Aortic wavelength as a determinant of the relation between heart rate and body size in mammals.

Measurements of aortic input impedance in the rat, dog, and man suggest a new hypothesis to explain the inverse correlation between rate and body size: that pulse wavelength and arterial length are matched in a way that minimizes cardiac work. The optimal rate is fast enough to avoid the high impedances produced by reflections at relatively low frequencies, yet slow enough to permit orderly excitation and recovery of the myocardium.