Aspirin resistance after CABG

Predictors of thromboxane levels in patients with non-ST-elevation acute coronary syndromes on chronic aspirin therapy

High levels of thromboxane A2 (TxA2), a key mediator of platelet activation and aggregation, are associated with an increased risk of cardiovascular events. We aimed at assessing the predictors of higher plasma levels of TxB2, the stable metabolite of TxA2, in consecutive patients presenting with non-ST-elevation acute coronary syndrome (NSTE-ACS) on previous aspirin (ASA) treatment undergoing coronary angiography. Ninety-eight consecutive patients (age 61 ± 11, 75% males) with NSTE-ACS, on previous chronic ASA treatment, were prospectively enrolled in this study. Coronary disease extent was assessed by angiography according to the Bogaty score. In all patients, admission plasma levels of TxB2 (pg/ml) were measured by enzyme-linked immunosorbent assay, and patients showing TxB2 levels in the fourth quartile were compared to patients showing TxB2 levels in the lower quartiles. Multivariable logistic regression analysis showed that platelet count (odds ratio [OR] 1.18, 95% confidence interval [CI] 1.02–1.63, p=0.04), multivessel coronary disease (OR 1.37, 95% CI 1.13–3.67, p=0.03), and coronary atherosclerosis extent index (OR 1.91, 95% CI 1.45–6.79, p=0.001) were independent predictors of TxB2 level upper quartile. Of note, C-reactive protein serum levels were similar in patients with TxB2 levels in the upper quartile as compared to those in the lower quartiles (p=0.49). In conclusion, NSTE-ACS patients with severe coronary atherosclerosis may have incomplete suppression of TxA2 production despite chronic ASA therapy. This finding suggests that additional efforts should be made to lower TxA2 levels in patients with widespread coronary artery disease.

Antiplatelet drugs in patients with enhanced platelet turnover: biomarkers versus platelet function testing

Platelets are key players in atherothrombosis. Antiplatelet therapy comprising aspirin alone or with P2Y12-inhibitors are effective for prevention of atherothrombotic complications. However, there is interindividual variability in the response to antiplatelet drugs, leaving some patients at increased risk of recurrent atherothrombotic events. Several risk factors associated with high on-treatment platelet reactivity (HTPR), including elevated platelet turnover, have been identified. Platelet turnover is adequately estimated from the fraction of reticulated platelets. Reticulated platelets are young platelets, characterised by residual messenger RNA. They are larger, haemostatically more active and there is evidence that platelet turnover is a causal and prognostic factor in atherothrombotic disease. Whether platelet turnover per se represents a key factor in pathogenesis, progression and prognosis of atherothrombotic diseases (with focus on acute coronary syndromes) or whether it merely facilitates insufficient platelet inhibition will be discussed in this state-of-the art review.

Early vein graft failure leading to acute myocardial infarction, dehiscence and haemopericardium treated by percutaneous coil embolisation and balloon tamponade

Early vein graft failure is a well-described early complication of coronary artery bypass grafting. Revascularisation with emergency percutaneous coronary intervention (PCI) may limit the extent of myocardial damage and is associated with lower procedural complications compared than with emergency redo bypass surgery. We describe a case of an early saphenous vein graft (SVG) thrombosis presenting as an inferior ST-elevation to our non-surgical PCI site, complicated by SVG graft dehiscence leading to cardiac tamponade, which we treated with coil embolisation and balloon tamponade during the patient's transfer to a surgical facility for emergent haemopericardium evacuation.

Clopidogrel improves aspirin response after off-pump coronary artery bypass surgery

We sought to assess the incidence of aspirin resistance after off-pump coronary artery bypass (OPCAB) surgery, and investigate whether clopidogrel can improve aspirin response and be safely applied early after OPCAB surgery. Sixty patients who underwent standard OPCAB surgery were randomized into two groups. One group (30 patients) received mono-antiplatelet treatment (MAPT) with aspirin 100 mg daily and the other group received dual antiplatelet treatment (DAPT) with aspirin 100 mg daily plus clopidogrel 75 mg daily. Platelet aggregations in response to arachidonic acid (PL_AA) and adenosine diphosphate (ADP) (PL_ADP) were measured preoperatively and on days 1 to 6, 8 and 10 after the antiplatelet agents were administered. A PL_AA level above 20% was defined as aspirin resistance. Postoperative bleeding and other perioperative variables were also recorded. There were no significant differences between the two groups in baseline characteristics, average number of distal anastomosis, operation time, postoperative bleeding, ventilation time and postoperative hospital stay. However, the incidence of aspirin resistance was significantly lower in the DAPT group than that in the MAPT group on the first and second day after antiplatelet agents were given (62.1% vs. 32.1%, 34.5% vs. 10.7%, respectively, both P < 0.05). There was no significant difference in postoperative complication between the two groups. DAPT with aspirin and clopidogrel can be safely applied to OPCAB patients early after the procedure. Moreover, clopidogrel reduces the incidence of OPCAB-related aspirin resistance.

