Transit-Time Flow Measurement as a Predictor of Coronary Bypass Graft Failure at One Year Angiographic Follow-Up

Comparison of Two Coronary Anastomosis Techniques in Terms of Flow Rate in Porcine Hearts

INTRODUCTION

The quality of coronary anastomoses is one of the important parameters that may affect graft patency in coronary artery bypass grafting patients. Therefore, we compared two different anastomotic techniques to improve graft flow and patency rates.

METHODS

This study was conducted by performing two different fashions of anastomosis with a human saphenous vein graft on 24 various coronary segments of five postmortem porcine hearts. Each arteriotomy was used for both anastomotic techniques. In the first method, epicardial fat tissue around the coronary artery was involved to the saphenous vein anastomosis line (coronary wall and epicardial fat tissue [CWE] technique). In the second method, the saphenous vein graft was sutured to the coronary wall only, without involving epicardial fat tissue (only coronary wall [OCW] technique).The time it tookfor 30 cc of 0.9% isotonic saline solution to pass through the anastomosis in a free-flow fashion by gravity was measured following each technique. Additionally, the anastomotic areas in mm2 were measured and compared between the two techniques.

RESULTS

The mean flow time for the CWE technique was 77.5 ± 21.4 seconds, whereas for the OCW technique, it was 87.2 ± 19.5 seconds (P<0.001). The flow rates were 23.2 ml/min and 20.6 ml/min, respectively. The anastomotic area was 3.947 mm2 for the CWE technique and 1.430 mm2 for the OCW technique.

CONCLUSION

When the sutures penetrate both the epicardial fat tissue and the coronary artery wall simultaneously, a larger anastomosis area can be created. Consequently, potentially better graft flow and hemodynamic performance could be achieved.

Current Trends and Perspectives of Pressure Wire-Based Coronary Artery Bypass Grafting

Fractional flow reserve (FFR) has been well validated as a modality for evaluating myocardial ischemia, demonstrating the superiority of FFR-guided percutaneous coronary intervention (PCI) over conventional angiography-guided PCI. As a result, the strategy for coronary artery bypass grafting (CABG) is shifting toward FFR guidance. However, the advantage of FFR-guided CABG over angiography-guided CABG remains unclear. While FFR-guided CABG can help avoid unnecessary grafting in cases of moderate stenosis, it may also carry the risk of incomplete revascularization. The limited use of FFR due to the need for hyperemia has led to the development of non-hyperemic pressure ratios (NHPRs). NHPR pullback provides trans-stenotic pressure gradients, which may offer valuable insights for CABG strategies. Recently, computed tomographic coronary angiography (CTCA) has emerged as a non-invasive modality that provides accurate data on lesion length, diameter, minimum lumen area, percentage stenosis, and the volume and distribution of high-risk plaques. With the introduction of FFR-CT, CTCA is now highly anticipated to provide both functional evaluation (of myocardial ischemia) via FFR-CT and anatomical information through serial quantitative assessment. Beyond the diagnostic phase, CTCA, augmented by automatic artificial intelligence, holds great potential for guiding therapeutic interventions in the future.

[MSB-62] Comparison of Left Internal Mammary Artery to the Left Anterior Descending Artery Graft Patency

Objective

This study aimed to compare the efficacy of the bidirectional palpation test and the results of transit time flow meter (TTFM) measurements by examining graft patency through early-period coronary computed tomography angiography.

Methods

The study was designed as a retrospective-prospective hybrid cohort study. Graft patency in the left internal mammary artery (LIMA) to left anterior descending artery anastomosis of 73 patients was evaluated. The results of the bidirectional palpation test and TTFM measurements performed during coronary artery bypass grafting were compared with contrast-enhanced coronary computed tomography angiography performed in the early postoperative period.

Results

Graft patency was statistically significantly higher in patients with a positive bidirectional palpation test compared to those with a negative test (p<0.001). Similarly, graft patency was significantly higher in patients with a mean flow of 10 mL/min or more compared to those with a mean flow below 10 mL/min (p=0.001).

Conclusion

A significant positive correlation was revealed between the bidirectional palpation test and the mean flow measured by TTFM. Additionally, both the bidirectional palpation test and TTFM accurately demonstrated the intraoperative LIMA graft patency. These findings indicate that both tests can be reliably used in the assessment of the LIMA to left anterior descending artery anastomosis.

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.

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.

The use of intraoperative transit time flow measurement can reduce postoperative myocardial injury

OBJECTIVE

This study investigates the relationship between the use of transit time flow measurement (TTFM) and postoperative myocardial injury in off-pump coronary artery bypass grafting (OPCABG).

METHODS

In this retrospective study, we collected basic data from patients hospitalized for OPCABG in the Department of Cardiothoracic Surgery, Changzhou Second People's Hospital Affiliated with Nanjing Medical University. According to the academic research consortium (ARC)-2 definition of significant myocardial injury, we used cardiac troponin I >2380 ng/L as a criterion for significant postoperative myocardial injury. We use logistic regression and forest plots to assess the association of TTFM use with myocardial injury outcomes.

