The Role of Color Doppler Ultrasonography in the Perioperative Period of Coronary Artery Bypass Grafting: Comparison with Transit-Time Flow Measurement

Abstract

<b><i>Introduction:</i></b> The value of color Doppler ultrasonography (CDUS) with the supraclavicular approach for preoperative evaluation of the native left internal mammary artery (LIMA) as well as for the postoperative detection of LIMA graft patency was recently suggested. However, the parameters such as the flow volume and pulsatile index (PI) have not been studied in detail. <b><i>Objectives:</i></b> The objectives of this study were to analyze the LIMA data in the perioperative period and explore the relationships between the intraoperative graft flow with transit-time flow measurement (TTFM) and the postoperatively measured parameters with CDUS. <b><i>Methods:</i></b> Fifty-eight patients with significant stenosis (≥70%) or occlusions in left anterior descending artery (LAD) who were referred for isolated coronary artery bypass grafting (CABG) were enrolled in this study and examined by CDUS prior to CABG from April to July 2016. The perioperative measurements of proximal LIMA by CDUS were compared. In addition, the correlation between the intraoperative graft flow, such as the mean graft flow (MGF) and PI, and the immediate postoperative measurements of CDUS in LIMA bypassed grafts was statistically analyzed. <b><i>Results:</i></b> Six patients were excluded due to screening failure, or insufficient visualization of CDUS images for analysis. Fifty-two patients with in situ LIMA-LAD graft, with or without additional arterial grafts or saphenous vein grafts, were included in the final analysis. The postoperative diameters of proximal LIMA were not significantly different from preoperative diameters (2.21 ± 0.18 vs. 2.27 ± 0.22 mm, <i>p</i> = 0.070). The flow volume on the early postoperative CDUS significantly increased (39.77 ± 21.59 vs. 25.96 ± 13.17 mL/min, <i>p</i> < 0.001) and the PI significantly decreased (1.43 ± 0.46 vs. 4.20 ± 1.49, <i>p</i> < 0.001) versus those of preoperative measurements. The MGF had a moderate correlation with the flow volume on the early postoperative CDUS (<i>r</i> = 0.414, <i>p</i> = 0.002), and the PI by TTFM had a weak correlation with that by CDUS (<i>r</i> = 0.353, <i>p</i> = 0.010) as well. <b><i>Conclusions:</i></b> The MGF and PI by TTFM in CABG were associated with in situ LIMA graft parameters measured by CDUS studies. CDUS is a useful functional noninvasive tool for the preoperative screening and postoperative follow-up of patients with in situ LIMA bypass.

Preoperative Assessment for Coronary Artery Bypass Graft: Going Back to the Basics

“…Therefore, this can potentially result in retrograde flow or steal phenomenon from the coronary circulation, with resultant myocardial ischemia [8]. The need for surgeons' awareness cannot be overemphasized, since detection of optimal ITA flow prior to CABG can reduce complications caused by post-ITA graft ischemia [4,6].…”

“…A typical example is the brachial gradient, a sinister sign of advanced atherosclerotic disease, which may alert the physician for the need to revise his surgical plan. Differential arm pressure will dictate further preoperative evaluation, which can be carried out either with color Doppler ultrasonography (CDUS), or CT angiography [4]. The examination of the subclavian artery (SCA), the left internal thoracic artery (LITA) and the postoperative evaluation of graft patency can be performed using the wellestablished CDUS technique [4].…”

Perioperative Ultrasound Flow Evaluation in Grafts and Native Vessel during CABG

“…Measurement of the proximal segment was performed through the supraclavicular window with linear probes and the distal segment through the parasternal window with TTE probes. Ultrasound scan of IMAs was possible in 80% of cases for all vessel lengths and 90% for only prox segment [10]. There was a difference in the flow curve of grafted and ungrafted IMAs.…”