Saphenous vein graft failure after coronary artery bypass surgery: pathophysiology, management, and future directions

OBJECTIVE

To review our current understanding of the epidemiology and pathogenesis of vein graft failure (VGF), give an overview of current preventive and interventional measures, and explore strategies that may improve vein graft patency.

BACKGROUND

VGF and progression of native coronary artery disease limit the long-term efficacy of coronary artery bypass graft surgery.

METHODS

We reviewed the published literature on the pathophysiology, prevention, and/or treatment of VGF by searching the MEDLINE (January 1, 1966-January 1, 2012), EMBASE (January 1, 1980-January 1, 2012), and Cochrane (January 1, 1995-January 1, 2012) databases. In addition, we reviewed references from the selected articles for studies not identified in the initial search. Basic science and clinical studies were included; non-English language publications were excluded.

RESULTS

Acute thrombosis, neointimal hyperplasia, and accelerated atherosclerosis are the 3 mechanisms that lead to VGF. Preventive measures include matching and quality assessment of conduit and target vessel, lipid-lowering drugs, antithrombotic therapy, and cessation of smoking. Treatment of VGF includes medical therapy, percutaneous intervention, and redo coronary artery bypass graft surgery. In patients undergoing graft intervention, the use of drug-eluting stents, antiplatelet agents, and embolic protection devices may improve clinical outcomes.

CONCLUSIONS

Despite advances in management, VGF remains one of the leading causes of poor in-hospital and long-term outcomes after coronary artery bypass graft surgery. New developments in VGF prevention such as gene therapy, external graft support, fully tissue-engineered grafts, hybrid grafts, and synthetic conduits are promising but unproven. Future efforts to reduce VGF require a multidisciplinary approach with a primary focus on prevention.

Prehospitalization antiplatelet therapy and outcomes after saphenous vein graft intervention

Antiplatelet therapy is recommended after coronary artery bypass grafting, because it improves saphenous vein graft (SVG) patency and clinical outcomes. We investigated the association between prehospital antiplatelet regimens and outcomes after SVG intervention. Patients who underwent SVG intervention from 2003 to 2008 were divided into 3 groups: (1) no antiplatelet therapy, (2) the use of aspirin or clopidogrel, and (3) the use of dual antiplatelet therapy (DAPT) at admission. Clinical follow-up examinations were performed at 30 days and 1 year. The primary outcome was the composite of all-cause mortality, myocardial infarction, the need for revascularization, and stroke at 30 days. The relation between antiplatelet therapy and outcomes was adjusted for factors associated with the outcomes. A total of 225 patients underwent SVG intervention, 87% were men, and the mean age was 70 years. Of the 225 patients, 21 (9.4%) were not receiving antiplatelet therapy, 102 (45.3%) were receiving aspirin/clopidogrel, and 102 (45.3%) were receiving DAPT. The patients without antiplatelet therapy were more frequently women, had presented earlier after coronary artery bypass grafting, and were less frequently taking other cardiac-related medications. The patients taking aspirin or DAPT were more often smokers and had a greater peripheral vascular burden. The incidence of the 30-day and 1-year primary outcomes was greater in patients without preadmission antiplatelet use (38.1% vs 14.9% and 13.9%, overall p = 0.01; 52.4% vs 29.5% and 28.3%, overall p = 0.03). After adjustment, antiplatelet use remained associated with the primary outcome. In conclusion, prehospital use of antiplatelet therapy was associated with a lower occurrence of major adverse cardiac events after SVG intervention. We did not find that DAPT improved outcomes compared to single antiplatelet therapy.

Aspirin resistance and ischemic heart disease on Iranian experience

BACKGROUND

Coronary artery disease (CAD) and myocardial infarction are the most common causes of mortality and morbidity all over the world. Aspirin resistance is an important part of therapeutic failure in patients who experience several atherosclerotic events despite aspirin therapy. Different studies have reported aspirin resistance between 5% and 45% all over the world. According to different responses to aspirin therapy in countries and lack of adequate studies on aspirin resistance in Iran, this study was designed for evaluation of aspirin resistance in ischemic patients.

