Mechanism of changes of the collagen matrix of reperfused myocardium in donor heart preservation.

Isolated canine hearts were preserved for 6 hours at 5 degrees C followed by normothermic reperfusion for 2 hours. Dogs were divided into two groups: group I (group Ia [n = 7] and group Ib [n = 3] with the left ventricle unloaded during reperfusion) received a preservation solution containing potassium (20 mmol/L), and group II (n = 9) received University of Wisconsin solution. Left ventricular diastolic function was better preserved in group II. Degradation and loss of the collagen network during reperfusion, as assessed by scanning electron microscopy, were more extensive and significantly more frequent in group Ia than in group II (6/7 versus 2/9; p < 0.05). Furthermore, extensive disruption of the collagen network was significantly more prevalent in hearts with a left ventricular end-diastolic pressure of more than 20 mm Hg than in hearts with a left ventricular end-diastolic pressure of less than 20 mm Hg (8/10 versus 0/6; p < 0.05), and no disruption of the collagen network occurred in group Ib, regardless of the type of preservation solution. These results suggest that the greatest disruption is caused by barotrauma resulting from an elevated left ventricular end-diastolic pressure after ventricular dysfunction caused by ischemic reperfusion injury.