Graft revision after transit time flow measurement in off-pump coronary artery bypass grafting

Small-diameter PCL/PU vascular graft modified with heparin-aspirin compound for preventing the occurrence of acute thrombosis

The occurrence of acute thrombosis, directly related to platelet aggregation and coagulant system, is a considerable reason for the failure of small-diameter vascular grafts. Heparin is commonly used as a functional molecule for graft modification due to the strong anticoagulant effect. Unfortunately, heparin cannot directly resist the adhesion and aggregation of platelets. Therefore, we have prepared a heparin-aspirin compound by coupling heparin with aspirin, an antiplatelet drug, and covalently grafted it onto the surface of polycaprolactone/polyurethane composite tube. In this way, the graft not only showed a dual function of both anticoagulation and antiplatelet, but also effectively avoided the rapid drug release and excessive toxicity to other organs caused by simple blending the medicine with material matrix. The compound retained the original function of heparin, showing good hydrophilicity and biocompatibility, which could promote the adhesion and proliferation of endothelial cells (ECs) and facilitate the process of tissue regeneration. What's more, the compound showed more effective than heparin in reducing platelet activation and preventing thrombosis. The graft modified by this compound maintained completely unobstructed for one month of implantation, while severe obstruction or stenosis occurred in PCL/PU and PCL/PU-Hep lumen at the first week, verifying the effect of the compound on preventing acute thrombosis. In general, this study proposed a designing method for small-diameter vascular graft which could prevent acute thrombosis and promote intimal construction.

Assessment of the Graft Quality and Patency during and after Coronary Artery Bypass Grafting

Coronary artery bypass grafting (CABG) is the gold standard procedure for multi vessels and left main coronary artery disease. The prognosis and survival outcomes of CABG surgery are highly dependent on the patency of the bypass graft. Early graft failure which can occur during or soon after CABG remains a significant issue, with reported incidences of 3-10%. Graft failure can lead to refractory angina, myocardial ischemia, arrhythmias, low cardiac output, and fatal cardiac failure, emphasizing the importance of ensuring graft patency during and after surgery to prevent such complications. Technical errors during anastomosis are among the leading causes of early graft failure. To address this issue, various modalities and techniques have been developed to evaluate graft patency during and after CABG surgery. These modalities aim to assess the quality and integrity of the graft, thus enabling surgeons to identify and address any issues before they lead to significant complications. In this review article, we aim to discuss the strengths and limitations of all available techniques and modalities, with the goal to identify the best modality for evaluating graft patency during and after CABG surgery.

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

Objective

Transit time flow measurement (TTFM) can detect critical anastomotic stenosis during coronary artery bypass grafting. However, the identification of subcritical stenosis remains challenging. We hypothesized that diastolic resistance index (DRI), a novel TTFM metric, is more effective in evaluating subcritical stenosis than the currently available TTFM metrics. DRI is used to measure changes in the diastolic versus systolic resistance of distal anastomosis.

Methods

A total of 123 coronary bypass anastomoses in 35 patients were prospectively analyzed. During coronary artery bypass grafting, the mean graft flow (Q_mean), pulsatility index, and diastolic filling were obtained. DRI was calculated using the intraoperative recordings of TTFM and arterial pressure. Postoperatively, stenosis of anastomoses was categorized into successful (<50%), subcritical (50%-74%), and critical (≥75%) via multidetector computed tomography scan.

Results

In total, 93 (76%), 13 (10%), and 17 (14%) anastomoses were graded as successful, subcritical, and critical, respectively. DRI and diastolic filling could distinguish subcritical from successful anastomoses (P < .01 and < .01, respectively), whereas Q_mean and pulsatility index could not (P = .12 and .39, respectively). The receiver operating characteristic curves were established to evaluate the diagnostic ability for detecting ≥50% stenosis. In left anterior descending artery grafting (n = 55), DRI had the highest area under the curve (0.91), followed by diastolic filling (0.87), Q_mean (0.74), and pulsatility index (0.65).

Conclusions

DRI and diastolic filling had a reliable diagnostic ability for detecting ≥50% stenosis during coronary artery bypass grafting. In left anterior descending artery grafting, DRI had a more satisfactory detection capability than other TTFM metrics.

Transit-Time Flow Measurement of Saphenous Vein Graft Used for Surgery of Acute Type A Aortic Dissection with Coronary Malperfusion

PURPOSE

Transit-time flow measurement (TTFM), consisting of pulsatility index (PI), mean graft flow, and diastolic filling, is mainly used as a bypass assessment for coronary artery disease (CAD). However, little was known about TTFM in the case of coronary malperfusion (CMP). This study aimed to clarify the difference in the results of TTFM between two different diseases.

