Clinical value of intra-operative transit-time flow measurement for coronary artery bypass grafting: a prospective angiography-controlled study

Preoperative Quantitative Flow Ratio, Intraoperative Transit Time Flow Measurement Parameters, and Their Predictive Value for Short-Term Graft Failure After Coronary Artery Bypass Grafting

BACKGROUND

Studies on the relationship between the preoperative quantitative flow ratio (QFR) and parameters of intraoperative transit time flow measurement (TTFM) are extremely rare. In addition, the predictive value of QFR and TTFM parameters for early internal mammary artery (IMA) failure after coronary artery bypass grafting still needs to be validated.

METHODS AND RESULTS

We retrospectively collected data from 510 patients who underwent in situ IMA grafting to the left anterior descending (LAD) artery at Fuwai Hospital. Spearman correlation coefficients between preoperative QFR of the LAD artery and intraoperative TTFM parameters of the IMA were -0.13 (P=0.004) for mean graft flow (Qm) and 0.14 (P=0.002) for the pulsatility index (PI). QFR and TTFM exhibited similar and good predictive value for early IMA failure (5.7% at 1 year), and they were better than percentage diameter stenosis (area under the curve 0.749 for QFR, 0.733 for Qm, 0.688 for PI, and 0.524 for percentage diameter stenosis). The optimal cut-off value of QFR was 0.765. Both univariate and multivariable regression analyses revealed that QFR >0.765, Qm ≤15 mL/min, and PI >3.0 independently contributed to early IMA failure.

CONCLUSIONS

There were statistically significant correlations between preoperative QFR of the LAD artery and intraoperative TTFM parameters (Qm, PI) of the IMA. Preoperative QFR and intraoperative Qm and PI exhibited excellent predictive value for early IMA failure.

External stenting for saphenous vein grafts reduces early postoperative graft failure

OBJECTIVES

Multiple studies have shown that external stenting (ExSt) mitigates the progression of vein graft disease years after coronary artery bypass grafting (CABG). We used computed tomography to evaluate the effect of ExSt on perioperative vein graft patency.

METHODS

This study assessed graft patency rates of saphenous vein grafts (SVG) in consecutive patients with isolated coronary artery bypass grafting (CABG) between 2018 and 2021. Logistic regression analyses were conducted to compare the outcomes of supported and non-supported groups at both patient and graft levels, with age, EuroSCORE II, gender, diabetes and arterial grafts as covariates. Subgroup analyses were performed based on different covariates. The goal of the study was to provide valuable insights into the clinical outcomes of SVG in patients having CABG.

RESULTS

The study examined a total of 357 patients who met the inclusion criteria and evaluated 572 vein grafts. Of these, 150 patients (205 SVGs) received ExSt, whereas 207 patients (337 SVGs) did not receive ExSt. The study results indicated that the likelihood of overall SVG patency at discharge was higher in the stented group than in the non-stented group, both at the level of the grafts [93.8% vs 87.8%, odds ratio (OR) 2.1; 95% confidence interval (CI) 1.0-4.5; P = 0.05] and at the patient level (90.1% vs 83.5%, OR 1.8; 95% CI 0.9-3.6; P = 0.1). It is worth noting that the difference between the stented and non-stented groups was most significant in the subgroup that received 2 arterial grafts (96.5% vs 89.6%, OR 3.2; 95% CI 1.2-8.4; P = 0.02) and in the subgroup with a higher EuroSCORE II (median >1.1) (98.6% vs 88.6%, OR 8.8; 95% CI 1.1-72.7; P = 0.04).

CONCLUSIONS

The ExSt is associated with improved perioperative SVG patency at both the graft and the patient levels. Moreover, SVGs to the right territory and high-risk patients appear to have an advantage using ExSt.

How to harvest the left internal mammary artery-a randomized controlled trial

OBJECTIVES

It is uncertain whether Thunderbeat has a place in harvesting the left internal mammary artery (LIMA) and whether skeletonization is superior to pedicle-harvested LIMA. Some investigations have shown improved flowrates in the skeletonized graft. The aim of this study was to compare 3 groups of harvesting techniques: Pedicled, surgical skeletonized and skeletonized with Thunderbeat in terms of flow rates in the LIMA and postoperative in-hospital outcomes.

METHODS

Patients undergoing coronary artery bypass grafting with the LIMA to the anterior descending artery were randomized to pedicled (n = 56), surgical skeletonized (n = 55) and skeletonized with Thunderbeat (n = 54). Main outcomes were blood flow and pulsatility index in the graft.

RESULTS

No statistical difference between groups regarding flow in LIMA or pulsatility index. Similarly, no difference in postoperative bleeding or days of hospitalization. The duration of harvesting was faster for the pedicled technique compared with surgical skeletonized and skeletonized with Thunderbeat [mean total min: pedicled 20.2 min standard deviation (SD) ± 5.4; surgical skeletonized 28.6 min SD ± 8.7; skeletonized with Thunderbeat 28.3 min SD ± 9.11, P < 0.001]. No grafts discarded due to faulty harvesting and there was no graft failure within hospital stay.

CONCLUSIONS

We found no difference between the harvesting methods except for a significantly faster harvesting time with the pedicled technique. However, non-touch skeletonized LIMA harvesting with Thunderbeat seems to be an effective alternative to traditional surgical skeletonized LIMA. The future will reveal whether patency is harvesting dependent.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT05562908.

Transient time flow measurement in arterial grafts

Coronary artery bypass grafting (CABG) is one of the foundations of treatment for coronary artery disease. While it has improved substantially since its inception more than 50 years ago, including a rising use of multiple arterial grafting, intraoperative quality assessment is yet to be disseminated as an integral part of the procedure. Herein we review the fundamentals of intraoperative quality assessment in CABG using transient time flow measurement (TTFM) with a focus on its use in arterial grafting.

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

Objective

The 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.

Methods

EFCAD 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.

Results

Between 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).

Conclusions

Data 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.

