Oral antiplatelet agents in cardiovascular disease

[Survey on blood thinning therapy in patients with age-related macular degeneration]

BACKGROUND

Patients with age-related macular degeneration (AMD) often receive concomitant systemic blood thinning medications. These are known to increase the risk of severe hemorrhage also in connection with AMD, which can lead to extensive subretinal hemorrhaging.

OBJECTIVE

The purpose of this study was to investigate the proportion of patients with AMD and concomitant blood thinning treatment, including the type and reason for blood thinning treatment.

METHODS

This survey was prospectively conducted at the University Eye Hospital, Bonn, Germany. Volunteers were recruited during retinal consultations and the consultations for intravitreal injections (IVOM).

RESULTS

The questionnaire was completed by 178 patients. The mean age was 81.7 years (58-100) and 101 patients (57.7%) were undergoing blood thinning treatment. The majority of patients were taking antiplatelet agents (n = 59; 58.4%), especially ASA (n = 55; 54.5%). Direct oral anticoagulants (DOAC) were taken by 33 patients (32.7%), including most frequently apixaban (17.8%). Vitamin K antagonists (VKA) was taken by 4 patients (4%). The most common reason for blood thinning treatment was atrial fibrillation (n = 32, 31.7%), followed by stent implantation (n = 20, 19.8%) and stroke (n = 12, 11.9%) but 13 patients (12.9%) did not know why they were undergoing blood thinning treatment. No clear indications for the use of blood thinners were found in 31 patients (30.7%).

CONCLUSION

A large proportion of patients with AMD undergo blood thinning treatment; however, not every patient has a clear indication. Due to the increased risk of bleeding, the use of blood thinners should be critically evaluated in close cooperation with primary care physicians and cardiologists.

Micro- and Macrovascular Effects of Inflammation in Peripheral Artery Disease-Pathophysiology and Translational Therapeutic Approaches

Inflammation has a critical role in the development and progression of atherosclerosis. On the molecular level, inflammatory pathways negatively impact endothelial barrier properties and thus, tissue homeostasis. Conformational changes and destruction of the glycocalyx further promote pro-inflammatory pathways also contributing to pro-coagulability and a prothrombotic state. In addition, changes in the extracellular matrix composition lead to (peri-)vascular remodelling and alterations of the vessel wall, e.g., aneurysm formation. Moreover, progressive fibrosis leads to reduced tissue perfusion due to loss of functional capillaries. The present review aims at discussing the molecular and clinical effects of inflammatory processes on the micro- and macrovasculature with a focus on peripheral artery disease.

Microvascular Thrombosis as a Critical Factor in Severe COVID-19

Platelet-endothelial interactions have a critical role in microcirculatory function, which maintains tissue homeostasis. The subtle equilibrium between platelets and the vessel wall is disturbed by the coronavirus disease 2019 (COVID-19), which affects all three components of Virchow's triad (endothelial injury, stasis and a hypercoagulable state). Endotheliitis, vasculitis, glycocalyx degradation, alterations in blood flow and viscosity, neutrophil extracellular trap formation and microparticle shedding are only few pathomechanisms contributing to endothelial damage and microthrombosis resulting in capillary plugging and tissue ischemia. In the following opinion paper, we discuss major pathological processes leading to microvascular endothelial activation and thrombosis formation as a possible major adverse factor driving the deterioration of patient disease course in severe COVID-19.

Antiplatelet and anticoagulant therapy in patients with submacular hemorrhage caused by neovascular age-related macular degeneration

Purpose

Patients with extensive submacular hemorrhage (SMH) caused by age-related macular degeneration (AMD) have a poor visual prognosis despite surgical intervention. Systemic blood-thinning drugs, which are commonly prescribed in the same age group, are known to increase the risk of severe hemorrhage in many parts of the body. This study aimed to investigate whether systemic blood-thinning drugs have an impact on the severity of SMH and if there are differences between the different types of blood-thinning medication.

Methods

We reviewed the medical records of patients who suffered from surgically treated SMH between 2020 and 2022. All patients received a full ophthalmologic examination upon presentation including best-corrected visual acuity (BCVA) and optical coherence tomography. Other characteristics that were recorded included size of hemorrhage, blood-thinning therapy, and reason for intake.

Results

A total of 115 patients with a mean age of 82 years were included in this retrospective analysis. Eighty-three patients (72.2%) were on blood-thinning therapy. The mean size of SMH was 32.01 mm2. Mean BCVA at initial presentation was 1.63 logMAR and 1.59 logMAR 1 year after surgery. The size of SMH was significantly larger in patients on blood-thinning medication (35.92 mm2 vs. 21.91 mm2) (p = 0.001) and their BCVA postoperatively was worse with 1.68 logMAR compared to 1.30 logMAR after 1 year (p = 0.503). Patients with vitamin K antagonists had larger SMH size and worse outcomes regarding BCVA compared to direct oral anticoagulants.

