Recent advances in microscopic diagnosis of cardiomyopathies.

A substantial proportion of cardiomyopathies (CMP) harbour non-specific microscopic findings and the diagnosis is based on the clinical phenotype. Therefore a majority of dilated and hypertrophic CMP are encountered by a pathologist as explanted hearts or during autopsy. The indication for the endomyocardial biopsy usually follows clinical suspicion for infiltrative disease and plays an important role in paediatric patients, where the metabolic CMP are more frequent. Due to suggestive microscopic appearance of these diseases, a histopathological examination represents an important part of the diagnostic algorithm. The biopsy is relevant especially in case of restrictive CMP, because this disease is often caused by amyloid depositions. In case of hypertrophic CMP, the endomyocardial biopsy is considered usually in paediatric population since the majority of storage and mitochondrial disorders manifest hypertrophic phenotype. Diagnosis of dilated CMP is based on the clinical grounds and the main task for the pathologist is to rule out myocarditis.