METHODS

Between 2010 and 2020, 138 patients underwent aortic surgery and coronary artery bypass grafting (CABG) with vein grafts. Patients were divided into two groups: CMP (n = 26) and CAD (n = 27). Their results were compared. The primary endpoints were the results of TTFM. Secondary endpoints were the relation between TTFM and mortality, morbidity, and short-term patency in each group.

RESULTS

The PI in the CMP group was significantly higher than the other group (4.7 ± 2.9 vs. 3.4 ± 1.9, p = 0.04). There was no statistical significance in the other two elements. In both groups, the short-term graft patency, mortality, and morbidity but for cardiac tamponade did not significantly change depending on the TTFM results.

CONCLUSIONS

Patients with CMP tended to have a higher PI than those with CAD. With additional CABG for aortic dissection, insufficient TTFM results did not necessarily mean poor short-term graft patency, complications, or case mortality.

Intraoperative Blood Flow Analysis of DIEP vs. ms-TRAM Flap Breast Reconstruction Combining Transit-Time Flowmetry and Microvascular Indocyanine Green Angiography

Background: Vascular patency is the key element for high flap survival rates. The purpose of this study was to assess and compare the blood flow characteristics of deep inferior epigastric perforator (DIEP) and muscle-sparing transverse rectus abdominis musculocutaneous (ms-TRAM) flaps for autologous breast reconstruction. Methods: This prospective clinical study combined Transit-Time Flowmetry and microvascular Indocyanine Green Angiography for the measurement of blood flow volume, vascular resistance, and intrinsic transit time. Results: Twenty female patients (mean age, 52 years) received 24 free flaps (14 DIEP and 10 ms-TRAM flaps). The mean arterial blood flow of the flap in situ was 7.2 ± 1.9 mL/min in DIEP flaps and 11.5 ± 4.8 mL/min in ms-TRAM flaps (p < 0.05). After anastomosis, the mean arterial blood flow was 9.7 ± 5.6 mL/min in DIEP flaps and 13.5 ± 4.2 mL/min in ms-TRAM flaps (p = 0.07). The arterial vascular resistance of DIEP flaps was significantly higher than that of ms-TRAM flaps. The intrinsic transit time of DIEP flaps was 52 ± 18 s, and that of ms-TRAM flaps was 33 ± 11 s (p < 0.05). The flap survival rate was 100%. One DIEP flap with the highest intrinsic transit time (77 s) required surgical revision due to arterial thrombosis. Conclusion: In this study, we established the blood flow characteristics of free DIEP and ms-TRAM flaps showing different blood flow rates, vascular resistances, and intrinsic transit times. These standard values will help to determine the predictive values for vascular compromise, hence improving the safety of autologous breast reconstruction procedures.

Newly Developed Graft Failure Detected Using Computed Tomography Within 1 Year After Coronary Artery Bypass Grafting Surgery: One Single-Center Experience

Background

Newly developed graft failure negatively affects the short- and long-term outcomes of patients who experience coronary artery bypass grafting (CABG) surgery. This study explored the value of transit time flow measurement (TTFM) parameters for predicting the risk of newly developed graft failure that occurs within 1 year after CABG, as well as investigated the relationship between newly developed graft failure and adverse cardiovascular events.

Methods

A total of 134 patients who underwent CABG and had CT angiography (CTA) data (1 year post-operatively) were divided into two groups: the patient group, in which patients did not have newly developed graft failure, and the occluded group, in which patients developed newly developed graft failure between 1 and 12 months after CABG. The patency rate of grafts in different targets was analyzed. The correlations between graft failure and TTFM parameters and between graft failure and the occurrence of adverse cardiovascular events were investigated.

Results

The overall rate of newly developed graft failure was 7.2%, the venous graft failure was 10.8%, and the arterial graft failure was 0.7%. The occluded group had a higher pulse index (PI) (2.9 vs. 2.4, P = 0.007), a lower mean graft flow (MGF) (20 vs. 25 ml/min, P = 0.028), and a lower diastolic flow fraction (DF) (63.5 vs. 70%, P = 0.019) than the patent group. The cut-off value for predicting newly developed graft failure was PI > 2.75 (P = 0.007), MGF < 23.5 ml/min (P = 0.03), and DF < 65.5% (P = 0.019). Compared with the patent group, the newly developed graft failure group had higher rates of recurrent angina (13.6 vs. 0.9%, P = 0.0014) and revascularization intervention (9.1 vs. 0% P = 0.026). However, there were no differences in death, cardiac death, myocardial infarction, and cerebral infarction after CABG operation between these two groups (P > 0.05).