Transit-Time Flow Measurement and Outcomes in Coronary Artery Bypass Graft Patients

Transit-time flowmetry (TTFM) is commonly used during coronary artery bypass grafting for intraoperative graft assessment. This study aimed to investigate whether TTFM values were predictive of graft failure and major adverse cardiac and cerebrovascular events (MACCEs). Between 2011 and 2018, 1933 patients with 3-vessel coronary artery disease who underwent off-pump coronary artery bypass were retrospectively analyzed. Among them, 1288 sequential venous grafts in 538 consecutive patients were measured using TTFM's 2 parameters, pulsatility index (PI) and flow (mL/min). The anastomoses were divided in the 3 groups depending on the anastomotic site: group A, first side-to-side anastomoses (n = 538), group B; second side-to-side (n = 212), group C; end-to-side (n = 538). MACCEs were related to TTFM. The mean clinical follow-up time was 64.8 ± 21.2 months. Postoperative graft patency was confirmed with multi-slice computed tomography or coronary angiography (follow-up interval: 64.8 ± 50.4 and 27.8 ± 20.5 months based on the date of examination). The 5-year survival rate was 93.7%. The mean graft flow was 59.1 ± 31.3, 41.0 ± 25.2, and 38.9 ± 22.8 mL/minute, and the PI was 2.2 ± 1.3, 2.5 ± 3.4, and 2.4 ± 2.5, in groups A, B, and C, respectively. Graft failure occurred in 23/1055 (2.2%) anastomoses. The 5-year MACCE rate was 6.9% (37/538 patients). Kaplan-Meier analysis revealed that graft patency was significantly lower in low MGF (p = 0.044) and high PI (p < 0.001). Multivariable logistic analysis showed that high PI (>5; HR 2.276; 95%CI 2.188-2.406, p < 0.001) was an independent risk factor for MACCEs. The cutoff values for PI of sequential grafts were 3.65, 3.55, and 3.17 in groups A, B, and C, respectively for the prediction of MACCE. A high PI predicts more predictive poor outcomes of sequential venous grafts after surgery than the low mean graft blood flow.

Intraoperative transit time flow measurements during off-pump coronary artery bypass surgery: The impact of coronary stenosis on competitive flow

BACKGROUND

Combining preoperative angiography findings with intraoperative transit time flow measurements (TTFM) may improve patency of coronary artery bypass grafts. Nevertheless, graft flow might be impaired by native coronary flow based on the severity of stenoses, with inferior long-term outcomes. This study investigates the impact of left anterior descending artery (LAD) stenosis on competitive flow measured in left internal mammary artery (LIMA) grafts during off-pump coronary artery bypass grafting.

METHODS

Fifty patients were included in this prospective single-center cohort study. LAD stenosis was assessed with quantitative coronary analysis (QCA) and stratified into three groups based on its severity. TTFM of LIMA grafts were performed with LAD open and temporarily occluded. Change in mean graft flow after LAD snaring was the primary endpoint. Secondary endpoints included further TTFM parameters, clinical outcomes, and competitive flow index (CFI), defined as the ratio of mean graft flow with open or closed LAD.

RESULTS

Mean LAD stenosis as objectified with QCA was 58 ± 15%. Mean LIMA graft flow increased from 20 ml/min with open LAD to 30 ml/min with snared LAD (p < .001). TTFM cut-off values for graft patency improved in 26%-42% of patients after LAD occlusion. Median CFI was 0.66 (IQR: 0.56-0.82). Postoperative myocardial infarction occurred in 2.0% of patients, 120-day mortality was 0%, and 2-year mortality was 6.0%.

CONCLUSIONS

Routine snaring of the LAD with CFI calculation during coronary artery bypass grafting is useful to detect significant competitive flow in LIMA grafts, potentially preventing unnecessary intraoperative graft revisions.

The Use of Intraoperative Transit Time Flow Measurement for Coronary Artery Bypass Surgery: Systematic Review of the Evidence and Expert Opinion Statements

Transit time flow measurement (TTFM) allows quality control in coronary artery bypass grafting but remains largely underused, probably because of limited information and the lack of standardization. We performed a systematic review of the evidence on TTFM and other methods for quality control in coronary artery bypass grafting following PRISMA standards and elaborated expert recommendations by using a structured process. A panel of 19 experts took part in the consensus process using a 3-step modified Delphi method that consisted of 2 rounds of electronic voting and a final face-to-face virtual meeting. Eighty percent agreement was required for acceptance of the statements. A 2-level scale (strong, moderate) was used to grade the statements based on the perceived likelihood of a clinical benefit. The existing evidence supports an association between TTFM readings and graft patency and postoperative clinical outcomes, although there is high methodological heterogeneity among the published series. The evidence is more robust for arterial, rather than venous, grafts and for grafts to the left anterior descending artery. Although TTFM use increases the duration and the cost of surgery, there are no data to quantify this effect. Based on the systematic review, 10 expert statements for TTFM use in clinical practice were formulated. Six were approved at the first round of voting, 3 at the second round, and 1 at the virtual meeting. In conclusion, although TTFM use may increase the costs and duration of the procedure and requires a learning curve, its cost/benefit ratio seems largely favorable, in view of the potential clinical consequences of graft dysfunction. These consensus statements will help to standardize the use of TTFM in clinical practice and provide guidance in clinical decision-making.

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

INTRODUCTION

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.

OBJECTIVES

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.

METHODS

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.

RESULTS

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, p = 0.070). The flow volume on the early postoperative CDUS significantly increased (39.77 ± 21.59 vs. 25.96 ± 13.17 mL/min, p < 0.001) and the PI significantly decreased (1.43 ± 0.46 vs. 4.20 ± 1.49, p < 0.001) versus those of preoperative measurements. The MGF had a moderate correlation with the flow volume on the early postoperative CDUS (r = 0.414, p = 0.002), and the PI by TTFM had a weak correlation with that by CDUS (r = 0.353, p = 0.010) as well.

CONCLUSIONS

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.

Predictive value of graft patency and major adverse cardiac and cerebrovascular events (MACCEs) in coronary artery bypass grafting (CABG) based on Fourier transform (FFT)

BACKGROUND

Transit time flow measurement (TTFM) is widely used in coronary artery bypass grafting (CABG); however, its predictive value is unclear. We aimed to identify new factors to evaluate graft quality using fast Fourier transform (FFT).

METHODS

Intraoperative and postoperative 2-year follow-up data of 114 patients undergoing CABG from January 2017 to December 2018 were collected. The TTFM waveform was transformed by FFT. Mean graft flow (MGF), pulse index, the amplitude of the main wave in FFT (H0), the amplitude of the first harmonic (H1), H0/H1, and the frequency of the first harmonic (P) were analyzed as predictors using logistic regression and receiver operating characteristic (ROC) curves.

