Prognostic value of plasma von Willebrand factor and its cleaving protease ADAMTS13 in patients with atrial fibrillation.

BACKGROUND: The von Willebrand factor (vWF) is essential for platelet adhesion and arterial thrombosis. It is degraded into less active multimers by ADAMTS13. Patients with atrial fibrillation (AF) exhibit higher plasma vWF and lower ADAMTS13 antigen levels. The vWF/ADAMTS13-ratio might help to estimate the pro-thrombotic risk of patients with AF. We therefore investigated whether a high ratio of vWF/ADAMTS13, independently of clinical risk scores, predicts major adverse cardiovascular events (MACE) in patients with AF. METHODS: This prospective longitudinal single center study included 269 patients with AF. Blood samples were analyzed for vWF and ADAMTS13-antigen concentration by means of enzyme-linked immunoassay kits. RESULTS: After adjustment for all univariable predictors for MACE (p ≤ 0.1), ADAMTS13≤49.77% (HR 1.833 (95% CI 1.089-3.086); p=0.023) and vWF/ADAMTS13-ratio>27.57 (HR 2.174 (95% CI 1.238-3.817); p=0.007) remained independently associated with outcome. vWF>1434.92 mU/ml (HR 1.539 (95% CI 0.883-2.682); p=0.128) alone failed to independently predict MACE. In patients with low and intermediate risk for MACE according to the CHADS2-score the addition of high vWF/ADAMTS13-ratio levels (>27.57) had significant impact on the patients' outcome. CONCLUSION: A high ratio of vWF/ADAMTS13 independently predicts MACE in patients with AF. Therefore, vWF and its cleaving protease ADAMTS13 might play an important role in the development and perpetuation of vascular disease in AF patients. This might be a novel target for future treatment strategies or an additional help for risk stratification in AF patients.

Antiplatelet function variability in clopidogrel-treated patients: need for new antiplatelet agents.

Antiplatelet therapy is obligatory in patients with coronary artery disease (CAD) both in acute coronary syndromes (ACS) and in secondary prevention. Aspirin in combination with clopidogrel has been recommended as the main therapeutic regimen for many years. However, the high inter-individual variability of platelet aggregation seen with clopidogrel, caused by the underlying disease (more pronounced in diabetic patients and patients with ACS), drug interactions as well as by genetic variants leading to a reduced formation of the active metabolite of the prodrug clopidogrel, has confronted clinical practice with increasing numbers of adverse clinical events in patients following an ACS. Therefore, new antiplatelet agents have been investigated showing a more favorable efficacy/safety profile. Prasugrel as well as ticagrelor are meanwhile part of the recently published revascularization guidelines of the European Society of Cardiology based on their favorable results with respect to reducing a combined ischemic efficacy endpoint in patients with ACS in the TRITON-TIMI-38 (prasugrel) and PLATO (ticagrelor) trials. Different to clopidogrel, their effects are independent of genetic variants and also drug interactions seem neglectable. This article discusses the reasons for antiplatelet function variability of clopidogrel and presents clinical data of the new ADP-receptor inhibitors by reviewing the recently published trials and prespecified post hoc analyses of these trials as well as the potential use of the new antiplatelet agents in the near future.

New anticoagulants for the prevention of stroke in atrial fibrillation.

Oral anticoagulation in atrial fibrillation is obligatory to lower the risk of spontaneous cerebrovascular and systemic thromboembolism. For this purpose, vitamin K antagonists (coumarins) have been recommended as the most effective drugs for a long time. However, problems with the practical use of these agents, e.g. the need for frequent and regular coagulation controls, the inter-individual differences in maintaining a stable therapeutic range, as well as drug or food interactions, have led to the search and investigation of alternative compounds characterized by a more simple use (e.g. without regular controls of therapeutic levels), high efficacy, as well as low risk of bleeding. The direct thrombin inhibitor dabigatran and the direct factor Xa inhibitors rivaroxaban and apixaban have recently been investigated to prove whether they fulfill the high expectancy of an ideal anticoagulant with respect to a more favorable efficacy/safety profile and without the need for coagulation controls, thereby improving quality of life. Dabigatran (RE-LY) achieved an impressive reduction in stroke and non-central nervous system (non-CNS) embolism (110 mg: 1.5%/year; 150 mg: 1.1%/year) in contrast to warfarin (1.7%/year; P = 0.34 and P < 0.001) with a favorable action on bleeding hazards. The results of rivaroxaban which were obtained in the ROCKET AF study (on treatment analysis: stroke and non-CNS embolism: 1.7%/year vs. 2.15%/year with warfarin; P = 0.015; primary safety endpoint major and minor bleeding: 14.91 vs. 14.52%; P = 0.442) point in the same direction. And finally, compared to aspirin, apixaban reduced the combined primary efficacy endpoint by 52% with comparable rates of bleeding (AVERROES). This review gives a summary of the current knowledge about these agents and their potential future importance.

