THE ROLE OF AUTONOMIC AND MYOCARDIAL FACTORS IN CARDIAC CONTROL*

Abstract

The response of canine left ventricle to muscular exercise (galvanic stimulation) was studied in 4 groups of anesthetized dogs. Cardiac innervation was intact in 1 group; vagectomized in 2nd; sympathectomized in 3rd; and totally absent in 4th. Change in left ventricular volume was followed each 1/30 sec. by cinefluorographic means. It was concluded that in dogs with cardiac sympathectomy, vagectomy, or total cardiac denerva-tion the left ventricle is able to respond to exercise by increase in output and integrated minute work; intrinsic myocardial factors, whereby the animals respond to exercise, are not solely a property of the isolated heart-lung preparation; and response of left ventricle to exercise under these circumstances appears, by elimination, to be initiated by increased ventricular filling.