Concerning Contraction of Heart Muscle

Publisher Website
Google Scholar
Abstract
The heart walls of small mammals (guiena pigs, kittens, puppies, rats) were perfused (chambers empty). Simultaneous ecgs. and records of contraction, using a transducer and a strain gauge amplifier, were recorded. Summation and incomplete tetanus were recorded in these hearts over a wide range of temp. Summation occurs when the heart is not hypodynamic. The summed beat develops greater tension than a normal beat. In tetanus, previous to fatigue, the base line also writes up indicating an increase of tension. Previous reports of summation and tetanus in heart muscle are discussed. Evidence that heart muscle has unit structure and is not a syncytium is reviewed. It is suggested that summation and tetanus occur when additional units are activated while other units are still in the contracted state.