Conclusions

A high PI and low MGF and DF are risk factors for newly developed graft failure. The patients with newly developed graft failure had higher rates of recurrent angina and revascularization intervention. TTFM parameters may be used to predict the occurrence of newly developed graft failure in patients after CABG surgery.

Intraoperative Assessment of Coronary Resistances: A New Quality Marker and Potential Tool to Predict Early Graft Failure after Coronary Artery Bypass Grafting?

Intraoperative assessment of graft patency is pivotal for successful coronary revascularization. In the present study we aimed to propose a new, easy to perform tool to assess anastomotic quality intraoperatively, and to investigate its potential reliability in predicting early graft failure. Intraoperative graft flowmetry of 63 consecutive patients undergoing CABG were prospectively collected. Transit time flowmetry and its derivatives were recorded. Coronary resistances were calculated according to Hagen–Poiseuille equation both during cardioplegic arrest and after withdrawal from cardiopulmonary bypass. Angiographic evidence of graft occlusion at follow-up was cross-checked with intraoperative recordings. After a mean follow-up of 10.4 ± 6.0 months, 22 grafts were studied, and occlusion was documented in five (22.7%). Occluded grafts showed lower flows and higher resistances recorded during aortic cross-clamping. Coronary resistances, recorded during aortic cross-clamping, greater than 2.0 mmHg/mL/min, showed a sensitivity of 80% and a specificity of 100% to predict graft failure. We propose the routine recording of coronary resistances during aortic cross-clamping as an additional tool to overcome the acknowledged limitation of TTF to predict graft occlusion at 1 year.

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.

Correlation between Preoperative Coronary Artery Stenosis Severity Measured by Instantaneous Wave-Free Ratio and Intraoperative Transit Time Flow Measurement of Attached Grafts

Background and Objectives: To assess the correlation between the degree of target coronary artery stenosis measured by instantaneous wave-free ratio (iFR) and the intraoperative transit time flow measurement (TTFM) of attached grafts as well as evaluate flow competition between the native coronary artery and the attached graft according to the severity of stenosis. Materials and Methods: In total, 89 grafts were subjected to intraoperative transit time flow measurement after coronary artery bypass grafting (CABG) in 25 patients with multivessel coronary artery disease (CAD). The iFR was evaluated for all coronary arteries with grafts. The coronary artery stenoses were divided into three groups based on the iFR value: iFR < 0.86 (group 1); iFR 0.86–0.90 (group 2); and iFR > 0.90 (group 3). Results: The mean graft flow (MGF) was 46.9 ± 18.4 mL/min for group 1, 45.3 ± 20.9 mL/min for group 2, and 31.3 ± 18.5 mL/min for group 3. A statistically significant difference was confirmed between groups 1 and 3 (p = 0.002) and between groups 2 and 3 (p = 0.025). The pulsatility index (PI) was 2.49 ± 1.20 for group 1, 2.66 ± 2.13 for group 2, and 4.70 ± 3.66 for group 3. A statistically significant difference was found between groups 1 and 3 (p = 0.006) and between groups 2 and 3 (p = 0.032). Backward flow was detected in 7.5% of grafts for group 1, in 16.6% of grafts for group 2, and in 16% of grafts for group 3. A statistically significant difference was found between groups 1 and 2 (p = 0.025) and between groups 1 and 3 (p = 0.029). Conclusions: The iFR is a useful tool for predicting the impact of competitive flow observed between a native artery and an attached graft. The effect of competitive flow significantly increases when the graft is attached to a vessel with mild coronary stenosis. In a coronary artery where the iFR was not hemodynamically significant, the MGF was lower, the PI was higher, and a larger proportion of grafts with backward flow (BF) was detected compared to when there was significant stenosis (iFR < 0.86).

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.

