Survival outcomes of patients with concomitant acute variceal bleeding and acute coronary syndrome, and the role of antiplatelet agents: an institutional experience from a lower middle-income Country

BACKGROUND

There is strong evidence demonstrating the incidence of Acute Coronary Syndrome (ACS) among patients with cirrhosis, with the initiation of antiplatelet therapy being subject to debate due to an increased risk of bleeding. This study aimed to determine mortality among patients presenting with concomitant Acute Variceal Bleeding (AVB) and ACS at Index admission. Furthermore, the recurrence of AVB and ACS among patients discharged with or without antiplatelet therapy was determined.

METHODS

This retrospective study was conducted at the Aga Khan University Hospital, Karachi, Pakistan on patients ≥ 18 years of age admitted to our ER with concomitant ACS and AVB between January 2002 to December 2017. Follow-up for 6 months or till death (if < 6 months), was observed, to help determine the incidence of recurrent AVB and ACS. The incidence of AVB and ACS was then compared amongst patient groups based on the usage of anti-platelet drugs on discharge.

RESULTS

A total of 29 patients were included, with a mean age of 58.7 ± 11.0 years. Seven patients died on admission, having worse underlying liver disease. No mortality was reported among the remaining 22 patients. All 22 patients underwent surveillance endoscopy with variceal band ligation until obliteration, as needed. Only 7 patients from the surviving cohort received antiplatelet therapy. After 6.05 ± 1.1 months of follow-up, 1/22 (4.5%) developed recurrent AVB and 2/22 (9.1%) developed cardiovascular events. Importantly, there was no significant difference in the incidence of recurrent AVB (P = 1.000) and ACS (P = 0.091), depending on the use of antiplatelet therapy.

CONCLUSION

Concomitant AVB and ACS is a severe disorder with increased mortality among cirrhotic patients at presentation. The incidence of AVB does not seem to exacerbate with the use of antiplatelet agents, provided successful obliteration of varices is achieved using elective band ligation.

Microfludic platforms for the evaluation of anti-platelet agent efficacy under hyper-shear conditions associated with ventricular assist devices

Thrombus formation is a major adverse event affecting patients implanted with ventricular assist devices (VADs). Despite anti-thrombotic drug administration, thrombotic events remain frequent within the first year post-implantation. Platelet activation (PA) is an essential process underling thrombotic adverse events in VAD systems. Indeed, abnormal shear forces, correlating with specific flow trajectories of VADs, are strong agonists mediating PA. To date, the ability to determine efficacy of anti-platelet (AP) agents under shear stress conditions is limited. Here, we present a novel microfluidic platform designed to replicate shear stress patterns of a clinical VAD, and use it to compare the efficacy of two AP agents in vitro. Gel-filtered platelets were incubated with i) acetylsalicylic acid (ASA) and ii) ticagrelor, at two different concentrations (ASA: 125 and 250 µM; ticagrelor: 250 and 500 nM) and were circulated in the VAD-emulating microfluidic platform using a peristaltic pump. GFP was collected after 4 and 52 repetitions of exposure to the VAD shear pattern and tested for shear-mediated PA. ASA significantly inhibited PA only at 2-fold higher concentration (250 µM) than therapeutic dose (125 µM). The effect of ticagrelor was not dependent on drug concentration, and did not show significant inhibition with respect to untreated control. This study demonstrates the potential use of microfluidic platforms as means of testing platelet responsiveness and AP drug efficacy under complex and realistic VAD-like shear stress conditions.

Safety and efficacy of anti-thrombotic regimens in patients with percutaneous coronary intervention requiring oral anticoagulation: A traditional and network meta-analysis

BACKGROUND

Previous reports have been inconsistent in generating a consensus for optimal treatment strategy for patients with percutaneous coronary intervention (PCI) who also require oral anticoagulation (OAC). We conducted a traditional and network meta-analysis to evaluate the safety and efficacy of anti-thrombotic regimens in this subset of patients.

METHODS

30 articles were recovered through preferred reporting items for systematic reviews and meta-analyses (PRISMA) using MEDLINE, EMBASE and Cochrane Central Register of Controlled Clinical Trials (CENTRAL) from inception to December 2016.

RESULTS

Dual antiplatelet therapy (DAPT) was found to be the safest treatment modality when compared to triple therapy (TT) or combination of OAC and single antiplatelet agent (OAC+SAP) [Major bleeding: (DAPT vs OAC+SAP: odds ratio (OR), 0.53; 95% credible interval (CrI), 0.30-0.91) (DAPT vs TT: OR, 0.45; 95% CrI, 0.31-0.64)]. There were no significant differences in major adverse cardiovascular events (MACE), myocardial infarction (MI), cardiovascular (CV) or total survival, stent thrombosis or target vessel revascularization (TVR) amongst the three treatment arms. TT was ranked superior for stroke reduction (SUCRA, 69%) followed by OAC+SAP and DAPT. When traditional analysis was adjusted for randomized data, OAC+SAP was equivalent to TT with regards to stroke (OR, 0.74; 95% confidence interval (CI), 0.38-1.46; p=0.39) and showed significant reduction in MACE and total mortality.

