EXPERIMENTAL AORTO-CORONARY DIRECT 
REVASCULARIZATION IN THE DOG 
Gerard S. Kakos* and H. Newland Oldham, Jr.' 
The effects of aorto-coronary artery vein bypass graft 
on coronary hemodynamics in the presence and/or 
absence of coronary collateral flow were examined in an 
experimental canine model. In animals without coronary 
collaterals, construction of a bypass graft to the circum- 
flex coronary artery produced no significant quantitative 
or qualitative changes in distal or adjacent coronary 
hemodynamics. Proximal coronary inflow was de- 
creased, however, and functional occlusion occurred if 
the proximal segment had significant stenosis prior to 
bypass. In animals which underwent bypass six weeks 
after ameroid constriction of the circumflex coronary 
artery, significant collateral vessels were present. These 
were associated with an elevation of peripheral circum- 
flex pressure and reduction of graft flow. Occlusion of 
the left anterior descending artery in these animals 
increased graft flow and reduced peripheral circumflex 
artery pressure. Conversely, after graft occlusion, left 
anterior descending artery flow increased and peripheral 
pressure decreased. The data document an initial de- 
crease in aorto-coronary graft flow in the presence of 
extensive collateral vessels, but demonstrate a reduction 
in collateral flow following graft insertion. 
INTRODUCTION*** 
Aorto-coronary artery direct revasculariza- 
tion has become a frequently employed method 
for treatment of occlusive coronary artery dis- 
ease. Basic questions, however, regarding the 
effects of this procedure on proximal and distal 
coronary hemodynamics, ventricular functions, 
and the role of collateral vessels remain largely 
unanswered because of the difficulties encoun- 
tered with producing a workable experimental 
model. This study was undertaken to produce 
canine preparations which would allow evalua- 
tion of these parameters and to evaluate both 
the acute effects of direct coronary artery by- 
pass (vein graft) on proximal and distal coro- 
nary hemodynamics and the influence of col- 
*From the Departments of Surgery, The Ohio State University 
Hospitals, Columbus, Ohio and 
**Duke University Medical Center, Durham, N.C.^ 
♦♦♦Supported by N.I.H. Grants HE-90315, GMO-1709, and GM1B39- 
06. 
lateral coronary vessels on the hemodynamic 
function of aorto-coronary bypass grafts. 
I. ACUTE CORONARY HEMODYNAMICS 
Methods 
Twenty-eight mongrel dogs, weighing be- 
tween 20 and 26 kg were anesthetized with 
pentobarbital, 25 mg/kg, and ventilated through 
a mixing chamber with air and a 95% O2-CO2 
mixture using a volume respirator. Through a 
left thoracotomy, a jugular or saphenous venous 
autograft was used to construct a bypass graft 
from the transverse aortic arch to the side of 
the mid circumflex coronary artery. The cor- 
onary anastomosis was performed during tem- 
porary circumflex occlusion without employing 
cardiopulmonary bypass or a local shunt. To 
prevent serious arrhythmias, lidocaine (40-50 
mg) was given as a single, intravenous bolus 
prior to this manipulation. Ten of the 28 dogs 
survived with normal electrocardiograms and 
stable hemodynamic conditions and form the 
basis of this report. 
Electromagnetic flow probes (Statham M 4001 
flowmeter) were placed on the ascending aorta, 
proximal left anterior descending coronary ar- 
tery (LAD), circumflex coronary artery distal 
to the vein graft anastomosis, and on the vein 
graft. Short, rigid catheters were inserted into 
the ascending aorta and distal circumflex cor- 
onary artery and attached to matched Statham 
P23 Db transducers for pressure monitoring. 
An adjustable occluder was positioned around 
the circumflex coronary artery 2.5-3 cm prox- 
imal to the vein graft insertion (Figure 1). Oc- 
cluders were also placed about the vein graft 
and proximal LAD. Central aortic pressure, " 
circumflex coronary pressure, ascending aorta 
flow, LAD flow, distal circumflex coronary ar- 
tery, vein graft flow, and the electrocardiogram 
347 
