348 SURGERY 
Figure 1. — Schematic representation of model 
Ac — Aorta 
LAD — Left Anterior Descending Coronary Artery 
CCA — Circumflex Coronary Artery 
EMF — Electromagnetic Flow Probe 
Note: Pressure monitoring system and adjustable 
occluders. 
were recorded simultaneously using a multi- 
channel, direct writing oscillograph (Hewlett- 
Packard, Sanborn 7700 Series). Mean and pul- 
satile flow and pressure measurements were ob- 
tained after a 90 minute stabilization period. 
Control values were gathered with the graft 
totally occluded allowing a normal source of 
coronary blood flow through the open circumflex 
coronary artery. Multiple measurements were 
then obtained under the following conditions: 
1) graft open, proximal circumflex coronary 
artery open, 2) graft open, proximal coronary 
artery totally occluded, and 3) graft open, 
proximal circumflex artery subtotally occluded 
to varying degrees. Hyperemic responses, when 
TRANSPLANTATION 
induced, were allowed to regress prior to data 
collection. 
The heart rate was not controlled, but data 
was measured only at rates of 140-160 beats per 
minute. Hematocrit and arterial blood gas anal- 
yses for pH, P02, and PCO2 also were obtained. 
Results 
Hematocrit determinations varied less than 
5% (±) in all animals while P02 was 140-240 
mm Hg, Pcoo 20-34 mm Hg, and pH 7.32-7.39. 
Control mean flow through the unobstructed cir- 
cumflex artery in all animals was 63 ± 15 cc/ 
min (mean ± SD) and was 22 i 2 cc/min in 
the LAD. During this period cardiac output was 
2300 ± 300 cc/min and the mean aortic pres- 
sure 102 ± 10 mm Hg. Central circumflex cor- 
onary artery pressure (mean 100 ± 10 mm Hg) 
equaled aortic pressure. During temporary 
proximal circumflex artery obstruction, periph- 
eral circumflex pressure was 10 + 4 mm Hg, 
indicating the absence of significant collateral 
circulation. 
Data was collected with the graft open and 
the circumflex coronary artery unobstructed 
to assess the source of flow to the distal circum- 
flex artery. The graft supplied 57 ± 10% 
(mean ± SD) of the distal circumflex flow 
while 43 ± 10% entered through the unob- 
structed proximal circumflex coronary artery. 
Total distal circumflex flow was identical to 
control flow (graft occluded, circumflex open) 
and did not change when all flow was routed 
through the vein graft by totally obstructing the 
proximal circumflex vessel. Except for 4 to 8 
msec acceleration delays noted in three animals 
in the latter group, the distal circumflex cor- 
onary artery phasic flow patterns were inde- 
pendent of the origin of flow and appeared 
identical to control data. During these inter- 
ventions, LAD flow, cardiac output, and aortic, 
main circumflex and peripheral circumflex pres- 
sures remained constant. 
An additional series of recordings was ob- 
tained -while producing varying degrees of sub- 
total, proximal coronary artery stenosis by ad- 
justing the proximal circumflex snare. With the 
graft occluded, proximal circumflex occlusion 
of less than 75% (cross-sectional area using 