Outcome of hybrid compared to conventional revascularization in multivessel coronary artery disease

OBJECTIVES

Evaluation of 3-year clinical outcome of hybrid myocardial revascularization (HMR) compared to conventional revascularization strategies in patients with multivessel coronary artery disease involving the proximal left anterior descending artery. Design. Retrospective matched cohort study based on a prospective feasibility study including 103 elective patients undergoing staged HMR from October 2010 until February 2012. The Western Denmark Heart Registry was used to identify patients who underwent coronary artery bypass grafting (CABG) and multivessel percutaneous coronary intervention (PCI) by matching on number of diseased vessels, age and comorbidity score. Primary endpoint was the composite rate of major adverse cardiovascular and cerebrovascular events (MACCE) at 3-year follow-up. Secondary endpoints included individual MACCE components, acute kidney injury, and cardiovascular readmissions. Results. There was no difference between MACCE in the three groups (HMR 31.1%; CABG 20.4%; PCI 20.4%, p = .11). Estimates of repeat revascularization were significantly increased with HMR versus CABG. In the CABG group, fewest patients required cardiovascular readmissions though with the highest incidence of acute kidney injury. Conclusions. HMR was not superior with respect to MACCE compared with CABG and PCI. It may, however, represent a safe alternative to conventional revascularization treatment considering the specific procedure-associated morbidity.

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.

[Effect of the degree of stenosis of the right coronary artery on remote results of bypass grafting]

AIM

The purpose of this study was to assess the long-term results of right coronary artery bypass grafting and identify predictors of coronary artery bypass graft occlusion.

PATIENTS AND METHODS

Our retrospective single-centre study included a total of 245 patients subjected to isolated coronary artery bypass graft operations during the follow up period from 2010 to 2015. All patients endured bypass grafting of the right coronary artery (RCA) with either autovenous or autoarterial conduits. Control coronary bypass angiography was performed in all patients in connection with a relapse of angina pectoris. The duration of the follow up period amounted to 43.7±20.2 months. The patients were divided into two groups depending on the type of the conduit used to bypass the RCA. Group One patients (n=106) endured bypass grafting of the RCA and its branches using the internal thoracic artery. Group Two patients (n=139) underwent autovenous coronary artery bypass grafting of the RCA basin. By the main clinical, demographic and intraoperative parameters the groups were statistically homogeneous (p>0.05). The effect of the degree of proximal stenosis, the diameter of the grafted artery on the viability of bypass grafts was assessed.

RESULTS

During the follow-up period up to 84 months, 19 (17.9%) occluded arterial and 29 (20.9%) venous conduits were revealed. The Kaplan-Meier analysis showed that the probability of the absence of venous graft occlusion during the follow-up period up to 84 months was significantly lower than that of arterial grafts (log rank=0.012). The Cox regression analysis results revealed that shunt occlusion was influenced by the degree of proximal stenosis and the diameter of the shunted artery.

CONCLUSION

When shunting a moderate stenosis of the RCA (up to 70%), an advantage of autovenous conduits was revealed. When shunting the RCA with a critical stenosis and occlusion, advantages were revealed for the internal thoracic artery.

Twenty-Year Experience With Off-Pump Coronary Artery Bypass Grafting and Early Postoperative Angiography

BACKGROUND

We have performed off-pump coronary artery bypass grafting and also performed early postoperative angiography to assess anastomosis accuracy and patency in most of our patients requiring surgical revascularization.

METHODS

Of 3083 patients who underwent isolated coronary artery bypass grafting between 1998 and 2017, 2919 patients (94.7%) underwent off-pump coronary artery bypass grafting. Conduits for distal anastomoses were left internal thoracic artery (n = 2764), right internal thoracic artery (n = 866), right gastroepiploic artery (n = 997), radial artery (n = 16), and saphenous vein (n = 1505). Since the introduction of transit-time flow measurement in 2000, we revised abnormal grafts intraoperatively. Early (≤7 days) angiography was performed in 2820 patients (96.6%) at 1.5 ± 1.2 postoperative days, and surgical intervention was performed based on angiographic findings.

RESULTS

Operative mortality was 1.1% (32 of 2919). Average number of distal anastomoses was 3.2 ± 1.0. Intraoperative flowmetry-guided revision for distal anastomosis failures was performed in 109 of 8585 distal anastomoses (1.3%). Angiography showed an overall patency of 98.2% (8836 of 9001): 99.0% (5484 of 5540) for arterial and 96.9% (3352 of 3461) for venous conduits (P < .001). Patency of venous conduits was 87.2% (231 of 265) for free grafts and 97.7% (3121 of 3196) for composite grafts (P = .001). After the introduction of transit-time flow measurement, patency of arterial conduits became significantly higher (97.2% vs 99.2%; P = .038); however, patency of free venous conduits was not significantly improved (86.0% vs 91.4%; P = .181). Early re-intervention according to angiographic findings was performed in 76 patients (2.7%). Reevaluation of graft patency before discharge in 31 who underwent revision of distal anastomoses showed improved patency (65.1% [56 of 86] vs 95.3% [82 of 86]; P < .001).

