Comparison of the Postoperative Blood Flow Waveforms of the Bypassing Grafts in Patients Following Minimally Invasive Direct Coronary Artery Bypass

Abstract

To use Doppler ultrasound velocimetry to detect and compare the postoperative flow characteristics of the bypassing grafts in patients following minimally invasive direct coronary artery bypass surgery (MIDCAB). From January 1997 to June 1999, 34 patients underwent MIDCAB with the left internal thoracic artery (LITA) to the left anterior descending coronary artery (LAD) [n = 23], with the right gastroepiploic artery (RGEA) to the right posterior descending artery (RPD) [n = 3], or with the LITA with a saphenous vein graft extension to the LAD (n = 6), the diagonal coronary artery (n = 1), or the right acute coronary artery (n = 1). There were two patients with LITA to the LAD and RGEA to the RPD. Patients underwent MIDCAB due to coronary artery stenosis (100% occlusion, n = 10; 90 to 99% stenosis, n = 18; < 90% stenosis, n = 5) or unsuccessful percutaneous transcoronary angioplasty with dissection (n = 1). All patients underwent flow velocity measurement by Doppler ultrasound velocimetry in the immediate postoperative period, and at 6-month and 12-month intervals; graft flows were quantified based on Doppler velocimetric data. The results showed that in a patient with a totally occluded LAD or RPD, typical biphasic velocity waveforms were consistently observed. However, a delayed diastolic wave was noted in RGEA grafts. In patients with less-occluded stenotic lesions or with strong back flows, the flow velocity patterns showed biphasic waveforms but systolic reversal was observed in the area closest to the anastomotic site. The presence of an LAD or RPD stenosis proximal to the anastomotic site significantly affects the LITA or RGEA graft flow volume. The biphasic flow pattern proves that an LITA or RGEA graft transports the blood primarily to coronary arteries during the diastolic phase.