Tissue factor-mediated activation of the prothrombin complex concentrate (PCC) is differently inhibited by dabigatran, rivaroxaban, and apixaban: potential clinical implication

Short- and long-term outcome of patients with spontaneous echo contrast or thrombus in the left atrial appendage in the era of the direct acting anticoagulants

Background

Thrombi and spontaneous echo contrast (SEC) in the left atrial appendage (LAA) are associated with thromboembolic events and poor prognosis. There are very few data on long-term outcome, especially with the use of direct acting anticoagulants (DOAC).

Methods

In this retrospective study, all transoesophageal echocardiographies performed at a tertiary care university hospital from 2015 to 2020 were analyzed. All patients with thrombus or SEC in the LAA were included. Medical history, laboratory, echocardiographic parameters and medication at discharge were documented. The primary endpoint of the study was a composite endpoint (all-cause mortality, non-fatal stroke or transient ischaemic attack [TIA], non-fatal systemic embolization, non-fatal major bleeding and non-fatal myocardial infarction).

Results

Of a total of 4062 transoesophageal echocardiographies, thrombi were detected in 51 patients (1.2%) and SEC in 251 patients (6.2%). These patients formed the final study cohort (n = 302). During a mean follow-up period of 956 ± 663 days, 87 patients (29%) suffered the primary point. The following baseline characteristics predicted the primary endpoint: age, haemoglobin, a previous coronary artery bypass grafting, dialysis and choice of anticoagulation. Prescription of apixaban at discharge was associated with lower rate of adverse events (hazard ratio 0.564, confidence interval 0.331–0.960; p = 0.035) while prescription of dabigatran was associated with higher rate of adverse events (hazard ratio 3.091, confidence interval 1.506–6.347; p = 0.002).

Conclusion

Even in the DOAC era, the occurrence of thrombus or SEC in the LAA is associated with a high rate of MACCE. Our study suggests that the choice of DOAC therapy may have an impact on long-term survival.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s00392-021-01926-8.

First evidence: rivaroxaban and apixaban reduce thrombin-dependent platelet aggregation

Rivaroxaban and apixaban are direct oral anticoagulants whose target specificity is to activate factor X (FXa). It is still not fully understood how xabans impact platelet function. This single-center observational study aimed to assess in vitro platelet function in patients with atrial fibrillation receiving rivaroxaban or apixaban. It examined quantification of platelet aggregation assessed by light transmission aggregometry in thirty-four patients treated with apixaban or rivaroxaban. The thrombin-induced platelet aggregation was significantly lower 2 h after taking selected xabans compared to baseline value (69.55 ± 32.15% vs. 44.79 ± 34.97.9%; p < 0.0001). This effect was only observed in patients who received rivaroxaban or apixaban for more than 1 week. The thrombin-induced platelet aggregation is reduced in cardiovascular patients receiving rivaroxaban or apixaban. This reduction is likely to depend on the duration of the treatment. Duration of treatment should be considered in future studies focusing on DOACs and platelet aggregation.

Reversal of apixaban anticoagulation by four-factor prothrombin complex concentrates in healthy subjects: a randomized three-period crossover study

Essentials Prothrombin complex concentrates (PCCs) may reverse the effect of factor Xa (FXa) inhibitors. We conducted an open-label, randomized, placebo-controlled, three-period crossover study in 15 subjects. Both PCCs rapidly reversed apixaban-mediated decreases in mean endogenous thrombin potential. Four-factor PCC administration had no effect on apixaban pharmacokinetics or anti-FXa activity.