RESULTS

The overall graft patency rate was 80.3%, and the incidence of major adverse cardiac and cerebrovascular events (MACCEs) was 14.9%. The results demonstrate that compared with the graft failure group, MGF, H0, and H1 were higher, but H1 and P were lower in the patent group. With univariate and multivariate logistic regression analyses, the decrease in H0 and H1 and the increase in P were independent risk factors for graft failure, while the decrease in MGF and the increase in H0/H1 were only statistically significant with a univariate analysis. In the cardiovascular events group, the increase in P was an independent risk factor. With a ROC curve analysis, MGF, H0, H1, H0/H1, and P predicted graft failure, while only P predicted cardiovascular events. None of the indicators showed predictive value for MACCEs.

CONCLUSIONS

TTFM waveforms after FFT can be used to evaluate graft quality and cardiovascular events, but have no predictive value for MACCEs.

Intraoperative angiography during coronary artery bypass grafting

INTRODUCTION

The aim of this study was to evaluate the incidence rate of technical failure of graft patency while performing intra-operative angiography after coronary artery bypass grafting.

METHODS

This prospective pilot study included 50 patients with multi-vessel coronary artery disease who underwent coronary artery bypass grafting, in addition to intra-operative angiographic graft assessments, on open-chest. Overall, 144 grafts and 160 distal anastomoses were assessed in a hybrid operating room.

RESULTS

Intra-operative angiography allowed the identification of 23 angiographic defects (15.9% of all grafts) in 22 patients (44%): three graft defects (2% of all grafts), 17 anastomotic defects (10.6% of all distal anastomoses), and three target artery errors (1.8% of all grafted arteries). Ten re-interventions (43.4%) were performed based on the angiographic defects detected. During the follow-up period, computed tomography angiography of the attached grafts at a mean of 224 days (range, 80-318 days) showed that all repaired grafts were patent. During surgery, the total mean dose of radiation was 1.848 ± 0.54 mSv (range, 0.78-3.4 mSv) per patient and investigation time was 19.4 ± 4.94 minute (range, 9-31 minute).

CONCLUSIONS

Intra-operative angiography is a powerful tool allowing the identification of graft defects, anastomotic defects and target vessel errors. Assuming relatively low level of exposure to radiation and short investigation time, intra-operative angiography could be included in routine practice as safe procedure improving surgery quality.

A new way to use transit-time flow measurement for coronary artery bypass grafting

OBJECTIVES

Transit-time flow measurement is a recognized method for graft evaluation in coronary surgery. However, single flow measurement has been associated with a low specificity for detecting graft dysfunction. The goal of this study was to assess the value of transit-time flow measurement for assessing in situ internal mammary artery grafts during non-existent native coronary circulation and the relevance of collateral blood flow in target vessels.

METHODS

Between 2014 and 2018, a total of 134 patients undergoing on-pump coronary artery bypass grafting were evaluated using transit-time flow measurement. We analysed 111 single left internal mammary artery and 57 single right internal mammary artery bypasses. Correlations between coronary relevant parameters were calculated using Spearman's ρ coefficient. Risk factors for decreased flow with an arrested heart (FAH) <30 ml/min and an increased pulsatility index (PI) >3.0 as well as flow reduction >30% were calculated.

RESULTS

FAH correlated with the diameter of the target vessel (Spearman's ρ = 0.32; P < 0.001), the amount of blood distribution (Spearman's ρ = 0.34; P < 0.001), the PI (Spearman's ρ = 0.19; P = 0.019) and the degree of stenosis (Spearman's ρ = -0.17; P = 0.042). The percentage of flow change was found to correlate with the PI (Spearman's ρ = -0.47; P < 0.0001), the degree of stenosis (Spearman's ρ = 0.42; P < 0.001), the diameter of the target vessel (Spearman's ρ = -0.22; P = 0.008) and the area of blood distribution (Spearman's ρ = -0.19; P = 0.018). A small blood distribution area was the only risk factor for decreased FAH [odds ratio (OR) 8.43, confidence interval (CI) 95% (3.04-23.41); P < 0.001]. Binary logistic regression identified PI [OR 2.05, CI 95% (1.36-3.10); P = 0.001], FAH [OR 0.98, CI 95% (0.97-0.99); P = 0.005] and degree of stenosis [OR 0.95, CI 95% (0.92-0.99); P = 0.011] as risk factors for decreased flow after cardiopulmonary bypass (<30 ml/min). An increased PI (>3) was mainly influenced by percentage of flow change [OR 0.99, CI 95% (0.98-1.00); P = 0.031].

CONCLUSIONS

FAH and percentage of flow change are related to the dimensions of the target vessel and the degree of stenosis. The addition of flow measurements with the heart arrested provides additional information about the bypass graft, the quality of the anastomosis and the physiology of the coronary circulation.

Coronary Artery Bypass Grafting Transit Time Flow Measurement: Graft Patency and Clinical Outcomes

BACKGROUND

This subanalysis of the Randomized On-Off Bypass (ROOBY) trial examined transit time flow measurement (TTFM) use and its impact on graft patency and long-term clinical outcomes after coronary artery bypass graft surgery.

METHODS

Use of TTFM for ROOBY centers and surgeons was assessed. Comparative patient outcomes based on TTFM use included 1-year graft patency and 1-year and 5-year major adverse cardiac events: all-cause mortality, nonfatal myocardial infarction, and revascularization (percutaneous coronary intervention or repeat coronary artery bypass graft surgery).

RESULTS

Transit time flow measurement was used in 1067 patients (TTFM group) and not used in 501 patients (non-TTFM group); of the TTFM group, median percentage TTFM use was 79% (interquartile range, 41% to 98%) among 18 Veterans Affairs Medical Centers, and 74% (interquartile range, 13% to 98%) among 48 surgeons. Patients were comparable in age (63 ± 8.5 years TTFM vs 62 ± 8 years non-TTFM, P = .30) and estimated 30-day mortality risk (1.8 ± 1.7 TTFM vs 1.9 non-TTFM, P = .53). One-year FitzGibbon A patency was 83% (1600 of 1988 grafts) for TTFM assessed grafts and 78% (629 of 803) for non-TTFM assessed grafts (P < .01). Fewer TTFM patients had an occluded graft (29%, vs 38% non-TTFM; P = .01). Comparing TTFM patients with non-TTFM patients, 5-year major adverse cardiac event rates were 30% vs 25% (P = .06). Individual component rates were 14% vs 11% for death (P = .06), 12% vs 8.8% for myocardial infarction (P = .07), and 13% vs 12% for revascularization (P = .62).

