Incorporation of bleeding as an element of the composite end point in clinical trials of antithrombotic therapies in patients with non-ST-segment elevation acute coronary syndrome: validity, pitfalls, and future approaches

Exploration of Bivalirudin Use during Percutaneous Coronary Intervention for High Bleeding Risk Patients with Chronic Total Occlusion

The safety and efficacy of bivalirudin during percutaneous coronary intervention (PCI) in high bleeding risk patients with chronic total occlusion lesions (CTO) has not been studied till date. The use of bivalirudin may increase the thrombotic events during CTO-PCI.Between May 2013 and April 2014, a total of 117 high bleeding risk patients with CTOs underwent PCI. Bivalirudin was used in 89 cases with different strategies, including standard usage, combination of heparin, and additional bolus of bivalirudin on the basis of standard usage. The clinical characteristics, procedural details and antithrombotic strategies were assessed, and the bleeding and ischemic events were evaluated. The first 7 of 9 patients with standard application of bivalirudin exhibited acute thrombogenesis in the procedure. Heparin was then added in decreasing amounts in the next 8 patients wherein no thrombosis occurred; however, 2 patients had bleeding complications. The subsequent 72 patients were randomly assigned to the heparin bolus or additional bivalirudin bolus groups before the percutaneous transluminal coronary angioplasty (PTCA) was performed. The baseline clinical characteristics and procedure information were identical in both the groups. There were no ischemic and bleeding events in both the groups during the 6-month follow-up.Monotherapy with bivalirudin in CTO-PCI should be treated with caution, as the potential risk of thrombogenesis may be due to the long procedure time, the frequent change of equipment and temporary blood flow convection. Combination of heparin or an additional bolus of bivalirudin before PTCA was observed to be likely to decrease the incidence of thrombogenesis.

Which long-term antiplatelet regimen for patients with acute coronary syndromes?

Dual antiplatelet therapy (DAPT ) is recommended up to 12 months in patients with acute coronary syndromes, but the risk of cardiovascular events in this group of subjects remains high, also in the long-term follow-up. The potential benefit of a prolonged period of DAPT has recently been assessed in three large-volume randomized clinical trials (PEGASUS, DAPT-MI, TRA2P-TIMI 50) but final results are quite difficult to interpret and clear indications for the clinical practice are so far lacking. A direct comparison of the three studies is challenging since relevant differences exist as to clinical features and risk profile of the study populations. Different anti-platelet drugs have been tested in addition to aspirin making it difficult to understand which antithrombotic regimen guarantees the best balance between thrombotic and haemorragic events. Finally, specific designs of these trials, evaluating complex composite end-points, may generate further difficulties in the interpretation of data. We believe that the use of total mortality rather than cardiovascular death as end-point, would better describe the long-term outcome incorporating the catastrophic consequences of bleeding. This review seeks to highlight strengths and weaknesses of these three large-volume trials and tries to establish whether or not prolonging DAPT beyond 12 months in patients with acute coronary syndromes is useful and which anti-thrombotic regimen would offer the best balance between thrombotic and bleeding risk.

Power and sample size calculations for the Wilcoxon-Mann-Whitney test in the presence of death-censored observations

We consider a clinical trial of a potentially lethal disease in which patients are randomly assigned to two treatment groups and are followed for a fixed period of time; a continuous endpoint is measured at the end of follow-up. For some patients; however, death (or severe disease progression) may preclude measurement of the endpoint. A statistical analysis that includes only patients with endpoint measurements may be biased. An alternative analysis includes all randomized patients, with rank scores assigned to the patients who are available for the endpoint measurement on the basis of the magnitude of their responses and with 'worst-rank' scores assigned to those patients whose death precluded the measurement of the continuous endpoint. The worst-rank scores are worse than all observed rank scores. The treatment effect is then evaluated using the Wilcoxon-Mann-Whitney test. In this paper, we derive closed-form formulae for the power and sample size of the Wilcoxon-Mann-Whitney test when missing measurements of the continuous endpoints because of death are replaced by worst-rank scores. We distinguish two approaches for assigning the worst-rank scores. In the tied worst-rank approach, all deaths are weighted equally, and the worst-rank scores are set to a single value that is worse than all measured responses. In the untied worst-rank approach, the worst-rank scores further rank patients according to their time of death, so that an earlier death is considered worse than a later death, which in turn is worse than all measured responses. In addition, we propose four methods for the implementation of the sample size formulae for a trial with expected early death. We conduct Monte Carlo simulation studies to evaluate the accuracy of our power and sample size formulae and to compare the four sample size estimation methods.

Bivalirudin versus heparin in patients planned for percutaneous coronary intervention: a meta-analysis of randomised controlled trials

BACKGROUND

Bivalirudin is an alternative to heparin in patients undergoing percutaneous coronary intervention (PCI). We aimed to define the effects of a bivalirudin-based anticoagulation regimen compared with a heparin-based anticoagulation regimen on ischaemic and bleeding outcomes.