SUMMARY

Background Currently, there is no approved reversal agent for direct activated factor Xa (FXa) inhibitors; however, several agents are under investigation, including prothrombin complex concentrates (PCCs). Objective This open-label, randomized, placebo-controlled, three-period crossover study assessed the effect of two four-factor PCCs on apixaban pharmacodynamics and pharmacokinetics in 15 healthy subjects. Methods Subjects received apixaban 10 mg twice daily for 3 days. On day 4, 3 h after apixaban, subjects received a 30-min infusion of 50 IU kg-1 Cofact, Beriplex P/N (Beriplex), or saline. Change in endogenous thrombin potential (ETP), measured with a thrombin generation assay (TGA), was the primary endpoint. Secondary endpoints included changes in other TGA parameters, prothrombin time (PT), International Normalized Ratio (INR), activated partial thromboplastin time, anti-FXa activity, apixaban pharmacokinetics, and safety. Results Apixaban-related changes in ETP and several other pharmacodynamic measures occurred following apixaban administration. Both PCCs reversed apixaban's effect on ETP; the differences in adjusted mean change from pre-PCC baseline to end of infusion were 425 nm min (95% confidence interval [CI] 219.8-630.7 nm min; P < 0.001) for Cofact, and 91 nm min (95% CI - 31.3 to 212.4 nm min; P > 0.05) for Beriplex. Both PCCs returned ETP to pre-apixaban baseline levels 4 h after PCC infusion, versus 45 h for placebo. For both PCCs, mean ETP peaked 21 h after PCC initiation, and then slowly decreased over the following 48 h. Both PCCs reversed apixaban's effect on TGA peak height, PT, and INR. Apixaban pharmacokinetic and anti-FXa profiles were consistent across treatments. Conclusions Cofact and Beriplex reversed apixaban's steady-state effects on several coagulation assessments.

First Evidence: TRAP-Induced Platelet Aggregation Is Reduced in Patients Receiving Xabans

The availability of direct oral anticoagulants has caused a paradigm shift in the management of thrombosis. Rivaroxaban and apixaban are 2 direct oral anticoagulants whose target specificity is activated factor X (FXa). However, it is still not fully understood if and how xabans impact platelet function. This observational study aimed to assess the in vitro platelet function in patients with atrial fibrillation receiving xabans. This was a single-center study quantifying platelet aggregation in 41 patients treated with apixaban or rivaroxaban by light transmission aggregometry. The thrombin receptor activating peptide (TRAP)-induced platelet aggregation was significantly lower 2 hours after taking rivaroxaban or apixaban compared to baseline value (56.15% [8.53%] vs 29.51% [12.9%]; P = .000). Moreover, concomitant use of angiotensin-converting enzyme blockers, proton pump inhibitors, and statins reduces the efficiency of xabans. The TRAP-induced platelet aggregation was reduced in patients with cardiovascular disease 2 hours after receiving xabans.

Resolution of a warfarin and dabigatran-resistant left atrial appendage thrombus with apixaban

The majority of embolisms associated with atrial fibrillation (AF) are from the left atrial appendage (LAA). To treat the existing thrombus, warfarin and novel anticoagulants have been used. However, there has been no clinical information regarding the difference of the effects of congealing the fibrinogenolysis system among these oral anticoagulants. Here, we report a case of persistent AF, in whom apixaban, factor Xa inhibitor resolved an LAA clot refractory to warfarin and direct thrombin inhibition. Factor Xa inhibitor, apixaban, could resolve the left appendage thrombosis refractory to warfarin and dabigatran.

Two-week administration of rivaroxaban resolved left atrial thrombus

An 89-year-old man visited our hospital complaining of palpitation. Electrocardiography showed atrial fibrillation, and transthoracic echocardiography demonstrated a mobile thrombus of 28.6 mm × 20.8 mm in the left atrium. Administration of a direct factor Xa inhibitor rivaroxaban (10 mg/day) was started. The thrombus reduced its size and disappeared completely 2 weeks after the commencement of rivaroxaban treatment. To our knowledge, this is the first case report that rivaroxaban successfully dissolved left atrial thrombus during a short period. Rivaroxaban might have a potential, not only to prevent de novo thrombus formation, but also to dissolve established thrombi by direct inhibition of free and thrombus-associated factor Xa. <Learning objective: The incidence of nonvalvular atrial fibrillation is increasing, and left atrial thrombus is the major cause of cardiogenic thrombo-embolism that we need to prevent. Recently, novel oral anticoagulants have been developed. The effects of these agents on intracardiac thrombus resolution have not been fully elucidated. Data from a large cohort study would be required to assess efficacy of novel oral anticoagulants for thrombus resolution.>.