A number of artefacts may be seen in endomyocardial biopsies. The more important of these are illustrated below. These artifacts may be misinterpreted by the unwary as being significant pathologies even though they are not.
When endomyocardial biopsies are taken and placed into formalin they must be handled gently to prevent crush artefact occurring. But however gently they are treated, myocyte retraction is inevitable because the biopsy is, by definition, at a cut edge of myocardium. The banding is worsened if the fixative is chilled rather than at room temperature. The Z bands become thickened and the sarcomeres become hypercontracted but myofibrils remain intact. The result is contraction banding. This is commonly observed and is often extensive, but is not of pathologic significance.
Contraction banding must be differentiated from contraction band necrosis/ myocytolysis, seen in post-operative/post-intervention reperfusion injury, in patients on high inotrope therapy in a wide range of clinical circumstances and in the hearts of donors who have died from intra-cranial haemorrhage This form of necrosis affects single cells or small groups of cells surrounded by normal-appearing myocardium. The Z bands linking individual myocytes are broken up. Sarcomeric myofibrils fragment and take on a granular basophilic hue often because of mineralization due to intracellular deposition of calcium.
Telescoping of blood vessels
A common artefact intrinsic to the biopsy tissue is "telescoping" of arteriolar vessels due to the elastic recoil of the media that occurs when the bioptome cuts and pulls the biopsy from the septum. The vessel recoils into itself and the resulting appearance can mislead the unwary to misinterpret it as small-vessel cardiac allograft vasculopathy (CAV) as the lumen is inevitably occluded in the process. However, close inspection, aided by a connective tissue stain, such as Miller's Elastic Van Gieson stain, shows a normal intima and clearly outlines the internal and external elastic lamina of the vessel wall.
Telescoping is of no clinical significance but simply reflects the site of the biopsy - close to the interventricular septum where small penetrating branches of left anterior descending coronary artery may be inadvertently biopsied. However CAV may be diagnosed very occasionally by this route so close checking of vessel architecture is recommended!
Occasionally the procurement of biopsy pieces can cause tissue hemorrhage. Unlike the hemorrhage seen in severe rejection (Grade 3R), this hemorrhage typically is not associated with marked inflammation or tissue edema.
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