Aspirin in coronary artery bypass surgery: new aspects of and alternatives for an old antithrombotic agent

Safety outcomes of anti-platelet therapy post coronary artery bypass graft surgery: A systematic review and network meta-analysis of randomized control trials

BACKGROUND

Antiplatelet therapy is used to decrease the risk of graft failure post coronary artery bypass graft surgery. We aimed to compare dual antiplatelet therapy (DAPT) with monotherapy along with a comparison of Aspirin, Ticagrelor, Aspirin+Ticagrelor (A+T) and Aspirin+Clopidogrel (A+C) to determine the major and minor bleeding risk, risk of postoperative myocardial infarction (MI), stroke, and all-cause mortality (ACM).

METHODS

Randomized Controlled Trials comparing the four groups were included. Odds ratio (OR) and Absolute Risk (AR) were employed to assess the mean and standard deviation (SD) with 95% confidence intervals (CI). The Bayesian random-effects model was used for statistical analysis. Risk difference and Cochran Q tests were used to calculate rank probability (RP) and heterogeneity, respectively.

RESULTS

We included 10 trials, consisting of 21 arms and 3926 patients. For the risk of major and minor bleed, A + T and Ticagrelor showed the lowest mean value of 0.040 (0.043) and 0.067 (0.073), respectively, and the highest RP of being the safest group. While a direct comparison between DAPT and monotherapy resulted in an OR of 0.57 [0.34, 0.95] for the risk of minor bleed. A + T was found to have the highest RP and the lowest mean value in terms of ACM, MI, and stroke.

CONCLUSION

No significant difference was found between monotherapy or dual-antiplatelet therapy for the major bleeding risk safety outcome, however DAPT was found to have a significantly higher rate of minor bleeding complications post-CABG. DAPT should be considered as the antiplatelet modality of choice post-CABG.

Dual-Antiplatelet Therapy After Coronary Artery Bypass Grafting: A Survey of UK Cardiac Surgeons

OBJECTIVE

Antiplatelet therapy after coronary artery bypass grafting (CABG) is important in postoperative medical management. Although cardiac surgeons are well-versed in the guidelines regarding discontinuation of dual-antiplatelet therapy (DAPT; aspirin and a P2Y12 antagonist) before CABG to minimize bleeding risk, there is considerable variability in DAPT dosing after CABG. The objective of this study was to explore the current trends in DAPT after CABG in the UK to improve understanding of the existing practice.

DESIGN

This study used an online survey with 9 questions about the use of DAPT after CABG. An invitation to participate was sent to all adult cardiac surgeons currently in practice in the UK and the Republic of Ireland.

SETTING

The study was conducted in the UK and the Republic of Ireland.

PARTICIPANTS

Participants in this study were adult cardiac surgeons currently in practice in the UK and the Republic of Ireland.

INTERVENTIONS

There were no interventions in this study.

MEASUREMENTS AND MAIN RESULTS

Responses were received from across the UK (85.4% UK; 4% each from Scotland and Northern Ireland, 1.3% from Wales) and 5.3% from the Republic of Ireland. Fifty-seven percent of the respondents performed between 50 and 100 CABGs per year. Ninety-one percent of the respondents prescribe DAPT postoperatively, but the choice of which patients receive it varied. Most responding surgeons used DAPT for selective patient cohorts, such as those with acute coronary syndrome (51%), diffuse coronary artery disease (42%), perioperative myocardial infarction (36%), coronary endarterectomy (31%), or when bypassing a stented coronary artery (23%). Thirty-eight percent of the respondents began all their patients with CABGs on DAPT. The most preferred P2Y12 antagonist was clopidogrel, used by 75% of respondents and introduced on day 1 after surgical revascularization (71%). The routine duration for DAPT is 12 months, which 78% of the respondents preferred. The main reason for not starting DAPT in those surveyed was the bleeding risk associated with DAPT (72%).

CONCLUSIONS

The survey uncovered variation in the use of DAPT after CABG. However, DAPT remains the preferred strategy after CABG in the UK. The study highlighted the need to develop standardized protocols for DAPT after CABG.

Saphenous Vein Graft Failure: Current Challenges and a Review of the Contemporary Percutaneous Options for Management

The use of saphenous vein grafts (SVGs) in the surgical management of obstructive coronary artery disease remains high despite a growing understanding of their limitations in longevity. In contemporary practice, approximately 95% of patients receive one SVG in addition to a left internal mammary artery (LIMA) graft. The precise patency rates for SVGs vary widely in the literature, with estimates of up to 61% failure rate at greater than 10 years of follow-up. SVGs are known to progressively degenerate over time and, even if they remain patent, demonstrate marked accelerated atherosclerosis. Multiple studies have demonstrated a marked acceleration of atherosclerosis in bypassed native coronary arteries compared to non-bypassed arteries, which predisposes to a high number of native chronic total occlusions (CTOs) and subsequent procedural challenges when managing graft failure. Patients with failing SVGs frequently require revascularisation to previously grafted territories, with estimates of 13% of CABG patients requiring an additional revascularisation procedure within 10 years. Redo CABG confers a significantly higher risk of in-hospital mortality and, as such, percutaneous coronary intervention (PCI) has become the favoured strategy for revascularisation in SVG failure. Percutaneous treatment of a degenerative SVG provides unique challenges secondary to a tendency for frequent superimposed thrombi on critical graft stenoses, friable lesions with marked potential for distal embolization and subsequent no-reflow phenomena, and high rates of peri-procedural myocardial infarction (MI). Furthermore, the rates of restenosis within SVG stents are disproportionately higher than native vessel PCI despite the advances in drug-eluting stent (DES) technology. The alternative to SVG PCI in failed grafts is PCI to the native vessel, 'replacing' the grafts and restoring patency within the previously grafted coronary artery, with or without occluding the donor graft. This strategy has additional challenges to de novo coronary artery PCI, however, due to the high burden of complex atherosclerotic lesion morphology, extensive coronary calcification, and the high incidence of CTO. Large patient cohort studies have reported worse short- and long-term outcomes with SVG PCI compared to native vessel PCI. The PROCTOR trial is a large and randomised control trial aimed at assessing the superiority of native vessel PCI versus vein graft PCI in patients with prior CABG awaiting results. This review article will explore the complexities of SVG failure and assess the contemporary evidence in guiding optimum percutaneous interventional strategy.

