Platelet inhibition beyond conventional antiplatelet agents: expanding role of angiotensin receptor blockers, statins and selective serotonin reuptake inhibitors

SSRI/SNRI Therapy is Associated With a Higher Risk of Gastrointestinal Bleeding in LVAD Patients

BACKGROUND

Gastrointestinal bleeding (GIB) is common in left ventricular assist device (LVAD) patients. Serotonin release from platelets promotes platelet aggregation, and selective serotonin reuptake inhibitor/serotonin-norepinephrine reuptake inhibitor (SSRI/SNRI) therapy inhibits the transporter responsible for re-uptake.

METHODS

We reviewed the records of LVAD (HeartMateII™, Abbott Medical, Lake Bluff, IL, USA and Heartware™, Medtronic, Minneapolis, MN, USA) patients at the Medical University of South Carolina and Johns Hopkins Hospital between January 2009 and January 2016. After exclusions, 248 patients were included for analysis. After univariate analysis, logistic regression multivariate analysis was performed to adjust for any demographic, cardiovascular, and laboratory data variables found to be associated with GI bleeding post-LVAD.

RESULTS

Gastrointestinal bleeding occurred in 85 patients (35%) with 55% of GIBs due to arteriovenous malformations (AVMs). Of the total cohort, 105 patients received an SSRI or SNRI during LVAD support. Forty-four (44) SSRI/SNRI (41.9%) and 41 non-SSRI/SNRI (28.7%) patients had a GIB (RR 1.46, p = 0.03). Twenty-six (26) (24.8%) of the SSRI/SNRI patients had a GIB due to AVMs versus 21 (14.7%) of the non-SSRI/SNRI patients (RR 1.69, p = 0.05). In fully-adjusted multivariate regression analysis, SSRI/SNRI therapy was independently associated with GIB (OR 1.78, p = 0.045). For GIB, the number needed to harm (NNH) was 7.6.

CONCLUSION

In conclusion, SSRI/SNRI therapy is independently associated with an increased risk of GIB in LVAD patients.

High proportion of patients with bleeding of unknown cause in persons with a mild-to-moderate bleeding tendency: Results from the Vienna Bleeding Biobank (VIBB)

INTRODUCTION

Data on clinical characteristics and the prevalence of underlying coagulopathies in patients with mild-to-moderate bleeding disorders (MBDs) are scarce.

AIM

We established the Vienna Bleeding Biobank (VIBB) to characterize and thoroughly investigate Austrian patients with MBDs.

RESULTS

Four hundred eighteen patients (female = 345, 82.5%) were included. A platelet function defect (PFD) was diagnosed in 26 (6.2%) and a possible PFD in 30 (7.2%) patients. Eight patients (1.9%) were diagnosed with von Willebrand disease (VWD) (type 1 n = 6; type 2 n = 2), and 29 patients had low VWF (30-50 IU/dL). Deficiencies in factor VIII, IX, XI or XIII were found in 11 (2.6%), 3 (0.7%), 3 (0.7%) and 1 patient(s), 2 patients had dysfibrinogenaemia, and further 2 had possible PFD and FXI deficiency. Probable causal mutations were detected in 8 of 11 patients with FVIII deficiency, 2 of 3 patients with FIX deficiency and 2 of 8 patients with VWD. Three hundred three patients (72.5%) had normal results in the coagulation assays and were categorized as patients with bleeding of unknown cause (BUC). The bleeding score did not differ between patients with and without established diagnosis. A diagnosis of a bleeding disorder was more frequently made in men than in women (49.3% vs 22.9%). Male sex (OR 3.55, 95% CI: 2.02-6.22; P < .001) and blood group 0 (OR 1.86, 95% CI: 1.17-2.94; P = .008) were independently associated with diagnosis of a bleeding disorder.

CONCLUSION

The high rate of patients with BUC despite in-depth haemostatic assessment underlines the incompleteness of available routine laboratory tests. Males with MBDs were more likely to be diagnosed with an established bleeding disorder than females.

Do the Effects of Secondary Prevention of Cardiovascular Events in PAD Patients Differ from Other Atherosclerotic Disease?

