Current role of endomyocardial biopsy in the management of cardiomyopathies

Endomyocardial biopsy remains controversial

In this context the role of endomyocardial biopsy (EMB) in diagnosis and treatment of cardiomyopathies remains controversial (4), and the practice varies widely even among cardiovascular centers. A need for EMB exists because specific myocardial disorders that have unique prognoses and treatment are seldom diagnosed by noninvasive testing (1).

Ardeheli et al. for example evaluated 845 patients with initially unexplained cardiomyopathy who underwent EMB between 1982 and 1997. For each patient, an initial clinical diagnosis, an EMB based diagnosis, and a final diagnosis prior to discharge based on all available data was established. The final diagnosis differed from the initial clinical diagnosis in 264 (31%) of these patients and EMB 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%) or amyloidosis (18%). EMB was more sensitive than clinical diagnosis and proved to be very specific in detecting myocarditis, hemochromatosis and amyloidosis. The conclusion was drawn that in patients with unexplained cardiomyopathy after a standard evaluation, the clinical assessment of the etiology is inaccurate in 31% of patients. EMB establishes the final diagnosis in 75% of these patients with a high degree of specificity.

To define the current role of EMB in the management of cardiovascular disease, a multidisciplinary group of experts in cardiomyopathies and cardiovascular pathology was convened by the American Heart Association (AHA), the American College of Cardiology (ACC), and the European Society of Cardiology (2). This Writing Group was charged with reviewing the published literature on the role of EMB in cardiovascular diseases, summarized this information, and made useful recommendations for clinical practice with classifications of recommendations and levels of evidence for investigation of endomyocardial biopsy. The novel result of this effort is a set of distinct clinical scenarios from which a practical decision to proceed with EMB can be made.

The clinical reason for the biopsy determines how many samples are removed and how they are fixed. In general, at least 2-3 samples are submitted for light microscopic examination, but transmission electron microscopy may also be helpful for the assessment of suspected infiltrative disorders such as amyloidosis, glycogen storage diseases, lysosomal storage diseases, and occasionally viral myocarditis. 2-3 pieces may be snap-frozen at -80°C for molecular studies, immunofluorescence, or immunohistochemistry that may be required for suspected myocarditis, storage diseases, tumor typing, amyloid classification, or viral genome analysis.

Conclusion:

In summary there is the recommendation for EMB in different clinical settings of heart failure including a recommendation for EMB in patients in whom an inflammatory, viral or infiltrative disorder of the heart is suspected. Diagnosis of the causative agent in cardiomyopathies is needed, if more than classic heart failure treatment is intended. In the case of viral persistence in inflammatory DCM, i.v. immunoglobulin treatment or IFN can be adequate choices, in autoreactive myocarditis, immunosuppression could be the option, but all of those therapies should be evaluated in clinical studies or in a post hoc analysis.