RESULTS

One hundred and forty-six patients were included in this study. The overall median age of these patients was 65.05 years, and 32 (21.92%) experienced a postoperative myocardial injury. TTFM was independently associated with the incidence of postoperative myocardial injury (odds ratio = 0.34 [95% confidence interval = 0.15-0.78]; p = .01), and we found similar trends in regression analyses across subgroups of sex, age, number of bridging vessels, hypertension, diabetes mellitus, BMI, and percutaneous coronary revascularization. One hundred and six patients were followed for 1-year vessel permeability, and seven patients (6.6%) were occluded.

CONCLUSIONS

The use of TTFM is independently associated with a reduced incidence of postoperative myocardial lesions during off-pump coronary bypass surgery. The TTFM procedure in OPCABG deserves to be actively promoted to reduce the incidence of postoperative myocardial injury.

The Algorithm for Using Transit-time Flow Measurement and High-resolution Epicardial Ultrasound for Intraoperative Grafts Assessment during Coronary Artery Bypass Surgery

Aim      To develop an algorithm for using ultrasonic flowmetry (USF) and epicardial ultrasonic scanning (EpiUSS) for intraoperative assessment of anatomic and functional viability of conduits.Material and methods  For viability assessment of 460 coronary grafts in 150 patients who were operated at the Bakulev National Medical Research Center for Cardiovascular Surgery (2018-2021 г.), markers of graft failure were analyzed using the USF and EpiUSS data confirmed by results of graft angiography. According to RОС analysis, the Qmean and PI values indicative of the graft failure were determined. A CHAID decision tree was developed for assessing the prognostic significance of the analyzed parameters. Based on this prognostic model, an algorithm was developed for intraoperative diagnosis of anatomic and functional graft viability during coronary bypass surgery.Results The Qmean ≤20.5 ml/min values were associated with an increased relative risk (RR) of detecting graft failure (RR, 8.2; 95 % confidence interval, CI, 4.4-15.2). The developed model shows a high accuracy of predicting the graft failure (AUC = 0.906±0.03). The RR of graft failure at PI ≥2.65 was 3.3 (95 % CI, 2.17-5.08). The prognostic model for PI (AUC = 0.745±0.042) was sufficiently accurate with respect of possible graft failure. Nodes of high and low risk for graft failure were determined in the developed decision tree. The obtained model was characterized by high sensitivity and specificity (100 and 84.3 %, respectively).Conclusion      The combined use of USF and EpiUSS allows a highly accurate assessment of both morphological and functional characteristics of graft flow. The developed algorithm for the intraoperative diagnosis of anatomic and functional graft viability can be recommended for clinical use.

Graft flow assessment and early coronary artery bypass graft failure: a computed tomography analysis

OBJECTIVES

We evaluated graft patency by computed tomography and explored the determinants of intraoperative mean graft flow (MGF) and its contribution to predict early graft occlusion.

METHODS

One hundred and forty-eight patients under a single surgeon were prospectively enrolled. Arterial and endoscopically harvested venous conduits were used. Intraoperative graft characteristics and flows were collected. Graft patency was blindly evaluated by a follow-up computed tomography at 11.4 weeks (median).

RESULTS

Graft occlusion rate was 5.2% (n = 22 of 422; 8% venous and 3% arterial). Thirteen were performed on non-significant proximal stenosis while 9 on occluded or >70% stenosed arteries. Arterial and venous graft MGF were lower in females (Parterial = 0.010, Pvenous = 0.009), with median differences of 10 and 13.5 ml/min, respectively. Arterial and venous MGF were associated positively with target vessel diameter ≥1.75 mm (Parterial = 0.025; Pvenous = 0.002) and negatively with pulsatility index (Parterial < 0.001; Pvenous < 0.001). MGF was an independent predictor of graft occlusion, adjusting for EuroSCORE-II, pulsatility index, graft size and graft type (arterial/venous). An MGF cut-off of 26.5 ml/min for arterial (sensitivity 83.3%, specificity 80%) and 36.5 ml/min for venous grafts (sensitivity 75%, specificity 62%) performed well in predicting early graft occlusion.

CONCLUSIONS

We demonstrate that MGF absolute values are influenced by coronary size, gender and graft type. Intraoperative MGF of >26.5 ml/min for arterial and >36.5 ml/min for venous grafts is the most reliable independent predictor of early graft patency. Modern-era coronary artery bypass graft is associated with low early graft failure rates when transit time flow measurement is used to provide effective intraoperative quality assurance.

Transit Time Flow Measurement in Robotic Totally Endoscopic Coronary Artery Bypass: What Do the Numbers Mean?

Objective

Transit time flow measurement (TTFM) is valuable for assessing intraoperative graft patency in coronary artery bypass surgery (CAB). The significance of competitive native coronary flow on patency, as predicted by percentage of backflow (%BF) on TTFM, is unknown. This study aims to evaluate intraoperative TTFM parameters, and specifically %BF, in predicting graft patency in robotic totally endoscopic CAB (TECAB).

