Progressive loss of perfusion-contraction matching during sustained moderate ischemia in pigs

Abstract

It is unclear whether perfusion-contraction matching (PCM) is maintained during prolonged myocardial ischemia. In 27 anesthetized pigs, left anterior descending coronary arterial inflow was reduced to decrease an anterior work index (WI) at 5 min of hypoperfusion by 40% and then maintained at this level for 12 or 24 h. With 12 h of hypoperfusion, the myocardium remained viable in 6 of 7 pigs (with triphenyltetrazolium chloride; TTC) and with 24 h of hypoperfusion in 5 of 11 pigs (TTC, histology). The reduction in WI to 62 ± 4 and 62 ± 3% of baseline in the two groups was matched to the reduction of transmural blood flow (TBF; microspheres) at 5 min of hypoperfusion, averaging 59 ± 4 and 60 ± 2% of baseline. With prolonged hypoperfusion, WI decreased to 30 ± 5% at 12 h and 18 ± 3% at 24 h; TBF remained unchanged (53 ± 4 and 54 ± 4%). The added calcium concentration required for the half-maximal increase in WI increased from 121 ± 25 μg/ml blood at baseline to 192 ± 26 μg/ml blood at 12 h of hypoperfusion. Thus, with hypoperfusion for 24 h, PCM is progressively lost, and calcium responsiveness is reduced.