Transit Time Flow Measurement Research Articles

Transit time flow measurement in off-pump surgery: is it a functional index of the biological graft integrity?

Transit-time flow measurement (TTFM) represents a valid tool in the assessment of the quality of the anastomosis during coronary artery bypass graft (CABG). Nevertheless, a high variability limits its standardized use, lacking univocally accepted cut-off flow values. Our study analyzes TTFM data collected from a study population that underwent off-pump CABG (OP-CABG), with the aim to differentiate into subgroups according to the presence of diabetes mellitus. Patients referred to the Cardiovascular Unit of S. Michele Hospital (Caserta, Italy) for coronary artery disease (CAD) and underwent OP-CABG between January 2015 and December 2019 were enrolled, and intraoperative TTFMs data were recruited and evaluated. Mean graft flow (MGF) and pulsatility index (PI) values were collected and analyzed. The study population was composed of 342 patients who underwent OP-CABG with TTFM data regarding 824 grafts. Diabetic patients shared a higher cardiovascular risk profile. The TTFM assessment showed better results for the use of the arterial grafts in diabetic patients, especially for those insulin-dependent; conversely, venous grafts showed worse data with lower MGF and higher PI values. In particular, the anastomoses of the saphenous vein graft with marginal obtuse (MO) coronary artery showed worse MGF results in the insulin-dependent rather than normoglycemic subgroup (28.66 vs. 38.44, p=0.003). Diabetic patients, especially in the insulin-dependent subgroups, have demonstrated lower MGF and higher PI values collected from venous anastomoses with, conversely, inverse results from the arterial one. These results might be correlated to an altered biological adaptability caused by the effects of the diabetic endocrine disorder.

Intraoperative transit time flow measurement predicts maturation of radiocephalic arteriovenous fistulas

ObjectiveThe arteriovenous fistula (AVF) is the first choice for gaining vascular access for hemodialysis. However, 20% to 50% of AVFs fail within 4 months after creation. Although demographic risk factors have been described, there is little evidence on the intraoperative predictors of AVF maturation failure. The aim of this study was to assess the predictive value of intraoperative transit time flow measurements (TTFMs) on AVF maturation failure. MethodsIn this retrospective cohort study, intraoperative blood flow, measured using TTFM, was compared with AVF maturation after 6 weeks in 55 patients. Owing to its significantly higher prevalence and risk of nonmaturation, the radiocephalic AVF (RCAVF) was the main focus of this study. A recommended cutoff point for high vs low intraoperative blood flow was determined for RCAVFs, using a receiver operating characteristic curve. ResultsThe average intraoperative blood flow in RCAVFs was 156 mL/min. Patients with an intraoperative blood flow equal or lower than the determined cutoff point of 160 mL/min, showed a 3.03 times increased risk of AVF maturation failure after 6 weeks, compared with patients with a higher intraoperative blood flow (P < .001). ConclusionsThe intraoperative blood flow in RCAVFs measured by TTFM provides an adequate means of predicting AVF nonmaturation 6 weeks after surgery. For RCAVFs, a cutoff point for intraoperative blood flow of 160 mL/min is recommended for maximum sensitivity and specificity to predict AVF maturation failure after 6 weeks.

Wide dynamic range measurement of blood flow in vivo using laser speckle contrast imaging.

Laser speckle contrast imaging (LSCI) is a real-time wide-field technique that is applied to visualize blood flow in biomedical applications. However, there is currently a lack of relevant research to demonstrate that it can measure velocities over a wide dynamic range (WDR), which is critical for monitoring much higher and more pulsatile blood flow in larger size myocardial vessels, such as the coronary artery bypass graft, and visualizing the spatio-temporal evolution of myocardial blood flow perfusion in cardiac surgery. We aim to demonstrate that the LSCI technique enables measuring velocities over a WDR from phantom experiments to animal experiments. In addition, LSCI is preliminarily applied to imaging myocardial blood flow distribution in vivo on rabbits. Phantom and animal experiments are performed to verify that the LSCI method has the ability to measure blood velocities over a wide range. Our method is also validated by transit time flow measurement, which is the gold standard for blood flow measurement in cardiac surgery. Our method is demonstrated to measure the blood flow over a wide range from 0.2 to . To validate the phantom results, the varying blood flow rate from 0 to is detected in the rat carotid artery. Additionally, our technique also obtains blood flow maps of different myocardial vessels, such as superficial large/small veins, veins surrounded by fat, and myocardial deeper arteriole. Our study has the potential to visualize the spatio-temporal evolution of myocardial perfusion in coronary artery bypass grafting, which would be of great benefit for future research in the life sciences and clinical medicine.

