Acute effects of tourniquet occlusion and intraluminal shunts in beating heart surgery.

Objective: MIDCAB and OPCAB revascularization is currently performed with temporary tourniquet occlusion of the coronary artery to achieve a bloodless surgical field. However, a trauma of the vessel wall due to snaring sometimes occurs. The use of temporary intraluminal shunts (TILS) have recently been advocated as an alternative. The aim of this experimental study was to evaluate the acute ultrastructural effects of TILS versus tourniquet occlusion on the coronary vessel wall.
Methods: Twelve pigs (40+/-3 kg) were investigated. In group A (n=6) the left anterior descending (LAD) artery was temporarily occluded with a tourniquet over 20 min. In group B (n=6) a commercially available silicone TILS (1.5-mm diameter, 12-mm length, AnastaFlo, Research Medical Inc.) was placed in the LAD. After 20 min perfusion the TILS was removed and the insertion was repaired. After 30 min reperfusion all animals were killed. Three LAD territories of each animal were examined histopathologically by scanning electron microscopy (SEM), light microscopy (LM) and transmission electron microscopy (TEM). Areas of occlusion or placement of the TILS olives were investigated.
Results: SEM revealed ultrastructural alterations in both groups. While marked intimal rupture appeared in all animals of group A, only two of the six animals of group B exhibited superficial endothelial abrasions. LM showed differences of intimal thickness in all groups while TEM revealed severe edema of subendothelial tissue in four of six animals in group A.
Conclusion: The intimal lesions observed after tourniquet occlusion in our experimental off-pump surgery model confirmed other recent studies. In contrast, utilization of TILS caused only minor damage of the vessel wall. The endothelial abrasions detected in this group may be a consequence of micro-dislocations or insertion maneuvers. Chronic studies are necessary to verify as to whether the mild injury after TILS insertion will result in a reduction or even absence of de-novo stenoses compared with tourniquet occlusion.