The Association between Glycosylated Hemoglobin Level and Platelets Reactivity in Patients with Diabetes Mellitus Undergoing Elective Coronary Artery Bypass Grafting

BACKGROUND

Diabetic patients tend to have increased platelet reactivity after coronary artery bypass grafting (CABG). The aim of this study was to determine the association between hemoglobin A1c (HbA1c) values and platelet reactivity and to evaluate the consequent impact on clinical outcomes in patients undergoing CABG.

METHODS

This prospective observational trial consecutively enrolled 225 diabetic patients undergoing CABG, between February 2014 and October 2018. HbA1c levels and platelet function (multiple electrode aggregometry [MEA]) were analyzed the day before surgery and on postoperative day 4 (POD 4). Patients were divided into two groups according to the HbA1c value: HBA1c < 7% and HbA1c ≥ 7%.

RESULTS

Significantly higher postoperative ASPI (platelet function test based on arachidonic acid) and ADP (platelet function test based on adenosine diphosphate) test values were observed at POD 4 compared with preoperative values (ASPI test: p < 0.001; ADP test: p < 0.001). The prevalence of preoperative aspirin resistance (AR) was 46.4% relative to 57.2% after surgery showing consistent increase in postoperative AR by approximately 10%. In addition, the prevalence of AR in the HbA1c < 7% group was higher by 10% compared with the HbA1c ≥ 7% group, both before and after surgery. We did not demonstrate differences in clinical outcomes between the HbA1c groups.

CONCLUSION

Perioperative assessment of platelet reactivity in diabetic patients detects those with AR who may be at increased risk of adverse ischemic events. A personalized approach guided by MEA and administration of early and more potent antiaggregation therapy after CABG can be beneficial in this group of patients.

Pathophysiology and management of saphenous vein graft disease

INTRODUCTION

The saphenous vein graft (SVG) is the most used conduit in CABG. With standardization of its use as a conduit came an understanding of its accelerated atherosclerosis, known as saphenous vein graft disease (SVGD). Given its extensive use, a review of the pathophysiology and management of SVGD is important as we optimize its use.

AREAS COVERED

For this review, an extensive literature search was completed to identify and examine the evolution of SVG in CABG, mechanisms driving SVGD, and methods developed to prevent and manage it. This includes a review of relevant major papers and trials in this space.

EXPERT OPINION

Eras of evolution in SVG usage in CABG include an experimental era, era of SVG dominance in CABG, and the current era of mixed venous and arterial grafting. As SVGD was studied, the mechanisms behind it became more understood, and prevention and management methods were developed. As advances in surgical techniques and pharmacotherapy continue to reduce occurrence and severity of SVGD, long-term patency of SV grafts continues to improve and remain excellent in optimized settings. With continued innovation and improvement in operative techniques, the SVG conduit is and will remain an important player in the field of coronary bypass.

Ticagrelor for patients undergoing coronary artery bypass grafting: A meta-analysis of randomized controlled trials

OBJECTIVE

Ticagrelor may be an alternative to aspirin as it provides robust and consistent platelet inhibition. However, the effect of ticagrelor treatment in patients undergoing coronary artery bypass grafting (CABG) has not been well confirmed. We conducted a meta-analysis to appraise whether ticagrelor therapy affects outcomes in CABG patients.

METHODS

We searched PubMed, Embase, EBSCO, and Cochrane databases from its inception up to 4 December 2020 for randomized controlled trials that assessed ticagrelor versus non-ticagrelor in patients undergoing CABG. The primary outcome was the incidence of saphenous vein graft (SVG) occlusion at 1 year after CABG. Secondary outcomes were SVG occlusion at 7 days, major adverse cardiovascular events (MACE), and bleeding requiring reoperation.

RESULTS

Seven trials including 4305 patients (2153 randomized to ticagrelor therapy and 2152 to non-ticagrelor therapy) were included. One-hundred and thirty of 1140 patients (11.4%) randomized to the ticagrelor group versus 175 of 1220 patients (14.3%) randomized to the non-ticagrelor group experienced SVG occlusion at 1 year after CABG. Compared to the control group, ticagrelor therapy yielded a significantly lower risk of SVG occlusion [RR 0.79 (0.64-0.97), p = 0.03]. In the subgroup analysis, ticagrelor plus aspirin compared with aspirin alone did not decrease the risk of SVG occlusion after 1 year [RR 0.65 (0.40-1.07), p = 0.09]. There was no difference in the incidence of SVG occlusion at 7 days [RR 0.67 (0.42-1.06), p = 0.09], MACE up to 1 year [RR 0.99 (0.81-1.21), p = 0.90], or bleeding requiring reoperation [RR 1.16 (0.80-1.70), p = 0.44].

CONCLUSIONS

Compared with non-ticagrelor therapy, ticagrelor decreased the risk of saphenous vein graft occlusion after 1 year in patients undergoing elective CABG with saphenous vein grafting.

Ticagrelor versus aspirin 2 years after coronary bypass: Observational analysis from the TARGET trial

BACKGROUND

Compared to conventional aspirin therapy, ticagrelor did not improve vein graft patency 1 year after coronary bypass surgery (CABG) in the ticagrelor antiplatelet therapy to reduce graft events and thrombosis (TARGET) trial. However, it is unknown whether ticagrelor may impact graft patency long-term following surgery.

METHODS

In the TARGET multicenter trial, 250 CABG patients were randomized to aspirin 81 mg or ticagrelor 90 mg twice daily. In this observational analysis, 2 years after surgery, vein graft occlusion and clinical events were compared among subjects who agreed to a second year of double-blind study drug administration (N = 156).