Methods

We reviewed TTFM parameters in 311 patients undergoing robotic off-pump TECAB at our institution between February 2016 and January 2020. Patients with sequential or Y grafts were excluded, leaving 277 patients with a total of 387 isolated end-to-side grafts (248 left internal mammary artery [LIMA], 149 right IMA [RIMA]). Mean graft flow, diastolic flow, pulsatility index, and %BF were measured intraoperatively. Early postoperative angiograms were obtained in 83 patients undergoing percutaneous coronary intervention for hybrid revascularization, with a total of 125 grafts. Angiograms were independently analyzed and separated into 2 groups based on IMA graft patency, which were patent (FitzGibbon A/B) and nonpatent (FitzGibbon O) groups.

Results

Early angiographic patency at a median of 31.0 days after surgery showed 123 (97.1%) patent grafts and 3 (2.9%) occluded grafts in both LIMA and RIMA grafts to both left anterior descending (LAD) and non-LAD targets. Mean graft flow was 77.4 ± 41.6 mL/min. There was no difference in mean flow, pulsatility index, or %BF between the patent and occluded grafts.

Conclusions

Excellent intraoperative flow parameters and early angiographic patency can be obtained via robotic, off-pump TECAB. Our data did not demonstrate an association between intraoperative TTFM evidence of competitive native coronary flow and early angiographic graft outcomes.

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.

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.

Intraoperative transit-time flow measurement and high-frequency ultrasound in coronary artery bypass grafting: impact in off versus on-pump, arterial versus venous grafting and cardiac territory grafted

OBJECTIVES

Despite society guideline recommendations, intraoperative high-frequency ultrasound (HFUS) and transit-time flow measurement (TTFM) use in coronary artery bypass grafting (CABG) has not been widely adopted worldwide. This retrospective review of the REQUEST (REgistry for QUality assESsmenT with Ultrasound Imaging and TTFM in Cardiac Bypass Surgery) study assesses the impact of protocolled high-frequency ultrasound/TTFM use in specific technical circumstances of CABG.

METHODS

Three REQUEST study sub-analyses were examined: (i) For off-pump (OPCAB) versus on-pump (ONCAB) procedures: strategy changes from preoperative plans for the aorta, conduits, coronary targets and graft revisions; and for all REQUEST patients, revision rates in: (ii) arterial versus venous grafts; and (iii) grafts to different cardiac territories.

RESULTS

Four hundred and two (39.6%) of 1016 patients undergoing elective isolated CABG for multivessel disease underwent OPCAB procedures. Compared to ONCAB, OPCAB patients experienced more strategy changes regarding the aorta [14.7% vs 3.4%; odds ratios (OR) = 4.03; confidence interval (CI) = 2.32-7.20], less regarding conduits (0.2% vs 2.8%; OR = 0.09; CI = 0.01-0.56), with no differences in coronary target changes or graft revisions (4.1% vs 3.5%; OR = 1.19; CI = 0.78-1.81). In all REQUEST patients, revisions were more common for arterial versus venous grafts (4.7% vs 2.4%; OR = 2.05; CI = 1.29-3.37), and inferior versus anterior (5.1% vs 2.9%; OR = 1.77; CI = 1.08-2.89) and lateral (5.1% vs 2.8%; OR = 1.83; CI = 1.04-3.27) territory grafts.

CONCLUSIONS

High-frequency ultrasound/TTFM use differentially impacts strategy changes and graft revision rates in different technical circumstances of CABG. Notably, patients undergoing OPCAB experienced 4 times more changes related to the ascending aorta than ONCAB patients. These findings may indicate where intraoperative assessment is most usefully applied.

CLINICAL TRIAL REGISTRATION NUMBER

ClinicalTrials.gov: NCT02385344.

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 size as a predictor of Y-graft patency following coronary artery bypass surgery

This study aims to evaluate the association between target vessel size and graft patency in the right IMA-right coronary territory anastomosis.A total of 402 patients who underwent CABG between 2005 and 2016 using the right IMA Y-graft to the posterolateral branch or posterior descending artery were enrolled. Preoperative coronary angiography was utilized to measure the size of the target coronary arteries in the right territory. Follow-up angiography and computed tomography at 6 to 12 months were used to determine graft patency.Thirty patients (7.5%) were found to have occluded graft. Larger target vessel size was associated with lower risk of graft occlusion (OR: 0.18, 95% CI:0.05-0.62, P = .007). The receiver operating characteristic (ROC) curve showed that the cutoff-value of 1.93 mm was found to have the maximum sum of sensitivity and specificity for graft patency (Area under the curve (AUC): 0.65, P = .01). Excluding patients with right coronary artery total occlusion, the discriminative performance of target vessel size became more prominent (AUC: 0.76, P < .01), with same cutoff value.In the setting of bilateral IMA composite grafting, the patency of right IMA to right coronary territory was influenced by the size of the target coronary artery. The influence of target coronary artery size was prominent in non-total occlusion patients. Careful selection of a target anastomosis site is recommended.

