The Response of the Normal and Abnormal Heart to Exercise

FOR MANY YEARS physiologists and clinicians have sought means of assessing the functional capacity of the human heart. Universal agreement, however, has not been achieved in such fundamental principles as the role played by stroke volume in augmenting cardiac output in the normal subject. In cardiac disease consistent patterns of abnormal behavior of the heart, excluding pressure measurements, have not been fully documented. This investigation was undertaken with the premise that, in the final analysis, cardiac output represents the only role of the heart, and that an integral part of this role is to increase its output proportional to tissue demands, at least within certain limits. With use of graded exercise as a mechanism of stress, the response of the cardiac output and related measurements was characterized in normal human beings and compared with the results of identical studies of people with uns-lected heart disease. Derived from our data are concepts relating to the performance of the normal and failing human heart.