THE CONTROL OF THE FUNCTION OF THE HEART 49 1 



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strafing thai under certain circumstances the heart 

 could be induced to contract more forcefully and 

 produce more external work even though its end 

 diastolic volume and filling pressure were lower. 

 Such phenomena were construed by many as a 

 violation of the relationship elaborated by Starling. 

 He can be expected to have been aware of the studies 

 performed in his own laboratory by Anrep (3) in 

 1912, and Patterson {71) in 191 5, studies which 

 demonstrated that catecholamines can cause the 

 mammalian heart to contract more forcefulh' from a 

 smaller end diastolic volume, and he certainly made 

 his position clear with regard to this matter (112, 113). 

 In 1952, a broad-scale reinvestigation of the prob- 

 lem was initiated using the relationship between 

 filling pressure and the external stroke work of the 

 heart in the open-chested anesthetized dog (96). The 

 plot of this relation, a ventricular function curve, is at 

 least one definitive manner of describing myocardial 

 contractilitv. It became clear tliat if the biochemical 

 environment of the myocardium and the physical 

 parameters are not altered a consistent and repro- 

 ducible relation between filling pressure and external 

 stroke work can be obtained in anv' given heart. It 

 became equally clear that no single ventricular func- 

 tion curve can adequatelv explain the performance 

 characteristics of a given heart, since it was possible 

 to shift from one curve to another as the result of 

 certain interventions, such as giving or withdrawing 

 catecholamines (96, 98). That is to say, a family of 

 curves rather than a single curve could readily be 

 elicited. In retrospect, it seems that the authors were 

 then faced with the simple alternative of abandoning 

 the Frank-Starling concept, as had been done by 

 some, or of retaining its basic merits while helping 

 to broaden it so as to have it embrace the spectrum 



of observed phenomena. The latter of these alterna- 

 tives was chosen for two main reasons. The first is 

 that to have abandoned Starling's law would have 

 left them without any organized system of thought 

 with which to attempt to appreciate cardiac phe- 

 nomena. Of greater importance, however, was the 

 conviction that the ability to elicit changes in myo- 

 cardial contractility over the whole range of filling 

 pressures made possible not only the more precise 

 definition of those influences which do alter con- 

 tractility, but also provided the basis for a broader 

 appreciation of the physiological significance of such 

 observed effects (96, 98). 



Relation between left ventricular end diastolic (H'ED) 

 pressure, myocardial segment length, and stroke work. The 

 three curves plotted in figure i show certain of the 

 static variables relevant to a consideration of het- 

 erometric autoregulation. Curve .-1 shows the relation 

 between LVED pressure and stroke work (VTClv). 

 Curve B shows the relation of changes in the length 

 of a segment of left ventricular myocardium to 

 changes in LVED pressure (pressure-length curve). 

 C'urve C shows the relation between clianges in 

 ventricular segment length and changes in stroke 

 work (\TCkl)- As anticipated from the postmortem 

 ventricular pressure-volume curve (53, 96), the curve 

 expressing the relation between fiber length and 

 stroke work (C) has a more nearly linear relation 

 than does either the curve relating LVED pressure 

 to stroke work or the curve relating LVED pressure 

 to fiber length. Such observations support the de- 

 sirability of continuing to think of the fiber length- 

 stroke work relation as the most appropriate and 

 biologically meaningful point of departure in the 

 analysis of the control of cardiac function even 



