The human heart has one of highest metabolic requirements in the body: even in a resting physiologic state it must work to circulate approximately 5 L/min to 8 L/min of blood against systemic vascular afterload. In addition, overall cardiac mechanical efficiency is only 20% to 25%,¹ with cellular maintenance and heat production accounting for the balance of energetic requirements. A dense network of mitochondria, which contain the machinery of oxidative phosphorylation, is needed to maintain the balance of cellular adenosine triphosphate (ATP) utilization and production in the setting of such a high energetic demand. Indeed, cardiac myocytes have one of highest mitochondrial volume densities of any cell in the body, with mitochondria occupying almost one-third of the cell volume.²

This network is highly vulnerable to injury, and therefore impaired function, due to a combination of patient factors and stressors encountered in the context of cardiac surgery. A discussion of normal and pathologic cardiac mitochondrial function, specific perioperative stressors, and protective strategies for cardiac surgical patients follows.