RESULTS

Two-year graft assessment was performed for 142 patients (80 aspirin patients, 62 ticagrelor patients, 425 total grafts), with an overall 2-year graft occlusion rate of 10.6%. Vein graft occlusion at 2 years, the primary outcome of this study, did not significantly differ between the two groups (15.7% vs. 13.2%, aspirin vs. ticagrelor, p = .71). The incidence of vein grafts with any disease (stenosis or occlusion) did not significantly differ between the groups (19.4% vs. 19.8%, aspirin vs. ticagrelor, p = 1.00), and the number of patients with vein graft disease did not significantly differ between the groups (30.0% vs. 29.0%, aspirin vs. ticagrelor, p = 1.00). Vein grafts developing new disease did not significantly differ between the two groups (1.5% vs. 3.8%, aspirin vs. ticagrelor, p = .41). Freedom from major adverse cardiovascular events at 2 years was similar between the groups (p = .75).

CONCLUSION

Compared to conventional aspirin therapy, ticagrelor did not significantly reduce vein graft disease 2 years after CABG.

Ticagrelor versus aspirin and vein graft patency after coronary bypass: A randomized trial

BACKGROUND

Antiplatelet therapy prevents saphenous vein graft (SVG) occlusion and improves outcomes after coronary artery bypass graft surgery (CABG). However, the optimal postoperative antiplatelet regimen remains unclear. The goal of the Ticagrelor Antiplatelet Therapy to Reduce Graft Events and Thrombosis (TARGET) trial was to assess whether early postoperative ticagrelor reduces SVG occlusion compared to conventional aspirin therapy.

METHODS

In this multi-center double-blind randomized trial, 250 patients who had CABG with SVG were randomized to receive either aspirin 81 mg twice daily or ticagrelor 90 mg twice daily. The primary outcome was SVG occlusion at 1 year.

RESULTS

Altogether, 123 patients were randomized to aspirin and 127 received ticagrelor. One-year graft assessment was performed in 202 patients (80.8%), examining 588 grafts, yielding an overall graft occlusion rate of 10.9%. The primary outcome, SVG occlusion at 1 year, did not significantly differ between the two groups (17.4% vs. 13.2%, aspirin vs. ticagrelor, p = .30). The incidence of vein grafts with any disease (stenosis or occlusion) did not significantly differ between the groups (21.5% vs. 22.3%, aspirin vs. ticagrelor, p = .90), and the number of patients with vein graft disease did not significantly differ between the groups (29.4% vs. 28.0%, aspirin vs. ticagrelor, p = .88). Freedom from major adverse cardiovascular events at 1 year was similar between the groups (p = .60).

CONCLUSIONS

Compared to conventional aspirin therapy, ticagrelor did not significantly reduce vein graft occlusion 1 year after CABG. Further study will assess the impact of ticagrelor on 2-year graft patency for this cohort.

Comparative study on the effect of aspirin, TP receptor antagonist and TxA2 synthase inhibitor on the vascular tone of human saphenous vein and internal mammary artery

AIMS

Thromboxane (TxA₂) is synthesized from arachidonic acid (AA) via thromboxane synthase (TxS) enzyme and induces vasoconstriction via TP receptor. Our aim is to compare the effects of aspirin, TxS inhibitor and TP receptor antagonist on vascular reactivity of bypass grafts (saphenous vein and internal mammary artery).

MAIN METHODS

Using isolated organ bath, saphenous vein and internal mammary artery preparations were incubated with TP receptor antagonist, TxS inhibitor, aspirin, IP or EP4 receptor antagonist. Then prostaglandin (PG)E₂, PGF_2α, phenylephrine and AA were administered in concentration-dependent manner. The expression of prostanoid receptor and PGI₂ synthase (PGIS) enzyme was determined by Western Blot.

KEY FINDINGS

TP receptor antagonist inhibited the contraction induced by PGE₂, PGF_2α, and AA but not that induced by phenylephrine in both types of vessels. Aspirin increased phenylephrine-induced contraction only in internal mammary artery and decreased AA-induced contraction in saphenous vein. TxS inhibitor decreased both PGE₂ and AA-induced contraction in both types of vessels. This decrease was reversed by co-incubation of TxS inhibitor and IP/EP4 receptor antagonists. The expressions of EP3 receptor and PGIS enzyme were greater in internal mammary artery compared to saphenous vein while IP and TP receptors expressed at similar levels.

SIGNIFICANCE

TP receptor antagonist and TxS inhibitor are more effective to reduce contraction induced by different spasmogens in comparison to aspirin. Our results suggest that TP receptor antagonist and TxS inhibitor might have an advantage over aspirin due to their preventive effect on increased vascular reactivity observed in post-operative period of coronary artery bypass grafting.

Blood loss after coronary artery bypass by aspirin responsiveness assessed with preoperative VerifyNow aspirin testing

BACKGROUND

Aspirin is important for preventing thrombotic events but also increases bleeding complications. Minimizing bleeding while preventing thrombotic events remains challenging in patients undergoing coronary artery bypass grafting (CABG). Establishing the patient's preoperative aspirin response could distinguish patients at risk for perioperative blood loss.

OBJECTIVE

Aim was to compare 12-h blood loss after CABG between aspirin-sensitive and aspirin-resistant patients.

PATIENTS/METHODS

The primary analysis of this substudy of the POPular CABG trial (NCT02352402) included patients that used aspirin monotherapy preoperatively. A preoperative platelet function test by the VerifyNow aspirin assay was performed before CABG and patients were classified as aspirin-sensitive or aspirin-resistant based on an aspirin reaction units cutoff value of 550. The primary end point was 12-hour blood loss after CABG. The secondary end point was, among others, clinical bleeding events after CABG.

RESULTS

A total of 128 patients were included in the primary analysis. Of these, 116 patients were aspirin sensitive and 12 were aspirin resistant. Mean blood loss 12 hours after CABG was 555 ± 278 mL in aspirin-sensitive patients and 406±110 mL in aspirin-resistant patients (P = .04). All bleeding events (n = 15; 11.7%) occurred in aspirin-sensitive patients.

CONCLUSIONS

In patients who are on aspirin preoperatively, aspirin sensitivity was associated with 12-hour blood loss after CABG, suggesting that preoperative VerifyNow aspirin testing could identify patients undergoing CABG at high risk for perioperative bleeding.

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.

