecting any or all cardiac chambers. Although biopsy is the gold standard for the diagnosis, it is of limited utility especially in acute myocarditis, because of the patchy nature of active inflammation. In a series of over 2,000 patients with clinically suspected myocarditis, endomyocardial biopsy was only positive in 10% of the cases [48-50]. Given the potential risks of biopsy and the limited value it offers, its use should be limited to the patients with left ventricular dysfunction unresponsive to conventional therapy [51].

The various histologic patterns of myocarditis include either lymphocytic (including viral and autoimmune forms), eosinophilic (in which hypersensitivity myocarditis is the most common, followed by cases of hypereosinophilic syndrome), granulomatous (sarcoid and giant cell myocarditis), neutrophilic (bacterial, fungal, and early forms of viral myocarditis), and reperfusion type/contraction band necrosis (present in catecholamine-induced injury and reperfusion injury). Figure 6 represents the microscopic picture of acute perimyocarditis after diphtheria-tetanus vaccination.

Fig. 6. Right ventricular endomyocardial biopsy. A . Haematoxylin-eosin, original magnification 200x: Diffuse interstitial oedema with scattered inflammatory cells. B. Immunohistochemical staining with anti-CD45 antibody, original magnification 400x: Lymphocyte inflammatory infiltrate associated with myocyte damage. C. Mallory triple stain, original magnification 200x: minimal interstitial fibrosis mixed with interstitial oedema. D. Haematoxylin-eosin, original magnification 200x: One focus of interstitial haemorrhage. Adapted from Journal of Chinese Clinical Medicne;2008,9;Vol.3,No.9. [24]

Myocarditis may be focal or diffuse affecting any or all cardiac chambers. Although biopsy is the gold standard for the diagnosis, it is of limited utility especially in acute myocarditis, because of the patchy nature of active inflammation. In a series of over 2,000 patients with clinically suspected myocarditis, endomyocardial biopsy was only positive in 10% of the cases [48-50]. Given the potential risks of biopsy and the limited value it offers, its use should be limited to the patients with left ventricular dysfunction unresponsive to

The various histologic patterns of myocarditis include either lymphocytic (including viral and autoimmune forms), eosinophilic (in which hypersensitivity myocarditis is the most common, followed by cases of hypereosinophilic syndrome), granulomatous (sarcoid and giant cell myocarditis), neutrophilic (bacterial, fungal, and early forms of viral myocarditis), and reperfusion type/contraction band necrosis (present in catecholamine-induced injury and reperfusion injury). Figure 6 represents the microscopic picture of acute perimyocarditis

Fig. 6. Right ventricular endomyocardial biopsy. A . Haematoxylin-eosin, original magnification 200x: Diffuse interstitial oedema with scattered inflammatory cells. B. Immunohistochemical staining with anti-CD45 antibody, original magnification 400x: Lymphocyte inflammatory infiltrate associated with myocyte damage. C. Mallory triple stain, original magnification 200x: minimal interstitial fibrosis mixed with interstitial oedema. D. Haematoxylin-eosin, original magnification 200x: One focus of interstitial haemorrhage. Adapted from Journal of Chinese Clinical Medicne;2008,9;Vol.3,No.9. [24]

**9. Endomyocardial biopsy** 

conventional therapy [51].

after diphtheria-tetanus vaccination.
