Background/Aims: The diagnostic value of endomyocardial biopsies (EMBs) for numerous cardiac disorders including myocarditis, cardiomyopathies, cardiotoxicity, amyloidosis and other storage disorders is undisputed. EMB remains the gold standard for diagnosing many primary and secondary cardiac conditions and plays a pivotal role in the implementation of therapeutic strategies. Here, we investigated the diagnostic significance of an advanced differential diagnostics from more than 6000 patients with unexplained heart failure.

Methods: In total 6053 initial EMBs from patients with the suspicion of myocarditis, storage disease or unexplained heart failure were retrospectively investigated and classified according to their diagnostic outcome.

Results: Differential diagnostics of 6053 biopsies revealed an incidence of 4.6% (n=277) of acute myocarditis including active myocarditis (n=72), giant cell myocarditis (n=98), sarcoidosis (n=90) and eosinophilic myocarditis (n=17). A large proportion of analyzed EMBs were virus-positive (67.5%, n=4084), of which the majority revealed Parvovirus B19 DNA (93%, n=3798) and other single- or co-infections including human herpes virus 6 (n=692), Epstein-Barr virus (n=125), Coxsackievirus B3 (n=50) and Adenovirus (n=6). Virus-negative inflammatory cardiomyopathy was diagnosed in 14.3% (n=865) of the patients, whereas 7.2% (n=438) of the biopsies were both virus- and inflammation-negative. Finally, 6.4% (n=389) of the patients were diagnosed for storage disorders including AL amyloidosis (n=133) and ATTR amyloidosis (n=247), Morbus Fabry (n=3), lipomatosis (n=4) and heamochromatosis (n=2).