Assessment of myocardial oxygenation with MRI

As an aerobic organ in a living body, the beating heart relies almost exclusively on the oxidation of energy-providing substrates such as free fatty acids (60-90%) for its primary contractile function. Specifically, chemical energy is generally produced in aerobic metabolic pathways through oxidative phosphorylation of ADP to ATP. Myocytes utilize the chemical energy stored in ATP molecules and transform it into mechanical energy. Accordingly, cardiac cells have to consume large amounts of O₂ for the contraction process, which accounts for over 80% of oxygen cost. The remaining <20% is consumed by other physiological processes not directly associated with contraction, i.e., membrane depolarization and repolarization. For this reason, the heart can only develop a small oxygen debt. Oxygen supply and demand has to match to maintain normal myocardial contractility.