A randomized, double-blind, placebo-controlled trial investigating the effect of ticagrelor on saphenous vein graft patency in patients undergoing coronary artery bypass grafting surgery-Rationale and design of the POPular CABG trial

RATIONALE

An estimated 15% of saphenous vein grafts (SVGs) occlude in the first year after coronary artery bypass grafting (CABG) despite aspirin therapy. Graft occlusion can result in symptoms, myocardial infarction, and death. SVG occlusion is primarily caused by atherothrombosis, in which platelet activation plays a pivotal role. Evidence regarding the effect of stronger platelet inhibition on SVG patency after CABG is limited. The main objective of the POPular CABG trial is to determine whether dual antiplatelet therapy with aspirin plus ticagrelor improves SVG patency when compared to aspirin alone.

STUDY

The POPular CABG is a randomized, double-blind, placebo-controlled, multicenter trial investigating the effect of adding ticagrelor to standard aspirin therapy on the rate of SVG occlusion. A total of 500 patients undergoing CABG with ≥ 1 SVG are randomized to ticagrelor or placebo. The primary end point is SVG occlusion rate, assessed with coronary computed tomography angiography at 1 year. Secondary end points are stenoses and occlusions in both SVGs and arterial grafts and SVG failure at 1 year, defined as a composite of SVG occlusion on coronary computed tomography angiography or coronary angiography, SVG revascularization, myocardial infarction in the territory supplied by an SVG, or sudden death. Safety end points are bleeding events at 30 days and 1 year.

CONCLUSION

The POPular CABG trial investigates whether adding ticagrelor to standard aspirin after CABG reduces the rate of SVG occlusion at 1 year.

Adventitial Collagen Crosslink Reduces Intimal Hyperplasia in a Rabbit Arteriovenous Graft Model

BACKGROUND

Intimal hyperplasia (IH) is the initial lesion of vein graft failure after coronary artery bypass grafting. The weak venous wall is likely one of the primary reasons for IH after exposure to the arterial environment. We investigate whether adventitial collagen cross-link by glutaraldehyde (GA) reinforces the venous wall and then reduces IH.

MATERIALS AND METHODS

Adventitial collagen cross-link by 0.3% GA was performed on the rabbit jugular veins. The degree of cross-link was accessed by tensile test. The jugular vein with or without cross-link was implanted into the carotid artery of rabbit. Vein dilatation at the immediate anastomosis and pathological remodeling of vein graft after 4 wk was assessed.

RESULTS

Tensile test indicated that the mechanical property of 3-min cross-linked veins more closely resembled that of the carotid artery. In rabbit arteriovenous graft models, 3-min adventitial collagen cross-link limited overdistension (diameter: 3.24 mm versus 4.65 mm, P < 0.01) at the immediate anastomosis and reduced IH (intima thickness: 78.83 μm versus 140.19 μm, P < 0.01) of vein grafts 4 wk after implantation in the cross-link group as compared with the graft group (without cross-link). Compared with the cross-link group, the expression of proliferating cell nuclear antigen and vascular cell adhesion molecule-1 increased significantly at both the mRNA and protein levels within the graft group (P < 0.01), but the expression of smooth muscle-22α decreased significantly (P < 0.01).

CONCLUSIONS

Adventitial collagen cross-link by GA increased the vessel stiffness and remarkably reduced IH in a rabbit arteriovenous graft model.

Aspirin Resistance Incidence and Associations Between Aspirin Effect and Outcomes in Cardiac Surgery

BACKGROUND

When, and on whom, aspirin should be ceased before elective cardiac surgery is controversial. This study assessed the incidence of preoperative aspirin resistance and whether the quantitative antiplatelet effect of aspirin was associated with perioperative outcomes.

METHODS

Aspirin-induced antiplatelet effect was measured by multiple electrode aggregometry in 250 adult cardiac surgical patients within 24 hours before surgery. Aspirin resistance was defined by a normal platelet function testing result for those who had continued taking aspirin until the day before the platelet function testing.

RESULTS

Aspirin resistance was observed in 16 (11.9%) patients (95% confidence interval [CI], 7.4-18.4). Of the 250 patients included, 75 (30%) required allogeneic blood product transfusion subsequently. Aspirin induced antiplatelet effect (odds ratio [OR], 0.991 per unit increment in the area under the curve on the platelet function testing, with a smaller area indicating more platelet inhibition; 95% CI, 0.982-0.999; P = .035), a higher EuroSCORE [European System for Cardiac Operative Risk Evaluation] II risk (OR, 1.184 per EuroSCORE II risk percentage increment; 95% CI, 1.017-1.379; P = .001), and a lower body mass index (OR, 0.926 per unit increment; 95% CI, 0.867-0.990; P = .024) were the only factors independently associated with requiring perioperative allogeneic blood product transfusion.

CONCLUSIONS

The degree of aspirin effect immediately before cardiac surgery was weakly associated with the risks of postoperative bleeding and allogeneic blood product transfusion, suggesting that measuring aspirin-induced antiplatelet effect before cardiac surgery may be useful as an adjunct in optimizing patient blood management for patients who are at high risk of bleeding and requiring allogeneic blood transfusion.

Randomized trial of ticagrelor vs. aspirin in patients after coronary artery bypass grafting: the TiCAB trial

Aims

The antiplatelet treatment strategy providing optimal balance between thrombotic and bleeding risks in patients undergoing coronary artery bypass grafting (CABG) is unclear. We prospectively compared the efficacy of ticagrelor and aspirin after CABG.

Methods and results

We randomly assigned in double-blind fashion patients scheduled for CABG to either ticagrelor 90 mg twice daily or 100 mg aspirin (1:1) once daily. The primary outcome was the composite of cardiovascular death, myocardial infarction (MI), repeat revascularization, and stroke 12 months after CABG. The main safety endpoint was based on the Bleeding Academic Research Consortium classification, defined as BARC ≥4 for periprocedural and hospital stay-related bleedings and BARC ≥3 for post-discharge bleedings. The study was prematurely halted after recruitment of 1859 out of 3850 planned patients. Twelve months after CABG, the primary endpoint occurred in 86 out of 931 patients (9.7%) in the ticagrelor group and in 73 out of 928 patients (8.2%) in the aspirin group [hazard ratio 1.19; 95% confidence interval (CI) 0.87–1.62; P = 0.28]. All-cause mortality (ticagrelor 2.5% vs. aspirin 2.6%, hazard ratio 0.96, CI 0.53–1.72; P = 0.89), cardiovascular death (ticagrelor 1.2% vs. aspirin 1.4%, hazard ratio 0.85, CI 0.38–1.89; P = 0.68), MI (ticagrelor 2.1% vs. aspirin 3.4%, hazard ratio 0.63, CI 0.36–1.12, P = 0.12), and stroke (ticagrelor 3.1% vs. 2.6%, hazard ratio 1.21, CI 0.70–2.08; P = 0.49), showed no significant difference between the ticagrelor and aspirin group. The main safety endpoint was also not significantly different (ticagrelor 3.7% vs. aspirin 3.2%, hazard ratio 1.17, CI 0.71–1.92; P = 0.53).

