Biomarkers of Thrombotic Status Predict Spontaneous Reperfusion in Patients With ST-Segment Elevation Myocardial Infarction

Platelet reactivity and activated clotting time predict hemorrhagic site complications in patients with chronic coronary syndromes undergoing percutaneous coronary interventions

BACKGROUND

Radial access is preferred in patients with chronic coronary syndromes (CCSs) treated with ad hoc percutaneous coronary intervention (PCI). Antithrombotic and antiplatelet treatment before PCI may affect outcomes at vascular access sites. QuikClot Radial is a kaolin-based band that may shorten hemostasis time. Using point-of-care testing, we investigated the effect of antithrombotic and antiplatelet treatment on access-site complications.

METHODS

This prospective observational study included consecutive patients with CCS on chronic aspirin therapy referred for ad hoc PCI. The activated clotting time (ACT), global thrombosis test and VerifyNow P2Y 12 test were done sequentially after unfractionated heparin (UFH) and clopidogrel administration. Patients were monitored for radial artery patency, bleeding and local hematoma until discharge.

RESULTS

We enrolled 40 patients [mean age, 68.8 ± 8.8 years; men, 30 (75%)] who received UFH (median dose, 8000 IU; interquartile range, 7000-9000 IU) and clopidogrel (600 mg). All radial arteries remained patent during follow-up. Local bleeding and hematomas were noted in 11 patients (27.5%) each. Patients with bleeding had lower mean platelet activity at 2 h [122.5 ± 51 platelet reactivity units (PRU) vs. 158.7 ± 43 PRU, P  = 0.04] and higher ACT (216.9 ± 40 s vs. 184.6 ± 28 s, P = 0.006) than patients without bleeding. An ACT >196 s at 2 h predicted bleeding or hematoma (AUC, 0.72; 95% CI, 0.56-0.85, P = 0.008).

CONCLUSION

Lower platelet activity and higher ACT after PCI were associated with higher bleeding risk at a vascular access site. Point-of-care testing of ACT after the procedure may help identify patients with CCS undergoing PCI who are at higher risk of access-site bleeding.

Impact of very low dose rivaroxaban in addition to dual antiplatelet therapy on endogenous fibrinolysis in acute coronary syndrome: The VaLiDate-R study

BACKGROUND

Impaired endogenous fibrinolysis is adverse cardiovascular risk factor in acute coronary syndrome (ACS) patients. Addition of very low dose rivaroxaban (VLDR) to dual antiplatelet therapy (DAPT) reduces cardiovascular events but increases bleeding.

OBJECTIVE

We aimed to assess whether addition of VLDR to DAPT can enhance endogenous fibrinolysis.

METHODS

In a prospective, open-label trial, we assessed endogenous fibrinolysis in whole blood, in 549 patients with ACS using the Global Thrombosis Test (GTT) and Thromboelastography (TEG). Patients (n = 180) who demonstrated impaired endogenous fibrinolysis (lysis time [LT] >2000s with the GTT) were randomised 1:1:1 to (i) clopidogrel 75 mg daily; (ii) clopidogrel 75 mg daily plus rivaroxaban 2.5 mg twice daily; or (iii) ticagrelor 90 mg twice daily, for 30 days, in addition to aspirin. Fibrinolytic status was assessed at 0, 2, 4 and 8 weeks. The primary outcome was the change in LT from admission to week 4. We also measured thrombotic occlusion time (OT) at high shear, and rivaroxaban level.

RESULTS

There was no difference between the groups with respect to LT or clot lysis with TEG, and no change in these parameters compared to baseline during study drug allocation. In the rivaroxaban plus clopidogrel group, OT was prolonged compared to the other groups, although rivaroxaban levels were low, suggesting non-compliance.

CONCLUSION

Addition of rivaroxaban 2.5 mg twice daily to DAPT does not affect endogenous fibrinolysis of thrombus formed at either high or low shear. Further studies are needed to determine whether higher doses of rivaroxaban can favourably modulate fibrinolysis.

CONDENSED ABSTRACT

Impaired endogenous fibrinolysis is a strong risk factor in ACS. We aimed to assess whether adding very low dose rivaroxaban (VLDR) to DAPT can enhance fibrinolysis. Fibrin and clot lysis were assessed in whole blood. ACS patients with impaired fibrinolysis were randomised 1:1:1 to clopidogrel 75 mg daily; clopidogrel 75 mg plus VLDR; or ticagrelor 90 mg twice daily, in addition to aspirin. At 30-days, there was no difference in lysis time between the groups, nor change from baseline. VLDR does not improve fibrinolysis at high or low shear. Further studies are needed to determine whether alternative antithrombotic regimens can enhance endogenous fibrinolysis.

Measuring Thrombus Stability at High Shear, Together With Thrombus Formation and Endogenous Fibrinolysis: First Experience Using the Global Thrombosis Test 3 (GTT-3)

Thrombus formation in a severely stenosed artery is initiated by high shear activation of platelets, with soluble platelet agonists, such as ADP and thromboxane, playing only a secondary role in the growth and stability of the thrombus. Conventional platelet function tests, however, assess only the soluble agonist-dependent pathway of platelet aggregation. As the thrombus evolves, its stability and ability to withstand dislodgement by arterial flow will determine whether complete and persistent vessel occlusion will occur. The Global Thrombosis Test (GTT), an automated point-of-care technique, simulates the formation of thrombus in whole blood under high shear flow (shear rate >12 000 s-1) and measures the time for occlusive thrombus formation and spontaneous, endogenous thrombolysis/fibrinolysis. The latest GTT-3 model subjects the growing thrombus to upstream pressure, resembling that in a medium-sized artery, and provides an additional assessment of thrombus stability and fibrinolysis rate. It can be used in 3 programs, including a new "hypershear" mode, whereby repetitive cycles of pressure are applied to the growing thrombus, increasing shear rate to ∼22 000 s-1, such as that in patients on mechanical circulatory support. In addition to assessing the risk of arterial thrombosis, the GTT-3 could be used to assess the impact of antithrombotic medications on thrombus stability at high shear. Although current antiplatelet medications target the biochemical axis of platelet aggregation (soluble agonists) and also increase bleeding risk, novel shear-selective antiplatelet therapies may prevent thrombosis while preserving hemostasis. Future studies are needed to assess the usefulness of assessing thrombus stability on cardiovascular and pharmacological evaluation.