[Experimental study on coronary bypass grafts--functional and pathologic comparison of late changes in various coronary grafts].

The internal thoracic artery (ITA) has excellent long-term patency when used as a conduit for coronary artery bypass (CAB), but there are still some problems, such as flow capacity and limited graft length of the ITA. This study was performed to evaluate the functional and pathologic late changes in left ITA grafts (LITAG), vein grafts (VG), ITA-vein (ITA-VG) and ITA-ITA composite grafts (ITA-ITAG) in a canine model of coronary artery bypass. Twenty-nine adult mongrel dogs underwent bypass of the left circumflex coronary artery (CX) with one of the above grafts. More than five months postoperatively (mean follow up period 245 +/- 78 days), changes in graft flow (CX flow in control group), mean aortic pressure (AoP), left ventricular end diastolic pressure (LVEDP), diastolic pressure time index/tension time index (DPTI/TTI), left atrial pressure (LAP) and right atrial pressure (RAP) with atrial pacing were compared with control group, and postmortem specimens were examined microscopically. With atrial pacing, AoP and RAP did not change in any group. Increases in graft flow, LVEDP and LAP with decrease in DPTI/TTI were observed in ITAG and ITA-ITAG groups, but these changes were similar to control group. On the other hand, increases in LVEDP and LAP with decreases in graft flow and DPTI/TTI were observed in VG and ITA-VG groups, and these changes were different from control group. No atherosclerotic change without anastomotic site was observed in any ITA which was used in ITAG, ITA-ITAG and ITA-VG groups, while intimal thickening and irregular dilatation were observed in al veins which were used in VG and ITA-VG groups. In conclusion, this study shows that ITA is a excellent conduit for CAB because of sufficient flow capacity and no atherosclerosis without anastomotic site in a long-term period. And to elongate ITA as a CAB graft, ITA-ITAG could be more appropriate than ITA-VG.