Conclusion

In this prematurely terminated and thus underpowered randomized trial of ticagrelor vs. aspirin in patients after CABG no significant differences in major cardiovascular events or major bleeding could be demonstrated.

ClinicalTrials.gov Identifier

NCT01755520.

Does Early Post-operative Administration of Aspirin Influence the Risk of Bleeding After Coronary Artery Bypass Graft Surgery? A Prospective Observational Study

Background:

Aspirin has a proven role in preventing thrombotic diseases. However, given its anti-platelet activity, it is often assumed that its early post-operative administration significantly increase the amount of post-operative bleeding.

Aim:

The aim of this study was to determine whether early post-operative administration of aspirin influence the risk of bleeding in patients undergoing coronary artery bypass graft (CABG) surgery.

Methods:

In a prospective observational study, 100 consecutive patients undergoing first time elective CABG surgery were include in the study. Patients received a low dose of aspirin (75-150 mg per day) either 1 hours (the early aspirin group; n=43) or 6 hours after surgery (the late aspirin group; n=57). Total mediastinal blood drainage, blood drainage after 6 hours, incidences of re-operation for the control of bleeding and transfusion of red blood cells (RBCs) and blood products were recorded and followed until chest tube removal.

Results:

The groups were found to be matched for the confounding variables and no significant differences were found between post-aspirin bleeding (p=0.37), RBCs and blood product usage (p=0.90) or incidences of re-operation for control of bleeding (p=1.00) between the two groups.

Conclusions:

Early administration (1 hour after surgery) of aspirin did not appear to increase the risk of post-operative bleeding in patients undergoing CABG. Thereby, its early administration in such cases may be considered. Although further well-designed randomized controlled trials to confirm the safety and efficacy of early administration of aspirin after CABG surgery are warranted.

Antithrombotic therapy in patients receiving saphenous vein coronary artery bypass grafts: a protocol for a systematic review and network meta-analysis

INTRODUCTION

The current evidence for the prevention of saphenous vein graft failure (SVGF) after coronary artery bypass graft (CABG) surgery consists of direct head-to-head comparison of treatments (including placebo) in randomised-controlled trials (RCTs) and observational studies. However, summarising the evidence using traditional pairwise meta-analyses does not allow the inclusion of data from treatments that have not been compared head to head. Exclusion of such comparisons could impact the precision of pooled estimates in a meta-analysis. Hence, to address the challenge of whether aspirin alone or in addition to another antithrombotic agent is a more effective regimen to improve SVG patency, a network meta-analysis (NMA) is necessary. The objectives of this study are to synthesise the available evidence on antithrombotic agents (or their combination) and estimate the treatment effects among direct and indirect treatment comparisons on SVGF and major adverse cardiovascular events, and to generate a treatment ranking according to their efficacy and safety outcomes.

METHODS

We will perform a systematic review of RCTs evaluating antithrombotic agents in patients undergoing CABG. A comprehensive English literature search will be conducted using electronic databases and grey literature resources to identify published and unpublished articles. Two individuals will independently and in duplicate screen potential studies, assess the eligibility of potential studies and extract data. Risk of bias and quality of evidence will also be evaluated independently and in duplicate. We will investigate the data to ensure its suitability for NMA, including adequacy of the outcome data and transitivity of treatment effects. We plan to estimate the pooled direct, indirect and the mixed effects for all antithrombotic agents using a NMA.

ETHICS AND DISSEMINATION

Due to the nature of the study, there are no ethical concerns nor informed consent required. We anticipate that this NMA will be the first to simultaneously assess the relative effects of multiple antithrombotic agents in patients undergoing CABG. The results of this NMA will inform clinicians, patients and guideline developers the best available evidence on comparative effects benefits of antithrombotic agents after CABG while considering the side effect profile to support future clinical decision-making. We will disseminate the results of our systematic review and NMA through a peer-reviewed journal.

PROSPERO REGISTRATION NUMBER

CRD42017065678.

Use of aspirin and bleeding-related complications after hepatic resection

Background

The operative risk of hepatectomy under antiplatelet therapy is unknown. This study sought to assess the outcomes of elective hepatectomy performed with or without aspirin continuation in a well balanced matched cohort.

Methods

Data were retrieved from a multicentre prospective observational study. Aspirin and control groups were compared by non-standardized methods and by propensity score (PS) matching analysis. The main outcome was severe (Dindo–Clavien grade IIIa or more) haemorrhage. Other outcomes analysed were intraoperative transfusion, overall haemorrhage, major morbidity, comprehensive complication index (CCI) score, thromboembolic complications, ischaemic complications and mortality.

Results

Before matching, there were 118 patients in the aspirin group and 1685 in the control group. ASA fitness grade, cardiovascular disease, previous history of angina pectoris, angioplasty, diabetes, use of vitamin K antagonists, cirrhosis and type of hepatectomy were significantly different between the groups. After PS matching, 108 patients were included in each group. There were no statistically significant differences between the aspirin and control groups in severe haemorrhage (6·5 versus 5·6 per cent respectively; odds ratio (OR) 1·18, 95 per cent c.i. 0·38 to 3·62), intraoperative transfusion (23·4 versus 23·7 per cent; OR 0·98, 0·51 to 1·87), overall haemorrhage (10·2 versus 12·0 per cent; OR 0·83, 0·35 to 1·94), CCI score (24 versus 28; P = 0·520), major complications (23·1 versus 13·9 per cent; OR 1·82, 0·92 to 3·79) and 90-day mortality (5·6 versus 4·6 per cent; OR 1·21, 0·36 to 4·09).