Impact of transit-time flow measurement in patients undergoing on-pump coronary artery surgery

Impact of transit-time flow measurement in patients undergoing on-pump coronary artery surgery

Coronary Artery Bypass Grafting Using the No-Touch Great Saphenous Vein Graft Harvesting Technique: A Retrospective Study.

Background We focused on coronary artery bypass grafting using the great saphenous vein and compared the no-touch great saphenous vein and conventional great saphenous vein. Methods Coronary artery bypass grafting using the great saphenous vein was performed at our hospital over a 15-year period from 2007/04 to 2022/08. The primary endpoint was the patency of the great saphenous vein at discharge, and secondary endpoints were delayed healing of the great saphenous vein harvest wound, delayed healing of the mid-thoracic wound, and factors related to coronary artery bypass surgery. Results There were 183 patients who underwent coronary artery bypass surgery using the great saphenous vein during the study period. There were 131 male patients (72%) and 52 female patients (28%) with a mean age of 69 years (38-94 years). The method of harvesting the great saphenous vein was a no-touch great saphenous vein graft (NT-SVG) in 29 cases (16%) and conventional SVG in 154 cases (84%). Patients were divided into two groups: the NT-SVG group and the standard-collection saphenous vein graft (SVG) group. We compared graft patency at discharge, healing failure of the lower leg wound, healing failure of the mid-thoracic wound, and flow by transit-time flow measurement (TTFM). Conclusion There were no significant differences in perioperative outcomes between the NT-SVG and conventional SVG groups in this study.

Intraoperative transit-time flow measurement of caval veins before and after bidirectional cavopulmonary anastomosis.

Haemodynamic changes in caval venous flow distribution occurring during bidirectional cavopulmonary anastomosis operation are still largely unknown. Transit time flow measurements were performed in 15 cavopulmonary anastomosis operations. Superior and inferior caval vein flows were measured before and after the cavopulmonary anastomosis. Ratio of superior caval vein to overall caval veins flow was calculated. Mean superior caval vein flow ratio before cavopulmonary anastomosis was higher than previously reported for healthy children. Superior caval vein flow ratio decreased in 14/15 patients after cavopulmonary anastomosis: mean 0.63 ± 0.12 before versus 0.43 ± 0.14 after. No linear correlation between intraoperative superior caval vein pressure and superior caval vein flow after cavopulmonary anastomosis was found. Neither Nakata index nor pulmonary vascular resistance measured at preoperative cardiac catheterisation correlated with intraoperative flows. None of patients died or required a take down. The higher mean superior caval vein flow ratio before cavopulmonary anastomosis compared to healthy children suggests flow redistribution in univentricular physiology to protect brain and neurodevelopment. The decrease of superior caval vein flow ratio after cavopulmonary anastomosis may reflect the flow redistribution related to trans-pulmonary gradient. The lack of correlation between superior caval vein pressure and superior caval vein flow could be explained by limited sample size and multifactorial determinants of caval veins flow, although pressure remain essential. Larger sample of measurements are needed to find flow range potentially predictive for clinical failure. To authors' knowledge, this is the first intraoperative flow measurement of both caval veins during cavopulmonary operations.