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.

Angiographic patency after robotic beating heart totally endoscopic coronary artery bypass grafting facilitated by automated distal anastomotic connectors

OBJECTIVES

Robotic totally endoscopic coronary artery bypass (TECAB) on the beating heart has been facilitated in our experience using distal coronary anastomotic connectors. In this study, we retrospectively reviewed graft patency in all robotic TECAB patients who underwent formal angiography at our current institution over a 5-year period.

METHODS

Between July 2013 and June 2018, 361 consecutive patients underwent robotic beating-heart TECAB. Of these patients, 121 had a follow-up angiogram, which assessed graft patency. Eighty-four patients had an angiogram as part of planned hybrid procedures and 37 patients underwent an unplanned angiogram for clinical indications. Retrospective analysis of angiographic patency and clinical outcomes was performed.

RESULTS

The mean Society of Thoracic Surgeons predicted risk of mortality was 1.8%. Single-vessel bypass was performed in 40 (33%) patients and multivessel grafting in 81 (67%). Average flow (ml/min) and pulsatility index in the grafts was 74.7 ± 39.1 and 1.42 ± 0.52, respectively. The number of grafts evaluated was 204 (130 left internal mammary artery and 74 right internal mammary artery grafts). The median time to angiography was 1.0 and 16.0 months and graft patency was 98% and 91% in the hybrid and non-hybrid groups, respectively. Overall graft patency was 95.6% (left internal mammary artery = 96%; right internal mammary artery = 93%). Left internal mammary artery to left anterior descending artery graft patency was 97%. Clinical follow-up was available for 316 (88%) patients at mean 22.5 ± 15.1 months. Freedom from major adverse cardiac events at 2 years was 92%.

CONCLUSIONS

In this consecutive series of patients undergoing formal angiography after robotic single and multivessel TECAB, we found satisfactory graft patency and 2-year clinical outcomes. Longer-term follow-up is warranted.

Patient and haemodynamic factors affecting intraoperative graft flow during coronary artery bypass grafting: an observational pilot study

Transit-time flow measurement (TTFM) is frequently used to evaluate intraoperative quality control during coronary artery bypass grafting (CABG) and has the ability to assess graft failure intraoperatively. However, perioperative factors affecting TTFM during CABG remain poorly understood. Patients who underwent CABG at a single institution between July 2016 and May 2018 were prospectively evaluated. TTFM and blood viscosity were measured haemodynamically, while mean flow (mL/min), pulsatility index, and diastolic filling were recorded. Arterial blood gas was analysed immediately after left internal mammary artery to left descending artery anastomosis and before sternal closure. Factors associated with TTFM were assessed using multiple linear regression analysis. We evaluated 57 of the 62 patients who underwent CABG during the study period, including 49 who underwent off-pump and 8 who underwent on-pump surgeries. Blood viscosity was not significantly associated with TTFM (p > 0.05). However, TTFM was significantly associated with body mass index, systolic blood pressure, and cardiac index (p < 0.05 each). In conclusion, maintaining the SBP in the perioperative period and maintaining the CI with inotropic support or fluid resuscitation can be important in improving blood flow of graft vessels after surgery.

Saphenous vein graft disease, pathophysiology, prevention, and treatment. A review of the literature

BACKGROUND

The saphenous vein remains the most frequently used conduit for coronary artery bypass grafting, despite reported unsatisfactory long-term patency rates. Understanding the pathophysiology of vein graft failure and attempting to improve its longevity has been a significant area of research for more than three decades. This article aims to review the current understanding of the pathophysiology and potential new intervention strategies.

METHODS

A search of three databases: MEDLINE, Web of Science, and Cochrane Library, was undertaken for the terms "pathophysiology," "prevention," and "treatment" plus the term "vein graft failure."

RESULTS

Saphenous graft failure is commonly the consequence of four different pathophysiological mechanisms, early acute thrombosis, vascular inflammation, intimal hyperplasia, and late accelerated atherosclerosis. Different methods have been proposed to inhibit or attenuate these pathological processes including modified surgical technique, topical pretreatment, external graft support, and postoperative pharmacological interventions. Once graft failure occurs, the available treatments are either surgical reintervention, angioplasty, or conservative medical management reserved for patients not eligible for either procedure.

CONCLUSION

Despite the extensive amount of research performed, the pathophysiology of saphenous vein graft is still not completely understood. Surgical and pharmacological interventions have improved early patency and different strategies for prevention seem to offer some hope in improving long-term patency.

Beyond patency: Functional assessment of adequacy using internal mammary artery grafting to the left anterior descending artery

INTRODUCTION

Arterial graft physiology influences the long-term outcome of coronary artery bypass grafting (CABG). We studied factors that can affect the overall resistance to flow using internal mammary artery grafting to the left anterior descending artery.

