THE CONTROL OF THE FUNCTION OF THE HEART 



509 



LV ENO-OIASTOLIC PRESSURE-CM H,0 



FIG. 17 



nephrine infusion, and with those of Katz el al. (54), 

 who suggested that norepinephrine produced an 

 "increase in ventricular diastolic tone." 



The shortening of systole and the consequent 

 lengthening of diastole resulting from sympathetic 

 stimulation would appear to be of great importance 

 at high rates and/or large stroke volumes, since both 

 tend to shorten the ratio of diastole to total cycle 

 time (14, 60, 79). The positive inotropic effect of 

 sympathetic efferent impulses and the consequent 

 shortening of systole is, therefore, a most appropriate 

 concomitant of the tachycardia induced by sympa- 

 thetic chronotropic influences, since the positive 

 inotropic effect provides means whereby the "normal" 

 ventricular pressure-length relation is more likely to 

 be retained at high heart rates. Such a view is remi- 

 niscent of the 1920 studies of Wiggers & Katz (125), 

 who foimd that the length of systole during accelera- 

 tor nerve stimulation and during the action of epi- 

 nephrine was markedly less than that indicated by 

 the theoretical curve for what these values should 

 have been at the increased rates. They concluded 

 "that the accelerator nerves have a specific effect on 

 the ventricidar musculature which operates to reduce 

 the contraction period." 



The lack of a change in the relation between 

 ventricular end diastolic pressure and myocardial 

 segment length during stellate stimulation (when 

 diastole is initially adequate) shows that, under such 

 stimulation, the ventricle contracts more forcefully 

 from any given fiber length as well as from any given 

 ventricular end diastolic pressure (67, 105). This is 



depicted in figure 17 which shows A: the relation 

 between LVED pressure and LV stroke work before 

 (solid circles) and during (open circles) stellate 

 ganglion stimulation, B: the relation between changes 

 in LVED pressure and changes in myocardial seg- 

 ment length before (solid circles) and during (open 

 circles) stellate stimulation, C: the work produced 

 from any given myocardial segment length before 

 (solid circles) and during (open circles) stellate stimu- 

 lation. In this study heart rate was held constant by 

 atrial pacing and both vagi had been sectioned. Data 

 for the curves shown in panels A, B, and C were ob- 

 tained simultaneously. 



More complete systolic emptying from any gix'en 

 end diastolic pressure or length during stellate 

 ganglion stimulation is evident from the results 

 described above; i.e., stellate stimulation induced the 

 delivery of a substantially greater stroke volume as 

 W'Cll as stroke work from any given left ventricular 

 end diastolic segment length or pressure. This ob- 

 servation is in support of the early experiments of 

 Anrep (3), and of Patterson (71), the clearly stated 

 position of Starling (112, 114), the experiments of 

 Gotten & Maling (28), the series of studies by Rush- 

 mer and his colleagues (84, 85, 88-91), and the 

 recent oncometer experiments of Kelso & Randall 

 (55) as well as earlier experiments from that labora- 

 tory (77, 80). 



SVNCHRONICITY OF VENTRICUL.AR CONTR.4CTION. L^n- 



like a piston pump in which the positive stroke 

 produces an elevated pressure in a rigid housing. 