CONCLUSIONS

The association of TTFM use with graft patency and clinical outcome is uncertain. Future randomized studies that account for patient risk factors and practice variation would help address this knowledge gap.

Noninvasive flow evaluations of coronary artery bypass grafting using dynamic cardiac CT

We aimed to investigate the correlation of graft flow measurements between transit-time flow measurement (TTFM) during coronary artery bypass grafting (CABG) surgery and dynamic cardiac CT after the surgery.Fourteen patients underwent CABG with TTFM and postoperative dynamic cardiac CT; 11 internal thoracic artery (ITA) grafts and 15 saphenous venous grafts (SVGs) were included for analysis. Pearsons correlation analysis was performed for the comparisons of the TTFM and cardiac dynamic CT flow parameters.TTFM was not significantly correlated with the CT flow of the ITA grafts (r = -0.23, P = .49), but it had a very strong correlation with the CT flow of the SVGs (r = 0.83, P < .01).In patients who underwent CABG surgery, dynamic cardiac CT enabled quantitative evaluation of SVG flow, with good correlation with TTFM.

Improving coronary artery bypass grafting: a systematic review and meta-analysis on the impact of adopting transit-time flow measurement

Despite there being numerous studies of intraoperative graft flow assessment by transit-time flow measurement (TTFM) on outcomes after coronary artery bypass grafting (CABG), the adoption of contemporary TTFM is low. Therefore, on 31 January 2018, a systematic literature search was performed to identify articles that reported (i) the amount of grafts classified as abnormal or which were revised or (ii) an association between TTFM and outcomes during follow-up. Random-effects models were used to create pooled estimates with 95% confidence intervals (CI) of (i) the rate of graft revision per patient, (ii) the rate of graft revision per graft and (iii) the rate of graft revision among grafts deemed abnormal based on TTFM parameters. The search yielded 242 articles, and 66 original articles were included in the systematic review. Of those articles, 35 studies reported on abnormal grafts or graft revisions (8943 patients, 15 673 grafts) and were included in the meta-analysis. In 4.3% of patients (95% CI 3.3–5.7%, I² = 73.9) a revision was required and 2.0% of grafts (95% CI 1.5–2.5%; I²=66.0) were revised. The pooled rate of graft revisions among abnormal grafts was 25.1% (95% CI 15.5–37.9%; I²=80.2). Studies reported sensitivity ranging from 0.250 to 0.457 and the specificity from 0.939 to 0.984. Reported negative predictive values ranged from 0.719 to 0.980 and reported positive predictive values ranged from 0.100 to 0.840. This systematic review and meta-analysis showed that TTFM could improve CABG procedures. However, due to heterogeneous data, drawing uniform conclusions appeared challenging. Future studies should focus on determining the optimal use of TTFM and assessing its diagnostic accuracy.

[Role of intraoperative flowmetric assessment of coronary artery bypass grafts established on-pump]

AIM

This study was undertaken to evaluate the efficacy of three-stage measurement of the transit-time flow through coronary bypass grafts with the help of flowmetry for early verification of technical errors during on-pump coronary artery bypass graft surgery.

PATIENTS AND METHODS

We performed an intraoperative analysis of 214 bypass grafts with the help of three-stage flowmetry. The first stage of measuring was performed on-pump with and without the proximal loop test, the second stage of measurement was performed after weaning the patient off the heart-lung machine, and the third stage of measurement was carried out after heparin inactivation prior to chest wound closure.

RESULTS

Amongst the 214 transplants regarded as functioning, intraoperative flowmetry revealed insufficient blood flow in 9 (4.2%) cases. Technical surgical errors were confirmed in these shunts during revision thereof. In 6 (2.8%) of the 9 such grafts we detected non-optimal parameters of flowmetry during the first measurement (while the heart was stopped); of these, in 5 (2.3%) cases non-optimal blood flow was verified with the use of the proximal loop test on the target coronary artery and in 1 (0.47%) case without it. In another one (0.47%) of the nine such transplants, inadequate blood flow was revealed during the second measurement, which confirmed technical errors in proximal anastomoses. In a further 2 (0.93%) of the 9 such transplants we observed low parameters of blood flow during the third measurement, which was related to kinking of the shunts due to their excessive length. All surgical errors were corrected immediately at the stage of verification thereof.

CONCLUSION

The strategy of three-stage assessment of flowmetry makes it possible to ensure and confirm adequate functionality of coronary artery bypass grafts at all stages of the operation, thus allowing timely verification and immediate correction of any technical problems with coronary artery bypass grafts.

Initial Experience with Epicardial Ultrasound Scanning in Coronary Artery Bypass Grafting

BACKGROUND

The benefits of epicardial ultrasound scanning (EUS) in coronary artery bypass grafting (CABG) have not yet been established. The aim of this study was to evaluate the usefulness of EUS in CABG, including in the assessment of the quality of distal anastomoses, the identification of epicardial target vessels, and the evaluation of any graft issues other than the distal anastomoses.

METHODS

Fifty-three patients undergoing CABG were enrolled between March 2018 and February 2019. Intraoperative EUS was performed along with transit-time flow measurement (TTFM). Graft evaluations were performed early (shortly after surgery) and 1 year after surgery for 53 (100%) and 47 (88.7%) patients, respectively.

RESULTS

EUS was applied to assess the quality of all distal anastomoses, 32 target vessels, and 2 conduit trunks. Insufficient TTFM findings were obtained for 18 grafts. However, graft revision was performed for only 3 distal anastomoses; based on the EUS findings, the remaining 15 sites were not revised. The early and 1-year overall graft patency rates were 100% (141 anastomoses) and 96.1% (122 of 127 anastomoses), respectively. All 15 of the distal anastomoses that were not revised despite insufficient TTFM results were patent at the 1-year mark.

CONCLUSION

The routine application of EUS in CABG could be beneficial by confirming the quality of surgery and reducing unnecessary procedures.