Atherosclerosis is considered a generalized disease. Similar or identical etiopathogenetic mechanisms and risk factors are involved in various atherosclerotic diseases, and the positive effects of preventive measures on atherogenesis in different parts of the arterial system were shown. However, until know, great emphasis has been placed on the aggressive pharmacological management of coronary artery disease (CHD), while less attention has been devoted to the management of peripheral arterial disease (PAD), despite its significant morbidity and mortality. Data on the efficacy of preventive measures in PAD patients have mostly been gained from subgroup analyses from studies devoted primarily to the management of coronary patients. These data have shown that treatment of risk factors for atherosclerosis with drugs can reduce cardiovascular events also in patients with PAD. The effects of some preventive procedures in PAD patients differ from coronary patients. Aspirin as a basic antiplatelet drug has been shown to be less effective in PAD patients than in coronary patients. The latest Antithrombotic Trialists' Collaboration (ATC) meta-analysis demonstrates no benefit of aspirin in reducing cardiovascular events in PAD. Statins reduce cardiovascular events in all three of the most frequently presented cardiovascular diseases, including PAD to a comparable extent. Recent studies indicate that in PAD patients, in addition to a reduction in cardiovascular events, statins may have some hemodynamic effects. They prolong walking distance and improve quality of life. Similarly, angiotensin enzyme inhibitors are also effective in the prevention of cardiovascular events in coronary, cerebrovascular, as well as PAD patients and show positive effects on the walking capacity of patients with intermittent claudication. In PAD patients, the treatment of hypertension and diabetes also effectively prevents cardiovascular morbidity and mortality. As PAD patients are at a highest risk of cardiovascular complications, the risk factors of atherosclerosis should be treated intensively in this group of patients. Most of the preventive measures, including the drugs used for prevention of CHD, are also effective in PAD patients.

A brief review on high on-aspirin residual platelet reactivity

Although aspirin is effective in secondary prevention in coronary heart disease, new thromboembolic events in patients on aspirin are frequently seen. In trials on aspirin-treated patients, platelet function tests have revealed large variability in platelet aggregation. This phenomenon has been named aspirin resistance, aspirin non-responsiveness or high-on-aspirin residual platelet reactivity. The mechanism of aspirin antiplatelet effect is due to the inhibition of cyclooxygenase-1 enzyme in platelets. In some trials, almost all patients on aspirin have a very low level of serum thromboxane B2, indicating that the measured platelet reactivity in aspirin-treated patients might be due to platelet activation via other pathways, such as ADP or thrombin. The prevalence of real aspirin resistance seems to be very low, and probably the term "high-on-aspirin residual platelet reactivity" should be preferred to describe this phenomenon.

Tranexamic Acid Tamponade to Control Postoperative Surgical Hemorrhage

When preparing for oral surgery, patients taking anticoagulants usually should not discontinue their medication because of the risk of a thromboembolic event. The therapeutic effect of many anticoagulants is not readily measured, so preoperatively, the surgeon cannot know the true risk for postoperative hemorrhage. The risk of a thromboembolic event usually outweighs the concerns of controlling postoperative hemorrhage. Hemophilia patients are also at risk for postoperative bleeding. Single extractions probably do not pose a serious risk for postoperative hemorrhage. However, when a mucogingival flap is raised in these patients, there may be prolonged bleeding. Surgical sponges saturated with aqueous tranexamic acid solution and compressed onto the bleeding site with biting pressure may stop bleeding. Bleeding was stopped in the case example presented here after three 10-minute compressions over 30 minutes in a patient taking aspirin and clopidogrel for a previous thromboembolic event and a metal coronary stent. The clot formed is very fragile and is prone to bleeding, so it should not be disturbed. This technique needs to be studied for efficacy.

Selective serotonin reuptake inhibitors reduce P2Y12 receptor-mediated amplification of platelet aggregation

Selective serotonin reuptake inhibitors (SSRIs) have been reported to reduce platelet aggregation induced by ADP. ADP induces platelet aggregation through two purinergic receptors P2Y1 and P2Y12. We characterized the inhibitory properties of SSRIs on ADP-induced platelet aggregation and investigated the effects of SSRIs on the signaling pathways downstream of P2Y1 and P2Y12 receptors. Specific antagonists were used to evaluate which purinergic receptor-mediated aggregation was influenced by SSRIs. The primary phase of ADP-induced aggregation was not inhibited by citalopram. Citalopram failed to influence ADP-induced platelet shape change, intracellular calcium mobilization and the early phosphorylation of PKCα. Differently, citalopram inhibited the secondary phase of ADP-induced platelet aggregation in a concentration-dependent manner. Other SSRIs, including fluoxetine and sertraline, exhibited the same anti-platelet effects. Under P2Y1 blockade, citalopram inhibited platelet aggregation and integrin αIIbβ3 activation in response to ADP, indicating that citalopram inhibited P2Y12-mediated aggregation. Citalopram concentration-dependently inhibited the phosphorylation of Akt, GSK3β, p38 MAPK and Syk induced by ADP, but showed no effect on the decrease of cAMP and VASP phosphorylation. With integrin αIIbβ3 blockade, however, the phosphorylation of Akt triggered by ADP was unaltered by the addition of citalopram. Taken together, under the stimulation of ADP, SSRIs inhibit the amplification of platelet aggregation secondary to the activation of P2Y12 receptor, and subsequently reduce the activation of the downstream molecules of the outside-in signaling pathways.

