Welcome to the Society for Cardiovascular Pathology (SCVP) and Association for the European Cardiovascular Pathology (AECVP) web tutorial on interpreting endomyocardial biopsy findings for cardiac transplant acute cellular rejection. The goal of this tutorial is to educate pathologists on a method of interpretation and on the histopathologic findings one sees on this biopsy material.
This tutorial contains 7 sections covering all aspects of the endomyocardial biopsy. The menu on the left hand side is clickable and can allow the user to move directly to an area of interest. All images can be enlarged by clicking on them (click on the picture to shrink it down). A self-testing quiz using virtual slides of actual cases has been created to make sure you are able to determine cellular rejection and not confuse other histologic findings.
This tutorial has gone through a two-step process of document creation and editing. The members of this committee can be found on the about page and they are solely responsible for the material contained herein. A tutorial focusing on specifically antibody-mediated rejection (AMR) is underway and will not be covered to any great length in this tutorial.
The endomyocardial biopsy
The endomyocardial biopsy (EMB) is an established clinical procedure used for obtaining myocardial tissue. It is typically performed under local anesthesia by passing a bioptome (schematic) through the right internal jugular vein across the tricuspid valve and into the right ventricle. Sampling is usually performed under fluoroscopic (or less commonly echocardiographic) guidance along the interventricular septum.
The most common and established indication for EMB is surveillance of cardiac transplant rejection status, including both cell-mediated and antibody-mediated types. It remains the only method to reliably diagnose cardiac rejection. The surveillance generally results in numerous biopsies, according to each transplant center's established protocol, especially within the first few months of transplant, which then trail off based on the individual style of the institution.
How to process a biopsy
Number of samples to obtain: The International Society for Heart and Lung Transplantation (ISHLT) recommendations are to obtain a minimum of 3 right ventricular samples to appropriately assess for transplant rejection; however increasing to 5 samples has been shown to improve sensitivity. Of note, these samples should be independently collected and not divided after procurement to increase the sample size.
Manipulation of tissue: The cardiolgy team should remove the specimen off the biopsy catheter with a needle and place it on gauze soaked in isotonic saline. The specimen should be minimally handled after procurement and should not be manipulated with forceps.
Processing of tissues: For assessing transplant rejection, the biopsy material should be immediately stored in 10% neutral buffered formalin. The specimen can then be embedded in paraffin, sectioned and stained according to established laboratory protocols. Depending on institution-specific laboratory protocols, immunofluorescence studies may be used to help monitor for antibody-mediated rejection. One additional sample should be snap frozen if immunofluorescence is planned.
Slides to Process: Most institutions generate 3 or 4 slides containing at least three 3-5um sections stained with H&E. Some institutions put up to 8 sections on a single slide. The important point is that to adequately evaluate the rejection process, a minimum of 10 sections should be viewed, on however many slides an institution chooses to use.
Ancillary studies: C4d immunofluorescence or immunohistochemistry is frequently ordered concurrently with the initial H&E sections to help assess the biopsy sample for changes of antibody-mediated rejection. Some institutions routinely use CD68 (a histiocyte marker) or C3d as part of their investigation of AMR. AMR will be covered extensively in a separate tutorial.
An adequate sample should consist of at least 3 fragments, containing at least 50% myocardium. If insufficient tissue appears to be present, assessing the block to ensure that it was adequately effaced is an important first step. Patients being assessed for rejection often have multiple biopsies. For mechanical reasons the bioptome tends to sample the same region of the ventricle. Therefore it is very likely to sample areas with fibrosis, fat infiltration etc. and it is quite common to see granulation tissue or scar formation from a previously sampled biopsy site. Cardiologists who have performed numerous biopsies become familiar with the color and texture of the biopsies and can differentiate myocardium from thrombus or scar.
What to do with an inadequate biopsy:
1. Assess the specimens for rejection, if cell- or antibody-mediated rejection is present, it should be reported regardless of the sample size.
2. If the specimen does not meet criteria for adequacy, and shows no rejection, a comment can be made that describes the inadequacy and the possibility of a false-negative result.
The pathology report should be concise and standardized to efficiently convey the relevant information to the patient's care provider (typically the treating cardiologist). In addition to the presence or absence of rejection, a complete diagnosis can include the number of specimens evaluated (as well as the number involved by rejection), the presence of Quilty lesions, as well as indicating whether features of infection or ischemia were present.
An example template for formatting of pathology reports is provided here.
The information on the Society for Cardiovascular Pathology's Web Site is provided with the understanding that the Society is not rendering medical advice, or recommendations. You should not rely on any information in the text files, messages, bulletin boards or articles on these pages to replace consultations with qualified health care professionals to meet your individual medical needs.