Perioperative observations of different bypass modes of a right coronary system based on instantaneous blood flow during the operation

Background

With the ageing of China’s population, the incidence and mortality of coronary atherosclerotic heart disease (CAD) is increasing year by year, which brings a heavy burden to the family and society [1]. We aimed to analyse the strategy of coronary artery bypass grafting (CABG) in the right coronary artery and to compare the haemodynamic characteristics of the sequential grafts with those of single grafts and to observe the patency rate of those grafts for 1 week after the operation.

Methods

A total of 242 patients (178 men, mean age 62.6 ± 8.8 years) underwent right coronary artery bypass grafting in our hospital from October 2016 to January 2019. The blood flow (Q, ml/min), pulsatility index (PI) and related parameters of the grafts were measured and recorded by TTFM during the CABG. The patency of the grafts was evaluated by coronary computed tomography (CT) for 1 week after the operation.

Results

The most common material used for the graft in the right coronary system of CABG is the greater saphenous vein (92.3%), followed by the radial artery (5.5%) and the internal mammary artery (1.9%). The highest frequency target of the right coronary artery is the posterior descending artery (PDA) (47.6%), followed by the right main coronary artery (RCA) (29.1%) and the posterior branch of the left ventricle (PL) (23.3%). The proportion of single grafts was the highest for the right coronary artery in CABG (178 cases, 67.9%), followed by a graft of the PDA-PL (42 cases, 16.0%) and other sequential grafts among the different coronary artery systems (including the system of the left anterior descending artery (LAD) and the left circumflex (LCX)). Whether there were sequential grafts of the PDA-PL or other sequential grafts among the different systems of the coronary artery, the instantaneous flow of a group of sequential grafts was higher than that of a single graft, and the difference had statistical significance (P < 0.01). However, there were no significant differences in the flow between the groups of sequential grafts (P = 0.410). Diastolic flow (DF) in the group of sequential grafts of the right coronary system was better than that in the non-sequential group (P < 0.001), and the difference had statistical significance. There was no significant difference between the DF of the groups of the other system of sequential grafts and that of the right coronary sequential grafts. Coronary artery CT suggested that there were 11 cases of poorly developing grafts or stenosis and occlusion a week after the operation, and those phenomenon mainly occurred in the group with a single graft. There was only one case that was occluded in the group of other systems of sequential grafts, and statistically significant differences existed between the two groups (P < 0.01).

Conclusions

In our centre, the most common form of CABG in the right coronary artery system is a non-sequential vein bridge to the PDA. Whether there are sequential grafts of the PDA-PL or other sequential grafts among the different coronary artery systems, the instantaneous flow of a group of sequential grafts is higher than that of a single graft. DF in the group of sequential grafts of the right coronary system was better than that in the non-sequential group.

Risk of perioperative coronary stent stenosis or occlusion in patients with previous percutaneous coronary intervention undergoing coronary artery bypass grafting surgery

OBJECTIVES

There is an ongoing discussion about how to treat coronary stents during bypass surgery: Should patent stents be left alone and the stented vessels be ungrafted, or should every stented coronary artery receive a bypass graft? This study aims to determine the relevance of perioperative stent stenosis or occlusion on postoperative outcomes up to 3 years postoperatively.

METHODS

Patients undergoing coronary artery bypass grafting surgery (CABG) (±concomitant procedures) with previous percutaneous coronary intervention from 4 centres were prospectively included in this observatory study between April 2015 and June 2017. A coronary angiography was conducted between the fifth and seventh postoperative days. The preoperative and postoperative angiograms were assessed in a core laboratory, assessing the patencies of coronary stents and bypass grafts. The core lab investigators were blinded to the patients' characteristics and perioperative course.

RESULTS

A total of 107 patients were included in the study. In the postoperative coronary angiography, 265 bypass grafts and 189 coronary stents were examined angiographically. Ninety-seven percent of preoperatively patent stents remained patent. New coronary stent stenoses were observed in 5 patients (4.7%). All 5 patients were asymptomatic and managed conservatively. Bypass stenoses were observed in 12 patients (11%), of whom were managed conservatively, 4 underwent percutaneous coronary intervention and 1 underwent redo-CABG. Two years postoperatively, 97% of patients were alive. Patients with new stent stenosis tended to have a better survival compared with patients with bypass stenosis (100% vs 73%; P = 0.09) up to 3 years postoperatively.

CONCLUSIONS

Perioperative coronary stent stenosis occurs rarely. It is safe to leave a patently stented coronary vessel without bypass grafting.

Peroperative epicardial ultrasonography of distal coronary artery bypass graft anastomoses using a stabilizing device. A feasibility study

Background

Widespread use of intraoperative epicardial ultrasonography (ECUS) for quality assessment of coronary artery bypass graft anastomoses during coronary artery bypass grafting (CABG) has not occurred - presumably due to technological and practical challenges including the need to maintain stable and optimal acoustic contact between the ultrasound probe and the target without the risk of distorting the anastomosis. We investigated the feasibility of using a stabilizing device during ultrasound imaging of distal coronary bypass graft anastomoses in patients undergoing on-pump CABG. Imaging was performed in both the longitudinal and transverse planes.

Methods

Single-centre, observational prospective feasibility study among 51 patients undergoing elective, isolated on-pump CABG. Ultrasonography of peripheral coronary bypass anastomoses was performed using a stabilizing device upon which the ultrasound transducer was connected. Transit-time flow measurement (TTFM) was also performed. Descriptive statistical tests were used.

Results

Longitudinal and transverse images from the heel, middle and toe were obtained from 134 of 155 coronary anastomoses (86.5%). After the learning curve (15 patients), all six projections were obtained from 100 of 108 anastomoses scanned (93%). Failure to obtain images were typical due to a sequential curved graft with anastomoses that could not be contained in the straight cavity of the stabilizing device, echo artefacts from a Titanium clip located in the roof of the anastomoses, and challenges in interpreting the images during the learning curve. No complications were associated with the ECUS procedure. The combined ECUS and TTFM resulted in immediate revision of five peripheral anastomoses.

Conclusions

Peroperative use of a stabilizing device during ultrasonography of coronary artery bypass anastomoses in on-pump surgery facilitates imaging and provides surgeons with non-deformed longitudinal and transverse images of all parts of the anastomoses in all coronary territories. Peroperative ECUS in addition to flow measurements has the potential to increase the likelihood of detecting technical errors in constructed anastomoses.

Trial registration

The study was registered on September 29, 2016, ClinicalTrials.gov ID: NCT02919124.

