Effects of Intra-Aortic Balloon Pumping on Graft Flow in Coronary Surgery: An Intraoperative Transit-Time Flowmetric Study

Background: We investigated hemodynamic effects of intra-aortic balloon pumping (IABP) in in-situ and aorta-coronary (A-C) grafts during coronary artery bypass grafting (CABG). Methods: One hundred seventy-two grafts, including 84 in-situ left internal thoracic arteries (LITAs), were examined intraoperatively with a transit-time flowmeter in 84 patients who had prophylactic IABP. The following measurements were obtained for each graft during off-IABP and on-IABP: mean flow, maximal flow, pulsatility index, and diastolic filling index. Coronary angiograms were performed 14 ± 5 days after coronary artery bypass graft surgery to verify the patency of the grafts. Results: All measurements of 163 patent and measurable grafts were significantly increased with IABP: mean flow 46 ± 27 to 51 ± 29 mL/min; maximal flow 87 ± 52 to 121 ± 69 mL/min; pulsatility index 2.2 ± 1.4 to 3.1 ± 1.4; and diastolic filling index 64% ± 8% to 71% ± 9% (p < 0.001). Among them, the degrees of increase of mean flow and diastolic filling index were significantly different between the in-situ LITAs and A-C grafts (mean flow 18% ± 20% versus 10% ± 15%, p = 0.04; diastolic filling index 10% ± 8% versus 14% ± 9%, p = 0.04). Conclusions: IABP assist significantly increases graft flow and also diastolic components of flow. The degree of increase is greater in the in-situ LITA supplying the left anterior descending artery than in A-C grafts anastomosed to other coronary arteries. IABP increases the diastolic component more in A-C grafts than in in-situ LITAs, probably because of different flow characteristics of the two grafts.