© 2004 by European Society of Cardiology
Copyright © 2004, European Society of Cardiology
Mechanoenergetic inefficiency in the septic left ventricle is due to enhanced oxygen requirements for excitation–contraction coupling
aDepartment of Digestive Surgery, University Hospital North Norway, Sykehusveien 38, N-9038 Tromsø, Norway
bDepartment of Cardiothoracic and Vascular Surgery, University Hospital North Norway, N-9038 Tromsø, Norway
cDepartment of Clinical Chemistry, University Hospital North Norway, N-9038 Tromsø, Norway
* Corresponding author. Tel.: +47-776-26000; fax: +47-776-26605. Email address: ebrahim.aghajani{at}fagmed.uit.no
Objective: Myocardial oxygen consumption (MVO2) in the septic myocardium is increased despite reduced left ventricular mechanical work. We investigated the mechanism behind this energetic inefficiency in the septic myocardium. Methods: To clarify whether energy consumption in basal metabolism or excitation–contraction (EC) coupling is elevated in the septic myocardium, we separated MVO2 used for these two processes. We assessed hemodynamics, left ventricular pressure–volume area, left ventricular MVO2, myocardial substrate metabolism and the inflammatory response in eight control pigs and in eight septic pigs receiving E. coli endotoxin. Using cardiopulmonary bypass (CPB), unloaded MVO2 was assessed before and after arrest of electromechanical activity using KCl infusions. Results: Unloaded MVO2 was significantly higher in the septic group compared to the control group (65.7±12.9 vs. 43.3±15.1 J·min–1·100 g LV–1, p<0.005), but basal MVO2 after 5 min KCl arrest was equal in the two groups. No difference in mechanical energy consumption or substrate metabolism was observed between groups. Conclusion: Basal MVO2 in the septic myocardium is not elevated, but an increased MVO2 for EC coupling is responsible for the energetic inefficiency.
KEYWORDS Endotoxins; Hemodynamics; Oxygen consumption; EC coupling; Septic shock