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

<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> &#x3c; 0.001) and the PI significantly decreased (1.43 ± 0.46 vs. 4.20 ± 1.49, <i>p</i> &#x3c; 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.

Sequential coronary grafting

Sequential distal grafting is a surgical technique in which a single conduit has two or more distal anastomosis for a single proximal anastomosis; in situ sequential arterial grafts may have no proximal anastomosis. Proponents of this method suggest that there is increased total graft flow due to improved distal run-off in sequential grafts, which leads to better graft patency over time, and that sequential grafting is more efficient in terms of conduit use, and reduces the amount of aortic manipulation during surgery.

The relationship between epicardial fat tissue thickness and transit time flow measurement values of coronary artery bypass grafts

Introduction: Epicardial fat tissue, the true visceral adipose depot of the heart, has been associated with changes in both cardiac function and morphology. This study aimed to show the relationship between epicardial fat tissue (EFT) thickness and graft flow dynamics in arterial and venous grafts in coronary artery bypass graft surgery (CABG). Methods: Patients underwent transthoracic echocardiography before surgery and epicardial fat thickness were evaluated. The patients were divided into two groups as EFT value <5.5 (group 1) mm and ≥5.5 (group 2) mm. One hundred eighty-one patients with a total of 434 grafts (162 arterial and272 venous) underwent isolated coronary artery bypass grafting surgery. All grafts were examined by transit time flow meter intraoperatively. Results: The mean epicardial fat tissue thickness values were 4.9±0.8 mm and 6.1±1.3 mm, respectively.Mean graft flow values of left internal mammary artery was 44.21±23.2 mL/min in group 1 and39.65 ± 19.2 mL/min in group 2 (P = 0.041). Similarly, mean graft flow values were higher in group1 in all venous grafts regardless of which vessel bypass was performed. There is a significant negative correlation between epicardial fat thickness and mean graft flow. Conclusion: Epicardial fat thickness measurement preoperatively might provide additional data for the faith of the graft.

Measurement of Intraoperative Graft Flow Predicts Radiological Hyperperfusion during Bypass Surgery in Patients with Moyamoya Disease

Introduction: Moyamoya disease (MMD) is a rare cerebrovascular disease associated with cerebral infarction or hemorrhage. Hyperperfusion is the most significant complication of direct bypass surgery. Previous research has shown that an increase in cerebral blood flow (CBF) is strongly related to symptomatic hyperperfusion and highlighted the importance of postoperative assessment of CBF. Objective: The principal aims of this study were to quantitatively analyze the relationship between intraoperative graft flow and increase in CBF and to evaluate the effectiveness of intraoperative graft flow measurement during bypass surgery for patients with MMD. Methods: This study included 91 surgeries in 67 consecutive adult patients with MMD who underwent direct revascularization surgery at our institution between November 2013 and September 2018. Intraoperative graft flow of the branches and main trunk was measured in all patients, after anastomosis had been established. Postoperative CBF measurements were performed under sedation, immediately after surgery. Radiological hyperperfusion was defined as focal high uptake, as determined by CBF imaging immediately after surgery. Patients were divided into two groups (radiological hyperperfusion and nonradiological hyperperfusion groups), and the relationship between intraoperative graft flow and radiological hyperperfusion was analyzed. Results: Significant differences were observed between the radiological hyperperfusion and nonradiological hyperperfusion groups in terms of intraoperative graft flow of both the branch (median 72 vs. 42 mL/min, respectively; p < 0.01) and main trunk (median 113 vs. 68 mL/min, respectively; p < 0.01). A receiver-operating characteristic analysis was performed to test the utility of intraoperative flow as a quantitative measure. We set the cutoff values for the intraoperative branch and main trunk flow at 57 mL/min (sensitivity: 0.707, specificity: 0.702; area under the curve [AUC]: 0.773; 95% confidence interval [CI]: 0.675–0.871) and 84 mL/min (sensitivity: 0.667, specificity: 0.771; AUC: 0.78; 95% CI: 0.685–0.875), respectively. Conclusions: Measuring intraoperative graft flow during bypass surgery may be an effective means of predicting hyperperfusion and could serve to facilitate early therapeutic intervention such as strict blood pressure control.