Effect of Somatostatin on hepatic blood flow: preliminary results

Background: Somatostatin (SOMATO) administration affects hepatic blood flow (HBF); however, its clinical effect remains ill-defined. The aim of this study is to assess the clinical effects of SOMATO administration on HBF during major abdominal surgery by comparing HBF in patients with and without intra-operative SOMATO admin-istration. Methods: This retrospective analysis used data from two separate prospective studies including patients undergoing pancreaticoduodenectomy and was approved by the Ghent University Hospital ethical committee. All patients received total intravenous an-esthesia, using target-controlled infusion, and guided by a depth of anesthesia monitor. Schnider model was used for propofol, and Minto model was used for remifentanil. All patients received goal-directed hemodynamic therapy guided and recorded by Pul-sioFlex monitoring (Getinge Group). Portal vein blood flow and arterial hepatic blood flow were measured using ultrasound transit time flow measurements (Medi-Stim®). Both PVF and HAF were indexed using cardiac index. Patients were divided in two groups, receiving SOMATO (group S) versus control group not receiving SOMATO (group C). The Shapiro-Wilk test was used for testing normal distribution. Statistical testing was done using a Welch T-test or a Wilcoxon test. Results: From 6/2017 to 10/2020, a total of thirty-seven patients were analyzed. Twenty-five patients received SOMATO (group S) whereas twelve patients did not (group C). In Group S, PVFi was significantly reduced in patients receiving SOMATO compared to the control group (p = 0.005). HAFi was similar in both groups. The net effect on total HBFi was significantly lower in group S (p = 0.027). Hemodynamic parameters did not differ between both groups. Conclusions: SOMATO significantly reduced PVFi in the surgical patients while HAFi remained similar in both groups. As a result, total HBFi was significantly lower in SO-MATO-treated patients.

Comparison of flowmeter (transit time flow measurement) values for graft flow in three different surgical methods for isolated coronary artery bypass surgery.

Graft patency is the most important factor in coronary artery bypass surgery. This study aimed to compare the relationship between three different surgical methods and transit time flow measurement (TTFM), which is used to detect technical problems in anastomoses performed during coronary artery bypass graft operations and to correct them if necessary. A total of 110 patients undergoing isolated coronary artery bypass surgery were analysed. Of these patients, 48 were operated on by inducing cardiopulmonary arrest (group 1), 33 were operated on without inducing cardiac arrest (group 2) during cardiopulmonary bypass surgery, and 29 underwent surgery on the off-pump beating heart (group 3). TTFMs were performed on all the patients' grafts. Additional surgical intervention requirements, the need for intra-operative and postoperative inotropic support, and all postoperative follow-up data were compared. In total, 110 patients were measured for 301 grafts. Due to insufficient measurements performed on these patients, additional surgical intervention was performed on five grafts in group 1, five grafts in group 2, and seven grafts in group 3. These interventions enabled a normal flow rate to be achieved. The number of grafts that required revision was highest in group 3. There was no difference between the groups in terms of demographic data, EuroSCORE II, preoperative ejection fraction, postoperative complications and mortality rate. TTFM is important for detecting technical problems in grafts. We believe that all surgical methods can be applied more safely by controlling graft flow.

Effects of Fractional Flow Reserve on Coronary Artery Bypass Graft Flow to Left Anterior Descending Artery.

The relationships between preoperative fractional flow reserve (FFR) values of the left anterior descending artery (LAD), FFRLAD, and intraoperative transit time flow measurement (TTFM) variables in coronary artery bypass grafting (CABG) remain unclear.Methods and Results: We retrospectively collected data for 74 in situ left internal thoracic artery (LITA) grafts and 27 saphenous vein grafts (SVGs) to the LAD that were shown to be patent on postoperative angiography. Spearman correlation coefficients were determined between FFRLADand TTFM parameters of the LITA graft, as follows: maximum flow (Qmax), -0.22 (P=0.077); minimum flow (Qmin), -0.40 (P=0.014); mean flow (Qm), -0.35 (P=0.039); pulsatility index (PI), 0.33 (P=0.008); diastolic filling (DF): 0.01 (P=0.83); and systolic reverse flow (SRF), 0.37 (P=0.002). Spearman correlation coefficients between FFRLADand TTFM parameters of the SVG to LAD were: Qmax, -0.65 (P=0.004); Qmin, -0.43 (P=0.044); Qm, -0.75 (P=0.001); PI, 0.53 (P=0.033); DF, 0.14 (P=0.48); and SRF, 0.61 (P=0.009). Both LITA grafts and SVGs to the LAD show negative correlations for FFRLADwith Qminand Qm, but positive correlations for FFRLADwith PI and SFR. These relationships between FFRLADand TTFM variables of CABG grafts to the LAD should be recognized.

Do chronic total occlusive lesions affect patency of coronary bypass grafts to the right coronary artery?