CONCLUSIONS

Intraoperative flowmetry and revision of abnormal grafts improved early arterial graft patency, and reoperation based on early angiographic findings may further improve graft patency at the time of discharge.

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.

Quality metrics in coronary artery bypass grafting

Studies on the association between care quality, case volume, and outcomes in coronary artery bypass grafting (CABG) have concluded that consistent adherence to quality measures improves mortality rates and outcomes. However, the quality metrics are not well-defined, and their significance to surgeons and healthcare providers remains uncertain. We review the concept of "quality and quality metrics" and discuss their importance in the context of CABG.

A case report on epicardial ultrasonography of coronary anastomoses using a stabilizing device without the use of ultrasound gel

BACKGROUND

Intraoperative epicardial ultrasonography of coronary artery bypass graft anastomoses is a procedure used for anatomical quality assessment of peripheral anastomoses during coronary artery bypass grafting. However, it may be difficult to keep the ultrasound transducer in steady contact with the anastomoses on the beating heart without causing any deformation. Furthermore, we are not aware of any sterile ultrasound gel approved for application into the pericardial space.

CASE PRESENTATION

We report a method using a stabilizing connecting device for an ultrasound transducer to be used for visualization of coronary anastomoses without application of ultrasound gel during on-pump coronary bypass surgery.

CONCLUSION

Use of a stabilizing device and coagulated blood from the patient as an alternative for ultrasound gel facilitates peroperative ultrasonography of coronary anastomoses. The procedure provides surgeons with non-deformed echocardiographic longitudinal and transverse images of all parts of the anastomoses.

TRIAL REGISTRATION

The patient participated in a still ongoing clinical feasibility study: Trial registration: ClinicalTrials.gov ID: NCT02919124 ; Registered September 29, 2016.

MIDCAB versus off-pump CABG: Comparative study

OBJECTIVE

To investigate the clinical significance of minimally invasive direct coronary artery bypass (MIDCAB).

METHODS

Three hundred patients admitted to the Second Hospital of Shandong University from March 2006 to February 2010 were retrospectively analyzed and received off-pump operation under general anesthesia. Depending on surgical methods, patients were divided into the MIDCAB group (n = 90) and the median sternotomy off-pump coronary artery bypass (OPCAB) group, named as the OPCAB group (n = 210). Preoperative clinical data, perioperative clinical data, and mid-term follow-up at 7 years after operation were analyzed and compared between the two groups.

RESULTS

Age and the number of vascular lesions in the OPCAB group were higher than those in the MIDCAB group, whereas left ventricular ejection fraction (LVEF) in the former was lower than that in the latter (p<0.05). The number of distal anastomotic stomas, operation time, blood transfusion volume, postoperative cardiac troponin I (cTnI) peak value, ventilator use time, intensive care unit (ICU) stay, and hospital stay in the MIDCAB group were significantly lower than those in the traditional OPCAB group (p<0.05). Among the 294 recovered cases, 201 cases completed 7 years of continuous follow-up, with a follow-up rate of 67.91%. The LVEF and the patency rate of vessels in the MIDCAB group were higher than those in the OPCAB group (p<0.05).

CONCLUSIONS

Compared with the median sternotomy OPCAB, MIDCAB is characterized by small incision, small trauma, positive efficacy, and safety; therefore, it is worthy of being promoted.

Transit time flow measurement and high frequency ultrasound epicardial imaging to guide coronary artery bypass surgery

BACKGROUND

Transit-time flow measurement (TTFM) should be routinely used in CABG surgery to verify graft function. Most recently, a 2D high-frequency-ultrasound (HF-US) epicardial imaging probe has been released (MiraQ™, Medistim, Oslo, Norway), which allows to evaluate the cannulation/clamping site of the aorta morphologically and to evaluate the completed anastomosis. We aimed to evaluate the use of TTFM and HF-US on surgical strategy during CABG surgery.

METHODS

A total of 65 consecutive patients undergoing CABG surgery were evaluated. The target vessels, the clamping/cannulation site and the anastomosis were evaluated by HF-US. TTFM was performed on all grafts and the mean flow (mL/min) and pulsatility indices (PI) were recorded. Troponin-I levels (ng/L) were obtained within the first 4 postoperative days.