Conclusion

This observational study suggested that aspirin continuation is not associated with a higher rate of bleeding-related complications after elective hepatic surgery.

Collagen External Scaffolds Mitigate Intimal Hyperplasia and Improve Remodeling of Vein Grafts in a Rabbit Arteriovenous Graft Model

Objectives. The aim of this study was to test the effects of collagen external scaffold (CES) in intimal hyperplasia of vein grafts and explore its underlying mechanisms. Methods. Thirty-six New Zealand white rabbits were randomized into no-graft group, graft group, and CES group. The rabbit arteriovenous graft model was established. In CES group, the vein graft was wrapped around with CES. The hemodynamic parameters of vein grafts were measured intraoperatively and 4 weeks after operation by ultrasonic examination. Histological characteristics of vein grafts were also evaluated 4 weeks later. The mRNA and protein levels of proliferating cell nuclear antigen (PCNA), active cleaved-caspase-3 (ClvCasp-3), and smooth muscle 22 alpha (SM22α) were measured 4 weeks later by quantitative real-time PCR and western blot. Results. CES significantly improved the hemodynamic stability of vein grafts, with higher blood velocity and blood flow. Similarly, CES also markedly mitigated intimal hyperplasia and inhibited dilatation of vein grafts. In CES group, the upexpression of PCNA and ClvCasp-3 and the downexpression of SM22α were inhibited. Conclusion. CES exerts beneficial effects in mitigating intimal hyperplasia and improving remodeling of autogenous vein grafts, which may be associated with reducing the proliferation and apoptosis and preserving the phenotype of VSMCs.

Prostanoids in the pathophysiology of human coronary artery

Coronary artery disease is one of the leading causes of death in wordwide. There is growing evidence that prostanoids are involved in the physiology and pathophysiology of the human coronary artery by controlling vascular tone, remodelling of the vascular wall or angiogenesis. In this review, the production of prostanoids and the expression of prostanoid receptors in human coronary artery in health or disease are described. In addition, the interactions between sex hormones and prostanoids, their participations in the development of coronary artery diseases have been addressed. Globally, most of the studies performed in human coronary artery preparations have shown that prostacyclin (PGI₂) has beneficial effects by inducing vasodilatation and promoting angiogenesis while reverse effects are confirmed by thromboxane A₂ (TxA₂). More studies are needed to determine the roles of the other prostanoids (PGE₂, PGD₂ and PGF_2α) in vascular functions of the human coronary artery. Finally, in addition to the in vitro data about the human coronary artery, myocardial infarction induced by cyclooxygenase-2 (COX-2) inhibitor and the protective effects of aspirin after coronary artery bypass surgery suggest that prostanoids are key mediators in coronary homeostasis.

A randomized, parallel group, double-blind study of ticagrelor compared with aspirin for prevention of vascular events in patients undergoing coronary artery bypass graft operation: Rationale and design of the Ticagrelor in CABG (TiCAB) trial: An Investigator-Initiated trial

BACKGROUND

For patients with coronary artery disease undergoing coronary bypass surgery, acetylsalicylic acid (ASA) currently represents the gold standard of antiplatelet treatment. However, adverse cardiovascular event rates in the first year after coronary artery bypass grafting (CABG) still exceed 10%. Graft failure, which is predominantly mediated by platelet aggregation, has been identified as a major contributing factor in this context. Therefore, intensified platelet inhibition is likely to be beneficial. Ticagrelor, an oral, reversibly binding and direct-acting P2Y12 receptor antagonist, provides a rapid, competent, and consistent platelet inhibition and has shown beneficial results compared with clopidogrel in the subset of patients undergoing bypass surgery in a large previous trial.

HYPOTHESIS

Ticagrelor is superior to ASA for the prevention of major cardiovascular events within 1 year after CABG.

STUDY DESIGN

The TiCAB trial (NCT01755520) is a multicenter, phase III, double-blind, double-dummy, randomized trial comparing ticagrelor with ASA for the prevention of major cardiovascular events within 12 months after CABG. Patients undergoing CABG will be randomized in a 1:1 fashion to either ticagrelor 90 mg twice daily or ASA 100 mg once daily. The study medication will be started within 24 hours after surgery and maintained for 12 months. The primary end point is the composite of cardiovascular death, myocardial infarction, stroke, and repeat revascularization at 12 months after CABG. The sample size is based on an expected event rate of 13% of the primary end point within the first 12 months after randomization in the control group, a 2-sided α level of .0492 (to preserve the overall significance level of .05 after planned interim analysis), a power of 0.80%, 2-sided testing, and an expected relative risk of 0.775 in the active group compared with the control group and a dropout rate of 2%. According to power calculations based on a superiority design for ticagrelor, it is estimated that 3,850 patients should be enrolled.

SUMMARY

There is clinical equipoise on the issue of optimal platelet inhibition after CABG. The TiCAB trial will provide a pivotal comparison of the efficacy and safety of ticagrelor compared with ASA after CABG.

Is Bilateral Internal Mammary Arterial Grafting Beneficial for Patients Aged 75 Years or Older?

BACKGROUND

Although bilateral internal mammary artery (BIMA) grafting is performed with increasing regularity in elderly patients, whether it is truly beneficial, and therefore indicated, in these patients remains uncertain. We retrospectively investigated early and late outcomes of BIMA grafting in patients aged ≥75 years.

METHODS AND RESULTS

We identified 460 patients aged ≥75 years from among 2,618 patients who underwent either single internal mammary artery (SIMA) grafting (n=293) or BIMA grafting (n=107). Early outcomes did not differ between the SIMA and BIMA patients (30-day mortality: 1.7% vs. 0%, P=0.39; sternal wound infection: 1.0% vs. 4.7%; P=0.057). Late outcomes, 10-year survival in particular, were improved in the BIMA group (36.6% vs. 48.1%, P=0.033). In the analysis of the results in propensity score-matched groups (196 patients in the SIMA group, 98 patients in the BIMA group), improved 10-year survival was documented in the BIMA group (34.8% vs. 47.6%, P=0.030). Cox proportional regression analysis showed SIMA usage (non-use of BIMA) to be a predictor for late mortality (hazard ratio: 0.65, 95% confidence interval: 0.43-0.98, P=0.042). We further compared outcomes between the total non-elderly patients (n=2,158) and total elderly patients (n=460). BIMA usage was similar, as was 30-day mortality (1.0% vs. 1.3%, respectively).

