Effect of Clopidogrel on Midterm Graft Patency following Off-Pump Coronary Revascularization Surgery

Is administration of dual-antiplatelet therapy beneficial for patients following off-pump coronary artery bypass grafting?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether administration of dual-antiplatelet therapy (DAPT) following off-pump coronary artery bypass grafting (OPCAB) would improve postoperative clinical outcomes or minimize the incidence of postoperative graft failure. In total, 101 papers were found using the reported search, 14 of which represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. One meta-analysis and 3 randomized controlled trials showed that DAPT following OPCAB is associated with decreased incidence of saphenous vein graft occlusion. One randomized controlled trial and 4 observational studies showed no effect of DAPT on mortality following OPCAB, whereas 3 observational studies showed that DAPT decreased mortality. One meta-analysis and 4 observational studies showed that DAPT reduced the incidence of cardiac events following OPCAB. One randomized controlled trial and 4 observational studies showed that DAPT did not increase the incidence of major or minor bleeding complications following OPCAB. The results presented suggest that administration of DAPT in patients following OPCAB for at least 3 months improves saphenous vein graft patency and could be protective against recurrence of cardiac events, especially acute coronary syndrome, in comparison with aspirin monotherapy. The administration of DAPT following OPCAB is safe and is not associated with increased incidence of major or minor bleeding complications when compared with aspirin alone.

Network meta-analysis of antiplatelet therapy following coronary artery bypass grafting (CABG): none versus one versus two antiplatelet agents

Background

Numerous agents have been trialed following coronary artery bypass grafting (CABG) to maintain long-term graft patency. While clear evidence exists for the use of aspirin in maintaining graft patency, the role of dual-antiplatelet therapy in CABG patients is not as well established. This network meta-analysis aimed to compare the short-term post-CABG graft patency outcomes for patients with none, one or two antiplatelet agents.

Methods

Electronic databases were queried for randomized controlled trials comparing CABG graft patency rates at three months and beyond using various antiplatelet agents or placebo. Drug and graft patency data were compared using a mixed treatment comparison under a Bayesian hierarchical framework. A random-effects consistency model was applied. Direct and indirect comparisons were made between drugs and used to determine the relative efficacy for graft patency.

Results

The literature search identified 16 papers fulfilling the inclusion criteria, including a total of 3,133 patients with an average of 2.43 [95% confidence interval (CI): 2.20-2.66] grafts per patient. Graft types were incompletely reported, however, saphenous vein grafts (SVGs) were predominantly used [where specifically reported: 4,490 SVG, 1,226 internal mammary artery (IMA) grafts]. In all, five different agents and placebo in various regimens were compared by results of angiographic follow-up conducted at a mean of 10.4 months (95% CI: 9.28-11.5 months). Compared to placebo, aspirin alone [odds ratio (OR) 1.9; 95% credible interval (CrI): 1.3-2.8], aspirin + dipyridamole (OR 1.9; 95% CrI: 1.3-2.6), aspirin + clopidogrel (OR 2.9; 95% CrI: 1.5-5.7) and aspirin + ticagrelor (OR 3.8; 95% CrI: 1.2-13.0) significantly improved graft patency. When compared to aspirin monotherapy, aspirin + clopidogrel (OR 1.6; 95% CrI: 0.86-2.7) and aspirin + ticagrelor (OR 2.0; 95% CrI: 0.69-6.3) had OR that suggested a trend favoring patency compared to aspirin monotherapy, however, these results did not reach significance. Sub-group analysis of SVG graft patency was unable to reach significance (only eight studies with six treatment comparisons were evaluated). Secondary endpoints of death, bleeding, myocardial infarction and cerebrovascular accident were incompletely reported and were pooled but not compared between drug treatment arms.

Conclusions

Aspirin monotherapy and dual antiplatelet therapy (DAPT) provided significant all-graft patency benefit compared to placebo at three months and beyond. A trend existed for DAPT to improve graft patency compared to aspirin, although this did not reach statistical significance. Further randomized controlled studies comparing aspirin monotherapy to DAPT are required to determine the utility of DAPT in CABG patients for maintaining graft patency.