Measurement of collagen- and serotonin-induced platelet aggregation in whole blood

Upon erosion and rupture of an atherosclerotic plaque, collagen and serotonin (5-hydroxytyramine [5-HT]) induce a process of simultaneous platelet aggregation and vasoconstriction. Simultaneous inhibition of these pathophysiological processes, attainable by 5-HT inhibition, is a potential drug target and could offer an attractive treatment modality. The availability of a reliable and accurate test to measure inhibition of 5-HT-induced platelet aggregation would facilitate the rational development of such new compounds. Therefore, we developed a validated method to measure the additive effect of 5-HT on platelet aggregation in human whole blood after an initial induction by a low-concentration collagen, using impedance aggregometry. This method is feasible to measure 5-HT-induced platelet aggregation in whole blood for the evaluation of promising platelet aggregation inhibitors possessing 5-HT antagonistic activity. The availability of this method will support and stimulate selective 5-HT antagonism as effective management of thrombosis.

Effects of selective serotonin reuptake inhibitors on platelet function: mechanisms, clinical outcomes and implications for use in elderly patients

Among the antidepressants, the selective serotonin reuptake inhibitors (SSRIs) are often preferred to other classes of antidepressants in the treatment of depression in the elderly because of their better safety profile. Most of the known effects of SSRIs, either beneficial or adverse, are linked to their inhibitory action on the serotonin reuptake transporter (5-HTT). This reuptake mechanism is present not only in neurons but also in other cells such as platelets. Serotoninergic mechanisms seem to play an important role in haemostasis, and their importance in this regard has long been underestimated. Abnormal activation may lead to a pro-thrombotic state, as may occur in patients with major depressive disorder, whilst downregulation, as occurs in patients treated with SSRIs, may have two clinical consequences, both of particular interest in the elderly. On the one hand, there may be an increased risk of bleeding; on the other hand, a reduction in thrombotic risk may be possible. Polymorphism in the promoter region of the gene that transcribes the 5-HTT has been shown to have a relevant impact on its function and, in turn, on the beneficial and adverse effects of SSRIs. Bleeding has been a concern since the introduction of SSRIs, with multiple case reports published and communicated to the pharmacovigilance systems. The first epidemiological study was published in 1999 and since then, 34 epidemiological studies from different areas, most of them including elderly patients in their study populations, have been published with a variety of results. Broadly, the epidemiological evidence supports a moderately increased risk of bleeding associated with the use of SSRIs, which may be critically dependent on patient susceptibility and the presence of risk factors. The impairment of primary haemostasis induced by SSRIs may result, as a beneficial counterpart, in a reduction in the thrombotic risk. A small number of clinical trials and an increasing number of epidemiological studies that include elderly patients have been conducted to clarify whether SSRIs reduce the risk of primary and secondary ischaemic disorders. However, the results have been inconclusive with some studies suggesting a preventive effect and others no effect or even an increased risk. Behind such contradictory results may be the role of depression itself as a cardiovascular risk factor and, therefore, a major confounding factor. How to disentangle its effect from that of the antidepressants is the methodological challenge to be overcome in future studies. In this complex scenario, the elderly seem to be at a crossroads, because they are the group in which both the risks and the benefits can be the greatest. Studies performed to date have provided us with some clues that can help orient clinicians in taking the most appropriate course of action. For instance, as the gastrointestinal bleeding risk appears to increase with age, prudent advice in patients with a previous history of upper-gastrointestinal bleeding or peptic ulcer, and in those who take NSAIDs, oral anticoagulants, antiplatelet drugs or corticosteroids, would be to suggest addition of an acid-suppressing agent to the drug regimen in those elderly patients in whom SSRIs are indicated.

