Mechanical Concepts Applied in Congenital Heart Disease and Cardiac Surgery.

All biological processes are governed by principles of physics that dictate the pathophysiology and even the treatment of congenital heart diseases. In this review, basic concepts such as flow, pressure, resistance, and velocity are introduced, followed by more complex laws that describe the relationship between these variables and the disease processes. Finally, physical phenomena such as turbulence, steal and runoff phenomenon, and energy loss are discussed. By application of these principles, one can accurately quantify modifications undertaken to treat diseases, for example, the size of a patch that augments a vessel and the angle of an anastomosis to allow a certain flow.