Enhancement of flow measurement for graft verification

Background

We aimed to evaluate multiple transit-time flow measurements during coronary artery bypass grafting.

Methods

Transit-time flow measurements were performed first on the arrested heart both with and without a proximal snare on the target coronary artery, second, after weaning from cardiopulmonary bypass, and third, before chest closure.

Results

Among the 214 grafts considered, 9 (4.2%) were patent and 6 (2.8%) were failing. In the failed grafts, an abnormal transit-time flow was found during the first measurement, in 5 (2.3%) cases with a proximal snare and in one (0.47%) without a snare. In these cases, technical errors with the distal anastomoses were found and immediately corrected. A problem with the proximal anastomosis was found in one graft during the second measurement and corrected right away. Bending due to excessive length was found in 2 (0.93%) grafts during the third measurement, and graft repositioning was performed. The first transit-time flow measurement showed that mean graft flow was significantly decreased with a proximal snare compared to without a proximal snare, throughout the entire coronary territory. Pulsatility index during the first transit-time flow measurement was higher with a proximal snare than without one.

Conclusions

The 3-time transit-time flow measurement strategy makes it possible to verify and immediately correct technical problems with coronary bypass grafts.

Transesophageal Echocardiographic Estimation of Coronary Sinus Blood Flow for Predicting Favorable Postoperative Transit Time Coronary Graft Flow Measurements: A Pilot Study

BACKGROUND

Augmentation of coronary artery flow by surgical grafting increases coronary sinus blood flow (CSBF), which can be quantified on transesophageal echocardiography (TEE). However, transit time flowmetry (TTF) technology remains the most used intraoperative technique for coronary artery graft assessment. The purpose of the present pilot study was to evaluate the predictive value of TEE-based CSBF estimation for identifying favorable TTF graft measurements.

DESIGN

Prospective observational study.

SETTING

Single university hospital.

PATIENTS

Forty patients undergoing triple vessel coronary artery bypass grafting.

MEASUREMENTS AND MAIN RESULTS

CSBF was assessed on TEE examination before and after revascularization, estimating the percentage increase in CSBF (∆CSBF). Postoperative TTF graft measurements were averaged to compute mean diastolic filling (DF) and pulsatility index (PI). Subjects were grouped based on favorable (PI ≤ 3, DF ≥ 50%) and unfavorable (PI > 3, DF < 50%) parameters. The group with PI ≤ 3 (n = 32) had significantly higher ∆CSBF compared with the group with PI > 3 (n = 8) (38.22% ± 12.05%, 13.75% ± 3.37%, p < 0.001). ∆CSBF was higher in the DF ≥ 50% group (n = 35) (36.40 ± 12.99) in contrast to DF < 50% group (n = 5) (11.80 ± 2.59%). A strong negative and significantly positive correlation was observed between ∆CSBF with PI, DF (r = -0.903, 0.571, respectively, p < 0.001). A ∆CSBF ≥15.5% was found to predict a mean PI ≤ 3 and DF ≥ 50% with sensitivity and specificity of 100% and 62.5% for PI and 100% and 100% for DF. A ∆CSBF ≥19% demonstrated a sensitivity and specificity of 100% and 100%, 100% and 91.4% for prediction of PI ≤ 3 and DF ≥ 50%, respectively.

CONCLUSION

TEE-based demonstration of an augmented CSBF can ensure favorable TTF graft parameters, guiding the adequacy of surgical revascularization.

Influence of residual coronary flow on bypass graft flow for graft assessment using near-infrared fluorescence angiography

PURPOSE

Near-infrared fluorescence angiography (NIR) detects the attenuation of fluorescence luminance intensity (FLI) through coronary artery bypass grafts affected by anastomotic stenosis. This study investigates the influence of residual blood flow of the host coronary artery (Ho) on bypass graft (Gr) FLI using a coronary artery bypass (CABG) model.

METHODS

A mock circuit system was created using artificial vessels and artificial blood was supplied to the Gr and the Ho. We used NIR to examine the changes in FLI through the Gr.

RESULTS

The Gr FLI was significantly attenuated according to the degree of Gr stenosis. The Gr FLI did not differ significantly among all degrees of Ho stenosis. High FLI grafts included grafts with degrees of Gr stenosis ≤ 75%, regardless of the severity of Ho stenosis. Moderate and low FLI grafts had 90 or 99% Gr stenosis, regardless of the severity of Ho stenosis. Gr FLI with 99% Gr stenosis was higher in 99% Ho stenosis than in ≤ 90% Ho stenosis.

CONCLUSIONS

A high Gr FLI indicated the absence of ≥ 90% stenosis in the anastomosis and a low Gr FLI indicated severe stenosis in the anastomosis despite Ho stenosis. High Ho stenosis may prevent the attenuation of Gr FLI in severely stenosed grafts.

State-of-the-Art Coronary Artery Bypass Grafting: Patient Selection, Graft Selection, and Optimizing Outcomes

Despite the progressive expansion of clinical indications for percutaneous coronary intervention and the increasingly high risk profile of referred patients, coronary artery bypass grafting (CABG) remains the mainstay in multivessel disease, providing good long-term outcomes with low complication rates. Multiple arterial grafting, especially if associated with anaortic techniques, might provide the best longer-term outcomes. A surgical approach individualized to the patients' clinical and anatomic characteristics, and surgeon and team experience, are key to excellent outcomes. Current evidence regarding patient selection, indications, graft selection, and potential strategies to optimize outcomes in patients treated with CABG is summarized.

Trials Comparing Percutaneous And Surgical Myocardial Revascularization: A Review

INTRODUCTION

Ischemic heart diseases are the major leading cause of death worldwide. Revascularization procedures dramatically reduced the overall risk for death related to acute coronary syndromes. Two kinds of myocardial revascularization can grossly be outlined: percutaneous coronary intervention (PCI) and surgical coronary artery bypass graft intervention (CABG). The net clinical benefit coming from these two kinds of procedures is still under debate.

METHODS

We have traced the state-of-the-art background about myocardial revascularization procedures by comparing the most important trials dealing with the evaluation of percutaneous interventions versus a surgical approach to coronary artery diseases.

RESULTS

Both PCI and CABG have become effective treatments for revascularization of patients suffering from advanced CAD. The advance in technology and procedural techniques made PCI an attractive and, to some extent, more reliable procedure in the context of CAD. However, there are still patients that cannot undergo PCI and have to be rather directed towards CABG.

