Long-term effect of chronic oral anticoagulation: focus on coronary artery disease

Dicoumarol activates Ca2+-permeable cation channels triggering erythrocyte cell membrane scrambling

Dicoumarol, a widely used anticoagulant, may cause anemia, which may result from enhanced erythrocyte loss due to bleeding or due to accelerated erythrocyte death. Erythrocytes may undergo suicidal death or eryptosis, characterized by cell shrinkage and phospholipid scrambling of the cell membrane. Eryptosis may be triggered by increase of cytosolic Ca(2+)-activity ([Ca(2+)](i)). The present study explored, whether dicoumarol induces eryptosis. [Ca(2+)](i) was estimated from Fluo3-fluorescence, cation channel activity utilizing whole cell patch clamp, cell volume from forward scatter, phospholipid scrambling from annexin-V-binding, and hemolysis from haemoglobin release. Exposure of erythrocytes for 48 hours to dicoumarol (=10 μM) significantly increased [Ca(2+)](i), enhanced cation channel activity, decreased forward scatter, triggered annexin-V-binding and elicited hemolysis. Following exposure to 30 μM dicoumarol, annexin-V-binding affected approximately 15%, and hemolysis 2% of treated erythrocytes. The stimulation of annexin-V-binding by dicoumarol was abrogated in the nominal absence of Ca(2+). In conclusion, dicoumarol stimulates suicidal death of erythrocytes by stimulating Ca(2+) entry and subsequent triggering of Ca(2+) dependent cell membrane scrambling.

Adjusted indirect comparison meta-analysis of prasugrel versus ticagrelor for patients with acute coronary syndromes

BACKGROUND

Clopidogrel is beneficial after ACS. Recent data suggest the superiority of prasugrel or ticagrelor compared with clopidogrel. However, there is no comparison of prasugrel vs. ticagrelor. We performed an adjusted indirect meta-analysis comparing prasugrel vs. ticagrelor for acute coronary syndromes (ACSs).

METHODS

Randomized trials were searched in PubMed. The primary end-point was the composite of death, myocardial infarction (MI) or stroke. Odds ratios (OR) were computed (95% confidence intervals).

RESULTS

Three trial (32,893) patients were included. Overall, either prasugrel or ticagrelor appeared significantly superior to clopidogrel for the 12-month risk of death, MI or stroke (OR=0.83 [0.77-0.89], p<0.001), death (OR=0.83 [0.74-0.93], p=0.001), MI (OR=0.79 [0.73-0.86], p<0.001), and stent thrombosis (OR=0.61 [0.51-0.74], p<0.001), without any significant difference in stroke or major bleeding (both p>0.05), despite more frequent drug discontinuation (OR=1.12 [1.05-1.19], p<0.001). Head-to-head comparison of prasugrel vs. ticagrelor showed no significant differences in overall death, MI, stroke, or their composite (all p>0.05). Prasugrel was associated with a significantly lower risk of stent thrombosis (OR=0.64 [0.43-0.93], p=0.020). Ticagrelor was associated with a significantly lower risk of any major bleeding (OR=1.43 [1.10-1.85], p=0.007), and major bleeding associated with bypass grafting (OR=4.30 [1.73-10.6], p=0.002). However, the more clinically relevant risk of major bleeding not related to bypass surgery was similar with either prasugrel or ticagrelor (OR=1.06 [0.77-1.45], p=0.34).

CONCLUSIONS

Prasugrel and ticagrelor are superior to clopidogrel for ACS. Head-to-head comparison suggests similar efficacy and safety of prasugrel and ticagrelor, but prasugrel appears more protective from stent thrombosis, while causing more bleedings.

Alternatives to clopidogrel for acute coronary syndromes: Prasugrel or ticagrelor?

Clopidogrel is a mainstay in the treatment of patients with acute coronary syndromes or those receiving endovascular prostheses. However, its efficacy has been challenged in the recent past by studies suggesting variable individual responsiveness and by new, more potent competitors, such as prasugrel and ticagrelor. But what is the actual body of evidence in support of clopidogrel? Is there any dark side of the moon? What is the role of prasugrel, which has already been approved in Europe and in the United States? And what will be the future role of ticagrelor, when approved for routine clinical practice? We hereby concisely summarize the scope of this clinical choice, providing arguments in favor and against each of the three antiplatelet agents: clopidogrel, prasugrel, and ticagrelor.