RESULTS

A total of 3.3±0.9 grafts were performed, with 98.5% LIMA use and a sequential graft was performed in 55.4%. The mean PI and flow (mL/min) were 2.3±2.7 and 70.8±50.6 for the right coronary artery system, 2.4±2.2 and 82.0±47.6 for the circumflex system, and 2.1±1.2 and 78.0±35.0 for the LAD system, respectively. Postoperative troponin-I levels showed a maximum on postoperative day 1. A surgical strategy change, based on imaging, was done in 15%. Moreover, we observed a correlation of PI and flow with maximum postoperative troponin-I levels.

CONCLUSIONS

The present study evaluated the combination of TTFM and HF-US in CABG surgery. Epicardial scanning was helpful to evaluate the potential opening site of the vessel, to evaluate the completed anastomosis or to evaluate the clamping or cannulation site. Troponin-I levels were directly correlated to mean graft flow and PI levels.

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.

CABG and Preoperative use of Beta-Blockers in Patients with Stable Angina are Associated with Better Cardiovascular Survival

Objective

In contrast to unstable angina, optimal therapy in patients with stable angina is debated. Our aim was to evaluate the outcomes of patients with stable angina scheduled for isolated coronary artery bypass grafts and the effect of preoperative use of beta-blockers. Overall and cardiovascular survivals were our primary outcome. Operative mortality and postoperative complications along with subgroup analysis of diabetic patients were our secondary outcomes.

Methods

Retrospective evaluation of patients with stable angina scheduled for isolated coronary artery bypass grafts was included. Pre- and postoperative variables were extracted from the institution database. Survival was obtained from the National Registry.

Results

We included 282 patients with stable angina, with a mean age of 65.6±9.5 years. 26.6% were female and 38.7% had diabetes. Three-vessel disease was present in 76.6% of patients. Previous beta-blocker treatment was evident in 69.9% of patients. 10-year overall survival in the whole population was 60.5% (95% confidence interval [CI]: 50.3-70.7%). Operative mortality during the study period was 3.5%. Patients with preoperative use of beta-blocker therapy had better overall survival (9.0 years, 95%CI: 8.6-9.5) than those without treatment (7.9 years, 95%CI: 7.1-8.8 years; P=0.048). Predictors for overall survival were: hypertension, diabetes, and age. Predictors for cardiovascular survival in diabetic patients were: beta-blocker use, gender, and age.

Conclusion

Coronary artery bypass grafts surgery in patients with stable angina carries low operative mortality, postoperative complications, and excellent long-term cardiovascular survival. The preoperative use of beta-blockers in diabetic patients is associated with better cardiovascular survival after coronary artery bypass grafts.

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.

A randomized comparison of flow characteristics of semiskeletonized and pedicled internal thoracic artery preparations in coronary artery bypass

Background

Harvesting the internal thoracic artery (ITA) with semiskeletonization is an alternative technique between conventional wide pedicle and skeletonization. It is almost as simple as pedicle harvesting; however, it is supposed to provide the advantage of graft flow and length. Since the heart is unique being the only organ which is perfused during diastole, for comparing the intraoperative graft flow characteristics of semiskeletonization and pedicle technique, we used diastolic filling (DF) using transit-time flow measurement as a primary result. The objective of this study is to compare if semiskeletonized ITA has a greater effect on the intraoperative DF of graft flow versus conventional pedicled ITA in coronary artery bypass.

Methods

Between July 2015 and May 2016, a prospective evaluation of 60 consecutive patients undergoing coronary artery bypass grafting for left anterior descending artery revascularization were randomized to having semiskeletonized (n = 30) or conventional pedicled (n = 30) ITA graft harvested by the same surgeon. Intraoperative transit-time flows were obtained. The DF of the ITA graft at the end of operation was evaluated in two groups.

Results

The intraoperative DF was significantly greater in the semiskeletonized grafts than in the pedicled grafts (70.50 ± 14.15 versus 57.6 ± 19.39%; p = 0.005). No statistical difference was observed comparing quantitative pulsatile flow and pulsatile index at the end of the operation in the two groups. However, the free flow of the conduit during the cardiopulmonary bypass before the anastomosis performed was greater in semiskeletonized group than in pedicled group (94 ± 48.37 versus 56.35 ± 34.90 ml/min; p = 0.003). The total operative time was comparable between two groups (p = 0.092).

Conclusions

Semiskeletonized ITA resulted in superior DF of left anterior descending bypass graft flow as compared with pedicled ITA. It is also provide a greater free flow and length of the graft without the long-delayed operative time.

