E. B. STINSON, P. L. TECKLENBERG, J. F, HOLLINGSWORTH AND K. W. JONES 
683 
peak circumferential fiber shortening rate in 
circumferences per second ( Vcf) • 
To facilitate comparisons between animals, 
the results of hemodynamic studies at each 
daily interval during the first 72 hours after 
transplantation and during the last 72 hours of 
life in the first group of 10 animals were aver- 
aged. The initial postoperative electrocar- 
diogram in all animals was taken as a baseline 
"control" to which subsequent electrocar- 
diograms were compared. Records from the sec- 
ond group of four animals were selected from 
the immediate postoperative period, the third 
postoperative day (chosen because the majority 
of dogs in the first group demonstrated maxi- 
mum hemodynamic recovery at this time), and 
from the time of diagnosed acute rejection 
(within 24 hours of terminal graft failure). 
Student's t-test was used to compare grouped 
observations, assigning a two-tailed significance 
level to the P value. 
RESULTS 
All dogs died of acute graft rejection four to 
12 days postoperatively (mean 6.5 days ±: 0.6 
S.E.). Histologic findings characteristic of ad- 
vanced first-set rejection^ were present. 
Initial Hemodynamics 
Immediately postoperatively, the average 
heart rate was 188 beats per minute (± 7.1 
S.E.) ; over the ensuing 72 hours, mean heart 
rate decreased gradually to 102 beats per min- 
ute (± 8.8 S.E.). Mean cardiac output was ini- 
tially quite low, 41.6 ml/kg/minute (±: 6.4 
S.E.) ; it then rose steadily over the next 48 to 
72 hours to reach a relatively stable plateau 
value of 78.6 ml/kg/min (± 6.4 S.E.). Simi- 
larly, stroke volume was markedly depressed 
immediately after transplantation with a mean 
value of 6.0 ml (± .8 S.E,), but rose over the 
next two to three days to 11.6 ml (± 1.1 S.E.). 
In contrast to the early postoperative increases 
in stroke volume and cardiac output, mean ar- 
terial pressure showed no significant variations 
from the time of transplantation until late in 
the courses of the animals (average approxi- 
mately 92 mm Hg) . Mean peak left ventricular 
dp/dt was 2707 mm Hg/second (± 215 S.E.) 
immediately after operation, and remained near 
this level throughout the first three days (Fig- 
ure 1) . 
Left ventricular internal transverse diameter 
at end-diastole ranged from 16.5 to 34 mm with 
an average of 24.9 mm immediately postopera- 
tively. Little change in end-diastolic diameter 
occurred throughout the first three postopera- 
tive days ; heart rates in these animals were rel- 
atively stable during this interval. The average 
maximum rate of systolic diameter shortening 
(-dD/dt) rose from 55.8 mm/second initially to 
62.5 mm/second (p>.05) on the third post- 
operative day (Figure 1). Normalized circum- 
ferential fiber shortening rate increased from 
2.6 to 2.9 circumferences/second (p>.05) 
(Figure 1). Percent systolic shortening of the 
transverse diameter rose in three of the four 
dogs throughout the defined recovery period, 
from an average 24.8% to 28% (p>.05) (Fig- 
ure 1) . 
In one animal systolic -dD/dt and Vcf were 
also determined at the point of peak total wall 
tension, which was derived as the instantaneous 
product of left ventricular pressure and radius 
divided by two (PR)/2. Although the absolute 
values for tension obtained in this manner were 
unreliable because of the limitations of pressure 
measurement, identification of relative changes 
in the tension state permitted an estimate of 
contractile element velocity during ejection 
(VCE) , at the point of maximum tension. Val- 
ues thus derived showed an approximate paral- 
lel relationship to peak -dD/dt and Vcf> demon- 
strating an increase from 41 mm/second and 
1.8 circs/second, respectively, at the time of 
transplantation to 67 mm/second and 2.6 
circs/second, respectively, on the third post- 
operative day. 
Acute Rejection 
All animals recovered to the point of normal 
or nearly normal ordinary activity over the first 
three to four postoperative days, and remained 
so until one to two days prior to death. Termi- 
nally, signs of low cardiac output were present, 
and auscultation consistently revealed a dias- 
tolic gallop heart sound. Only rarely, however, 
were abnormal breath sounds audible. 
