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

The Role of Preservation Solutions upon Saphenous Vein Endothelial Integrity and Function: Systematic Review and UK Practice Survey

The long saphenous vein is the most used conduit in cardiac surgery, but its long-term patency is limited by vein graft disease (VGD). Endothelial dysfunction is a key driver of VGD; its aetiology is multi-factorial. However emerging evidence identifies vein conduit harvest technique and preservation fluids as causal in their onset and propagation. This study aims to comprehensively review published data on the relationship between preservation solutions, endothelial cell integrity and function, and VGD in human saphenous veins harvested for CABG. The review was registered with PROSPERO (CRD42022358828). Electronic searches of Cochrane Central Register of Controlled Trials, MEDLINE, and EMBASE databases were undertaken from inception until August 2022. Papers were evaluated in line with registered inclusion and exclusion criteria. Searches identified 13 prospective, controlled studies for inclusion in the analysis. All studies used saline as a control solution. Intervention solutions included heparinised whole blood and saline, DuraGraft, TiProtec, EuroCollins, University of Wisconsin (UoW), buffered, cardioplegic and Pyruvate solutions. Most studies demonstrated that normal saline appears to have negative effects on venous endothelium and the most effective preservation solutions identified in this review were TiProtec and DuraGraft. The most used preservation solutions in the UK are heparinised saline or autologous whole blood. There is substantial heterogeneity both in practice and reporting of trials evaluating vein graft preservation solutions, and the quality of existing evidence is low. There is an unmet need for high quality trials evaluating the potential for these interventions to improve long-term patency in venous bypass grafts.

Intraoperative transit time flow measurement in patients with diffuse coronary artery disease in the prevention of aortocoronary bypass graft occlusion

Aim. To study the parameters of transit time flow measurement (TTFM) for coronary bypass grafts in patients with diffuse lesions with different diameter of target coronary arteries.

Material and methods. The study included 150 patients with diffuse coronary artery disease. All patients underwent microscope-assisted coronary artery bypass grafting (CABG), during which the TTFM parameters were evaluated. Depending on the diameter of target coronary arteries, patients were divided into 3 groups: group 1 included grafts to arteries ≤1 mm (n=101), group 2 — 1-1,5 mm (n=138), group 3 — ≥1,5 mm (n=308). Comparative analysis of TTFM parameters was performed.

Results. Mostly participants were male (76%); mean age was 62,9±7,6 years. During hospitalization, we recorded 1 death, 2 perioperative myocardial infarctions (1,3%) and 1 cerebrovascular accident (0,7%). TTFM analysis showed the worst hemodynamic parameters and a higher rate of suboptimal function in group 1; blood flow parameters were comparable in groups 2 and 3. The additional analysis in group 1 and combined groups 2 and 3 allows us to make an opinion about the negative impact of coronary artery diameter less than 1 mm on optimal blood flow through the grafts (odds ratio=2,1, 95% confidence interval, 1,2-3,8, p=0,011).

Conclusion. Diffuse coronary atherosclerosis with a diameter of target coronary arteries less than 1 mm significantly increase the risk of suboptimal graft function that requires considering more aggressive secondary prevention. TTFM demonstrate high effectiveness of microscope-assisted CABG in target coronary artery diameter of 1-1,5 mm and higher.

[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.

Enhancement of flow measurement for graft verification

Background

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

Methods

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

Results

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

Conclusions

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

The use of intraoperative graft assessment in guiding graft revision

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