Experimental Determination of the Influence of Abnormal Cardiac Rhythms on the Mechanical Efficiency of the Heart

INTRODUCTION The occurrence of an abnormal cardiac rhythm clinically involves two important and essentially different considerations. First, the information it may give as to the general pathologic condition of the heart and the prognosis of the disease, and second, the mechanical influence it exerts on the pumping action of the heart. The normal heart beat, in which there is a regular succession of auricular systoles within certain rates, each of which is followed after a definite interval by contraction of the two ventricles, is best adapted to the function of the heart as a pump. Anything which seriously interferes with the normal rate or coordination of beats, interferes, to a certain extent, with the mechanical efficiency of the heart. An excessive rate of contraction, even though the regularity and coordination of beats is maintained, reduces the amount of blood pumped by the heart by shortening and rendering insufficient the period