The role of ST-segment elevation in lead aVR in the risk assessment of patients with acute pulmonary embolism.

UNLABELLED: BACKGROUD AND AIM: Patients with acute pulmonary embolism (APE) present with highly variable symptoms and ECG abnormalities. As ST-elevation in lead aVR has recently been described to predict right ventricular dysfunction (RVD), we aimed to correlate this sign to the severity of APE. METHODS: Three-hundred ninety-six consecutive patients (in centers a and b) with proven APE were retrospectively analysed with respect to 12-lead-ECG, symptoms, thrombus location, echocardiograpy, troponin T, initial therapy and outcome. Data were then compared between patients with and without aVR-ST-elevation. RESULTS: On admission aVR-ST-elevation was present in 34.3% (n = 136). Presence of aVR-ST-elevation was assossiated with more severe clinical presentation (dyspnoea at rest 44.9 vs. 29.2%; p = 0.002, hypotension 17.0 vs. 6.5%; p = 0.001, syncope 16.2 vs. 6.5%; p = 0.002), higher median troponin T levels (0.035 [0.01-0.2] versus 0.01 [0.01-0.02]; p < 0.001), more frequent RVD (74.5 vs. 46.6%; p < 0.001) and central located thrombi (50.8 vs. 29.2; p < 0.001). Thrombolysis was used more frequently (29.1 vs. 7.5%; p < 0.001) and in-hospital-mortality was increased (10.3 vs. 5.4%; p = 0.07) when compared to patients without that sign. Mortality in intermediate-risk APE patients with aVR-ST-elevation was 8.9% compared to 0% in those without (p = 0.04). In contrast, the presence of other classical ECG pattern of APE did not further increase mortality in intermediate-risk patients. CONCLUSIONS: ST-elevation in lead aVR is associated with a more severe course of APE, especially in patients with intermediate-risk. Therefore, aVR-ST-elevation might be useful in risk stratification of APE.

Oral antiplatelet therapy in acute coronary syndromes: update 2012.

Dual antiplatelet therapy (DAPT), usually consisting of clopidogrel and acetylsalicylic acid (ASA), has come into discussion in recent years due to an increasing number of major adverse cardiac events based on insufficient ADP-mediated platelet inhibition with clopidogrel, mainly explained by drug interactions or genetic variants slowing or hindering the bioactivation of the prodrug clopidgrel into an active metabolite. Accordingly, new antiplatelet agents like prasugrel and ticagrelor were investigated in large prospective randomized clinical trials in patients with different entities of acute coronary syndromes (ACS). Based on their beneficial results in comparison to clopidogrel, these agents have found their way into the recent international guidelines for treatment of patients with acute coronary syndromes. Both antiplatelet agents demonstrated superiority with respect to the primary composite endpoint (cardiovascular death/non-lethal myocardial infarction/stroke). Ticagrelor even exhibited a mortality benefit over the comparator, but both compounds also increased the risk of spontaneous major bleedings to a significant extent. However, the efficacy/safety ratio of prasugrel and ticagrelor compared to clopidogrel is better. This article widens the insight into the recent changes in antiplatelet therapy in ACS by discussing the clinically most important data derived from the TRITON-TIMI 38 trial and the PLATO trial, including also the retrospective and pre-defined subgroup analyses. This article also gives information about the recommended duration of DAPT and the situation when patients who need permanent anticoagulation (e.g. in case of non-valvular atrial fibrillation) deserve also DAPT after coronary stenting ('triple therapy').

New oral anticoagulant agents after ACS.

Despite tremendous progress in the management of patients with an acute coronary syndrome (ACS), morbidity and mortality remains high even in stable patients after discharge. The benefit of adding vitamin K antagonists (VKA) on top of antiplatelet therapy to prevent recurrent ischaemic events after an ACS has been successfully studied in the past. Because of their need for frequent monitoring and drug and food interactions, however, systematic long-term use of VKA has not been recommended in this setting. The new oral anticoagulants offer several advantages compared to VKA, including a faster onset and offset of action and the absence of frequent monitoring. In this review, we evaluate the current evidence and practical consequences of using the oral direct thrombin inhibitor dabigatran or the oral anti factor Xa inhibitors apixaban, rivaroxaban, and darexaban in stable ACS patients.