Trial registration

Trial registration number (Study ID): TCTR20160913002

Date of registration: September 10, 2016

Intraoperative Analysis of Flow Dynamics in Arteriovenous Composite Y Grafts

Objective

Composite graft of left internal thoracic artery and great saphenous vein in revascularization of the left coronary system is a technique well described in literature. The aim of this study is to analyze blood flow dynamics in this configuration of composite graft especially in what concerns left internal thoracic artery's adaptability and influence of great saphenous vein segment on left internal thoracic artery's flow.

Methods

Revascularization of left coronary system with composite graft, with left internal thoracic artery revascularizing the anterior interventricular artery and a great saphenous vein segment, anastomosed to the left internal thoracic artery, revascularizing another branch of the left coronary system, was performed in 23 patients. Blood flow was evaluated by transit time flowmetry in all segments of the composite graft (left internal thoracic artery proximal segment, left internal thoracic artery distal segment and great saphenous vein segment). Measures were performed in baseline condition and after dobutamine-induced stress, without and with non-traumatic temporary clamping of the distal segments of the composite graft.

Results

Pharmacological stress resulted in increase of blood flow values in the analyzed segments (P<0.05). Non-traumatic temporary clamping of great saphenous vein segment did not result in statistically significant changes in the flow of left internal thoracic artery distal segment, both in baseline condition and under pharmacological stress. Similarly, non-traumatic temporary clamping of left internal thoracic artery distal segment did not result in statistically significant changes in great saphenous vein segment flow.

Conclusion

Composite grafts with left internal thoracic artery and great saphenous vein for revascularization of left coronary system, resulted in blood flow dynamics with physiological adaptability, both at rest and after pharmacological stress, according to demand. Presence of great saphenous vein segment did not alter physiological blood flow dynamics in distal segment of left internal thoracic artery.

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.

Importance of Full-Length Scan of Arterial Grafts in Coronary Artery Bypass Grafting

Cardiac ischemia after coronary artery bypass grafting is often caused by graft occlusion. Short- and long-term graft patency is related to the quality of the surgical technique during harvesting and anastomosis. Transit time flow measurement is a recognized technique for the quality control of grafts but may not rule out structural abnormalities in the conduits, which can cause graft occlusion. This article reports on two cases of suspected intra-arterial dissection of the left internal mammary artery despite satisfactory flow measurements. Routine ultrasound scanning of arterial conduits is helpful in distinguishing dissection and hematoma in the graft conduits.

Temporary biventricular pacing improves bypass graft flows in coronary artery bypass graft patients with permanent atrial fibrillation

OBJECTIVES

We have previously demonstrated the impact of univentricular pacing modalities on bypass graft flow (BGF) in the coronary artery bypass graft (CABG) patient with permanent atrial fibrillation (AF). The aim of the present study was to determine the mechanism of this improved coronary conduit and, in addition, to explore the possible benefits with biventricular pacing in patients with and without severe left ventricular dysfunction.

METHODS

In 43 CABG patients [mean age 69.5 ± 1.3 years; ejection fraction (EF) 49 ± 2%] with AF, we analysed coronary vascular resistances (CVRs) and the contemporary changes in the BGF obtained during right ventricular outflow tract (RVOT), right- (RV), left- (LV) and right-left ventricular pacing (biventricular pacing, BiVP) using the ultrasonic transit-time methodology.

RESULTS

BiVP resulted in the highest percentage decrease of CVR in the overall study group by 17.5 ± 3.0% (P < 0.001), followed by RVOT pacing with 13.9 ± 3.9%. Accordingly, the highest mean BGF was achieved during BiVP, resulting in a 21.6 ± 2.6% increase when compared with no pacing and 16 ± 3.7% when compared with RV pacing. Analysis of patients according to their preoperative LV function (EF ≥50%, n = 26; EF <50%, n = 17) showed significantly lower CVR (P < 0.037) and higher BGF during BiVP in patients with lower EF.

CONCLUSIONS

Placement of an additional LV pacing wire offered a significant improvement in BGF by minimizing CVR in patients with AF and poor EF.

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.

Evaluation of a novel laser-assisted coronary anastomotic connector - the Trinity Clip - in a porcine off-pump bypass model

To simplify and facilitate beating heart (i.e., off-pump), minimally invasive coronary artery bypass surgery, a new coronary anastomotic connector, the Trinity Clip, is developed based on the excimer laser-assisted nonocclusive anastomosis technique. The Trinity Clip connector enables simplified, sutureless, and nonocclusive connection of the graft to the coronary artery, and an excimer laser catheter laser-punches the opening of the anastomosis. Consequently, owing to the complete nonocclusive anastomosis construction, coronary conditioning (i.e., occluding or shunting) is not necessary, in contrast to the conventional anastomotic technique, hence simplifying the off-pump bypass procedure. Prior to clinical application in coronary artery bypass grafting, the safety and quality of this novel connector will be evaluated in a long-term experimental porcine off-pump coronary artery bypass (OPCAB) study. In this paper, we describe how to evaluate the coronary anastomosis in the porcine OPCAB model using various techniques to assess its quality. Representative results are summarized and visually demonstrated.

