The Second Law of Thermodynamics and the Heart

The second law of thermodynamics explains the phenomenon of irreversibility and the increasing entropic trend of nature. Similar to human-made machines, living structures are subjected to entropy generation, becoming 'worn' and 'damaged' from use. However, they have the possibility of eluding or deferring these processes. According to nonequilibrium thermodynamics, the heart could be considered as an open dissipative system, since it has the potential to offset the body's increasing entropic burden by using energy to export entropy to the surroundings. By organizing the tissues' molecules in order to perform external work as a result of its ability to provide oxygen and nutrients and remove waste products, the heart maintains the organization of the living structure and acts as an open dissipative system. However, the increase in tissues' randomness and disorder as a result of a number of disease states may be responsible for the intervening cardiac damage and entropy generation. This effect is known as the 'Dorian Gray effect' of the heart. Technical advances, including MRI and 3D echocardiography, may provide a means to improve the understanding of thermodynamic aspects of cardiovascular physiology and heart disease.