To evaluate the impact of chronic total occlusion (CTO) lesions on the patency of bypass grafts to the right coronary artery territory. Two hundred patients undergoing primary isolated coronary artery bypass grafting with revascularization to the right coronary artery territory between April 2015 and July 2022 were retrospectively analyzed. Study patients were divided into two groups according to their right coronary artery lesion: patients with CTO lesions (n = 76) and those without CTO lesions (n = 124). Graft flow of the right coronary artery territory was evaluated by intraoperative transit time flow measurement and patency of the bypass graft was evaluated by multidetector row computed tomography. A total of 200 patients (76 patients with CTO and 124 patients without CTO) were included in this study. Intraoperative transit time flow measurement demonstrated that there was no significant difference in the median mean graft flow (30 ml/min vs. 25 ml/min; p = 0.114), pulsatility index (2.1 vs. 2.4; p = 0.079), and diastolic filling rate (65% vs. 64%; p = 0.844) between patients with CTO and those without CTO. Postoperative multidetector row computed tomography demonstrated that the patency of bypass grafts to the right coronary artery territory was similar between the groups (94.7% in patients with CTO vs. 96.0% in those without CTO; p = 0.733). In patients with CTO, the patency of bypass graft tended to be worse in subgroup with rich collateral blood flow (Rentrop grade 3). Chronic total occlusion lesions do not affect the patency of bypass grafts to the right coronary artery territory.

The Value of Left Internal Mammary Artery Flow Velocity in Predicting the Prognosis of Patients After Coronary Artery Bypass Grafting.

The purpose of this study was to explore the value of the left internal mammary artery flow velocity (LIMAV) measured by ultrasound before coronary artery bypass grafting (CABG) in predicting the prognosis of patients after left internal mammary artery (LIMA) bypass grafting. One hundred and four patients who underwent CABG with LIMA as the bridge vessel in the cardiovascular surgery department of our hospital between May 2018 and June 2019 were selected. All patients underwent transthoracic Doppler ultrasonography to measure LIMAV preoperatively. Intraoperatively, mean graft flow (MGF) and pulsatility index (PI) of the LIMA bridge were measured using transit time flow measurement (TTFM). The primary endpoint event in this study was cardiac death within 18 months after surgery. The Cox survival analysis showed that the MGF, the LIMAV and left ventricular ejection fraction (LVEF) were risk factors for death after CABG. The cut-offs of MGF, LIMAV and LVEF for the prediction of death after CABG were ≤ 14 mL/min (area under the curve (AUC): 0.830; sensitivity: 100%; specificity: 65.6%), ≤ 60 cm/s (AUC: 0.759; sensitivity: 65.5%; specificity: 85.3%), and ≤ 44% (AUC: 0.724; sensitivity: 50%; specificity: 88.5%), respectively. Compared with the use of MGF, MGF + LIMAV, combination of the MGF + LIMAV + LVEF (AUC: 0.929; sensitivity: 100%; specificity: 81.1%) resulted in a stronger predictive value (MGF vs. MGF + LIMAV + LVEF: P = 0.02). LIMAV measured by preoperative transthoracic ultrasound combined with intraoperative MGF and LVEF may have a greater value in predicting patients' risk of cardiac death after CABG.

Analysis of a multicenter registry on evaluation of transit-time flow in coronary artery disease surgery

ObjectiveThe Evaluation of Transit-Time Flow in Coronary Artery Disease Surgery (EFCAD) registry aims to assess the influence of transit-time flow measurement (TTFM) in daily practice. MethodsEFCAD is a prospective, multicenter study involving 9 centers performing TTFM during isolated coronary artery bypass grafting. Primary end point was occurrence and risk factors of major adverse cardiac events, including perioperative myocardial infarction, urgent postoperative coronary angiogram and/or revascularization, and hospital mortality. Secondary end points were rate of graft revision during surgery and factors affecting graft flow. We respected the limit values set by the experts: mean graft flow >15 mL/minute and pulsatility index ≤5. ResultsBetween May 2017 and March 2021, 1616 patients were registered in the EFCAD database. After review, 1414 were included for analyses. Of those, 1176 were eligible for primary end point analysis. Graft revision, mainly due to inadequate TTFM values, occurred in 2% (29 patients). The primary end point occurred in 46 (3.9%) patients, and it was related with left anterior descending artery graft flow ≤15 mL/minute (odds ratio, 3.64; P < .001). Graft flow was related with number of grafts (3 vs 1-2, β = −1.6; 4-6 vs 1-2, β = −4.1; P < .001; β > 0 indicates higher flow), and graft origin (aorta vs Y, β = 9.2; in situ left internal thoracic artery vs Y, β = 3.2; in situ right internal thoracic artery vs Y, β = 2.3; P < .001). ConclusionsData from EFCAD study suggest that TTFM is reliable to evaluate graft flow, and acceptance of inadequate flow on left anterior descending artery anastomosis influence postoperative outcomes. In our opinion, TTFM assessment should be routinely used in coronary artery bypass procedures, even if interpretation depends on learning curves.