CONCLUSIONS

A survival advantage, with no increase in early mortality, can be expected from BIMA grafting in patients aged ≥75 years. (Circ J 2016; 80: 1756-1763).

Perivenous application of cyanoacrylate tissue sealants reduces intimal and medial thickening of the vein graft and inflammatory responses in a rabbit model of carotid artery bypass grafting

OBJECTIVES

Effective therapies to prevent vein graft failure after coronary artery bypass grafting (CABG) are still lacking. α-Cyanoacrylate (α-CA, 99% n-octyl-α-cyanoacrylate + n-butyl-α-cyanoacrylate) has been increasingly used as a tissue sealant for wound closure because of its bacteriostatic, biodegradable and haemostatic properties. As a strong tissue adhesive, α-CA might prevent an arterial circulation-induced mechanical stretch on vein graft to attenuate intimal hyperplasia. Here, we investigated the effects of perivenous application of α-CA on the vein graft in a rabbit model of carotid artery bypass grafting.

METHODS

Healthy New Zealand white rabbits were randomized into no graft, graft or graft + α-CA group (n = 10 per group). Rabbit carotid artery was bypassed with the jugular vein. α-CA sealants were sprayed on the entire jugular graft including both anastomotic sites after completion of anastomoses. Blood flow parameters and histological characteristics of the vein grafts including vessel wall thickness, number of medial elastic lamina and proliferation index were evaluated 4 weeks after the surgery. The mRNA or protein levels of proinflammatory factors, chemokine (C-C motif) ligand-2 (CCL-2) and tumour necrosis factor-α (TNF-α) were measured 4 weeks after the operation by quantitative reverse transcription polymerase chain reaction or enzyme-linked immunosorbent assay.

RESULTS

Compared with the untreated vein grafts at Week 4 after the operation, the α-CA spray significantly improved graft flow (39.4 ± 1.5 vs 27.8 ± 2.9 ml/min, P < 0.01), attenuated intimal and medial thickening (116.3 ± 1.0 vs 159.7 ± 0.9 μm, P < 0.01), reduced anti-proliferating cell nuclear antigen proliferation index of the vein grafts (15.0 ± 0.4 vs 23.6 ± 0.4%, P < 0.01), decreased the mRNA levels of plasminogen activator inhibitor-1 and CCL-2, and reduced the serum levels of TNF-α (92.9 ± 1.7 vs 102.7 ± 1.8 pg/ml, P < 0.01).

CONCLUSION

Perivenous application of α-CA sealants exerts short-term beneficial effects on the vein graft and reduces inflammatory responses in a rabbit model of carotid artery bypass grafting. Long-term effects of α-CA on vein graft remodelling and the clinical significance of α-CA in CABG remain to be determined in future studies.

Prevention of dipyrone (metamizole) induced inhibition of aspirin antiplatelet effects

We have recently shown that dipyrone (metamizole), a non-opioid analgesic, can nullify aspirin (acetylsalicylic acid; ASA) antiplatelet effects in patients with coronary artery disease (CAD). In this study, we analysed the aspirin and dipyrone drug-drug interaction in order to identify strategies to prevent the dipyrone induced inhibition of asprin antiplatelet effects. Platelet function was measured by arachidonic acid-induced light-transmission aggregometry, thromboxane (TX) B2- formation by immunoassay. Dipyrone metabolite plasma levels were determined by high-performance-liquid-chromatography (HPLC). In seven healthy individuals, in vitro ASA (30 µM/ 100 µM/ 300 µM/ 1,000 µM) and dipyrone (10 µM) coincubation revealed, that the aspirin and dipyrone interaction can be overcome by increasing doses of aspirin. In 36 aspirin and dipyrone comedicated CAD patients, addition of ASA (30 µM/ 100 µM) in vitro inhibited, but did not completely overcome the dipyrone induced reduction of aspirin antiplatelet effects. Notably, the inhibition of thromboxane formation in aspirin and dipyrone comedicated CAD patients coincided with dipyrone plasma levels. In a cross-over designed study in four healthy individuals, we were able to prove that inhibition of aspirin (100 mg/ day) effects by dipyrone (750 mg/ day) was reversible. Furthermore, aspirin (100 mg/ day) medication prior to dipyrone (750 mg/ day) intake prevented the inhibition of antiplatelet effects by dipyrone in 12 healthy individuals. In conclusion, aspirin medication prior to dipyrone intake preserves antiplatelet effects, circumventing the pharmacodynamic drug-drug interaction at the level of cyclooxygenase-1.

Impact of dual antiplatelet therapy on outcomes among aspirin-resistant patients following coronary artery bypass grafting

Coronary artery bypass grafting is pivotal in the contemporary management of complex coronary artery disease. Interpatient variability to antiplatelet agents, however, harbors the potential to compromise the revascularization benefit by increasing the incidence of adverse events. This study was designed to define the impact of dual antiplatelet therapy (dAPT) on clinical outcomes among aspirin-resistant patients who underwent coronary artery surgery. We randomly assigned 219 aspirin-resistant patients according to multiple electrode aggregometry to receive clopidogrel (75 mg) plus aspirin (300 mg) or aspirin-monotherapy (300 mg). The primary end point was a composite outcome of all-cause death, nonfatal myocardial infarction, stroke, or cardiovascular hospitalization assessed at 6 months postoperatively. The primary end point occurred in 6% of patients assigned to dAPT and 10% of patients randomized to aspirin-monotherapy (relative risk 0.61, 95% confidence interval 0.25 to 1.51, p = 0.33). No significant treatment effect was noted in the occurrence of the safety end point. The total incidence of bleeding events was 25% and 19% in the dAPT and aspirin-monotherapy groups, respectively (relative risk 1.34, 95% confidence interval 0.80 to 2.23, p = 0.33). In the subgroup analysis, dAPT led to lower rates of adverse events in patients with a body mass index >30 kg/m(2) (0% vs 18%, p <0.01) and those <65 years (0% vs 10%, p = 0.02). In conclusion, the addition of clopidogrel in patients found to be aspirin resistant after coronary artery bypass grafting did not reduce the incidence of adverse events, nor did it increase the number of recorded bleeding events. dAPT did, however, lower the incidence of the primary end point in obese patients and those <65 years.