METHODS

This was a prospective, nonrandomized observational study of 100 consecutive patients who underwent elective on-pump isolated or combined valve surgery and CABG. Coronary stenoses were assessed using conventional and quantitative coronary angiography assessment. The flow and pulsatility index (PI) of the grafts were assessed by transit-time flowmetry during cardioplegic arrest and at the end of the operation. Fractional polynomials were used to explore linearity, followed by multivariable regression analysis.

RESULTS

Univariate analysis demonstrated higher flows at the end of the operation in patients who had higher flows with the cross-clamp on (P < .001), in males (P = .004), in patients with a low PI at the end of the operation (P = .04), and in patients with a larger size of the recipient artery (P = .005). Multivariable regression analysis showed that the graft flow at the end of the operation was significantly associated with the mean flow with the cross-clamp on (P < .001), sex (P = .003), and PI at the end of the operation (P = .003). Concomitant valve surgery did not influence flows. Male patients had 18 mL/min higher flow.

CONCLUSIONS

The graft flow at the end of the operation can be determined by the flow with the cross-clamp on, the PI with the cross-clamp off and coronary artery. We reported differences in the graft flows between sexes, and for first the time, we introduced the concepts of "adequate flow" and "resistance-to-forward-flow" for patent coronary grafts.

The influence of hemodynamics on graft patency prediction model based on support vector machine

In the existing patency prediction model of coronary artery bypass grafting (CABG), the characteristics are based on graft flow, but no researchers selected hemodynamic factors as the characteristics. The purpose of this paper is to study whether the introduction of hemodynamic factors will affect the performance of the prediction model. Transit time flow-meter (TTFM) waveforms and 1-year postoperative patency results were obtained from 50 internal mammary arterial grafts (LIMA) and 82 saphenous venous grafts (SVG) in 60 patients. Taking TTFM waveforms as the boundary conditions, the CABG ideal models were constructed to obtain hemodynamic factors in grafts. Based on clinical characteristics and combination of clinical and hemodynamic characteristics, patency prediction models based on support vector machine (SVM) were constructed respectively. For LIMA, after the introduction of hemodynamic factors, the accuracy, sensitivity and specificity of the prediction model increased from 70.35%, 50% and 74.17% to 78.02%, 70% and 78.89%, respectively. For SVG, the accuracy, sensitivity and specificity of the prediction model increased from 63.24%, 40% and 76.91% to 74.41%, 60.1% and 82.73%, respectively. The performance of the prediction model can be improved by introducing hemodynamic factors into the characteristics of the model. The accuracy, sensitivity and specificity of the prediction results are higher with the addition of hemodynamic characteristics.

[Analysis of flowmetric parameters of blood flow through coronary bypass grafts in high-risk surgical patients]

Coronary artery bypass grafting is a widely used cardiosurgical intervention which may be performed either on the arrested heart in conditions of artificial circulation or on the beating heart without artificial circulation. However, in a series of works, the results of bypass grafting using both techniques had no significant differences. In our article, we analyse the flowmetric parameters of blood flow through the coronary bypass grafts in high-surgical risk patients presenting with ischaemic heart disease and undergoing coronary artery bypass grafting in conditions of artificial circulation and on the beating heart. For this purpose, a total of 148 patients enrolled into the study were divided into 2 groups depending on the technique of surgical treatment. The obtained statistical data showed comparable results in the both groups, however, operative interventions on the beating heart made it possible to significantly decrease the risk of the development of the majority of complications.

[Functionality of mammary-coronary bypass grafts according to the data of intraoperative flowmetry]

Improvement of surgical treatment for ischaemic heart disease is one of the main trends in modern medicine. After the operation of coronary bypass grafting, further functioning of blood flow in the grafts largely depends upon its domination over the native blood flow in the target coronary arteries. Therefore, intraoperative diagnosis of functional competence of coronary bypass grafts by means of flowmetry is currently of special importance. The purpose of this study was flowmetric quantitative assessment of the curves of blood flow through the coronary bypass grafts, depending on the degree of stenosis of the target coronary arteries. A total of 135 patients were examined during our study. We evaluated the curves of blood flow through the bypass grafts from the left internal thoracic artery to the anterior descending artery. The bypass grafts were divided into three groups: the 1st group (n=47) with moderate stenosis of the coronary arteries (from 50 to 75%); the 2nd group (n=42) with a more pronounced lesion of the target vessel (from 75 to 99%), and the 3rd group (n = 46) with occluded coronary arteries (100%). It was revealed that the flow rate (Q, ml/min) in group one was lower (17±3.1) than in group two (33±5.3) and group three (45±3.4). Also, differences were revealed in the resistance index of the grafts: it turned out to be higher in group one (5.2±1.1) and group two (4.5±0.9) as compared with group three (1.8±0.5). However, there was no between-group difference in diastolic filling of the grafts, which amounted to 58±13, 61±10 and 64±9% for groups one, two and three, respectively. By the shape of the curve, we assessed the reverse systolic peak whose presence prevailed in the grafts of group one (15 of 47; 31.9%) and group two (11 of 42; 26.2%) as compared with that in the grafts of group three (5 of 46; 10.8%). The obtained findings confirm higher frequency of the presence of competitive blood flow in the grafts used on non-occluded coronary arteries.

