Contractile damage from reperfusion after transient ischemia in the dog

The patterns of regional contractile function were examined with ultrasonic crystals in "open-chest" anesthetized dogs. In normal myocardium, the base-line end-diastolic segment length (EDL) was 1.63 +/- 0.12 cm. and the mean systolic length (MSL) was 1.47 +/- 0.17 cm. Mean velocity of shortening over the first one third of systole (V1/3) was 15.9 +/- 2.3 mm. per second. Coronary occlusion induced regional ischemia with segmental dyskinesia (MSL = 1.84 +/- 0.12 cm). Reperfusion after 5 or 10 minutes of occlusion induced rapid recovery of contractile function that was independent of catecholamine release, as demonstrated in animals pretreated with 6-OH dopamine. After initial recovery, however, contractile function deteriorated. There were an increase in EDL (from 1.73 +/- 0.11 to 1.78 +/- 0.11; p less than 0.001) and the appearance of early systolic dyskinesia. V1/3 diminished from 5.6 +/- 4.6 to -6.6 +/- 2.5 mm. per second (p less than 0.005). Thus reperfusion damage, defined as late deterioration after recovery from brief periods of ischemia, may be partly distinct from ischemic damage per se. It is possible that the deterioration of myocardial function which accompanies reperfusion of previously ischemic myocardium may be a contributing factor in the transient myocardial dysfunction that is occasionally seen following cardiopulmonary bypass.