LEFT VENTRICULAR HEMODYNAMIC AND DIMENSIONAL 
RESPONSES TO TREADMILL EXERCISES IN NORMAL 
AND CARDIAC DENERVATED DOGS 
E. B. Stinson, G. Rahmoeller, P. L. Tecklenberg, 
S. B. Colvin, K. W. Jones and J. E. Pierce* 
Five normal (N) and eight chronically cardiac-de- 
nervated (D) (regional neural ahlation) treadmill- 
trained dogs were studied during standardized five 
minute periods of treadmill exercise. Measurements in- 
cluded left ventricular pressure (minature solid-state 
pressure transducer), internal transverse LV diameter 
and derived velocity (piezoelectric crystals), and aortic 
flow (electromagnetic). Studies were performed in fully 
recovered animals one to three weeks after instrument 
implantation. 
At rest there were no significant differences between 
N and D dogs in heart rate, LV systolic pressure, LV 
dp/dt, cardiac output, stroke volume, or peak LV ejec- 
tion rate; average LV end-diastolic diameter was 
slightly greater in D than in N dogs (28.0 vs. 25.8 
mm) ; the average maximum systolic rates of change of 
internal diameter (dD/dt) were similar in D and N 
dogs (78.8 vs. 79.5 mm/sec) and calculated peak cir- 
cumferential velocities were comparable (3.4 vs. 3.9 
circs/sec). With exercise N dogs showed near-maximal 
responses in all parameters within the first 30 seconds; 
LV end-diastolic diameter and pressure showed variable 
slight changes. Maximal responses in D dogs were at- 
tained gradually over the first three minutes of exer- 
cise, and lower maximal values were achieved for heart 
rate (D 193 vs. 250 beats/min), dD/dt (D 96 vs. N 
110 mm/sec), peak Vcb' (D 4.3 vs. N 5.7 circs/sec), 
cardiac output (D 5.1 vs. N 5.9 L/min), and LV dP/dt 
(D 5,100 vs. N 7,000 mmHg/sec). LV end-diastolic di- 
ameter and pressure consistently increased in D dogs. 
Increases in stroke volume occurred in both groups, but 
were proportionately higher in D dogs. These studies 
emphasize the importance of neural control for rate-de- 
pendent responses of the heart to muscular exertion. 
INTRODUCTION 
Experience with clinical heart transplanta- 
tion has stimulated new interest in the function 
and adaptive mechanisms of the denervated 
heart. Donald and Shepard, on the basis of an 
extensive series of investigations of cardiovas- 
cular performance in cardiac-denervated dogs,^'^ 
suggested that human cardiac recipients 
would suffer no physical limitations attrib- 
* Clinic of Surgery, National Heart & Lung Institute, Bethesda, 
Maryland 20014 
utable to cardiac denervation per se? Their ex- 
periments demonstrated an unchanged capacity 
for exercise after regional cardiac denervation, 
with a linear and quantitatively normal rela- 
tionship between oxygen consumption and car- 
diac output during stress. They did note, how- 
ever, striking differences between normal and 
denervated dogs in the responses of heart rate 
and stroke volume at all levels of exercise. 
Whereas normal animals elevated cardiac out- 
put almost entirely by means of prompt in- 
creases in heart rate, denervated dogs utilized 
principally increases in stroke volume, espe- 
cially during mild exercise.^ 
Clinical experience has substantiated the ex- 
pectation that heart recipients can sustain ordi- 
nary physical activity without undue cardiac 
symptoms.^ Cardiac catheterization studies in 
eight patients one and two years after trans- 
plantation, however, have shown that although 
the output of the transplanted heart rises line- 
arly with increasing oxygen consumption dur- 
ing supine submaximal exercise, the absolute 
level of cardiac output is in the low normal 
range or subnormal, both at rest and during 
exertion.^ Increases in both heart rate and 
stroke volume contributed to the augmentation 
of cardiac output although the effect of stroke 
volume was predominant. Left ventricular end- 
diastolic pressure, which was normal at rest in 
all patients, promptly increased to abnormal 
levels with the onset of exercise, and remained 
elevated despite a gradual rise in heart rate to 
levels comparable to normal. Some patients ex- 
hibited a significant increase in stroke volume 
and mean left ventricular ejection rate, in asso- 
ciation with slightly diminished left ventricular 
end-diastolic pressure, after several minutes of 
steady exercise, suggesting a gradual enhance- 
ment of contractile state. 
We have attempted to further define differ- 
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