Interaction of heparin with human cardiac troponin complex and its influence on the immunodetection of troponins in human blood samples.

OBJECTIVES: Heparin is a highly charged polysaccharide used as an anticoagulant to prevent blood coagulation in patients with presumed myocardial infarction and to prepare heparin plasma samples for laboratory tests. There are conflicting data regarding the effects of heparin on the measurement of cardiac isoforms of troponin I (cTnI) and troponin T (cTnT), which are used for the immunodiagnosis of acute myocardial infarction. In this study, we investigated the influence of heparin on the immunodetection of human cardiac troponins. METHODS: Gel filtration (GF) techniques and sandwich fluoroimmunoassay were performed. The regions of сTnI and cTnT that are affected by heparin were investigated with a panel of anti-cTnI and anti-cTnT monoclonal antibodies, specific to different epitopes. RESULTS: Heparin was shown to bind to the human cardiac full-size ternary troponin complex (ITC-complex) and free cTnT, which increased their apparent molecular weights in GF studies. Heparin did not bind to the low molecular weight ITC-complex and to binary cTnI-troponin С complex. We did not detect any sites on cTnI in the ITC-complex that were specifically affected by heparin. In contrast, cTnT regions limited to approximately 69-99, 119-138 and 145-164 amino acid residues (aar) in the ITC-complex and a region that lies approximately between 236 and 255 aar of free cTnT were prone to heparin influence. CONCLUSIONS: Heparin binds to the ITC-complex via cTnT, interacting with several sites on the N-terminal and/or central parts of the cTnT molecule, which might influence the immunodetection of analytes in human blood.

Effects of Antiplatelet Drugs on Platelet-Dependent Coagulation Reactions.

Activated platelets are involved in blood coagulation by exposing phosphatidylserine (PS), which serves as a substrate for assembling coagulation complexes. Platelets accelerate fibrin formation and thrombin generation, two final reactions of the coagulation cascade. We investigated the effects of antiplatelet drugs on platelet impact in these reactions and platelet ability to expose PS. Washed human platelets were incubated with acetylsalicylic acid (ASA), ticagrelor, ASA in combination with ticagrelor, ruciromab (glycoprotein IIb-IIIa antagonist), or prostaglandin E1 (PGE1). Platelets were not activated or activated by collagen and sedimented in multiwell plates, and plasma was added after supernatant removal. Fibrin formation (clotting) was monitored in a recalcification assay by light absorbance and thrombin generation in a fluorogenic test. PS exposure was assessed by annexin V staining using flow cytometry. Ticagrelor (alone and in combination with ASA), ruciromab, and PGE1, but not ASA, prolonged the lag phase and decreased the maximum rate of plasma clotting and decreased the peak and maximum rate of thrombin generation. Inhibition was observed when platelets were not treated with exogenous agonists (activation by endogenous thrombin) and pretreated with collagen. Ticagrelor (alone and in combination with ASA), ruciromab, and PGE1, but not ASA, decreased PS exposure on washed platelets activated by thrombin and by thrombin + collagen. PS exposure on activated platelets in whole blood was lower in patients with acute coronary syndrome receiving ticagrelor + ASA in comparison with donors free of medications. These results indicate that antiplatelet drugs are able to suppress platelet coagulation activity not only in vitro but also after administration to patients.

Comparative Safety and Efficacy of Left Atrial Appendage Occlusion with the Watchman Device and Amplatzer Cardiac Plug: Results of the Russian National Registry.

PURPOSE: This multicenter, prospective registry evaluated the comparative safety and efficacy of left atrial appendage occlusion (LAAO) using the Watchman device (WD) and the Amplatzer Cardiac Plug (ACP) in patients with nonvalvular atrial fibrillation (NVAF) in real-world clinical practice in Russia. METHODS: The study included data from 200 consecutive NVAF patients (66.8 ± 7.8 years, 44.5% female, median CHA2DS2VASc 4, median HAS-BLED 3) who had undergone LAAO implantation using WD (n = 108) or ACP (n = 92) from September 2015 to December 2017 in 5 medical centers in Russia. The primary safety endpoint was the procedure-related major adverse events, and the primary efficacy endpoint was the composite of thromboembolic events, device thrombosis, hemorrhagic events, and unexplained death during the 12-month follow-up. RESULTS: Successful LAAO was performed in all 92 (100%) patients with ACP and 105 (97.2%) with WD (p = 0.053). At 12 months, primary safety endpoint occurred in 6.5% of patients in the ACP group with no events in the WD group (6.5% vs. 0%, p = 0.008). During the 12-month follow-up, the primary efficacy endpoint has occurred in 8.3% of patients in the WD group (n = 9) and 1.1% of patients in the ACP group (n = 1) (p = 0.016). CONCLUSIONS: In this multicenter prospective registry, LAA closure with the WD was associated with significantly higher thromboembolic events rate in NVAF patients. Patients, receiving the ACP, had more procedure-related major adverse events. However, further multicenter studies are necessary to evaluate these findings.