A selective serotonin reuptake inhibitor, citalopram, inhibits collagen-induced platelet aggregation and activation

Clinical depression is a significant risk factor for cardiovascular diseases and confers an increased risk of mortality. Increased platelet reactivity may predispose depressed patients to cardiovascular diseases. The antidepressants selective serotonin reuptake inhibitors (SSRIs) have been found to have cardioprotective effects probably via the attenuation of platelet activation independently in addition to treatment of depression itself. However, the characters of the inhibitory effect of SSRIs on platelets remain largely unknown. Here we show that an SSRI, citalopram, specifically inhibited collagen-induced platelet aggregation. Citalopram, however, revealed only little inhibitory effect on platelet aggregation induced by thrombin, U46619, and ionomycin, and failed to inhibit reversible platelet aggregation induced by adenosine diphosphate with fibrinogen. Collagen-induced of αIIbβ3 integrin activation in platelets under a static condition was not influenced by citalopram. Citalopram inhibited convulxin-induced platelet aggregation and αIIbβ3 integrin activation. In the experiments with fibrinogen-induced aggregation in elastase-treated platelets, citalopram inhibited only collagen-induced αIIbβ3 activation but not the binding activities between activated αIIbβ3 integrin and fibrinogen. Moreover, citalopram inhibited α-granule and dense granule secretion from platelets in response to collagen, as determined by a reduced expression of P-selectin and adenosine triphosphate release, respectively. In addition, collagen-induced thromboxane A2 release in platelets was attenuated by citalopram pretreatment. These findings might specify the mechanisms of inhibitory effects of citalopram on collagen mediated platelet activation and aggregation, and further support the cardioprotective effect of SSRIs.

The pleiotropic effects of statins and omega-3 fatty acids against sepsis: a new perspective

The available therapeutic options for sepsis are restricted by their effectiveness and high cost. Emerging preliminary data suggest that statins and omega-3 fatty acids (OM3FA) may be associated with improved outcomes in terms of prevention and treatment of sepsis. We sought to review the current evidence on the effectiveness of their combined administration against sepsis, by carrying out a review of PubMed and Scopus databases for relevant studies, without imposing language or time restrictions. No clinical studies were identified regarding the effect of the combination treatment with statins and OM3FA on sepsis in terms of prevention or treatment. However, there is experimental evidence that both statins and OM3FA inhibit the inflammatory process at different levels, but also enhance inhibition at those levels that are common. There are also preliminary data supporting the beneficial effect of this combination on platelet function and other haemostatic mechanisms. Appropriately designed and powered clinical trials are warranted to investigate the effectiveness and safety of the combined administration of statins and OM3FA for the prevention and treatment of sepsis.

Clinical importance of aspirin and clopidogrel resistance

Aspirin and clopidogrel are important components of medical therapy for patients with acute coronary syndromes, for those who received coronary artery stents and in the secondary prevention of ischaemic stroke. Despite their use, a significant number of patients experience recurrent adverse ischaemic events. Interindividual variability of platelet aggregation in response to these antiplatelet agents may be an explanation for some of these recurrent events, and small trials have linked "aspirin and/or clopidogrel resistance", as measured by platelet function tests, to adverse events. We systematically reviewed all available evidence on the prevalence of aspirin/clopidogrel resistance, their possible risk factors and their association with clinical outcomes. We also identified articles showing possible treatments. After analyzing the data on different laboratory methods, we found that aspirin/clopidogrel resistance seems to be associated with poor clinical outcomes and there is currently no standardized or widely accepted definition of clopidogrel resistance. Therefore, we conclude that specific treatment recommendations are not established for patients who exhibit high platelet reactivity during aspirin/clopidogrel therapy or who have poor platelet inhibition by clopidogrel.

Aspirin resistance: focus on clinical endpoints

INTRODUCTION

Via its antiplatelet effect, aspirin reduces the odds of an arterial thrombotic event in high-risk patients by approximately 25%. However, 10% to 20% of patients with an arterial thrombotic event who are treated with aspirin have a recurrent arterial thrombotic event during long-term follow-up. Nevertheless, the effectiveness of aspirin has been questioned by the emergence of the concept of aspirin resistance, which has been introduced as an explanation of the fact that a considerable proportion of patients treated with aspirin exhibit normal platelet function.

OBJECTIVES AND METHODS

We systematically reviewed all available evidence till March 2008 on prevalence of aspirin resistance and its association with clinical outcome. We also collected articles showing the possible way of treatment.

CONCLUSION

Analyzing the data of different laboratory methods aspirin resistance seems to be associated with poor clinical outcome, although currently no standardized or widely accepted definition of aspirin resistance exists. The widely used laboratory methods might not be comparable with each other; therefore, specific treatment recommendations for patients who exhibit high platelet reactivity during aspirin therapy or who have poor platelet inhibition by aspirin are not established.

Spectrum of pleiotropic effects of statins in heart failure

The syndrome of heart failure is characterized by increased levels of circulating inflammatory mediators, which have been implicated in the pathogenesis of heart failure. Recently, a number of studies have suggested that statins may exert salutary effects in patients who have heart failure by virtue of their pleiotropic (non-lipid lowering) actions. This article focuses on the non-lipid lowering effects of statins, with an emphasis on the anti-inflammatory properties of these agents.