The Occluded Artery Trial (OAT) Viability Ancillary Study (OAT-NUC): influence of infarct zone viability on left ventricular remodeling after percutaneous coronary intervention versus optimal medical therapy alone.

BACKGROUND: The Occluded Artery Trial (OAT) showed no difference in outcomes between percutaneous coronary intervention (PCI) versus optimal medical therapy (MED) in patients with persistent total occlusion of the infarct-related artery 3 to 28 days post-myocardial infarction. Whether PCI may benefit a subset of patients with preservation of infarct zone (IZ) viability is unknown. METHODS AND RESULTS: The OAT nuclear ancillary study hypothesized that (1) IZ viability influences left ventricular (LV) remodeling and that (2) PCI as compared with MED attenuates adverse remodeling in post-myocardial infarction patients with preserved viability. Enrolled were 124 OAT patients who underwent resting nitroglycerin-enhanced technetium-99m sestamibi single-photon emission computed tomography (SPECT) before OAT randomization, with repeat imaging at 1 year. All images were quantitatively analyzed for infarct size, IZ viability, LV volumes, and function in a core laboratory. At baseline, mean infarct size was 26% ± 18 of the LV, mean IZ viability was 43% ± 8 of peak uptake, and most patients (70%) had at least moderately retained IZ viability. There were no significant differences in 1-year end-diastolic or end-systolic volume change between those with severely reduced versus moderately retained IZ viability, or when compared by treatment assignment PCI versus MED. In multivariable models, increasing baseline viability independently predicted improvement in ejection fraction (P = .005). There was no interaction between IZ viability and treatment assignment for any measure of LV remodeling. CONCLUSIONS: In the contemporary era of MED, PCI of the infarct-related artery compared with MED alone does not impact LV remodeling irrespective of IZ viability.

Levels of von Willebrand factor and ADAMTS13 determine clinical outcome after cardioversion for atrial fibrillation.

Von Willebrand factor (vWF) plays an essential role in platelet adhesion and thrombus formation. Patients with atrial fibrillation (AF) exhibit higher plasma vWF and lower ADAMTS13 antigen levels compared to controls. Little is known about vWF and ADAMTS13 in AF patients treated with cardioversion (CV). Thus we investigated the alterations of plasma vWF and ADAMTS13 after CV and evaluated the predictive value of these parameters for recurrence of AF. In this observational study we determined plasma levels of vWF and ADAMTS13 in 77 patients before and immediately after CV, as well as 24 hours (h) and six weeks thereafter, by means of commercially available assays. The vWF/ADAMTS13-ratio was significantly elevated immediately after CV (p=0.02) and 24 h after CV (p=0.002) as compared to baseline levels. ADAMTS13, 24 h after CV, exhibited a significant association with recurrence of AF (HR: 0.97; p=0.037). Accordingly, tertiles of ADAMTS13 showed a stepwise inverse correlation with the risk of recurrent AF (HR: 0.50; p=0.009). After adjustment for confounders, ADAMTS13 remained significant as an independent predictor of recurrent AF (HR: 0.61; p=0.047). Similarly, the vWF/ADAMTS13-ratio, 24 h after CV, was associated with rhythm stability and remained an independent predictor of recurrent AF (HR: 1.88; p=0.028). The regulation of vWF and its cleaving protease ADAMTS13 after CV might play a critical role in producing a pro-thrombotic milieu immediately after CV for AF. Since ADAMTS13 plasma concentration and the vWF/ADAMTS13-ratio are independently associated with rhythm stability, these indexes might be used for prediction of recurrence of AF.

Antithrombotic therapy in patients with coronary artery disease and with type 2 diabetes mellitus.

Diabetes mellitus (DM) is a life-threatening disease. Patients with DM have a 2- to 4-fold higher risk of developing cardiovascular disease compared to their non-diabetic counterparts. Several drugs are available for the treatment of stable coronary artery disease (CAD) and acute coronary syndrome (ACS). Among oral antiplatelet agents (acetylsalicylic acid, ticlopidine, clopidogrel, and prasugrel), prasugrel has shown the highest efficacy in patients with DM and ACS. The use of glycoprotein IIb-IIIa receptor inhibitors in diabetic subjects with ACS undergoing percutaneous coronary intervention (PCI) reduces adverse clinical events in a greater extent than in non-diabetics. Several direct and indirect antithrombins are recommended for the treatment of ACS such as unfractionated heparin (UFH), enoxaparin, fondaparinux, and bivalirudin. Enoxaparin and bivalirudin have been shown to be superior to UFH among patients with ST-elevation MI (STEMI) and non-ST elevation MI (NSTEMI) also in diabetic subgroup analyses.

