10 DAYS EVOLUTION OF A STUNNED MYOCARDIUM MODEL DUE TO VERY BRIEF ANDREPEATED ISCHEMIAS

Introduction and objectives. In previous studies we have observed isch emic processes of very brief duration (2 minutes) and with brief reper fusion (3 minutes), which have been repeated 20 times (ischemic protoc ol [IP]). They are capable of producing contractile dysfunction of the ischemic tenet with a decrease of 28.6% at 24 hours, and coronary blo od flow maintenance (stunning). Methods. The aim of this study is to e xamine the evolution of this dysfunction. The IP designed in our labor atory was used on 24 adult mongrel dogs. We measured regional myocardi al function using a pair of implanted chronic ultrasonic crystals in t he ischemic area (depending on the left anterior descending coronary a rtery) and a second pair in the control zone (depending an the left ci rcumflex coronary artery). Results. After analyzing results, we found that the shortening fraction decreased to 28.6% (p < 0.05) in 24 hours . During the subsequent five days the shortening fraction decreased to a minimum of 67.88% (p < 0.01), after which there was a progressive r ecovery that reached 18.95% (NS) below the base-line on the tenth da). We did not observe any significant variation in the hemodynamic param eters at any time. Conclusions. The repeated, very brief episodes of i schemia (in the experimental terms that we have explained) produced a contractile dysfunction which reached its maximum on the fifth day, an d returned to normal on the tenth day. We hypothesize that these alter ations could explain the episodes of left ventricular failure with spo ntaneous recuperation observed in stable myocardial ischemia, and for which no immediate cause has been found.