Intraoperative flow rate measurements of T-grafts: calculating a flow reserve.

Objective: To evaluate the inflow of the left internal thoracic artery (LITA) and the effect of adding a radial artery T-graft to distal LITA flow, and to calculate the LITA flow reserve.

Methods: Twenty-two patients underwent myocardial revascularization using the radial artery-LITA T-graft in which intraoperative flow measurements were recorded. An ultrasonic flowmeter was used to directly measure flow rates in the T-graft: 1) before completion of the distal anastomoses to measure maximum flow rates (free flow), and 2) after completion of distal anastomoses.

Results: The mean free flow rates of the LITA alone, radial artery graft alone, and T-graft (total flow) were 104 +/- 70, 151 +/- 89, and 230 +/- 102 ml/min, respectively. The mean flow rates on bypass of the distal LITA, radial artery graft, and T-graft after the distal anastomoses were completed were 24 +/- 16, 32 +/- 27, and 63 +/- 29 ml/min, respectively. The mean T-graft flow off bypass was 66 +/- 29 ml/min. The mean flow reserve was 70%.

Conclusion: The LITA has a flow reserve by which proximal flow rates will increase to accommodate the addition of a radial artery T-graft without compromising LITA flow distal to the T anastomosis.