Factors affecting the development of contraction band necrosis during reperfusion of the isolated isovolumic rat heart.

The effects of time, oxygen availability and transmural fibre location on the post-ischaemic development of contraction-band necrosis was investigated in isolated isovolumic rat hearts. Anoxic reperfusion after 60 min of total ischaemia was associated with the slow development of contraction bands (8% of myocytes affected after 20 min), particularly in the circumferentially oriented mid-myocardial muscle fibres. This could be completely prevented by the presence of 3 mM amytal. Oxygenated reperfusion caused a rapid development of contraction bands (6% of myocytes affected after 5 mins) which was significantly (P less than 0.05) increased to 18% of cells affected by 20 mins reoxygenation. The mid-myocardium always contained the greatest number of contraction bands with up to 46% of cells involved after 20 mins of oxygenated reperfusion. In all groups many cells were observed to have disrupted sarcolemmae irrespective of the presence or absence of contraction bands. The predominance of contraction bands in the constrictor muscles encircling the heart suggests that their formation may be influenced by the tension or strain imposed upon myocardial fibres during the ischaemic episodes.