[Predictors of early occlusion of coronary bypass grafts in patients with extremely low ejection fraction]

The authors carried out a retrospective study aimed at revealing predictors of early incompetence of coronary bypass grafts in patients with the ejection fraction below 30%. The study included a total of 104 patients presenting with coronary artery disease and the ejection fraction below 30%, who over the period from 2009 to 2016 underwent coronary artery bypass grafting with the use of autovenous and autoarterial conduits. 77 patients endured plasty of an aneurysm of the left ventricle (LV), 89 patients sustained plasty of the valvular apparatus. All patients were subjected to control coronary bypass angiography (CBA) within 12 postoperative months. Thus, we analysed a total of 184 autoarterial and 84 autovenous shunts. The findings of CBA revealed occlusions of 2 (1%) arterial and 10 (11%) venous conduits. Analysing the coronary bypass angiographies of the patients ranked according to the values of the effective stroke volume index demonstrated the following regularity: a decrease in the LV effective stroke volume index of less than 30 ml/m2 was accompanied bу increased incidence of thrombosis of autovenous shunts in the immediate postoperative period. Predictors of early occlusion of coronary bypass grafts were revealed by means of the Cox regression analysis. It was determined that using an autovein increased the risk of occlusion of the shunt by 26%, a decrease in the effective stroke volume index of the left ventricle by 1 ml/m2 increased the risk of early occlusion of coronary bypass grafts by 18%, a decrease in the diameter of the shunted artery by 0.5 mm increased the risk for early occlusion of the shunt by 12%, a decrease in the blood flow velocity (Qmean) by 1 ml/m2 increased the risk for occlusion of the shunt by 10%, a decrease in the peripheral resistance index (RI) by 1 unit elevated the risk of early occlusion of the bypass graft by 12%. Analysing the revealed independent predictors with the help of the neural network method demonstrated that the strongest influence on early incompetence of the coronary bypass graft was exerted by the type of the conduit and effective stroke index.

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.

Off-pump onlay-patch grafting using the left internal mammary artery for a diffusely diseased left anterior descending artery: in-hospital and mid-term outcomes

BACKGROUND

The aims of this study were to evaluate the in-hospital and mid-term outcomes of the off-pump onlay-patch grafting procedure using the left internal mammary artery (LIMA) for a diffusely diseased left anterior descending artery (LAD) and to identify the risk factors for postoperative LIMA graft failure in a single-center retrospective study.

PATIENTS AND METHODS

A total of 63 patients (52 males, 65.7±9.0 years) undergoing LAD arteriotomy with or without concomitant endarterectomy, followed by reconstruction using LIMA onlay-patch at the time of off-pump coronary artery bypass grafting at our institute from January 2014 to December 2016 were reviewed. The operative mortality, major postoperative morbidity, follow-up all-cause mortality, major adverse cardiac events at follow-up, and postoperative LIMA graft patency were analyzed. The risk factors for postoperative LIMA graft failure on the basis of baseline and surgical characteristics were identified by multivariable logistic regression analysis.

RESULTS

Eighteen (28.6%) patients underwent concomitant open LAD endarterectomy. The operative mortality rate was 1.6%. Major postoperative morbidity included perioperative myocardial infarction (3.2%), low cardiac output (1.6%), and reoperation for bleeding (1.6%). During the follow-up period of 24.2±9.5 months, all-cause mortality was 1.7% and the incidence of major adverse cardiac events was 6.8%. No repeat revascularization was recorded. In total, 88.1% of LIMA grafts showed FitzGibbon grade A patency determined by noninvasive coronary computed tomography angiography during follow-up. In addition, concomitant LAD endarterectomy and intraoperative LIMA graft flow were found to be independent risk factors for mid-term LIMA graft failure by multivariable logistic regression analysis (odds ratio=2.681, 95% confidence interval: 1.314-9.856, P=0.007 and odds ratio=0.932, 95% confidence interval: 0.791-0.976, P=0.021, respectively).

CONCLUSION

Revascularization of a diffusely diseased LAD using the off-pump LIMA onlay-patch technique results in encouraging clinical outcomes with favorable angiographic results. Concomitant LAD endarterectomy and intraoperative LIMA graft flow are associated with the risk of postoperative LIMA graft failure.

Intraoperative transit-time flowmetry in patients undergoing coronary surgery to determine relationships between graft flow and patency and prior coronary interventions and flow demand: a retrospective study

Background

The aim of this study was to delineate impacts of percutaneous coronary intervention (PCI), flow demand, and status of myocardium on graft flow.