Consensus Document ANMCO/ANCE/ARCA/GICR-IACPR/GISE/SICOA: Long-term Antiplatelet Therapy in Patients with Coronary Artery Disease

Dual antiplatelet therapy (DAPT) with aspirin and a P2Y12 receptor inhibitor is the cornerstone of pharmacologic management of patients with acute coronary syndrome (ACS) and/or those receiving coronary stents. Long-term (>1 year) DAPT may further reduce the risk of stent thrombosis after a percutaneous coronary intervention (PCI) and may decrease the occurrence of non-stent-related ischaemic events in patients with ACS. Nevertheless, compared with aspirin alone, extended use of aspirin plus a P2Y12 receptor inhibitor may increase the risk of bleeding events that have been strongly linked to adverse outcomes including recurrent ischaemia, repeat hospitalisation and death. In the past years, multiple randomised trials have been published comparing the duration of DAPT after PCI and in ACS patients, investigating either a shorter or prolonged DAPT regimen. Although the current European Society of Cardiology guidelines provide a backup to individualised treatment, it appears to be difficult to identify the ideal patient profile which could safely reduce or prolong the DAPT duration in daily clinical practice. The aim of this consensus document is to review contemporary literature on optimal DAPT duration, and to guide clinicians in tailoring antiplatelet strategies in patients undergoing PCI or presenting with ACS.

Vein graft failure: from pathophysiology to clinical outcomes

Occlusive arterial disease is a leading cause of morbidity and mortality worldwide. Aside from balloon angioplasty, bypass graft surgery is the most commonly performed revascularization technique for occlusive arterial disease. Coronary artery bypass graft surgery is performed in patients with left main coronary artery disease and three-vessel coronary disease, whereas peripheral artery bypass graft surgery is used to treat patients with late-stage peripheral artery occlusive disease. The great saphenous veins are commonly used conduits for surgical revascularization; however, they are associated with a high failure rate. Therefore, preservation of vein graft patency is essential for long-term surgical success. With the exception of 'no-touch' techniques and lipid-lowering and antiplatelet (aspirin) therapy, no intervention has hitherto unequivocally proven to be clinically effective in preventing vein graft failure. In this Review, we describe both preclinical and clinical studies evaluating the pathophysiology underlying vein graft failure, and the latest therapeutic options to improve patency for both coronary and peripheral grafts.

Should dual antiplatelet therapy be used in patients following coronary artery bypass surgery? A meta-analysis of randomized controlled trials

BACKGROUND

We assessed the effectiveness of dual antiplatelet therapy (DAPT) post elective or urgent (i.e., post acute coronary syndrome [ACS]) coronary artery bypass graft surgery (CABG).

METHODS

We systematically searched MEDLINE, EMBASE, and the Cochrane Registry from inception to August 2015. Randomized controlled trials (RCTs) in adults undergoing CABG comparing either dual vs. single antiplatelet therapy or higher- vs. lower-intensity DAPT were identified.

RESULTS

Nine RCTs (n = 4,887) with up to 1y follow-up were included. Five RCTs enrolled patients post-elective CABG (n = 986). Two multi-centre RCTs enrolled ACS patients who subsequently underwent CABG (n = 2,155). These 7 RCTs compared clopidogrel plus aspirin to aspirin alone. Two other multi-centre RCTs reported on ACS patients who subsequently underwent CABG comparing higher intensity DAPT with either ticagrelor (n = 1,261) or prasugrel (n = 485) plus aspirin to clopidogrel plus aspirin. Post-operative anti-platelet therapy was started when chest tube bleeding was no longer significant, typically within 24-48 h. There were no differences in all-cause mortality in clopidogrel plus aspirin vs. aspirin RCTs; conversely, all-cause mortality was significantly lower in ticagrelor and prasugrel vs. clopidogrel RCTs (risk ratio[RR] 0.49, 95% confidence interval[CI] 0.33-0.71, p = 0.0002; 2 RCTs, n = 1695; I(2)  = 0%; interaction p < 0.01 compared to clopidogrel plus aspirin vs aspirin RCTs). There were no differences in myocardial infarctions, strokes, or composite outcomes. Overall, major bleeding was not significantly increased (RR 1.31, 95% CI 0.81-2.10, p = 0.27; 7 RCTs, n = 4500). There was heterogeneity (I(2)   = 42%) due almost entirely to higher bleeding reported for the prasugrel RCT which included mainly CABG-related major bleeding (RR 3.15, 95% CI 1.45-6.87, p = 0.004; 1 RCT, n = 437).

