G. SANDBERG, JR., F. MOLOKHIA, P. PONN, F. HUFFMAN AND J. NORMAN 
933 
sules was observed for physiologic and path- 
ologic eifects ; the 16 watt recipient survived 25 
months and the 24 watt recipient lived 26 
months. 
The rectal temperatures of all animals in- 
creased immediately after heat source implan- 
tation from one to 2.5 degrees centigrade, but 
within 24-72 hours, the temperatures had all 
returned to normal. (Recipients of the 24 watt 
capsule required external body cooling until 
the effects of anesthesia had disappeared.) 
Thereafter, the animals maintained normal 
rectal temperatures in spite of the intracor- 
poreal heat load. This indicates that an animal 
can dissipate, both in the acute phase and chron- 
ically, a thermal load of the magnitude expected 
from a thermal artificial heart power source. 
The two chronic survivors were monitored 
for evidence of adverse effects of the heat and 
radiation. Serial observation, physical exami- 
nations, and repeated batteries of blood studies 
revealed no evidence of significant abnormality 
of neurological, cardiovascular, gastrointestinal, 
hepatic, renal, endocrine, or hematologic func- 
tion. Serial studies of lymphocyte cultures for 
chromosomal aberration as a reflection of radia- 
tion effect were conducted; results of these 
studies can be found elsewhere in these Pro- 
ceedings. 
The recipient of the 16 watt capsule died of 
pulmonary embolism 25 months after implan- 
tation; the cause of the thromboembolus which 
came from a pelvic vein could not be related to 
the chronic heat or radiation exposure. The 
recipient of the 24 watt capsule was in good 
condition when it was sacrificed after 26 
months. At the time of sacrifice, blood tempera- 
tures were measured within the heat ex- 
changer tube. The maximum temperature was 
45.4°C; the temperature of the blood leaving 
the exchanger was 40.0°C while body tempera- 
ture and that of the blood entering the device 
was 38.6°C. In spite of these locally elevated 
blood temperatures no damage to the animal's 
formed blood elements, plasma proteins or co- 
agulation factors could be documented in serial 
samples of peripheral blood. Cardiac catheteri- 
zation at time of sacrifice revealed normal hemo- 
dynamic parameters with the exception of mar- 
ginally elevated pulmonary arterial pressure (80 
torr) after isoproterenol infusion. No structural 
etiology for this could be demonstrated at 
necropsy. 
An extensive gross and microscopic post- 
mortem examination was made of both long- 
term animals; effects of the chronic heat and 
radiation were specifically sought. Significant 
pathology was limited in both animals to the 
tissue which was located within one centimeter 
of the radiation source. In this tissue were seen 
necrosis, fibrosis, inflammation and rarely, fi- 
brocytes which showed some evidence of radia- 
tion effect. Lung tissue at about 1 cm from the 
source revealed mild radiation changes. In ad- 
dition, there was marrow depletion in a rib 
overlying the source which was probably the 
result of radiation exposure. This tissue had 
been exposed to approximately 1000 mrem/hr 
for 26 months. Beyond 1 cm, there was no ap- 
parent evidence of radiation damage; no neo- 
plastic changes were observed. 
CANINE RADIATION EQUIVALENT SOURCE 
(RES) MODEL 
The 238pu capsules exposed the recipients to 
both heat and nuclear radiation. In an attempt 
to separate their effects, the RES capsule was 
designed to have neutron and photon outputs 
similar to -^^Pu capsules but without thermal 
emission.13 A mixture of Americium-241 and 
Beryllium was selected as the neutron source 
and Strontium 90 as the source of photons. 
Alpha particles emitted by the decaying ^^lAm 
interact with Be nuclei, and neutrons are 
emitted by the (o:,n) reaction. Photons are pro- 
duced by the Bremsstrahlung effect as /S" 
emitted by the ^°Sr are decellerated by a graph- 
ite scatterer. The total radiation output of the 
RES capsule is similar to that of the 24 watt 
23^Pu source; the total tissue dose rate at the 
capsule surface is aproximately 2000 mrem/hr. 
Silastic encapsulated RES capsules have been 
implanted in the thoracic cavities or iliac fossae 
of six dogs. (Figure 2) Two (a male and a fe- 
male) are alive more than 50 months after im- 
plantation; they have produced 3 litters of off- 
spring. Another is a'live I14 years after 
implantation. Three died or were sacrificed at 
3, 5, and 14 months post-implantation. The 
