Patency of experimental microvascular autografts of the common carotid artery after balloon dilatation in rats

OBJECTIVE: To study the patency rates of anastomoses in damaged common carotid arteries in a training model of microvascular surgery (Wistar rats).

MATERIAL AND METHODS: Under general anaesthesia with xylazine (Rompun) and ketamine (Ketanest) balloon dilatation was repeated five times in 31 left common carotid arteries of female Wistar rats. One minute after reflow an autograft of 4 mm was harvested, turned 180 degrees, and reinserted into the artery. The flow through the vessels was investigated by micro-Doppler ultrasound (60 s after balloon dilatation and 30 min after insertion of the autograft). Autografts were fashioned in a further 26 common carotid arteries but left undamaged. A further 14 arteries were dilated, but no autografts were inserted. The vessels were harvested after perfusion with 3% glutaraldehyde after one day, seven days, and one month. The specimens were evaluated by light microscopy in longitudinal sections of 1.5 microm slides embedded in Epon. In addition, cross-sections were taken from arteries treated by balloon dilatation.

RESULTS: In no instance did dilatation lead to occlusion of the vessel as judged by micro-Doppler ultrasound. In the group with autografts that were not dilated, one vessel was occluded after flow had restarted. However, this vessel proved to be patent after perfusion and examination. In this group, therefore, all arteries were patent after perfusion. In the group in which dilatation preceded the insertion 13 vessels were occluded and 13 were patent on micro-Doppler ultrasound. At different perfusion times, 14 vessels were patent, and 12 vessels were completely thrombosed. The differences in patency in both groups with autografts was significant, both after Doppler imaging and on histological evaluation (P < 0.001).

CONCLUSION: Balloon dilatation is recommended for the removal of a thrombus or to dilate a spastic vessel segment in anastomosed vessels that threaten the success of microvascular flaps. For experimental research, balloon dilatation of the common carotid artery is an established model for the study of wound healing after angioplasty. In this study we have clearly shown the thrombogenic effect of balloon dilatation. Caution should therefore be exercised when using a balloon catheter for the dilatation of occluded arteries.