CONCLUSIONS

Most RCT data for DAPT post CABG is derived from subgroups of ACS patients in DAPT RCTs requiring CABG who resume DAPT post-operatively. Limited RCT data with heterogeneous trial designs suggest that higher intensity (prasugrel or ticagrelor) but not lower intensity (clopidogrel) DAPT is associated with an approximate 50% lower mortality in ACS patients who underwent CABG based on post-randomization subsets from single RCTs. Large prospective RCTs evaluating the use of DAPT post-CABG are warranted to provide more definitive guidance for clinicians.

Dual Antiplatelet Therapy After Coronary Artery Bypass Grafting in the Setting of Acute Coronary Syndrome

After acute coronary syndrome (ACS), dual antiplatelet therapy (DAPT) is the standard of care for both invasive management with percutaneous intervention and noninvasive (medical) management. Conversely, studies using dual antiplatelet in the population of patients presenting with ACS who undergo coronary artery bypass grafting (CABG) are conflicting. The appropriate antiplatelet regimen after CABG remains an area of controversy. Plaque stability, prevention of graft closure, and secondary thrombosis form the basis for using a second antiplatelet drug, whereas the additional risk of bleeding and lack of conclusive evidence should also be considered. After an extensive literature search, 12 clinical trials with efficacy outcomes were identified. Most of the studies are retrospective, nonrandomized single-center trials. A few large patient populations have been examined using database information. To date, there is only 1 prospective, multicenter, randomized trial published. Recommendations from national guidelines differ, proposing single antiplatelet therapy with aspirin or DAPT with the combination of aspirin and clopidogrel. The purpose of this report is to review the available clinical trial data and provide guidance to practitioners when caring for this patient population. In conclusion, there is no clear consensus regarding the use of DAPT in patients after CABG. If not contraindicated, it is reasonable to use DAPT, starting in the postoperative period, in patients presenting with ACS. Large, multicenter, randomized clinical trials are needed to definitively investigate the role of DAPT in patients with ACS after CABG.

Use of Aspirin and Clopidogrel After Coronary Artery Bypass Graft Surgery

Objective:

To evaluate the evidence for the use of dual antiplatelet therapy (DAPT) with aspirin and Clopidogrel following coronary artery bypass graft (CABG) surgery.

Data Sources:

Literature was accessed through PubMed (1950-November 2011), EMBASE (1976-November 2011), and the Cochrane databases using the terms Clopidogrel and coronary artery bypass graft. Citations from available articles were used for additional references and ClinicalTrials.gov was accessed for abstracts of ongoing studies.

Study Selection Ano Data Extraction:

Peer-reviewed studies that evaluated DAPT use after CABQ surgery in adult humans were assessed for inclusion.

Data Synthesis:

Four randomized clinical trials evaluating surrogate end points and 9 studies (3 subgroup analyses, 6 observational) evaluating clinical outcomes were reviewed. Three clinical trials assessing surrogate end points failed to demonstrate an improvement in graft patency with DAPT use, while 1 clinical trial found an increase in graft patency. As for clinical outcomes, 1 subgroup analysis demonstrated that the benefit of DAPT post-CABG after a non-ST-elevation acute coronary syndrome diminished following surgery, while an observational study demonstrated a trend toward decreased mortality. In post-CABG patients who did not experience acute coronary syndrome, 2 subgroup analyses proved inconclusive and an observational study found DAPT use to be associated with reducing in-hospital mortality, while another observational study was not associated with reduced long-term mortality. Three observational studies in off-pump CABG patients showed that DAPT use was feasible.

Conclusions:

Evidence for DAPT use following CABG is limited to subgroup analyses, observational studies, and trials with surrogate end points. The majority of clinical trials have failed to demonstrate an improvement in graft patency with DAPT. Current evidence does not support the use of DAPT to improve graft patency, and more evidence from randomized controlled trials assessing clinical outcomes is necessary to make definitive recommendations.

Aspirin plus clopidogrel versus aspirin alone after coronary artery bypass grafting: the clopidogrel after surgery for coronary artery disease (CASCADE) Trial

BACKGROUND

clopidogrel inhibits intimal hyperplasia in animal studies and therefore may reduce saphenous vein graft (SVG) intimal hyperplasia after coronary artery bypass grafting. The Clopidogrel After Surgery for Coronary Artery DiseasE (CASCADE) study was undertaken to evaluate whether the addition of clopidogrel to aspirin inhibits SVG disease after coronary artery bypass grafting, as assessed at 1 year by intravascular ultrasound.

