Intraoperative flow profiles of arterial and venous bypass grafts to the left coronary territory

OBJECTIVES The different mechanical and vasodilatory properties of arteries and veins may influence their flow profiles when used for coronary artery bypass grafting (CABG). This may be of significance when assessing the cut-off values for adequate flow. However, conduit-related flow differences are less examined. METHODS In a study of 268 patients, transit time flowmetry parameters of 336 arterial and 170 venous conduits all grafted to the left coronary territory were compared. With transit time flowmetry, the mean graft flow (MGF), pulsatility index, percentage of diastolic filling and percentage of backwards flow were measured. Conduit-related differences were further compared according to on- or off-pump CABG (ONCABG versus OPCABG) surgery. RESULTS Overall MGF and pulsatility index were comparable between arterial and venous grafts, but in arterial grafts, MGF was higher during ONCABG than during OPCABG (49.1 ± 35.3 ml/min vs 38.8 ± 26.6 ml/min; P = 0.003). Percentage of diastolic filling was higher in arterial grafts than in venous grafts (overall 71.0 ± 7.9% vs 63.7 ± 11.1%; ONCABG 69.9 ± 7.1% vs 63.9 ± 10.4%; OPCABG 71.9 ± 8.3% vs 63.4 ± 12.2%; all P < 0.001). Furthermore, percentage of backwards flow was higher in arterial grafts than in venous grafts in the overall (2.3 ± 3.2% vs 1.7 ± 3.2%, P = 0.002) and in the ONCABG (2.3 ± 3.2% vs 1.3 ± 2.5%, P < 0.001) cohorts. In venous grafts, percentage of backwards flow was lower during ONCABG versus OPCABG (1.3 ± 2.5% vs 2.6 ± 3.9%, P = 0.016). CONCLUSIONS No statistically significant difference was observed for MGF and pulsatility index between arterial and venous conduits. However, arterial grafts have significantly higher diastolic filling and backwards flow than venous grafts. Furthermore, arterial grafts have a significantly higher MGF in ONCABG versus OPCABG.