title: Endomyocardial biopsy plays a role in diagnosing patients with unexplained cardiomyopathy.
abstract: BACKGROUND
  The etiology of cardiomyopathy is usually inferred from clinical information and preliminary laboratory studies. Patients with unexplained cardiomyopathy may be referred for endomyocardial biopsy (EMBx). It is unknown whether pathological information obtained from EMBx is beneficial or alters the diagnosis established clinically. This study was undertaken to evaluate the utility of EMBx in confirming or excluding a clinically suspected diagnosis.
  
  
  METHODS
  We evaluated 845 patients with initially unexplained cardiomyopathy who underwent EMBx between 1982 and 1997 at The Johns Hopkins Hospital. For each patient, an initial clinical diagnosis, an EMBx diagnosis, and a final diagnosis prior to discharge based on all available data were established.
  
  
  RESULTS
  The final diagnosis differed from the initial clinical diagnosis in 264 (31%) of these patients; EMBx made the diagnosis in 196 (75%) of these cases. Initial diagnoses most frequently altered were myocarditis (34%) and idiopathic cardiomyopathy (25%). Initial diagnoses least likely to be altered were those in which biopsy was used to confirm or grade a previously documented illness, such as hemochromatosis (11%), amyloidosis (18%), or cardiomyopathy secondary to doxorubicin toxicity (0%). EMBx was more sensitive than clinical diagnosis in detecting myocarditis and amyloidosis, and proved to be very specific in detecting ischemic cardiomyopathy, myocarditis, amyloidosis, and hemochromatosis.
  
  
  CONCLUSIONS
  In patients with unexplained cardiomyopathy after a standard evaluation, the clinical assessment of the etiology is inaccurate in 31% of patients. EMBx establishes the final diagnosis in 75% of these patients with a high degree of specificity.
authors.affiliation: Division of Cardiology, Department of Medicine, The Johns Hopkins Hospital, Baltimore, Md, USA. hardehal@jhmi.edu
authors.forename: Hossein
authors.initials: H
authors.lastname: Ardehali
authors.forename: Atif
authors.initials: A
authors.lastname: Qasim
authors.forename: Thomas
authors.initials: T
authors.lastname: Cappola
authors.forename: David
authors.initials: D
authors.lastname: Howard
authors.forename: Ralph
authors.initials: R
authors.lastname: Hruban
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Hare
authors.forename: Kenneth L
authors.initials: KL
authors.lastname: Baughman
authors.forename: Edward K
authors.initials: EK
authors.lastname: Kasper
mesh_terms: D000686:Amyloidosis / Q000473:pathology; D001706:Biopsy; D009202:Cardiomyopathies / Q000145:classification / Q000209:etiology / Q000473:pathology*; D016009:Chi-Square Distribution; D004699:Endocardium / Q000473:pathology*; D006801:Humans; D009205:Myocarditis / Q000473:pathology; D012680:Sensitivity and Specificity