Mismatch of Local Blood Flow and Oxidative Metabolism in Stunned Myocardium

U. SCHWANKE, G. HEUSCH, J. D. SCHIPKE¹

Department of Pathophysiology, University of Essen, ¹Department of Surgery, Research Group Experimental Surgery, Heinrich-Heine-University, Düsseldorf, Germany

Received March 20, 2001
Accepted June 8, 2001

Summary
Myocardial blood flow is spatially heterogeneous, reflecting non-uniform oxygen supply. Also, myocardial oxida-tive metabolism is spatially heterogeneous. The effects of acute ischemia and reperfusion on the rela-tionship between local myocardial blood flow (LMF) and oxi-dative metabolism are still unknown. LMF was measured in isolated, blood-perfused rabbit hearts using colored microspheres and oxidation water labeled with ¹⁸O₂ (H₂¹⁸O). Three protocols were performed: ¹⁸O₂-perfusion during normoxia (N; n=7), during early reperfusion (ER; 10 min, n=6), and late reperfusion (LR; 40 min, n=6) following 20 min no-flow ischemia. LMF and local H₂¹⁸O residues were determined within defined myocardial samples (105 ± 15 mg). For interindividual comparison, values were normalized to the mean of the individual experiment and expressed as percentages. LMF ranged from 18 to 193 % (N), 12 to 250 % (ER), and 11 to 180 % (LR). The H₂¹⁸O tissue residue ranged from 63 to 132 % (N), 73 to 142 % (ER) and 32 to 148 % (LR). The correlation between LMF and local oxidative metabolism during N (r=0.77; n=56) was lost in the postischemic heart during ER and LR. LMF during N and ER were only weakly correlated (r=0.24; n=48), whereas LMF during N and LR correlated well (r=0.87; n=48). It is concluded that the heterogeneous LMF pattern at baseline is maintained in the stunned myocardium whereas that of local oxidative metabolism is not. Apart from the established mechanisms underlying myocardial stunning, a mismatch between local flow and oxidative metabolism might also con-tribute.

Key words
Myocardial stunning · Local blood flow · Local oxidative metabolism · Perfusion-metabolism mismatch · Heterogeneity

Reprint requests
JD Schipke, PhD, FESC, Zentrum für Operative Medizin I, Forschungsgruppe Experimentelle Chirurgie, Heinrich-Heine-Universität Düsseldorf, Universitätsstrasse 1, D-40225 Düsseldorf, Germany, e-mail: schipke@umed.uni-duesseldorf.de