CONCLUSION

DAPT was found to be the safest and equally effective regimen when compared to TT and OAC+SAP. However this strategy bears considerable risk to patients with high thromboembolic risk. This issue can be encountered by using OAC+SAP as an alternative of TT in patients with intermediate to high stroke risk and intermediate to high bleeding propensity.

Optimal pediatric dosing of anti-platelet agents for pipeline stent embolization -a case report and review of the literature

BACKGROUND

Various strategies are emerging for dosing antiplatelet therapies in preparation for pipeline stent embolization in adults. Hyper-response is associated with hemorrhagic complications. Hypo-response is associated with thromboembolic events. Dosing of antiplatelet agents is highly variable, with little consensus among experts for adults-and even more so for children. To date, pipeline stents have been deployed in 11 pediatric patients, ages 4-15. A variety of clopidogrel and aspirin dosing regimens have been used, with response tested in only three patients, who were all therapeutic. Thrombotic events occurred in two patients, neither of whom were tested.

CASE

We describe here the first case of a hemorrhagic complication in a hyper-responsive pediatric patient undergoing placement of a pipeline stent.

DISCUSSION

As the use of endovascular therapies requiring dual anti-platelet agents becomes more established, there is an increasing need to develop titration protocols that minimizes the risk of thrombotic and hemorrhagic events.

Effects of vorapaxar on platelet reactivity and biomarker expression in non-ST-elevation acute coronary syndromes. The TRACER Pharmacodynamic Substudy

Vorapaxar is an antagonist of the protease activated receptor-1 (PAR-1), the principal platelet thrombin receptor. The Thrombin Receptor Antagonist for Clinical Event Reduction (TRACER) trial evaluated vorapaxar compared to placebo in non-ST-elevation (NSTE)-acute coronary syndrome (ACS) patients. It was the study's objective to assess the pharmacodynamic effects of vorapaxar versus placebo that included aspirin or a thienopyridine or, frequently, a combination of both agents in NSTE-ACS patients. In a substudy involving 249 patients, platelet aggregation was assessed by light transmittance aggregometry (LTA) in 85 subjects (41 placebo, 44 vorapaxar) using the agonists thrombin receptor activating peptide (TRAP, 15 μM), adenosine diphosphate (ADP, 20 μM), and the combination of collagen-related peptide (2.5 μg/ml) + ADP (5 μM) + TRAP (15 μM) (CAT). VerifyNow® IIb/IIIa and vasodilator-stimulated phosphoprotein (VASP) phosphorylation assays were performed, and platelet PAR-1 expression, plasma platelet/endothelial and inflammatory biomarkers were determined before and during treatment. LTA responses to TRAP and CAT and VerifyNow results were markedly inhibited by vorapaxar. Maximal LTA response to TRAP (median, interquartile range) 2 hours post loading dose: placebo 68% (53-75%) and vorapaxar 3% (2-6%), p<0.0001. ADP inhibition was greater in the vorapaxar group at 4 hours and one month (p<0.01). In contrast to the placebo group, PAR-1 receptor number in the vorapaxar group at one month was significantly lower than the baseline (179 vs 225; p=0.004). There were significant changes in selected biomarker levels between the two treatment groups. In conclusion, vorapaxar caused a potent inhibition of PAR-1-mediated platelet aggregation. Further studies are needed to explore vorapaxar effect on P2Y12 inhibition, PAR-1 expression and biomarkers and its contribution to clinical outcomes.

Blocking the EP3 receptor for PGE2 with DG-041 decreases thrombosis without impairing haemostatic competence

AIMS

Haemostasis interrupts bleeding from disrupted blood vessels by activating platelet aggregation and coagulation. A similar mechanism termed thrombosis generates obstructive thrombi inside diseased arteries. As a consequence of this similarity, current anti-thrombotic agents increase the risk of bleeding. Atherosclerotic plaques produce significant amounts of prostaglandin E2 (PGE2), which activates its receptor EP3 on platelets and aggravates atherothrombosis. We investigated whether blocking EP3 could dissociate atherothrombosis from haemostasis.

METHODS AND RESULTS

Inhibiting in vivo the receptor EP3 for PGE2 with the blocking agent DG-041 reduced murine thrombosis triggered by local delivery of arachidonic acid or ferric chloride on healthy arteries. Importantly, it also reduced thrombosis triggered by scratching murine atherosclerotic plaques. PGE2 was not produced at the bleeding site after tail clipping. Consistently, blocking EP3 did not alter murine tail, liver, or cerebral haemostasis. Furthermore, blocking EP3 reduced murine pulmonary embolism and intensified platelet inhibition by clopidogrel leaving tail bleeding times unchanged. Human atherosclerotic plaques produced PGE2, which facilitated platelet aggregation in human blood and rescued the function of P2Y12-blocked platelets. Finally, in healthy patients, DG-041 reduced platelet aggregation, but did not significantly alter the cutaneous bleeding time at doses up to eight times the dose that inhibited the facilitating effect of PGE2 on platelets.

CONCLUSION

In mice, blocking EP3 inhibited atherothrombosis without affecting haemostasis and intensified efficiency of conventional anti-platelet treatment without aggravating the bleeding risk. In patients, blocking EP3 should improve the prevention of cardiovascular diseases, which is currently limited by the risk of bleeding.