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

Abstract

Objectives We investigated current mechanisms causing low graft flow (LGF) following coronary artery bypass grafting, particularly for the right coronary artery (RCA). Methods We retrospectively assessed 230 individual bypass grafts as the sole bypass graft for the RCA using preoperative and postoperative quantitative angiography. Overall, 155 in-situ gastroepiploic arteries (GEAs) and 75 saphenous vein grafts (SVGs) were included. The size and status of the revascularised area were examined to determine whether these factors were associated with LGF (defined as ≤ 20 mL/min with intraoperative flowmetry). A distal lesion was defined as stenosis at segment #4, whereas a proximal lesion was stenosis at #1, #2 and #3. Results Graft flow in the SVG and the GEA for distal lesion was significantly less compared with that for proximal lesion (34 ± 26 vs. 60 ± 46, p < 0.0001 and 22 ± 12 vs. 43 ± 28, p = 0.0004, respectively). For proximal lesion, LGF was significantly more frequent when the minimal luminal diameter was over 1.27 compared with when it was less than 1.27 (p = 0.02). Prior myocardial infarction significantly correlated with LGF in the GEA (p = 0.007) and the SVG (p = 0.03). In 55 bypass grafts with LGF, the causes were competitive flow in 20.0%, small revascularised area in 38.1% and prior myocardial infarction in 32.7%. Conclusions Along with the current strategy based on the severity of native coronary stenosis, the incidence of competitive flow decreased remarkably. This resulted in flow demand, myocardial status and collateral vessels more influential on graft patency.