Polymorphisms and high on-aspirin platelet reactivity after off-pump coronary artery bypass grafting

OBJECTIVES

High on-aspirin residual platelet reactivity (RPR) after coronary artery bypass grafting (CABG) is a transient phenomenon with important implications for graft patency. This study was designed to determine the role of polymorphisms [TBXA2R (T924C), GPIIIa (Pl(A1/A2)), P2Y1 (A1622G), and GP1Bα (C1018T)] on RPR in Chinese patients undergoing off-pump CABG (OPCAB).

METHODS

Of 420 patients recruited to this study, 210 patients underwent primary OPCAB and 210 controls with ischemic heart disease received optimal medical therapy. Arachidonic acid-induced platelet aggregation and urinary 11-dehydro thromboxane B2 were measured at baseline and following aspirin administration on days 1, 4, 10, and on 6th month. Four polymorphisms were identified [TBXA2R (T924C), P2Y1 (A1622G), Pl(A1/A2) and GP1Bα (C1018T)].

RESULTS

On the first post-operative day, 62 patients (29.5%) were with high RPR and 148 (70.5%) were with low RPR. Of the former, 33 (15.7%), 10 (4.6%), and 0 (0%) patients remained with high RPR on days 4, 10, and on 6 month, respectively. No individuals with high RPR was found in controls. Logistic regression identified TBXA2R-924TT (OR = 4.5; 95% CI, 1.8-11.1) and body mass index > 27 kg/m(2) (OR = 2.73; 95% CI, 1.1-7.0) as independent risk factors for high on-aspirin RPR.

CONCLUSIONS

High on-aspirin RPR after OPCAB is associated with genetic polymorphism TBXA2R-924TT and obesity.

Platelet mapping as part of modified thromboelastography (TEG®) in patients undergoing cardiac surgery and cardiopulmonary bypass

The platelet-mapping assay of the thromboelastograph was used to measure platelet aggregation and to examine the effect of cardiopulmonary bypass on multiple platelet receptors and the role of altered receptor activity in postoperative bleeding. The percentage platelet aggregation for collagen, adenosine diphosphate and arachidonic acid was measured in 40 patients divided post-hoc into high- or low-bleeding groups depending on postoperative 24-h chest tube output. Platelet aggregation was lower after cardiopulmonary bypass compared to before it using collagen (mean (SD) 45 (25) vs 19 (12)%, p<0.001), adenosine diphosphate (76 (23) vs 35 (24)%, p<0.001), and arachidonic acid (61 (33) vs 31 (35)%, p<0.001). Only platelet aggregation as measured using collagen pre- and post-cardiopulmonary bypass was significantly less in the high- compared to the low-bleeding group. This finding was significantly correlated with the 24-h chest tube drainage, and it predicted postoperative bleeding with a sensitivity of 83% and a specificity of 68%. Therefore, platelet aggregation is reduced following cardiopulmonary bypass, and this may play a role in predicting postoperative blood loss.

Aspirin resistance: current status and role of tailored therapy

Aspirin is integral in the primary and secondary prevention of coronary artery disease and acute coronary syndrome. Given the high clinical importance of aspirin in the management of coronary artery disease, much attention has been directed towards the concept of "aspirin resistance." Unfortunately, the term aspirin resistance is ill-defined in the literature, leading to a large variance in the reported prevalence of this phenomenon. In this review, the current understanding of aspirin resistance is discussed. Commonly used functional and diagnostic tests of platelet function, including their strengths and weakness, are reviewed. We next discuss several proposed mechanisms of aspirin resistance and special high-risk groups at risk for aspirin treatment failure. We then discuss optimal dosing and diagnostic strategies for those populations at risk for aspirin resistance with a focus on tailored aspirin therapy for high-risk groups. Finally, future topics of interest in the field of aspirin resistance are considered.

Thrombelastographic haemostatic status and antiplatelet therapy after coronary artery bypass surgery (TEG-CABG trial): assessing and monitoring the antithrombotic effect of clopidogrel and aspirin versus aspirin alone in hypercoagulable patients: study protocol for a randomized controlled trial

Background

Hypercoagulability, assessed by the thrombelastography (TEG) assay, has in several observational studies been associated with an increased risk of post-procedural thromboembolic complications. We hypothesize that intensified antiplatelet therapy with clopidogrel and aspirin, as compared to aspirin alone, will improve saphenous vein graft patency in preoperatively TEG-Hypercoagulable coronary artery bypass surgery (CABG) patients and reduce their risk for thromboembolic complications and death postoperatively.

Methods/Design

This is a prospective randomized clinical trial, with an open-label design with blinded evaluation of graft patency. TEG-Hypercoagulability is defined as a TEG maximum amplitude above 69 mm. Two hundred and fifty TEG-Hypercoagulable patients will be randomized to either an interventional group receiving clopidogrel 75 mg daily for three months (after initial oral bolus of 300 mg) together with aspirin 75 mg or a control group receiving aspirin 75 mg daily alone. Monitoring of antiplatelet efficacy and on-treatment platelet reactivity to clopidogrel and aspirin will be conducted with Multiplate aggregometry. Graft patency will be assessed with Multislice computed tomography (MSCT) at three months after surgery.

Conclusions

The present trial is the first randomized clinical trial to evaluate whether TEG-Hypercoagulable CABG patients will benefit from intensified antiplatelet therapy after surgery. Monitoring of platelet inhibition from instituted antithrombotic therapy will elucidate platelet resistance patterns after CABG surgery. The results could be helpful in redefining how clinicians can evaluate patients preoperatively for their postoperative thromboembolic risk and tailor individualized postoperative antiplatelet therapy.

Trial registration

Clinicaltrials.gov Identifier NCT01046942