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Abstract
The purpose of this study was to (1) relate myocardial high-energy phosphate stores
to functional recovery after ischemia and reperfusion, (2) assess the bioenergetics
and functional influence of clinically relevant myocardial hypothermia, and (3) examine
tissue pH as an independent indicator of postischemic recovery of function. Rabbit
hearts were perfused via a modified Langendorff technique, monitored for developed
pressure (DP) and left ventricular end-diastolic pressure (LVEDP) via an isovolumic
left ventricular balloon catheter, and placed in a Brucker NMR magnet (4.7 tesla)
to measure phosphocreatine (PCr), adenosine triphosphate (ATP), and pH. Hearts underwent
1 hour of global ischemia at 7 °, 17 °, 27 ° and 37 °C initiated by one dose of K+ cardioplegia followed by 30 minutes of reperfusion. After reperfusion, DP (expressed
as a percentage of preischemic control) and LVEDP (mm Hg) in 7 ° and 17 °C hearts
were no different (96 + 5% vs 97 ± 3%; 5 ± 2 mm Hg vs 6 ± 2 mm Hg; p = NS), but were
better (p < 0.01) than 27 ° hearts (72 ± 6%, 17 ± 6 mm Hg) and 37 ° hearts (31 ± 7%,
60 ± 6 mm Hg). PCr was severely depleted in all groups. ATP was 90 ± 7% and 87 ± 5%
of preischemic control in the 7 ° and 17 ° hearts, which was significantly better
than the 68 ± 3% and 21 ± 3% in the 27 ° and 37 ° groups (p < 0.01). The pH at end
ischemia was 6.83, 6.89, 6.54, and 5.86 for the 7 °, 17 °, 27 °, and 37 ° hearts,
respectively (7 ° vs 27 ° or 37 °, p < 0.01; 17 ° vs 27 ° or 37 °, p < 0.01). Linear
regression of DP on end-ischemic ATP (EIATP) and end-ischemic pH revealed: DP = 0.96
(EIATP) + 20 (r = 0.92) and DP = 60 (pH) −317 (r = 0.86). We conclude that (1) end-ischemic
ATP predicts recovery of ventricular function, and, furthermore, there appears a threshold
ATP concentration (80% of control) below which full recovery of function will not
occur; (2) end-ischemic pH predicts recovery of ventricular function; (3) 7 °C hypothermic
ischemia does not cause a clinically significant cold injury; and (4) in a single-dose
crystalloid cardioplegia model, end-ischemic pH is linearly related to recovery of
function (r = 0.86).
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Article info
Publication history
Accepted:
February 8,
1988
Identification
Copyright
© 1989 Published by Elsevier Inc.