Methods

We retrospectively assessed 736 individual coronary artery bypass grafts that had been created as the sole bypass graft for a vascular region in 405 patients. The grafts comprised 334 internal thoracic artery (ITA) to left anterior descending (LAD), 129 ITA and 65 saphenous vein grafts (SVG) to left circumflex (LCX), and 142 gastroepiploic artery (GEA) and 66 SVG to right coronary artery (RCA). Minimal luminal diameter, size of revascularized area, history of myocardial infarction, and PCI in the relevant area were examined to determine whether these factors are associated with flow insufficiency (FI), which was defined as ≤ 20 mL/min.

Results

FI developed in 123/736 grafts (16.7%) and correlated significantly with stenosis in the distal portion (23.0% vs. 12.8%, p = 0.0003). Prior myocardial infarction significantly correlated with FI in GEA–RCA (p = 0.002) and ITA–LCX grafts (p = 0.04). There was a history of PCI to the LAD (PCI group) in 54 ITA to LAD bypass grafts (16.2%), whereas the remaining 280 had no history of PCI to the LAD (no-PCI group). Graft flow was significantly greater in the no-PCI than in the PCI group (53 ± 29 vs. 42 ± 27; p = 0.006). The incidences of FI and graft failure were significantly higher in the PCI than the no-PCI group (22.2%, vs. 8.2%; p = 0.003; 9.2% vs. 1.8%; p = 0.003, respectively).

Conclusions

Prior PCI has a negative impact on graft flow. The influences of small revascularized area, myocardial infarction, and PCI are greater, necessitating consideration of factors associated with flow demand or microvasculature when planning revascularization.

Sequential Grafting of in Situ Skeletonized Left Internal Mammary Artery to the Left Coronary System

Sequential grafting may be an effective way to maximize the benefits of the left internal mammary artery (LIMA) conduit. Despite increasing clinical application, the strategy of sequential LIMA grafting has not been proven its superiority. This single-center retrospective study aimed to evaluate the in-hospital and mid-term outcomes of sequential grafting of in situ skeletonized LIMA to the left coronary system.According to the use of sequential or separate LIMA grafting, 1505 eligible patients were assigned to a sequential group (n = 230) and a control group (n = 1275). According to sequential LIMA graft configurations, patients with sequential LIMA grafting were divided into a DOM subgroup (n = 113) and a DLAD subgroup (n = 117). The clinical outcomes and LIMA graft patency were investigated and compared.Sequential LIMA grafting compared with separate LIMA grafting was not an independent predictor either of in-hospital adverse events or follow-up survival free from repeat revascularization during the follow-up period of 32.4 ± 8.5 months. Sequential LIMA grafting had similar LIMA graft patency with separate LIMA grafting (99.5% of 1st sequential sites and 97.7% of 2nd sites versus 98.2% of LIMA-LAD grafts) at 32.3 ± 8.5 months after coronary artery bypass grafting (CABG) surgery. Additionally, the two subgroups received similar mid-term clinical outcomes and graft patency of LIMA segments.Sequential grafting of in situ skeletonized LIMA to the left coronary system resulted in excellent clinical outcomes and graft patency. The two sequential LIMA graft configurations received similar clinical outcomes and graft patency.

Influence of coronary territory on flow profiles of saphenous vein grafts

Background

Differing perfusion of the left and right ventricular coronary territory may influence flow-profiles of saphenous vein grafts (SVGs). We compared flow parameters, measured by transit-time flowmetry (TTFM), in left- and right-sided SVGs during coronary artery by-pass grafting (CABG).

Methods

Routine TTFM measurements were obtained in 167 SVGs to the left territory (55%) and 134 SVGs to the right territory (total of 301 SVGs in 207 patients). The four standard TTFM parameters, [mean graft flow (MGF), pulsatility index (PI), percentage diastolic filling (%DF), and percentage backward flow (%BF)] were compared. Differences in flow parameters were also examined according to surgical technique (on- vs. off-pump).

Results

No significant difference between coronary territories was found for MGF, PI and %BF. However, a higher %DF was noted in left-sided SVGs in the overall cohort as well as in the on-pump (both p < 0.001) and the off-pump cohorts (p = 0.07). Further, a significantly higher %BF was found in SVGs performed off-pump to the left territory (1.2 ± 2.5 vs. 2.3 ± 3.0, p = 0.023). In a multivariate regression analysis, anastomosing a SVG to the left territory was weakly associated with higher PI (OR = 0.36, p = 0.026) and strongly associated with higher %DF (OR = 5.1, p < 0.001). No significant association was found for MGF, PI, %DF or %BF in either the on-pump nor the off-pump cohorts.

Conclusions

Although statistically significant, the established differences in TTFM parameters between left- and right-sided vein grafts were small and unlikely to be of clinical relevance.

