PETERS, DONOVAN, KAWAI, KWAN-GETT, ZWART AND KOLFF 
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designed cart. The critical variables to monitor 
after implantation of the artificial heart under 
li deep hypothermia are 1) arterial pH which 
tends to acidosis unless corrected during re- 
warming; 2) arterial p02 and arterial oxygen 
i saturation which will decrease if the pH and 
respiratory support during rewarming are not 
carefully controlled; and 3) arterial PCO2. 
I Double Bypass 
A second technique of implantation of the 
artificial heart without cardiopulmonary by- 
pass, was developed by Dr. Clifford Kwan- 
Gett. ^ In this method the calf, after anesthesia, 
is positioned midway between the dorsal and 
right lateral position for a fourth intercostal 
thoracotomy. The aortic graft is anastomosed 
to the descending aorta and the pulmonary graft 
is anastomosed to the pulmonary artery. The 
calf is then positioned on the dosal surface and 
a transverse thoracotomy completed. A left 
atrial connector is anastomosed and the left 
ventricle is attached and primed for pumping. 
In a like manner, the right ventricle is attached 
to the right atrial connector. After ventricular 
fibrillation is induced and both artificial ven- 
tricles are maintaining the circulation, the pul- 
monary artery and aortic roots are clamped, 
divided and sutured. The ventricles are then 
clamped and removed. The two artificial ven- 
tricles are then fitted into the middle of the 
thorax and attached to each other. Chest tubes 
are inserted and the chest is closed. 
Cardiopulmonary Bypass 
The standard method for open-heart surgery, 
cardiopulmonary bypass is used routinely in 
our laboratory along with our other proce- 
dures.* It is particularly useful for initial 
evaluation of a new artificial heart for which 
fit in the thorax and vessel connections are not 
standardized. It allows for direct end-to-end 
anastomosis of the great vessels as compared 
to the double bypass technique which utilizes 
end-to-side anastomosis. It allows more time 
for implantation compared to the deep hypo- 
thermia method (limit of circulatory and res- 
piratory arrest of one hour) which utilizes 
direct end-to-end anastomosis quick connects. 
A Bentley oxygenator is used with a prime 
of 2000 ml Ringer's lactate solution and 1000 
ml of Dextran 40. Blood drainage is from the 
inferior vena cava by way of the right atrium 
and the superior vena cava by way of the right 
jugular vein. Blood is returned to the right 
femoral artery. The duration of total bypass 
varies from one to three hours with an average 
of approximately one and one-half hour. 
PHYSIOLOGICAL MONITORING 
Cardiovascular 
There are two different types of experiments 
performed in this laboratory. In one type, we 
monitor central venous pressure, right atrial 
pressure, right ventricular pressure, pulmonary 
arterial pressure, left atrial pressure, left ven- 
tricular pressure, aortic pressure and femoral 
arterial pressure. In this type of experiment, the 
cardial output of the right heart is sometimes 
also monitored. Figure 5 shows the hemo- 
dynamic measurements made during one of 
these experiments. The purpose of this experi- 
ment, which is usually performed using a new 
design of artificial heart, is to determine as 
accurately as possible the hemodynamic re- 
sponse of the artificial heart in vivo. Once this 
has been accomplished for a particular design, 
we usually use the second type of experiment 
in which the only pressure measurements made 
are central venous pressure measured by a 
catheter inserted through the femoral vein 
and femoral arterial pressure. We do not use 
flow meters in these experiments. The purpose 
is to reduce the disturbance to the animal to a 
minimum. We have found that this allows us to 
obtain longer survival. The arterial pressure 
for a long survivor is shown in Figure 6 and 
composite plots of central venous pressure are 
illustrated in Figure 7. 
The ECG is monitored with safety-pin elec- 
trodes externally prior to cutting out the nat- 
ural heart. This is especially helpful during 
deep hypothermia to assess heart rate. Figure 8 
illustrates a composite of atrial electrical activ- 
ity in four calves measured with platinum wire 
electrodes sutured to the reminant natural 
atria. The electrical activity of the reminant 
atria attached to the artificial heart continues 
despite the removal of the coronary blood sup- 
ply. 