METHODS

We searched Medline, the Cochrane Library, and relevant meeting abstracts (search done on April 9, 2014) for randomised trials that assessed bivalirudin versus heparin in patients planned for PCI. The primary efficacy endpoint was the incidence of major adverse cardiac events (MACE) up to 30 days. Secondary efficacy endpoints were death, myocardial infarction, ischaemia-driven revascularisation, and stent thrombosis. The primary safety endpoint was major bleeding up to 30 days. We calculated pooled risk ratios and 95% CIs using random-effects models.

FINDINGS

We included data from 16 trials involving 33 958 patients, of whom 2422 experienced MACE and 1406 had a major bleed. There was an increase in the risk of MACE with bivalirudin-based regimens compared with heparin-based regimens (risk ratio 1·09, 95% CI 1·01-1·17; p=0·0204), which was largely driven by increases in myocardial infarction (1·12, 1·03-1·23) and seemingly also by ischaemia-driven revascularisation (1·16, 0·997-1·34) with bivalirudin compared with heparin, with no effect on mortality (0·99, 0·82-1·18). Bivalirudin increased the risk of stent thrombosis (risk ratio 1·38, 95% CI 1·09-1·74; p=0·0074), which was primarily due to an increase in acute cases in ST-segment elevation myocardial infarction (4·27, 2·28-8·00; p<0·0001). Overall, bivalirudin-based regimens lowered the risk of major bleeding (risk ratio 0·62, 95% CI 0·49-0·78; p<0·0001), but the magnitude of this effect varied greatly (p<0·0001) depending on whether glycoprotein IIb/IIIa inhibitors were used predominantly in the heparin arm only (0·53, 0·47-0·61; p<0·0001), provisionally in both arms (0·78, 0·51-1·19; p=0·25), or planned in both arms (1·07, 0·87-1·31; p=0·53).

INTERPRETATION

Compared with a heparin-based regimen, a bivalirudin-based regimen increases the risk of myocardial infarction and stent thrombosis, but decreases the risk of bleeding, with the magnitude of the reduction depending on concomitant glycoprotein IIb/IIIa inhibitor use. Physicians should weigh the trade-off between ischaemic and bleeding events when choosing between different anticoagulant regimens.

FUNDING

None.

Optimal oral antithrombotic regimes for patients with acute coronary syndrome: a network meta-analysis

OBJECTIVE

We performed a network meta-analysis to investigate the optimal antithrombotic regime by indirectly comparing new antithrombotic regimes (new P2Y12 inhibitors plus aspirin or novel oral anticoagulants on top of traditional dual antiplatelet therapy [DAPT]) in patients with acute coronary syndrome (ACS).

METHODS

A systematic search of MEDLINE, EMBASE, and the Cochrane databases was performed to identify all phase 3 randomized controlled trials (RCTs) involving novel oral anticoagulants or oral P2Y12 inhibitors in patients with ACS. Major adverse cardiac events (MACE) were regarded as the efficacy endpoint, and thrombolysis in myocardial infarction (TIMI) major bleeding events were used as the safety endpoint. The net clinical benefit was calculated as the sum of MACE and TIMI major bleeding events.

RESULTS

Five phase 3 RCTs with 64,476 ACS patients were included. Although there were no significant differences among new antithrombotic regimes, rivaroxaban 5 mg twice daily plus traditional DAPT might be the most effective in reducing the incidence of MACE, accompanying the highest risk of TIMI major bleeding. Ticagrelor plus aspirin presented slight advantage on the net clinical benefit over other new antithrombotic regimes, with the highest probability of being the best regimes for net clinical benefit (35.0%), followed by prasugrel plus aspirin (28.0%), and rivaroxaban 2.5 mg twice daily plus traditional DAPT (19.5%).

CONCLUSION

Novel antithrombotic regime with ticagrelor plus aspirin brings a larger clinical benefit in comparison with other regimes, suggesting that it may be the optimal antithrombotic regime for patients with ACS.

Lessons learned from negative clinical trials evaluating antithrombotic therapy for ischemic heart disease

The clinical trials that failed to demonstrate significant efficacy may not result in development of new therapy but contribute to better understanding of antithrombotic therapy for ischemic heart disease. Negative trials provide important messages about how to interpret and understand the results of clinical trials and apply these results to clinical practices. Although every aspect of clinical trials may influence the outcomes of trials and interpretation of their results, selection of study subjects, endpoints, and measuring risk/benefit are crucial to success of clinical trial. We will review the recent key negative trials on antithrombotic therapy for ischemic heart disease and discuss about their results and implications. The challenge in the future for the development of antithrombotic therapies is to leverage these "lessons learned" from negative clinical trials to improve the design, conduct, and interpretation of future randomized clinical trials.