Energy metabolism of cardiac pumping

The heart is the ultimate endurance muscle, as it cannot rest. As the most metabolically active organ, the heart is often the first to fail when species reach their critical limits, both with respect to temperature and oxygen (O2) availability. Sustained activity of the heart is maintained through aerobic oxidation of fuels in a series of metabolic pathways. This is achieved using mitochondria, organelles that are highly conserved across the greater part of all animals. Mitochondria consume O2 and substrates to produce ∼90% of cellular ATP energy in working hearts. In this article, we describe in detail the metabolism of the heart of fishes, how mitochondrial function supports heart contraction and how dysfunction may impact the beating heart.