Antiplatelet drug induced isolated profound thrombocytopenia in interventional cardiology: a review based on individual case reports.

A combination antithrombotic and antiplatelet therapy with clopidogrel, aspirin, glycoprotein IIb/IIIa receptor inhibitors and heparins is routinely used as adjunct therapy in patients undergoing percutaneous coronary intervention (PCI). As all substances inhibit platelet function, bleeding and thrombocytopenia may occur. We report on three patients who developed isolated profound thrombocytopenia (platelet count of < 20,000/mm(3)) within 24 h after initiation of combination antiplatelet and antithrombotic therapy during a 1 year observation period in 443 consecutive patients undergoing PCI and stent implantation. The data from our cardiology unit revealed an incidence of an isolated profound thrombocytopenia in 0.7% of all patients on combination antithrombotic therapy and in 1.5% of patients with GPIIb/IIIa-blockers. In all three cases with isolated profound thrombocytopenia GPIIb/IIIa-blockers were found to be the causative agents. Negative results of HIT-assays excluded heparin induced thrombocytopenia type II. Despite the extremely low platelet count no severe bleeding was observed and in all cases platelet counts normalized within 3-4 days without specific interventions except discontinuation of the responsible agent. These findings are discussed in conjunct with an overview of the recent literature.

[Direct and indirect antithrombins in acute coronary syndromes]. / Direkte und indirekte Antithrombine bei akuten Coronarsyndromen.

Unfractionated heparin (UFH) as well as low-molecular-weight heparins (LMWH), especially enoxaparin, are recommended by the current international guidelines for routine used in the conservative treatment of patients with acute coronary syndromes (ACS). UFH is still the recommended antithrombin as soon as percutaneous coronary interventions (PCI) are performed, although the results of different trials clearly have demonstrated the benefit of enoxaparin also in interventional cardiology. Bleeding complications along PCI procedures can be minimized by avoiding crossover from enoxaparin to UFH or vice versa and by reducing the dosage of indirect antithrombins, particularly of enoxaparin, in patients with chronic renal dysfunction and/or the elderly. Especially for those patient groups, bivalirudin offers already today an effective alternative. There is increasing expectation concerning the use of bivalirudin in patients undergoing PCI procedures but firm data exist at present only for low- and medium-risk patients with non ST-elevation ACS. Results of still ongoing trials (ACUITY, HORIZONS) will help to further confirm the role of bivalirudin in patients with high-risk acute coronary syndromes. For other direct antithrombins, e.g., fondaparinux (a pentasaccharide) or melagatran, comparably few data are available at present. Whether these agents will make their way into clinical use, future will tell.

Synergistic cytotoxicity of the ribonucleotide reductase inhibitor didox (3,4-dihydroxy-benzohydroxamic acid) and the alkylating agent carmustine (BCNU) in 9L rat gliosarcoma cells and DAOY human medulloblastoma cells.

PURPOSE: Ribonucleotide reductase (RR) is the rate-limiting enzyme of de novo DNA synthesis and has been shown to be upregulated linked with proliferation and malignant transformation. It was therefore identified as an excellent target for antitumor therapy. In the present study we investigated the biochemical and cytotoxic effects of didox, an inhibitor of RR, as a single agent and in combination with BCNU, an alkylating anticancer drug, in 9L rat gliosarcoma cells and DAOY human medulloblastoma cells. METHODS: The effect of didox on the intracellular concentrations of deoxynucleosidetriphosphates (dNTPs) was studied in 9L cells. Pool sizes were determined by HPLC. In addition, the cytotoxic effects of didox and BCNU as single drugs and in equimolar combination were tested in 9L and in DAOY cells. Combination effects were determined according to the equation of Chou and Talalay. The expression of DNA repair-related genes was determined after exposure of 9L cells to BCNU, didox and a combination of the two compounds, using a cDNA array. RESULTS: Incubation of 9L cells with 30 microM didox for 24 h significantly decreased the intracellular concentrations of the DNA precursors dCTP (61% of control) and dGTP (17% of control), and significantly increased the concentration of dATP (155% of control). This dNTP imbalance compromised DNA synthesis and repair and might therefore have been, at least in part, responsible for the highly synergistic cytotoxic effects seen when BCNU was used simultaneously with didox in 9L and in DAOY cells. With almost all combinations tested, highly synergistic effects were seen, as indicated by combination indices of <1 according to the equation of Chou and Talalay. In 9L cells, BCNU upregulated the expression of DNA repair-associated genes, whereas coincubation of the cells with didox reduced overexpression of some of these repair-related genes. CONCLUSION: A combination of BCNU and didox was proven to act in a synergistic manner in two cell lines, 9L rat gliosarcoma and DAOY human medulloblastoma cells. Further in vivo tests using these two compounds systemically and/or locally at the tumor site might be warranted.