CONCLUSION

CABG still remains the best strategy for the treatment of multiple vessel CAD due to improved results in term of survival and freedom from reintervention. Anyway, a systematic, multidisciplinary approach to revascularization is the fundamental behaviour to be chased in order to effectively help the patients in overcoming its diseases. The creation of the "heart team" seems to be a good option for the correct treatment of patients suffering from stable and unstable CAD.

The use of intraoperative graft assessment in guiding graft revision

Quality assurance (QA) in medicine is the practice of the prevention of errors and avoiding problems when delivering care in the form of medical therapy, both in terms of non-invasive and invasive procedures. It is rightly expected by patients. Up until the last 10 years, verification of intraoperative bypass graft patency was limited to a stable hemodynamic status, lack of electrocardiographic evidence of myocardial infarction and, if available, no new regional wall motion abnormalities on transesophageal echo. This perspective outlines two technologies for QA during coronary artery bypass graft (CABG) surgery: transit-time flow measurement (TTFM) for functional assessment of coronary grafts and anatomical evaluation with epicardial ultrasound (ECUS). TTFM is a seasoned technology, used since the late 1990s. ECUS is relatively new, used since 2012. TTFM alone, although useful for intraoperative bypass graft assessment, is not enough; 10-15% of graft values are ambiguous as to the efficacy of graft function. Therefore, although newer, ECUS is already being established as an indispensable tool for quality assessment in coronary surgery. The two modalities combined are vital for 'state of the art' intraoperative bypass graft assessment.

Intraoperative transit-time flow measurement in on-pump coronary artery bypass graft surgery: Single center experience

Background

This study aims to evaluate the effects of graft dysfunction detected by intraoperative transit-time flow measurement on the outcomes of on-pump coronary artery bypass graft surgery.

Methods

A total of 1,240 patients (856 males, 384 females; mean age 57.4±12.1 years; range, 47 to 74 years), who underwent isolated on-pump coronary artery bypass graft surgery via median sternotomy performed by the same surgical team, were reviewed retrospectively. With the introduction of transit-time flow measurement into practice at our clinic in 2006, all patients regularly underwent transit-time flow measurement during surgery in order to evaluate the graft patency. Interpretation of the data obtained using the transit-time flow measurement in patients who underwent surgery has directed our decision as to whether to perform graft revision. Patients were evaluated for early- and late-period mortality/ morbidity, perioperative and postoperative myocardial infarction, and intraaortic balloon requirement.

Results

A total of 3,596 grafts in the perioperative period was evaluated using transit-time flow measurement. Anastomosis/graft revision, new anastomosis/patch plasty to distal native artery or free left internal mammary artery graft was performed in 146 grafts of 143 patients in whom transittime flow measurement showed insufficient patency. Four of six patients who developed peri/postoperative myocardial infarction were found to have perioperative hypotension, ST elevation, and wall motion abnormality on transesophageal echocardiography before closure of the sternum. The flow was corrected by extending the short length of the grafts with insufficient flow after transit-time flow measurement and it was recorded that transit-time flow measurements were at normal values at these four grafts. Two patients developed acute myocardial infarction in the postoperative period and stent was applied in one vessel of each patient; however, one of these patients died. Sixteen patients were inserted intraaortic balloon pump, four of which being in the preoperative period. Revision surgery was performed due to bleeding in 56 patients and sternal infection in 12 patients. Of all patients, 28 (2.3%) died in the early postoperative period.

Conclusion

We believe that transit-time flow measurement may be an important tool in evaluating graft function and contribute to eliminate the causes of graft failure during surgery.

Current status of intra-operative graft assessment: Should it be the standard of care for coronary artery bypass graft surgery?

The "Achilles heel" of coronary artery bypass graft (CABG) surgery is graft patency. While long-term patency is determined by the type of conduit and the progression of graft and native vessel disease, short-term patency is affected by intra-operative technical issues. Transit-time flow measurements and epicardial ultrasound have been shown to accurately assess intra-operative graft patency. This review will examine the evidence to support the premise that intra-operative graft assessment is essential in determining graft patency and should be the standard of care when performing CABG surgery.

Physiological insights of recent clinical diagnostic and therapeutic technologies for cardiovascular diseases

Diagnostic and therapeutic methods for cardiovascular diseases continue to be developed in the 21st century. Clinicians should consider the physiological characteristics of the cardiovascular system to ensure successful diagnosis and treatment. In this review, we focus on the roles of cardiovascular physiology in recent diagnostic and therapeutic technologies for cardiovascular diseases. In the first section, we discuss how to evaluate and utilize left ventricular arterial coupling in the clinical settings. In the second section, we review unique characteristics of pulmonary circulation in the diagnosis and treatment of pulmonary hypertension. In the third section, we discuss physiological and anatomical factors associated with graft patency after coronary artery bypass grafting. In the last section, we discuss the usefulness of mechanical ventricular unloading after acute myocardial infarction. Clinical development of diagnostic methods and therapies for cardiovascular diseases should be based on physiological insights of the cardiovascular system.

Intraoperative graft verification in coronary surgery

Transit-time flow measurement (TTFM) is a reliable method to check the graft function intraoperatively in coronary surgery. The given parameters are: Mean Graft Flow (MGF); Pulsatility Index (PI) and Insufficiency Ratio (%BF). Some cutoffs of these parameters have been identified as predictors for unfair 1-y clinical outcome: mean graft flow (MGF) less than 20 ml/min and high pulsatility index greater than 5. Other cutoffs have been found as related to postoperative angiography: MGF 15 ml/min or less and pulsatility index at least 3 (sensitivity 94%; specificity 61%); MGF less than 15 ml/min and pulsatility index greater than 3 for left coronary artery or pulsatility index greater than 5 for right coronary artery (sensitivity 96%; specificity 77%); MGF 15 ml/min or less and pulsatility index at least 5.1 left coronary artery (sensitivity 98%; specificity 26%). Hence, with the need to improve the diagnostic accuracy of TTFM, high-resolution epicardic coronary ultrasound module has been added to graft flow evaluation providing 2D ultrasound imaging (either in short-axis or long-axis) and color-flow mapping, allowing an accurate morphological evaluation of body graft and anastomosis. An intraoperative method aimed to verify coronary grafts should be easy to handle, not time consuming, minimally invasive, easily meaningful and relatively cheap; in addition, it should offer objective parameters more than qualitative criteria. We herein report the results of our experience with intraoperative graft verification with TTFM and high-resolution imaging along with a systematic review of the literature in this field with the aim to provide a road map to be followed.