MATERIALS AND METHODS

Total 170 patients with documented coronary artery stenosis with were enrolled in this cross-sectional prospective study. Two cc urine samples were obtained from all the subjects. Then a questionnaire including questions about major risk factors (hypertension, diabetes, hyperlipidemia, obesity and smoking) was completed for each patient. Thromboxane B2 level in urine was measured two times for each patient by one kit of via ELISA method. Gensini modified was usedfor assessment of severity of coronary arteries involvement. Data were analyzed via SPSS 16. with general linear model (univariate).

RESULTS

75.3% of studied patients were aspirin resistant. There was significant relationship between angiography score and aspirin resistance (P<0.001).Our results also showed that aspirin resistance is more common in studied women than men (P=0.003).Significant correlation was observed between diabetes and aspirin resistance in studied subjects (P=0.023).

CONCLUSION

Our study showed aspirin resistance in a sample of Iranian ischemic patients is so prevalent which is higher than other studies in another communities and also aspirin resistance is more common in patients with severe CAD.

Aspirin resistance in off-pump coronary artery bypass grafting

OBJECTIVE

Anti-platelet therapy with aspirin is the cornerstone of treatment after coronary artery bypass grafting (CABG). Aspirin resistance describes the clinical observation of the inability of aspirin to prevent thrombotic complications or the laboratory phenomenon of absence of the effect of aspirin on platelet inhibition tests. Off-pump CABG (OPCAB) is associated with reduced platelet activation and turnover compared to on-pump surgery which may indicate that aspirin is more effective after OPCAB. Our aim was to evaluate the efficacy of aspirin and incidence of aspirin resistance in patients undergoing OPCAB.

METHODS

A total of 331 patients was recruited, of which 111 underwent primary OPCAB (group A) and 220 controls with ischaemic heart disease received medical therapy. Arachidonic acid-induced platelet aggregation and urinary 11-dehydro thromboxane B2 (11-dehydroTxB2) were measured at baseline and following aspirin administration on days 1, 4 and 10. A 6-month follow-up was completed in patients who developed aspirin resistance.

RESULTS

On the first postoperative day, 78 patients (70.3%) were aspirin sensitive (AS) and 33 (29.7%) were aspirin resistant (AR). Of the latter, 18 (16.2%) and five (4.5%) patients remained resistant on days 4 and 10, respectively. AR patients had significantly greater platelet aggregation and urinary 11-dehydroTxB2 levels at all time points than those in the AS group. All patients in the AR group were AS by 6 months. All controls were sensitive to aspirin with similar platelet aggregation and 11-dehydroTxB2 to those in the AS group.

CONCLUSIONS

Aspirin resistance is a transient phenomenon during the early postoperative period in approximately 30% of patients undergoing OPCAB.

Ketorolac improves graft patency after coronary artery bypass grafting: a propensity-matched analysis

BACKGROUND

The use of ketorolac, a potent cyclooxygenase-1 inhibitor, for analgesia after cardiac operations has been limited by concerns of increased cardiovascular events. However, a recent study found that its use after coronary artery bypass grafting was associated with improved survival.

METHODS

This was a retrospective study of patients who received coronary arteriograms for symptoms suggestive of recurrent ischemic heart disease. Patients who received postoperative ketorolac were matched with nonusers by propensity scores. Graft occlusion rates were compared, and their association with ketorolac use was compared using Cox proportional hazard modeling.

RESULTS

Although the rate of graft occlusion was similar in the two groups, in 184 of the 303 propensity-matched patients (61%) who received ketorolac vs 202 of the 303 patients (67%) who did not (p=0.13), there was a longer time to angiographically proven occlusion in the patients who received ketorolac (2.80±2.19 vs 2.04±1.63 years; p<0.001). Cox modeling to control for the other variables and the longer time to angiography in the ketorolac group showed that ketorolac use was associated with nearly a halving of the hazard ratio (0.561; 95% confidence interval, 0.454 to 0.692; p<0.001) for any graft occlusion.

CONCLUSIONS

The use of ketorolac after coronary artery bypass grafting was associated with a lower rate of angiographically proven graft closure and suggests a mechanistic (improved graft patency) explanation for the previously reported survival benefit of ketorolac.

Aspirin and clopidogrel resistance: methodological challenges and opportunities

Antiplatelet drug resistance is one of the urgent issues in current cardiovascular medicine. Many platelet function tests have been used to define responsiveness of patients with cardiovascular disease to aspirin and clopidogrel. In most studies, cut-off values of platelet function tests for defining responsiveness to antiplatelets were chosen arbitrarily. Different tests provided wide-ranging figures of the prevalence of aspirin and clopidogrel resistance, suggesting poor correlation between currently available platelet function tests. Measurement of platelet size seems to be a promising approach for monitoring antiplatelet drug therapy. This commentary highlights some limitations of studies on aspirin and clopidogrel resistance in patients undergoing coronary interventions.