In Situ Skeletonized Right Internal Mammary Artery Bypass Grafting to Left Anterior Descending Artery

This study aimed to evaluate the feasibility and the mid-term efficacy of an in situ skeletonized right internal mammary artery (IMA) bypass grafting to a left anterior descending artery (LAD), and to determine risk factors for IMA graft failure in a single-center study.From January 2012 to December 2015, 189 patients (173 males, 50.6 ± 6.0 years old) undergoing first isolated coronary artery bypass grafting surgery with the in situ skeletonized right IMA grafting to the LAD were included in this study. Baseline characteristics, peroperative data, and follow-up outcomes were investigated and analyzed.The length of the in situ skeletonized right IMA grafts was 18.6 ± 1.2 cm (17.0-22.0 cm). Intraoperative graft flow of the in situ skeletonized right IMA grafting to LAD was 42 ± 9 mL/minute (18-72 mL/minute) associated with measured pulsatility index of 0.8-4.3. In-hospital mortality was 0.5%. Postoperative morbidity included acute myocardial infarction (0.5%), stroke (0.5%), and deep sternal wound infections (1.1%). The mid-term survival was 97.2% and the incidence of repeat revascularization was 0.6%. The patency rate of the in situ skeletonized right IMA grafting to the LAD was 97.1% by computed tomography angiography examination during the follow-up period of 23.2 ± 9.7 months. Additionally, logistic regression analysis showed that intraoperative graft flow had an independent influence on the risk of the mid-term right IMA graft failure.The strategy of the in situ skeletonized right IMA grafting to the LAD is feasible and effective. Intraoperative graft flow was an independent risk factor for the mid-term right IMA graft failure.

Revascularization of Left Coronary System Using a Skeletonized Left Internal Mammary Artery - Sequential vs. Separate Grafting

BACKGROUND

To evaluate in-hospital and mid-term outcomes of sequential vs. separate grafting of in situ skeletonized left internal mammary artery (LIMA) to the left coronary system in a single-center, propensity-matched study.

METHODS AND RESULTS

After propensity score-matching, 120 pairs of patients undergoing first scheduled isolated coronary artery bypass grafting (CABG) with in situ skeletonized LIMA grafting to the left anterior descending artery (LAD) territory were entered into a sequential group (sequential grafting of LIMA to the diagonal artery and then to the LAD) or a control group (separate grafting of LIMA to the LAD). The in-hospital and follow-up clinical outcomes and follow-up LIMA graft patency were compared. Both propensity score-matched groups had similar in-hospital and follow-up clinical outcomes. Sequential LIMA grafting was not found to be an independent predictor of adverse events. During a follow-up period of 27.0±7.3 months, 99.1% patency for the diagonal site and 98.3% for the LAD site were determined by coronary computed tomographic angiography after sequential LIMA grafting, both of which were similar with graft patency of separate grafting of in situ skeletonized LIMA to the LAD.

CONCLUSIONS

Revascularization of the left coronary system using a skeletonized LIMA resulted in excellent in-hospital and mid-term clinical outcomes and graft patency using sequential grafting.

Mechanisms, Consequences, and Prevention of Coronary Graft Failure

Graft failure occurs in a sizeable proportion of coronary artery bypass conduits. We herein review relevant current evidence to give an overview of the incidence, pathophysiology, and clinical consequences of this multifactorial phenomenon. Thrombosis, endothelial dysfunction, vasospasm, and oxidative stress are different mechanisms associated with graft failure. Intrinsic morphological and functional features of the bypass conduits play a role in determining failure. Similarly, characteristics of the target coronary vessel, such as the severity of stenosis, the diameter, the extent of atherosclerotic burden, and previous endovascular interventions, are important determinants of graft outcome and must be taken into consideration at the time of surgery. Technical factors, such as the method used to harvest the conduits, the vasodilatory protocol, the storage solution, and the anastomotic technique, also play a major role in determining graft success. Furthermore, systemic atherosclerotic risk factors, such as age, sex, diabetes mellitus, hypertension, and dyslipidemia, have been variably associated with graft failure. The failure of a coronary graft is not always correlated with adverse clinical events, which vary according to the type, location, and reason for failed graft. Intraoperative flow verification and secondary prevention using antiplatelet and lipid-lowering agents can help reducing the incidence of graft failure.

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.

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.

Effects of intraoperative diltiazem infusion on flow changes in arterial and venous grafts in coronary artery bypass graft surgery

Objective

This study aimed to show the effects of intra-operative diltiazem infusion on flow in arterial and venous grafts in coronary artery bypass graft surgery.

Methods

Hundred fourty patients with a total of 361 grafts [205 (57%) arterial and 156 (43%) venous] underwent isolated coronary surgery. All the grafts were measured by intraoperative transit time flow meter intra-operatively. Group A (n=70) consisted of patients who received diltiazem infusion (dose of 2.5 microgram/kg/min), and Group B (n=70) didn't receive diltiazem infusion.

Results

Mean graft flow values of left internal mammary artery were 53 ml/min in Group A and 40 ml/min in Group B (P<0.001). Pulsatility index (PI) values of left internal mammary artery for Group A and Group B were 2.6 and 3.0 respectively (P<0.001). No statistically significant difference was found between venous graft parameters.

Conclusion

We recommend an effect of diltiazem infusion in increasing graft flows in coronary artery bypass graft operations.