False Positive Transit Time Flowmetry Graft Failure in Multivessel Coronary Spasm following Off-Pump Coronary Artery Bypass Grafting

Intraoperative Transit Time Flowmetry is currently recommended to assess graft patency during coronary artery bypass grafting (CABG), especially in presence of haemodynamic instability or inability to wean the patient from cardiopulmonary bypass, new regional wall motion abnormalities, or significant ventricular arrhythmias. The VeriQ™ system is one of the currently available systems, which detects imperfections that may be corrected by graft revision. In this case report, multivessel coronary spasm (CS) post-CABG interferes with these intraoperative parameters misleading initially into false results. Cardiac surgeons should bear in mind the limit of VeriQ in distinguishing between graft failure and CS. Angiography may be considered in patients with decreased graft flow despite revision of anastomosis and vasodilatory treatment for the definitive diagnosis.

Techniques and standards in intraoperative graft verification by transit time flow measurement after coronary artery bypass graft surgery: a critical review

Transit time flow measurement (TTFM) is a quality control tool for intraoperative graft evaluation in coronary artery bypass graft (CABG) surgery. A critical review of the literature available using TTFM in CABG surgery is the focus of this article. The main objectives will be to detail precise parameters for flow evaluation, to show limitations of TTFM and to prove its predictive impact on postoperative graft failure rate. Publications listed in the PubMed database were reviewed, searching for intraoperative graft verification in coronary surgery by TTFM, with postoperative imaging follow-up (FU) modality and with a special focus on publications released after European guidelines from 2010. Nine included publications revealed an overall graft failure rate of ∼12%. Mean graft flow had a positive predictive value in the largest study, and cut-offs, of at least 20 ml/min for internal mammary artery (IMA) grafts, therein partially confirming guidelines, and 30-40 ml/min for saphenous venous grafts (SVGs) were proposed. An explicit correlation between graft flow, patency rate and severity of coronary stenosis, by indicating the fractional flow reserve, was found for IMA grafts. Increased pulsatility index and increased systolic reverse flow probably predict worse outcome and may help identifying competitive flow. Diastolic filling, rarely indicated, could not be confirmed as the predictive marker. No significant correlation of TTFM and graft failure rate for radial and other arterial grafts could be found, partially due to the small number of these types of grafts analysed. Larger target vessels and lower postoperative CK-MB levels may predict better graft patency rates. Low sensitivity for TTFM to reliably detect graft failure is certainly a major issue, as found in randomized analyses. However, methodical limitations and varying threshold values for TTFM render a general consensus difficult. Influence of quantity (vessel territory distribution) and quality (myocardial scar) of the graft perfusion area, on TTFM and FU outcome, was not included by anyone and should be part of future research. TTFM is probably not the tool of choice to detect progressive late graft failure of SVG. Peroperative TTFM values should be correlated with one type of conduit, differentiating between early and late graft failure (by applying a uniform, appropriated definition), to precise and confirm threshold values.

Relationship of Intraoperative Transit Time Flowmetry Findings to Angiographic Graft Patency at Follow-Up

Early and late graft occlusion remains a significant complication of coronary artery bypass grafting. Transit time flowmetry is the most commonly used imaging technique to assess graft patency intraoperatively. Although the value of transit time flowmetry for intraoperative quality control of coronary anastomosis is well established, its standard variables for predicting eventual graft failure remain controversial. This review readdresses the issue of intraoperative transit time flowmetry, with a particular emphasis on defining cutoff values for standard variables and correlating them with the ability to predict midterm and long-term graft patency for arterial and venous conduits. Further research is warranted to support clinically useful recommendations on the intraoperative application and interpretation of transit time flowmetry.

New parameter of the right gastroepiploic arterial graft using the power spectral analysis device named MemCalc soft

OBJECTIVES

Transit-time flow measurement (TTFM) parameters such as mean graft flow (MGF, ml/min), pulsatility index (PI) and diastolic filling (DF, %) have been extensively researched for internal mammary arterial or saphenous vein grafts. In our experience of using the right gastroepiploic arterial (GEA) graft for right coronary artery (RCA) grafting, we observed unique GEA graft flow waveforms. We analysed the GEA graft flow waveforms for their effectiveness in determining GEA graft patency by power spectral analysis.

METHODS

Forty-five patients underwent off-pump coronary artery bypass using the GEA graft for RCA grafting individually. The means of intraoperative MGF, PI and DF were compared between patent and non-patent grafts, postoperatively. Furthermore, the GEA flow data were output and analysed using power spectral analysis.

RESULTS

Forty grafts were 'patent' and five were 'non-patent'. There were no significant differences in the mean TTFM parameters between the patent and non-patent grafts (MGF: 22 vs 8 ml/min, respectively, P = 0.068; PI: 3.5 vs 6.5, respectively, P = 0.155; DF: 63 vs 53%, respectively, P = 0.237). Results of the power spectral analysis presented clear differences; the power spectral density (PSD) of patent grafts presented high peaks at frequency levels of 1, 2 and 3 Hz, and the non-patent graft PSD presented high peaks that were not limited to these frequencies. The PSD had a sensitivity and specificity of 80 and 87.5%, respectively.

CONCLUSIONS

Power spectral analysis of the GEA graft flow is useful to distinguish between non-patent and patent grafts intraoperatively. This should be used as a fourth parameter along with MGF, PI and DF.

Intraoperative graft assessment during coronary artery bypass surgery

Coronary artery bypass grafting (CABG) is an established revascularization method for treating multivessel coronary artery disease. The goal of CABG is to achieve complete revascularization with a durable, patent graft without reintervention. However, early graft failure, including that associated with technical errors, has been reported. This makes intraoperative verification of graft patency one of the most important ways in which surgeons can reduce the rate of early graft failure. Conventional angiography is considered the gold standard for graft assessment. However, because it is invasive and inconvenient, several alternatives to intraoperative graft assessment have become available that help reduce early graft failure by allowing revision of the anastomosis intraoperatively. The aim of this article is to review the advantages and disadvantages of several intraoperative graft assessment methods for CABG.