Composite revascularization with sequential and Y-anastomoses using in situ left internal thoracic artery (LITA) is primarily beneficial for patients with limited graft options and those requiring avoidance of aortic manipulation. Although patency and unidirectional flow have been demonstrated in left coronary territory revascularization, Kang et al. innovatively assess the prevalence and outcomes of these anastomoses in the RCA distal segment.

The study included 642 patients who underwent off-pump coronary artery bypass grafting (OPCAB) using Y-composite grafts, with one terminal arm directed to revascularize the RCA. Mean age was 67.1 years, with 77% male. The saphenous vein (SV) served as the secondary conduit, except in 30 patients. Competitive flow in the RCA graft was defined when the flow towards the anastomosis originated not from the donor LITA but instead reversed from the native RCA. Initial patency was assessed by angiography within 24 hours postoperatively, and follow-up angiography was performed at one year. Subgroup analyses evaluated risk factors associated with competitive flow presence at the one-year follow-up.

A total of 1,507 distal anastomoses were performed with secondary conduits, with an average of 2.3 anastomoses per conduit. Mean stenosis in target coronary vessels was 81.7%. Early occlusion and competitive flow in the RCA distal anastomosis were observed in 4.4% and 10.7% of cases, respectively. Univariate and multivariable analyses identified that target vessel stenosis (p < .001) and the most severely diseased non-LAD vessel (p < .001) were significantly associated with competitive flow in RCA grafts. Diabetes mellitus was protective against competitive flow (p = .029). Competitive flow prevalence was significantly higher in terminal anastomoses to vessels with less than 90% stenosis (p < .001). At the one-year follow-up, 81% of patients underwent angiography. Of the 55 patients with competitive flow observed on initial angiography, 14 (24.5%) exhibited occlusion, and 17 (30.9%) experienced graft failure. Both univariate and multivariable analyses found early competitive flow to be the sole factor significantly associated with one-year RCA anastomosis occlusion (p = .015).

COMMENTARY:
In recent years, several studies have analyzed the patency of grafts in myocardial revascularization using composite grafts. Nakajima et al. conducted a similar study with the radial artery as a secondary conduit, emphasizing the importance of selecting the target vessel to enhance long-term patency. The IMPAG study analyzed preoperative FFR to improve patency at six months post-surgery, yielding values of 0.71 in the right system and 0.78 in the left system. These findings align with those of Kang et al. and also relate to the distance from the subclavian artery origin and the distal RCA anastomosis. Greater graft length results in a pressure drop, increasing the risk of competitive flow. Additionally, a drop in pressure across sequential anastomoses, particularly in the distal anastomosis, may restrict flow, especially when supplying a different territory from the left coronary system.

For cases requiring aortic non-manipulation, using an in situ right internal thoracic artery (RITA) or extending it with a secondary graft (utilizing the remaining graft with the LITA for left coronary revascularization) could shorten the distance to the RCA, thereby minimizing the risk of competitive flow.

The success of RCA revascularization depends on comprehensive analysis and strategic selection, considering the degree of terminal lesion, graft type, and patient characteristics for optimal surgical planning.

REFERENCE:

Kang Y, Kim JS, Sohn SH, Hwang HY. Competitive Flow of Terminal Anastomosis to Right Coronary Territory in “Y” Coronary Artery Bypass. Ann Thorac Surg. 2024 Sep;118(3):589-595. doi: 10.1016/j.athoracsur.2024.05.026.

Nakajima H, Takazawa A, Yoshitake A, Tokunaga C, Tochii M, Hayashi J, et al. Current mechanisms of low graft flow and conduit choice for the right coronary artery based on the severity of native coronary stenosis and myocardial flow demand. Gen Thorac Cardiovasc Surg. 2019 Aug;67(8):655-660. doi: 10.1007/s11748-019-01077-8. Epub 2019 Feb 8.

Glineur D, Rahouma M, Grau JB, Etienne PY, Fortier JH, Papadatos S, et al. FFR Cutoff by Arterial Graft Configuration and Location: IMPAG Trial Insights. JACC Cardiovasc Interv. 2020 Jan 13;13(1):143-144. doi: 10.1016/j.jcin.2019.08.013.