Comparing perioperative outcomes following off-pump multi-vessel minimally invasive via a single left intercostal space incision with median sternotomy coronary artery bypass grafting: A single-center retrospective cohort study.

The perioperative outcomes following off-pump multi-vessel minimally invasive surgery (MICS) coronary artery bypass grafting (CABG) via a single left intercostal space incision has not been well evaluated. From July 2019 to January 2022, a total of 444 patients with multi-vessel coronary artery disease (CAD) were enrolled and divided into MICS (n = 179) and sternotomy CABG (n = 265). Perioperative outcomes were compared between these two groups, including intraoperative blood loss, postoperative first 24h drainage, ventilation duration, length of stay (LOS) in ICU and total LOS in hospital. Intraoperative blood flow of graft vessels were measured by transit-time flow measurement after vascular anastomosis and mean flow (MF) and pulsatile index (PI) were compared. There were no significant differences in preoperative profiles between these two groups except younger and lower proportion of female in MICS. No significant difference in the number of graft vessels was observed between MICS (3.18 ± 0.74) and sternotomy CABG (3.28 ± 0.86). Compared to sternotomy CABG, patients with MICS showed longer operation duration [(4.33 ± 0.86)h versus (5.10 ± 1.09)h], fewer intraoperative blood loss [700 (600, 900)mL versus 500 (200, 700)mL], fewer postoperative first 24h drainage [400 (250, 500)mL versus 300 (200, 400)mL], shorter postoperative ventilation duration [16.5 (12.5, 19.0)h versus 15.0 (12.0, 17.0)h], LOS in ICU [20.0 (16.0, 23.0)h versus 18.0 (15.0, 20.0)h] and total LOS in hospital [(14.5 ± 3.9)d versus (12.6 ± 2.7)d] (all p < .001). MI and PI of graft vessels were similar and no significant differences in major perioperative complications and mortality were observed between MICS and sternotomy CABG (all p > .05). Off-pump multi-vessel MICS may be an alternative treatment for patients with multi-vessel CAD with better perioperative outcomes than sternotomy CABG.

Efficacy of off-pump minimally invasive via a single left intercostal space incision compared with median sternotomy multi-vesselcoronary artery bypass grafting

Objective: To compare the efficacy of off-pump minimally invasive cardiac surgery (MICS) via a single left intercostal space incision with median sternotomy multi-vesselcoronary artery bypass grafting (CABG). Methods: Patients who were diagnosed with multi-artery coronary artery disease (CAD) in the Ward 10 of the Department of Cardiac Surgery, Beijing Anzhen Hospital Affiliated to Capital Medical University and underwent CABG from July 2019 to January 2022 were retrospectively collected. All the patients were divided into MICS group and conventional CABG group according to the surgical methods. The perioperative outcomes were compared between thetwo groups, including intraoperative blood loss, postoperative 24 h thoracic drainage volume, ventilation duration, length of stay (LOS) in intensive care unit (ICU) and total LOS in hospital. Intraoperative blood flow of graft vesselswas measured by transit-time flow measurement (TTFM) after vascular anastomosis, and mean flow (MF) and pulsatile index (PI) were compared between the two groups. Results: A total of 444 patients were in the final analysis, with 351 males and 93 females, and the mean age of (62.0±8.9) years. There were 179 patients in MICS group and 265 cases in conventional CABG group, respectively. There were no statistically significant differences in the preoperative profiles between the two groups (all P>0.05) except that younger age [(60.7±9.3) years vs (62.8±8.5) years, P=0.017] and lower proportion of female [10.1% (18/179) vs 28.3% (75/265), P<0.001] were detected in MICS group. Likewise, there was no significant difference in the number of graft vessels between MICS group (3.18±0.74) and conventional CABG group (3.28±0.86) (P=0.234). Compared with those in conventional CABG group, patients in MICS group showed longer operation duration [ (5.10±1.09) h vs (4.33±0.86) h], fewer intraoperative blood loss [500 (200, 700) ml vs 700 (600, 900) ml], fewer postoperative 24 h thoracic drainage volume [300 (200, 400) ml vs 400 (250, 500) ml], shorter postoperative ventilation duration [15.0 (12.0, 17.0) h vs 16.5 (12.5, 19.0) h, P<0.001], LOS in ICU [18.0 (15.0, 20.0) h vs 20.0 (16.0, 23.0) h, P<0.001] and total LOS in hospital [(12.6±2.7) d vs (14.5±3.9) d, P<0.001]. MI and PI of graft vessels were similar between the two groups (both P>0.05). Moreover, there were no significant differences in major perioperative complications (i.e., repeat thoracotomy, incision infection, stroke) and mortality between the two groups (all P>0.05). Conclusion: MICS is an alternative treatment for patients with multi-vessel CAD with better perioperative outcomes compared with conventional CABG.

