volumes and body weight in mammals. Am. J. Physiol. 215(3): 704-715. 1968.-Left and right ventricular end-diastolic (EDV), endsystolic (ESV), and stroke volumes, heart rates, cardiac output, total peripheral resistance (TPR), and other cardiovascular variables have been measured in the control state in nine species of mammals varying 1,790-fold (rat to horse) in body weight. The log-log relationships between these variables and bodyweight (BW), body surface, metabolic rate, heart weight, and ventricular weight have been determined and are described bypower law equations. On the basis of these results relationships for each ventricle are described by equations in which ventricu lar volumes are related to BW1-0, heart rate to BW °-20, cardiac output to BW075, and TPR to BW"0-75. Evidence is presented that in the control state the heart rate of mammals is a function of metabolic rate per unit body weight, and left ventricular stroke work per unit body weight is constant. It is concluded that the EDV, ESV, and stroke volumes of mammals are linear functions of body weight and not of body surface or metabolic rate; and that cardiac output is a linear function of metabolic rate'and not a linear function of body surface area. It is sug gested that ventricular volumes be reported as volume per unit body weightheart; cardiovascular equations; heart-body weight functions; cardiac outputIn the wide range of mammals that have been studied (bat to elephant) body weight is inversely related to heart rate (3, 25) and directly related to blood volume and heart weight (3, 4, 10). There is considerable evidence that cardiac output, which is the product of stroke volume and heart rate, is related to metabolic rate (13). For more than 100 years basal metabolism has been related to body surface (16), and since the studies of Grollman (12) relating cardiac output to body surface area, it has become the practice to report the cardiac output of man in terms of flow per square meter of body surface (28). In 1932 Kleiber (21, 22) and later Brody (2) in a study of the metabolism of a wide variety of mam mals ranging from the mouse to the elephant, showed that basal metabolic rate was not related to body surface, which is a function of the two-thirds power of body weight, BW2", but is related to the 0.74 =fc 0.01 power. On the basis of these studies Kleiber suggested that, in ore r for data on the metabolism of mammals of different body sizes to be useful for the study of mammals in general, basal metabolic rate should be reported as a function of BW3/4. If the reporting of cardiac output per square meter of body surface is based on the assumption jhat cardiac output is related to metabolic rate, then it would appear more desirable to report cardiac output per BW"1 than per body surface area (13). The primary reason, however, for reporting cardiac output as a func tion of any power of body weight should rest on -peri-" mental evidence obtained in mammals extending over a wide range of body size.Assuming cardiac output to be a function of m...
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