Skeletonization of internal thoracic artery affects its innervation and reactivity

Objective: The studies showing the superior characteristics of ITA graft and its impact on the clinical results of coronary artery surgery were performed with ITA harvested almost exclusively as a pedicle. This study assesses the impact of ITA skeletonization on its innervation and reactivity. Methods: Segments of skeletonized and non-sketetonized ITA were stained with antibodies against protein S-100 to took for the presence of sympathetic nerve fibers. The functional studies were performed on segments of discarded human pedicled ITA that were divided into two 3 mm rings, one skeletonized and another non-skeletonized. We compared concentration-effect relationships for the contraction to norepinephrine and endothelium-dependent relaxation to acetylcholine and bradykinin, as well as endothelium-independent relaxation to sodium nitroprusside in skeletonized and non-sketetonized segments of the same ITA. Results: Skeletonized ITA was devoid of protein S-100 positive nerve fibers. It contracted stronger (maximal response 37.0 +/-+/- 2.04 vs. 25.4 +/- 1.83 mN (P < 0.001)) and was twice as sensitive to norepinephrine: pD(2) 6.03 +/- 0.10 vs. 5.70 +/- 0.12 (P=0.035). The endothelium-dependent relaxation responses did not differ between sketetonized and non-skeletonized ITA rings. The skeletonized ITA rings appeared over 10 times more sensitive to sodium nitroprusside: pD2 6.66 +/- 0.20 vs. 5.59 +/- 0.37 (P=0.012)-potency ratio 11.61. The maximal responses did not differ significantly: 112.0 +/- 6.71 vs. 129.4 +/- 16.4% (P=0.33). Conclusions: Skeletonization results in sympathectomy of ITA. It has no effect on endothelium-dependent relaxation but increases reactivity of ITA to norepinephrine. This augmented response to alpha-agonist is small, in comparison with over a ten-fold increase in sensitivity to sodium nitroprusside. Pedicled and skeletonized ITA are functionally significantly different vessels when studied in vitro. (c) 2005 Elsevier B.V. All rights reserved.