Reply to saphenous vein harvesting: Meta‐analysis, metaflammation, and adipose tissue remodeling

In their recent letter to the editor, Furuhashi et al. discuss the role of perivascular adipose tissue (PVAT) in the progression of or protection from atherosclerotic disease in coronary bypass conduits. They make the valid point that when comparing patency rates between arterial and venous grafts, one is in part comparing the effects of PVAT preservation (arterial grafts) versus removal (venous grafts). The superior patency of the no‐touch saphenous vein (NTSV) over conventional saphenous vein (SV) may be a direct effect of PVAT preservation, although their hypothesis is currently supported only by very limited data. The authors comment on the recent network meta‐analysis by Gaudino et al. in which the radial artery (RA) is ranked as the best “second” conduit (after the left internal thoracic artery) followed by the NTSV, questioning whether the NTSV is not as good as the RA. While this network meta‐analysis did use advanced statistical methodology to score and “rank” conduits, it must be noted that the rank score for the RA (0.87) and the rank score for the NTSV (0.85) were close, but the RA scored higher. It is notable that the rank score for the remaining conduits, the right internal thoracic artery (0.23), the gastroepiploic artery (0.29), and the conventional SV (0.25) were drastically inferior with statistical significance. The authors then proceed to discuss the randomized trial by Dreifaldt et al. in which 8‐year patency rates of the NTSV grafts were similar to the RA, and actually superior to the RA when analyzed by a number of coronary anastomoses. They emphasize the benefits of the NTSV over the RA, including its greater available length and several potential scenarios in which NTSV is superior to the RA. While the study by Driefaldt did demonstrate excellent outcomes for the NTSV, rivaling those of the RA, some of the above conclusions are not fully supported by the data. The somewhat superior results of the NTSV relative to the RA are in the setting of inappropriate use of the RA, as over one‐fourth (36/124) of RA anastomoses were to targets with <70%. Furthermore, of those RA grafts to targets with >70% stenosis, a number of them were to right‐sided targets with stenoses less than 90%. In the original 3‐year follow‐up report by Dreifaldt et al., all RA grafts to target vessels with >90% stenosis were patent at that time. Six of seven failed RA grafts were to the right coronary territory, which therefore must have all had stenoses <90%. Such inappropriate use of the RA was further compounded by the lack of any vasospasm prophylaxis and may have diluted the benefits of RA grafting. The NTSV did demonstrate significantly better results than the RA in the setting of moderate target vessel stenoses (<70%). However, no difference in patency other than trends was noted in the setting of poor vessel quality, small coronary arteries, or the right coronary system on subgroup analysis and therefore the emphasis on the benefits of the NTSV in these scenarios is not justified based on this data. Formal guidelines render the use of the RA a class I indication, and further define the degree of stenoses for which it should be used (>70% on the lateral territory and >90% on the inferior territory). The current evidence regarding the role of PVAT is only preliminary. The NTSV may have a future role to play, either in combination with or instead of currently recommended conduits, but additional data are needed.