Catecholamines and basal metabolism in the myocardium
Blood-based cardioplegia used to arrest the heart for cardiac surgery has elevated levels of endogenous catecholamines. However, myocardial exposure to catecholamines in cardioplegia may increase basal metabolism, or oxygen consumption (MVO$\sb2),$ in the arrested myocardium and contribute to poor p...
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| Format: | Dissertation |
| Language: | English |
| Published: |
ProQuest Dissertations & Theses
01-01-1998
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| Online Access: | Get full text |
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| Summary: | Blood-based cardioplegia used to arrest the heart for cardiac surgery has elevated levels of endogenous catecholamines. However, myocardial exposure to catecholamines in cardioplegia may increase basal metabolism, or oxygen consumption (MVO$\sb2),$ in the arrested myocardium and contribute to poor post-ischemic functional recovery. Isolated rabbit hearts (n = 5) were perfusion-arrested at $37\sp\circ$C with 20 mM K$\sp+$ Krebs-Henseleit buffer and exposed to 25 nM isoproterenol (Iso), which resulted in a significant increase in basal MVO$\sb2$ (0.054 $\pm$ 0.006 to 0.088 $\pm$ 0.009 mL O$\sb2$/min/g DW; p = 0.0009). Hearts exposed to 25 nM Iso in cardioplegia followed by 60 min of normothermic $(37\sp\circ$C) ischemia and then reperfusion, demonstrated a significant increase in diastolic pressure compared to control ($-$21.8 $\pm$ 3.0 mmHg vs. $-$12.5 $\pm$ 2.0 mmHg; p = 0.02). Hypothermia $(20\sp\circ$C) during ischemia prevented the deleterious effects of Iso. Furthermore, exposure of the beating myocardium to catecholamines prior to arrest was shown to be deleterious to post-ischemic functional recovery of systolic, diastolic, and developed pressures, which was again prevented by hypothermia during ischemia (p $<$ 0.01). End-reperfusion myocardial ADP, ATP, and total adenine nucleotide concentrations were significantly (p $\le$ 0.0002) better preserved in the hypothermia group. |
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| ISBN: | 9780612340855 0612340856 |