METHODS AND RESULTS

in this double-blind phase II trial, 113 patients undergoing coronary artery bypass grafting with SVGs were randomized to receive aspirin 162 mg plus clopidogrel 75 mg daily or aspirin 162 mg plus placebo daily for 1 year. The primary outcome was SVG intimal hyperplasia (mean intimal area) as determined by intravascular ultrasound at 1 year. Secondary outcomes were graft patency, major adverse cardiovascular events, and major bleeding. One-year intravascular ultrasound and coronary angiography were performed in 92 patients (81.4%). At 1 year, SVG intimal area did not differ significantly between the 2 groups (4.1 ± 2.0 versus 4.5 ± 2.1 mm(2), aspirin-clopidogrel versus aspirin-placebo, P=0.44). Overall 1-year graft patency was 95.2% in the aspirin-clopidogrel group compared with 95.5% in the aspirin-placebo group (P=0.90), and SVG patency was 94.3% in the aspirin-clopidogrel group versus 93.2% in the aspirin-placebo group (P=0.69). Freedom from major adverse cardiovascular events at 1 year was 92.9 ± 3.4% in the aspirin-clopidogrel group and 91.1 ± 3.8% in the aspirin-placebo group (P=0.76). The incidence of major bleeding at 1 year was similar for the 2 groups (1.8% versus 0%, aspirin-clopidogrel versus aspirin-placebo, P=0.50).

CONCLUSIONS

compared with aspirin monotherapy, the combination of aspirin plus clopidogrel did not significantly reduce the process of SVG intimal hyperplasia 1 year after coronary artery bypass grafting.

Evidence for using clopidogrel alone or in addition to aspirin in post coronary artery bypass surgery patients

Clopidogrel is recommended with aspirin for patients who undergo coronary artery bypass grafting (CABG) after non-ST elevation myocardial infarctions. Cardiothoracic surgeons widely use clopidogrel in addition to aspirin for post-CABG patients, including those with stable coronary artery disease. The aim of this study was to systematically review the published research to determine whether clopidogrel use after CABG is based on good trial data. Studies reporting safety and/or efficacy data for clopidogrel use with or without aspirin after on- or off-pump CABG were included. Fourteen studies met the inclusion criteria, of which 11 were reported trials and 3 are ongoing trials. Subgroup retrospective analyses of previously reported large trials of patients presenting with acute coronary syndromes (n = 1) or patients with stable coronary artery disease (n = 3) did not show a clear clinical benefit of clopidogrel when given in addition to aspirin after CABG. In contrast, there was a trend toward increased major and minor bleeding after the use of clopidogrel plus aspirin. Two small prospective trials providing data on surrogate end points and 5 small trials involving off-pump CABG patients were not of good quality to draw meaningful conclusions. In conclusion, summarized data based on subgroup analyses, surrogate end points, and observational cohort studies fail to demonstrate a clear beneficial effect of clopidogrel alone or in combination with aspirin on clinical outcomes after CABG.

Coronary vein graft disease: pathogenesis and prevention

Not long after coronary artery bypass grafting surgery was described, several reports presented follow-up angiographic data on large cohorts of patients, demonstrating that approximately one-half of saphenous vein grafts fail within 10 to 15 years of surgery and that graft failure is associated with worse clinical outcomes. Three processes are responsible for vein graft failure. Thrombosis, intimal hyperplasia and accelerated atherosclerosis contribute to graft failure in the acute, subacute and late postoperative periods, respectively. Studies have shown that perioperative antiplatelet therapy can reduce early thrombosis and graft failure. As in native coronaries, intensive lipid lowering can attenuate the process of atherosclerosis in vein grafts. Intimal hyperplasia in the vein graft is thought to be an adaptation of the vein to higher pressures in the arterial circulation. This process is further promoted by the loss of inhibition from the endothelial layer, which is injured during surgery. A new 'no-touch' technique for harvesting grafts may be effective in preventing disruption to the endothelial layer, and subsequent intimal hyperplasia and graft loss. Off-pump surgery and endoscopic vein harvesting, which are known to reduce surgical morbidity, have been shown to be no worse than on-pump surgery and open vein harvesting, respectively, in terms of vein graft patency. Various gene therapies can prevent intimal hyperplasia in animal models, but human data obtained so far have been disappointing. Placing an external stent around a vein graft may reduce tangential wall stress and subsequent intimal hyperplasia.