H. L. STONE AND H. SANDLER 
599 
SYSTOLIC RIGHT VENTRICULAR PRESS 
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SYSTOLIC LEFT VENTRICULAR PRESS 
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HEART RATE □ 
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0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 
DAYS AFTER SURGERY 
Figure 6. — Summary of pressure data for all animals in this study. 
nal or eircadian variation in pressure and heart 
rate are clearly demonstrated. 
DISCUSSION 
Previous hemodynamic studies in the chim- 
panzee have demonstrated the findings summa- 
rized in Table 11, Such findings have demon- 
strated elevated heart rates and mean arterial 
pressures by human standards. Response to 
ganglionic blockade and tilt have lead Schoen- 
feld and co-workers to conclude that heart rate 
is predominantly under sympathetic control 
rather than parasympathetic control as it is in 
man,^ The findings of this study support these 
conclusions. The use of implantable telemetry 
units has demonstrated markedly lower resting 
heart rate levels when compared to those pre- 
viously reported in the literature. These find- 
ings agree with those previously reported by 
Weissler who found that spontaneous heart rate 
changes could occur during the recording of 
routine EGG tracings depending on the emo- 
tional arousal of the animal.'^ Marked sinus ar- 
rythmia was regularly found in this later study 
when heart rates decreased below 125 beats/ 
min. These observations may help explain 
our findings during sernylan anesthesia where 
marked sinus arrythmia occurred. Heart rates 
are regularly below 125 beats/min with such 
anesthesia which also blocks emotional factors 
which may heavily influence observed findings 
in this animal. 
The results of the study demonstrate that 
techniques for studying cardiovascular response 
in the chimpanzee are now available and can be 
used with reasonable success for studying vary- 
ing stresses. These techniques allow for observ- 
ations in an awake and completely unrestrained 
animal which is known to be highly uncoopera- 
tive. These studies also show a labile highly re- 
active cardiovascular state. Although many 
