K. T. WEBER, R. A. RATSHIN, C. E. RACKLEY AND R. 0. RUSSELL, JR. 
171 
fasted for 24 to 48 hours prior to surgery and 
treated prophylactically with intramuscular 
penicillin. Following anesthesia using tech- 
niques previously reported,-'^ the animal was in- 
tubated and ventilation carried out with a pres- 
sure-cycled respirator. Blood gas tensions and 
pH were checked periodically and maintained 
within the physiological range.* 
The left chest was entered through the fifth 
intercostal space with the animal in a right lat- 
eral recumbent position. The following instru- 
mentation, which has been previously de- 
scribed,- was implanted in both the acute and 
chronic groups of animals (see Fig. 1) : Central 
aortic pressure catheter via the internal mam- 
mary artery; left ventricular implantable pres- 
sure transducer; electromagnetic flow probes 
placed around the aortic root and left main 
coronary artery or its branches ; limb or direct 
epicardial ECG leads; and specialized instru- 
mentation for inducing myocardial ischemia 
and infarction which are described below. 
Microsphere technique — A series of 17 ani- 
mals was utilized for the evaluation of myo- 
cardial ischemia and infarction following the 
Figure 1. — Diagrammatic representation of instru- 
mented calf heart. Included are an aortic root flow 
probe (AoQ); left main (LM) and left anterior de- 
scending (LAD) coronary artery flow probes; and 
left anterior descending and left circumflex (LC) 
coronary occluders. In addition, the left ventricular 
pressure transducer cable (LVP), and brachiocepha- 
lic pressure catheter (AP) are shown. 
injection of microspheres (6-14 micron diam- 
eter) into the left main coronary artery. Specif- 
ically, this included a group of nine animals^ 
with a four- to six-hour microsphere infusion 
of varying dose level (4-5 mg/kg body weight) 
while in the conscious state. Following the mi- 
crosphere infusion, the animals were evaluated 
over a period of 3 to 28 days. Angiotensin stress 
responses (2.5 mg angiotensin in 500 cc of 
saline) were also assessed during this time in- 
terval. At autopsy, the heart was weighed and 
left ventricular wall thickness measured. An- 
other group of animals (8) were studied during 
open thoracotomy with similar doses of micro- 
spheres.*' Here, however, the microsphere in- 
fusion was carried out over a period of 15 to 
30 minutes. 
Coronary occluder technique — vascular oc- 
cluders were positioned around the left anterior 
descending or circumflex coronaries in a group 
of five animals " studied in the conscious state. 
Hemodynamics 
All data were recorded on a direct writing 
multi-channel paper recorder (Beckman or 
Honeywell) as well as on analog tape. The tape 
was edited at a later date and various deriva- 
tions made. These included the following: left 
ventricular systolic and end diastolic pressure; 
mean and pulsatile arterial pressure; stroke 
volume and cardiac output; left ventricular 
mean ejection rate from stroke volume and left 
ventricular ejection time; the maximum rate of 
pressure rise from the first derivative of left 
ventricular pressure ; coronary blood flow ; sys- 
tolic time intervals including electromechanical 
systole (QS2), left ventricular ejection time 
(LVET) and pre-ejection period (PEP) ; and 
peripheral vascular resistance (mm Hg/liter/ 
minute) from mean arterial pressure and car- 
diac output. 
Specifics concerning the surgical technique, 
postoperative maintenance, calibration, and 
monitoring of the implantable pressure trans- 
ducer and other aspects of this instrumentation 
are being reported elsewhere in these Proceed- 
ings.'' Normal resting hemodynamics for this 
calf preparation have also been previously 
documented.- 
