R. Ferrari et al., METABOLIC ADAPTATION DURING A SEQUENCE OF NO-FLOW AND LOW-FLOW ISCHEMIA - A POSSIBLE TRIGGER FOR HIBERNATION, Circulation, 94(10), 1996, pp. 2587-2596
Background Myocardial hibernation is an adaptive phenomenon occurring
in patients with a history of acute ischemia followed by prolonged hyp
operfusion. Methods and Results We investigated, in isolated rabbit he
art, whether a brief episode of global ischemia followed by hypoperfus
ion maintains viability. Four groups were studied: group 1, 300 minute
s of aerobia; group 2, 240 minutes of total ischemia and 60 minutes of
reperfusion; group 3, 10 minutes of total ischemia, 230 minutes of hy
poperfusion (90% coronary flow reduction), and 60 minutes of reperfusi
on; and group 4, 240 minutes of hypoperfusion followed by reperfusion.
In group 3, viability was maintained. Ten minutes of ischemia caused
quiescence, a fall in interstitial pH (from 7.2+/-0.01 to 6.1+/-0.8),
creatine phosphate (CP), and ATP (from 54.5+/-5.0 and 25.0+/-1.9 to 5.
0+/-1.1 and 15.3+/-2.5 mu mol/g dry wt, P<.01). Subsequent hypoperfusi
on failed to restore contraction and pH but improved CP (from 5.0+/-1.
1 to 20.1+/-3.4, P<.01). Reperfusion restored pH, developed pressure (
to 92.3%), and NAD/NADH and caused a washout of lactate and creatine p
hosphokinase with no alterations of mitochondrial function or oxidativ
e stress. In group 4, hypoperfusion resulted in progressive damage. pH
fell to 6.2+/-0.7, diastolic pressure increased to 34+/-5.6 mm Hg, CP
and ATP became depressed, and oxidative stress occurred. Reperfusion
partially restored cardiac metabolism and function (47%). Conclusions
A brief episode of total ischemia without intermittent reperfusion mai
ntains viability despite prolonged hypoperfusion. This could be mediat
ed by metabolic adaptation, preconditioning, or both.