THE "PHYSIOLOGICAL MAXIMUM HEART RATE" AS AN ARTEFACT

Abstract

During the past 35 yrs. a series of investigators has reported experiments which have led to the conclusion that the heart innervated only by accelerator fibers beats at its physiological maximum rate, which can not be increased reflexly or by adrenalin injections. The present investigators show that in normal unanesthetized animals, with accelerator influence alone active, the heart rate varies greatly as the animals change from rest and calm to activity and excitement. In such animals anesthesia increases the rate to a point below the maximal and there fixes it, so that reflex and direct stimulations have little or no influence. The so-called "law" of the "physiological maximum rate of the heart" must be regarded, therefore, as descriptive of an artificial state induced by the anesthetic agent.