Biochemical modulation of Ara-C effects by amidox, an inhibitor of ribonucleotide reductase in HL-60 promyelocytic human leukemia cells.

Amidox, a new polyhydroxy-substituted benzoic acid derivative, is a potent inhibitor of the enzyme ribonucleotide reductase (RR), which catalyses the de novo synthesis of DNA. RR is considered to be an excellent target for anti cancer chemotherapy. We investigated the biochemical and antineoplastic effects of amidox as a single agent and in combination with Ara-C in human HL-60 promyelocytic leukemia cells. Amidox inhibited the growth of HL-60 cells in a growth inhibition assay with an IC50 of 25 microM. In a soft agar colony forming assay, amidox yielded a 50% inhibition of colony formation at 13 microM. We also investigated the effects of amidox treatment on the formation of deoxynucleosidetriphosphates. Amidox (50 and 75 microM for 24 hours) could significantly decrease intracellular concentrations of dCTP, dATP and dGTP pools, whereas dTTP levels increased. We then tested the combination effects of amidox with Ara-C; this combination yielded additive cytotoxic effects both in growth inhibition and in soft agar colony formation assays. This effect was due to the increased formation of Ara-CTP, the active metabolite of Ara-C, after preincubation with amidox. Preincubation of HL-60 cells with 75 and 100 microM amidox for 24 hours caused an increase in the intracellular Ara-CTP concentrations by 576% and 1143%, respectively. Therefore amidox might offer an additional option for the treatment of leukemia and thus be further investigated in in vivo studies as a single agent and in combination with Ara-C.

Combination effects of Ara-C and 5-fluorodeoxyuridine against leukemia cells in vitro and in mice.

BACKGROUND: Ara-C (1-beta-D-arabinofuranosylcytosine) is widely used for treatment of human leukemia. However, due to emergence of resistance, new drug combinations need to be developed. MATERIALS AND METHODS: We tested the combination of Ara-C with 5-FdUrd (5-fluorodeoxyuridine) in L1210 and P388D1 mouse leukemia cells in vitro and in vivo by growth inhibition and recovery assay in leukemia-bearing mice. RESULTS: Simultaneous incubation of cells with Ara-C and 5-FdUrd yielded more than additive effects for most combinations in both cell lines; synergy was seen in P388D1 cells. P388D1 cells showed delayed growth after treatment with Ara-C or 5-FdUrd in a growth recovery assay. In animal studies, simultaneous subcutaneous administration of the compounds did not show any significant beneficial effects as compared with monotherapy. Intraperitoneal administration of both compounds, however, significantly prolonged the survival of P388D1 animals. CONCLUSION: Depending on cell type and route of drug administration, the combination of Ara-C and 5-FdUrd might offer a promising additional treatment option for leukemia.

Trimidox, an inhibitor of ribonucleotide reductase, synergistically enhances the inhibition of colony formation by Ara-C in HL-60 human promyelocytic leukemia cells.

Ribonucleotide reductase is the rate-limiting enzyme for the de novo synthesis of deoxynucleoside triphosphates and therefore represents a good target for cancer chemotherapy. Trimidox (3,4,5-trihydroxybenzamidoxime) was identified as a potent inhibitor of this enzyme and was shown to significantly decrease deoxycytidine triphosphate (dCTP) pools in HL-60 leukemia cells. We now investigated the ability of trimidox to increase the antitumor effect of 1-beta-D-arabinofuranosyl cytosine (Ara-C). Ara-C is phosphorylated by deoxycytidine kinase, which is subject to negative allosteric regulation by dCTP. Therefore, a decrease of dCTP may cause increased Ara-C phosphorylation and enhanced incorporation of Ara-C into DNA. Ara-C incorporation indeed increased 1.51- and 1.89-fold after preincubation with 75 and 100 microM trimidox, respectively. This was due to the significantly increased 1-beta-D-arabinofuranosyl cytosine triphosphate pools (1.9- and 2.5-fold) after preincubation with trimidox. We also investigated the effects of a combination of trimidox and Ara-C on the colony formation of HL-60 cells. A synergistic potentiation of the effect of Ara-C could be observed, when trimidox was added. Trimidox, which decreases intracellular deoxynucleoside triphosphate concentrations thus leading to apoptosis, enhanced the induction of apoptosis caused by Ara-C. We conclude, that trimidox is capable of synergistically enhancing the effects of Ara-C and therefore this drug combination might be further tested in animals.