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Are intraoperative flow measurements sufficient to allay concerns about flow capacity of skeletonized internal thoracic arteries?

We read with great interest the recently published meta-analysis by Sá et al. in this journal [1]. The authors analysed available data on the effects of skeletonized and pedicled internal thoracic arteries (ITAs) on intraoperative flow capacity. They evaluated data of 8 studies comprising 907 grafts and concluded that skeletonized ITA conduits are superior to pedicled ITA conduits. Moreover they observed advantages of skeletonized ITA conduits in females, patients with advanced age and diabetes. Although we share the opinion that skeletonized ITA conduits are advantageous in numerous ways and should be used routinely, particularly in patients undergoing arterial coronary artery bypass grafting (CABG) using bilateral ITAs, we do not think that the data provided in this meta-analysis are sufficient to remove all concerns about flow in skeletonized conduits raised by surgeons over recent years. Corresponding to the findings of Sa et al., we published previously that skeletonized ITAs provide higher free flows during surgery, with maximum mean flows after papaverine of 197.2 ± 66.6 ml/min and thus significantly higher compared with pedicled ITA conduits (147.1 ± 70.5 ml/min) [2]. One may feel that, given the relatively low flow demand measured in left ITA to left anterior descending (LAD) grafts of between 30 and 60 ml/min, these high flow capacities do not provide any clinical advantage for patients. But keeping in mind that ITAs are increasingly used in a sequential fashion and complete arterial revascularization is also performed using T-grafts, in which total coronary flow is dependent on the flow provided by a single ITA, optimization of ITA flow is crucial to achieve excellent outcomes under these circumstances. Nevertheless, some surgeons do not only fear acute vasoconstriction of skeletonized ITA grafts during surgery, but also are concerned that postoperative graft physiology is affected by removing the pedicle from the ITA graft. For this reason, we also would like to make the authors aware of our previously published intravascular flow measurements in ITA grafts used for T grafts with bilateral ITAs or left ITA and radial artery grafts at 3 and 6 months post surgery. Results of these investigations showed maximum flows in skeletonized left ITAs with up to 136.34 ± 53.43 ml/min, with a coronary flow reserve comparable with single ITA grafts to the LAD [3]. In addition, we were able to demonstrate that left ITA flow in these T grafts was directly affected by the amount of native coronary artery disease, with their flow being highest in patients with occlusions in two main coronary territories (170–240 ml/min) [4]. These findings of normal bypass physiology in skeletonized ITA grafts in the mid-term course post CABG surgery should be sufficient to remove the last concerns about inferior long-term results in these grafts. For us, who have been performing CABG using skeletonized grafts now for nearly 20 years, it is quite surprising to note that there are still concerns about the reliability of these excellent conduits, which have revolutionized the way complete arterial revascularization can be provided to patients with coronary artery disease.