Abstract 9841: Expression of Mitochondrial Fusion Proteins is Increased in Hibernating Hearts Following Bypass Surgery
Background: Based on clinical studies, regional function within hibernating myocardium may not return to normal immediately following successful bypass surgery (CABG). We hypothesized that the mitochondrial proteome within chronically ischemic hibernating hearts does not fully recover early post-CABG and may in part, contribute to submaximal myocardial oxygen expenditure.
Methods: Twelve pigs underwent thoracotomy with placement of a constrictor around the LAD artery and had reduced regional function 12 weeks later. Six pigs then underwent sternotomy and off-pump revascularization with a left internal mammary artery graft to the LAD just beyond the chronic stenosis. A patent graft was confirmed by CTA at 4 weeks post-CABG. Five additional pigs underwent a SHAM operation and served as controls. Prior to sacrifice, regional blood flows by μspheres were determined at baseline and during high dose dobutamine (40 μg/kg/min). Post-sacrifice, the content of mitochondrial electron transport chain (ETC) and fusion proteins was determined by western gels.
Results: In the hibernating regions that underwent CABG, maximal blood flow during dobutamine was lower than Control hearts (2.5±0.2 vs 3.5±0.2 ml/min/g; NS). As shown in the Figure, the content of mitochondrial ETC proteins, when normalized to SHAM hearts, did not recover in hibernating hearts that had undergone CABG. Compared with non-revascularized hibernating hearts however, hearts that had undergone CABG demonstrated increased expression of fusion proteins.
Conclusion: Despite successful revascularization of hibernating heart tissue, maximal blood flow in response to a catecholamine challenge is submaximal at 4 weeks following CABG, at a time that the expression of ETC proteins has not recovered to normal. Mitochondrial fusion proteins are increased however, and may be an important dynamic mitochondrial process to restore maximal energetics of hibernating hearts following CABG.
- Cardiac surgery
- Myocardial revascularization
- Mitochondrial energetics, heart failure, arrhythmias
- Ischemic heart disease
- Energy metabolism
- © 2013 by American Heart Association, Inc.