Multiple composite grafts (k, π or double-Y) in coronary artery surgery: a choice or a necessity?

OBJECTIVES

Composite grafts allow complete arterial revascularization with minimal aortic manipulations. The Y-T configuration supplies all distal branches adequately, whereas it is unclear whether complex composite configurations (K, Π or double-Y) are equally at rest or when challenged by maximal requirements.

METHODS

Forty-seven patients who underwent off-pump coronary artery revascularization by multiple arterial composite grafts (K, Π or double-Y) were retrospectively evaluated. Indication for this surgical option was porcelain aorta or conduit unavailability. Composite systems were evaluated by intraoperative flow measurements and perioperative transthoracic Doppler ultrasonography, 12 months later also by exercise test, sestamibi scintigraphy at rest and during induced hyperaemia and by 64-slice multidetector CT angiography.

RESULTS

A total of 141 distal anastomoses were implanted as composite grafts. Perioperative flow measurements and 12-month Doppler ultrasonography were adequate at rest. At stress test, chest pain and/or induced ECG evidence of ischaemia are found in 16 patients (39%). During dipyridamole-induced hyperaemia, single-photon emission computed tomography image revealed that mean summed stress score was 7.2 ± 5.7, summed difference score 5.3 ± 4.2 and coronary flow reserve 1.7 ± 0.2.

CONCLUSIONS

Multiple composite grafts, albeit adequate at rest, were unable to meet flow requirements during maximal hyperaemia. In daily practice, their use must be not a choice but rather a necessity in those patients without alternative options.

Intra-operative Graft Blood Flow Measurements for Composite and Sequential Coronary Artery Bypass Grafting

Objectives

Intraoperative assessment of coronary artery bypass grafts (CABG) anastomotic quality can be performed using transit-time flowmetry (TTF). The aim of this study was to compare on- versus off-pump coronary graft TTF and early postoperative outcomes.

Materials and methods

Between January 2009 and January 2010, 521 distal graft flows were assessed using TTF measurements in 253 consecutive patients undergoing primary isolated CABG surgery. Data were analyzed using multilevel models accounting for clustering among surgeons and grafts performed in the same patient.

Results

Mean age was 66 ± 10 years and 22% were female (n = 55) with 34% diabetics (n = 86) and 40% pre-operative myocardial infarction (MI) (n = 101). The surgeries were performed off-pump in 67% (n = 170) with sequential vein grafts in 57% (n = 144) of patients. Off-pump patients had higher pre-operative left ventricular ejection fractions (LVEF), fewer urgent surgeries, fewer distal anastomoses, and fewer sequential vein grafts (all p<0.001). Intra-operative coronary graft TTF measurements were lower in sequential vein grafts performed off-pump versus on-pump. More patients in the on-pump group needed milrinone or dobutamine 24-48 h postoperatively (p = 0.005). Independent predictors of lower TTF included female gender and off-pump surgery, whereas predictors of better TTF were pre-operative MI, larger coronary diameter at the site of the distal anastomosis, and sequential vein grafting.

Conclusions

Lower intra-operative TTF measurements were found in sequential vein grafts in offpump CABG. However, off-pump patients experienced similar short-term outcomes compared to on-pump patients.

Use of the eSVS Mesh: external vein support does not negatively impact early graft patency

OBJECTIVE

The aim of this study was to assess early graft patency in eSVS Mesh-covered saphenous vein grafts (SVGs) in patients undergoing coronary artery bypass grafting.

METHODS

In 20 patients meeting criteria for double arterial grafting to the left-sided coronary system and eSVS Mesh-covered SVG to the right-sided coronary system, patency was evaluated intraoperatively by transit time flow measurement and at 5 days postoperatively by computed tomographic angiography.

RESULTS

Twenty patients underwent 49 arterial and 22 venous grafts (mean, 3.55/patient) using off-pump techniques. All grafts were determined to be patent intraoperatively. On computed tomographic angiography, arterial graft patency was 100%. In one venous anastomosis, the distal limb of a sequential graft was occluded, for an overall patency rate of 95%.

CONCLUSIONS

The eSVS Mesh does not compromise early SVG patency.