The preoperative myocardial perfusion and internal mammary artery graft blood flow relationship in patients with ischemic cardiomyopathy

Objective. The purpose of this study was to determine the association between preoperative myocardial perfusion data (obtained by SPECT) with transit time blood flow characteristics in left internal mammary artery (LIMA) to left anterior descending artery (LAD) grafts in patients with ischemic cardiomyopathy.Methods. The study group consisted of 57 patients with ischemic cardiomyopathy. Intraoperative transit-time flow measurement (TTFM) of LIMA-LAD grafts were performed in all patients. All patients were also examined with preoperative stress and rest myocardial perfusion SPECT with 99m Tc-MIBI. Anastomotic patency was considered satisfactory with a normal waveform of blood flow, diastolic-dominant blood filling, and a mean flow value greater than 11.5 ml/min.Results. All 57 patients with LIMA-LAD grafts were divided into two groups; those with graft satisfactory patency (n = 40) and those with unsatisfactory patency (n = 17) as determined by TTFM. We found differences among these groups in values of global summed rest score (20.7 ± 7.5 vs. 29.8 ± 4.0; p = 0.002), global total perfusion deficit (TPD) at rest (32.0 ± 11.4 vs. 43.0 ± 7.2; p = 0.01), and regional TPD at rest in the LAD territory (20.7 ± 7.5 vs. 29.8 ± 4.0; p = 0.002). Additionally, the flow characteristics were different in patients with and without surgical left ventricle reconstruction (Q (ml/min): 17 (11.5, 40.8) vs. 47 (25, 69.5), p = 0.013; PI: 3.9 (3.2, 7.4) vs. 2.4 (2.0, 3.6), p = 0.001; DF (%): 63.5 (44.5, 70.8) vs. 74 (66.0, 79.7), p = 0.019). TPD at rest was the best predictor of the LIMA-LAD graft satisfactory: area under curve = 0.771, cut-off value = 26.85 with 83.3% sensitivity and 78.1% specificity.Conclusions. Preoperative myocardial perfusion characteristics are associated with blood flow in LIMA-LAD graft in patients with ischemic cardiomyopathy. TPD at rest (assessed globally and in the LAD region) as well as global SRS value are potential predictors of early graft failure.

The Impact of Operative Strategy on Bypass Graft Haemodynamics Assessed With Transit Time Flow Measurement

To assess the impact of grafting configuration in coronary artery bypass surgery on bypass graft haemodynamic parameters (assessed by transit time flow measurement).

The Impact of Patient Factors on Bypass Graft Haemodynamics Assessed With Transit Time Flow Measurement

To assess the impact that coronary anatomy and patient factors have on bypass graft haemodynamic parameters, as assessed by transit time flow measurement (TTFM).

A novel transit-time flow metric, diastolic resistance index, detects subcritical anastomotic stenosis in coronary artery bypass grafting.

