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Am J Physiol Heart Circ Physiol 279: H1264-H1273, 2000;
0363-6135/00 $5.00
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Vol. 279, Issue 3, H1264-H1273, September 2000

Efficiency of energy transfer, but not external work, is maximized in stunned myocardium

Serge A. I. P. Trines, Cornelis J. Slager, Joost Van der Moer, Pieter D. Verdouw, and Rob Krams

Experimental Cardiology and Hemodynamics Laboratory, Thoraxcenter, Erasmus University Rotterdam, 3000 DR Rotterdam, The Netherlands

There is no evidence regarding the effect of stunning on maximization of regional myocardial external work (EW) or efficiency of energy transfer (EET) in relation to regional afterload (end-systolic stress, sigma es). To that end, we studied these relationships in both the left anterior descending coronary artery (LADCA) and left circumflex coronary artery regions in anesthetized, open-chest pigs before and after LADCA stunning. In normal myocardium, EET vs. sigma es was maximal at 75.4 (69.7-81.0)%, whereas EW vs. sigma es was submaximal at 12.0 (6.61-17.3) × 102 J/m3. Increasing sigma es increased EW by 18 (10-27)%. Regional myocardial stunning decreased EET (27%) and EW (36%) and caused the myocardium to operate both at maximal EW (EWmax) and at maximal EET (EETmax). EET and EW became also more sensitive to changes in sigma es. In the nonstunned region the situation remained unchanged. Combining the data from before and after stunning, both EWmax and EETmax displayed a positive relationship with contractility. In conclusion, the normal regional myocardium operated at maximal EET rather than at maximal EW. Therefore, additional EW could be recruited by increasing regional afterload. After myocardial stunning, the myocardium operated at both maximal EW and maximal EET, at the cost of increased afterload sensitivity. Contractility was a major determinant of this shift.

stunning; pig; contractility; regional energy


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S. A.I.P. Trines, C. J. Slager, T. A.M. Onderwater, J. M.J. Lamers, P. D. Verdouw, and R. Krams
Oxygen wastage of stunned myocardium in vivo is due to an increased oxygen cost of contractility and a decreased myofibrillar efficiency
Cardiovasc Res, July 1, 2001; 51(1): 122 - 130.
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