Transit time flow measurement (TTFM) can detect critical anastomotic stenosis during coronary artery bypass grafting. However, the identification of subcritical stenosis remains challenging. We hypothesized that diastolic resistance index (DRI), a novel TTFM metric, is more effective in evaluating subcritical stenosis than the currently available TTFM metrics. DRI is used to measure changes in the diastolic versus systolic resistance of distal anastomosis. A total of 123 coronary bypass anastomoses in 35 patients were prospectively analyzed. During coronary artery bypass grafting, the mean graft flow (Qmean), pulsatility index, and diastolic filling were obtained. DRI was calculated using the intraoperative recordings of TTFM and arterial pressure. Postoperatively, stenosis of anastomoses was categorized into successful (<50%), subcritical (50%-74%), and critical (≥75%) via multidetector computed tomography scan. In total, 93 (76%), 13 (10%), and 17 (14%) anastomoses were graded as successful, subcritical, and critical, respectively. DRI and diastolic filling could distinguish subcritical from successful anastomoses (P<.01 and<.01, respectively), whereas Qmean and pulsatility index could not (P=.12 and .39, respectively). The receiver operating characteristic curves were established to evaluate the diagnostic ability for detecting ≥50% stenosis. In left anterior descending artery grafting (n=55), DRI had the highest area under the curve (0.91), followed by diastolic filling (0.87), Qmean (0.74), and pulsatility index (0.65). DRI and diastolic filling had a reliable diagnostic ability for detecting ≥50% stenosis during coronary artery bypass grafting. In left anterior descending artery grafting, DRI had a more satisfactory detection capability than other TTFM metrics.

Transit time flow measurement as a predictor of graft failure and major adverse cardiac events following coronary artery bypass grafting surgery

IntroductionOur aims were to characterize the differences in transit time flow measurement (TTFM) between failed and normal grafts, and to determine the association between TTFM and related clinical factors and the likelihood of graft failure and major adverse cardiac events (MACE) following coronary artery bypass grafting.Material and methodsA retrospective observational analysis was performed on 279 patients admitted between 2017 and 2019, to compare the differences in TTFM between failed and normal grafts, and the association between TTFM and major adverse cardiac events (MACE) – specifically angina, myocardial infarction, and death.ResultsThere were no differences in TTFM between failed and normal grafts. There was a greater number of failed grafts with pulsatility index (PI) &gt; 5 compared to PI ≤ 5 (χ&lt;sup&gt;2&lt;/sup&gt; = 4.021, p = 0.045). Multivariate analysis showed no significant association between TTFM and MACE. Increased risk of graft failure is associated with the female gender (p = 0.031), history of congestive heart failure (p = 0.025), and poor renal function (p = 0.034). Increased risk of MACE is associated with a history of coronary intervention (p = 0.041), left coronary dominance (p = 0.018), and renal function (p = 0.009).ConclusionsPatency of graft is influenced by gender, congestive heart failure, and renal function, while MACE is influenced by history of coronary intervention and renal function.

The Importance of Perioperative Flow Evaluation and Prevention of Steal Syndrome in Arteriovenous Fistula Surgery Using Transit-Time Flow Measurement

Aim: Our aim is to evaluate the relationship between the survival time of arteriovenous (AV) fistula whose flows are measured with flow meter in patients with chronic renal failure who were operated for AV fistula (AVF) and present the results. Materials and Methods: In our clinic, we evaluated the flow meter measurement results with patency rates and usability after 6 months of AVF in 100 patients who underwent AVF operation due to chronic renal failure. Findings: In February 2012, transit-time flow measurement was put into use in our clinic. The last 50 consecutive patients with the same characteristics before this date constituted the control group (Group A) and the first 50 consecutive patients after this date constituted the study group. Radiocephalic fistula was made the most common (Group A, n = 50; Group B, n = 50). Nondominant upper extremity was selected when planning AVF for patients. First radiocephalic, then brachiocephalic AVF was performed. Fistulas flow was measured with an intraoperative flow meter. Those with bad flow were revised during the operation. Embolectomy was performed in one patient at the 2nd month due to fistula thrombosis, but it was not successful in one patient, and an AVF was opened with a graft. Results: While creating AVF, our aim is to use it effectively for a long time. By evaluating the fistula flows with the flow meter and make an intraoperative revision if necessary we ensure to extend the lifespan of a fistula.