Conclusion

Blood thinners in patients with AMD affect the severity of SMH. Consequently, the indication for their intake should be critically evaluated.

Antiplatelet Activity of Tetramethylpyrazine via Regulation of the P2Y12 Receptor Downstream Signaling Pathway

Background

Tetramethylpyrazine (TMP) is an alkaloid in Chinese herbal medicine, which possesses antiplatelet activity. TMP inhibits platelet activation in many ways. The platelet P2Y₁₂ receptor for adenosine 5′ diphosphate (ADP) plays a central role in platelet function, hemostasis, and thrombosis. Here, we investigated the inhibitory effect of TMP on P2Y₁₂ receptor-related platelet function.

Methods

The inhibitory potential of TMP was assessed using agonist-induced platelet aggregation, flow cytometric analysis of CD62p expression, PAC-1 activation, and fibrin clot retraction. After the P2Y12 receptor-related signaling pathway was inhibited using the blocker, platelet activation was studied by platelet aggregation, CD62p expression, and PAC-1 activation. The secretion of cyclic adenosine monophosphate (cAMP) was measured using enzyme-linked immunosorbent assay (ELISA), and the expression of signaling pathway protein, phosphorylation of vasodilator-stimulated phosphoprotein, and phosphorylation of Akt were investigated using western blotting. The release of platelet inflammatory mediators was measured using ELISA.

Results

TMP had an antiplatelet effect by inhibiting ADP-induced aggregation, P-selectin secretion, and glycoprotein (GP) IIb/IIIa expression and reducing the release of atherosclerotic-related inflammatory mediators (sCD40L and IL-1β). TMP decreased the area of clot retraction, reflecting inhibition of GPIIb/IIIa activation. TMP inhibited adenosine diphosphate-induced platelet activation via increased cAMP production, VASP^ser157 phosphorylation, and Akt dephosphorylation.

Conclusion

TMP selectively inhibits ADP-induced platelet activation via P2Y₁₂ receptor-related signaling pathways.

Platelet-to-Lymphocyte Ratio as Marker of Platelet Activation in Patients on Potent P2Y12 Inhibitors

A high platelet-to-lymphocyte ratio (PLR) has recently been associated with ischemic outcomes in cardiovascular disease. Increased platelet reactivity and leukocyte-platelet aggregate formation are directly involved in the progress of atherosclerosis and have been linked to ischemic events following percutaneous coronary intervention (PCI). In order to understand the relation of PLR with platelet reactivity, we assessed PLR as well as agonist-inducible platelet aggregation and neutrophil-platelet aggregate (NPA) formation in 182 acute coronary syndrome (ACS) patients on dual antiplatelet therapy with aspirin and prasugrel (n = 96) or ticagrelor (n = 86) 3 days after PCI. PLR was calculated from the blood count. Platelet aggregation was measured by multiple electrode aggregometry and NPA formation was determined by flow cytometry, both in response to ADP and SFLLRN. A PLR ≥91 was considered as high PLR based on previous data showing an association of this threshold with adverse ischemic outcomes. In the overall cohort and in prasugrel-treated patients, high PLR was associated with higher SFLLRN-inducible platelet aggregation (67 AU [50-85 AU] vs 59.5 AU [44.3-71.3 AU], P = .01, and 73 AU [50-85 AU] vs 61.5 AU [46-69 AU], P = .02, respectively). Further, prasugrel-treated patients with high PLR exhibited higher ADP- (15% [11%-23%] vs 10.9% [7.6%-15.9%], P = .007) and SFLLRN-inducible NPA formation (64.3% [55.4%-73.8%] vs 53.8% [44.1%-70.1%], P = .01) as compared to patients with low PLR. These differences were not seen in ticagrelor-treated patients. In conclusion, high PLR is associated with increased on-treatment platelet reactivity in prasugrel-treated patients, but not in patients on ticagrelor.

Decreased Platelet Inhibition by Thienopyridines in Hyperuricemia

PURPOSE

Hyperuricemia carries an increased risk of atherothrombotic events in acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI). This may at least in part be due to inadequate P2Y12 inhibition. The aim of this study was to prospectively investigate the potential association between hyperuricemia and decreased platelet inhibition by P2Y12 antagonists.

METHODS

Levels of uric acid as well as on-treatment residual platelet reactivity in response to adenosine diphosphate (ADP) were assessed in 301 clopidogrel-treated patients undergoing elective angioplasty and stenting, and in 206 prasugrel- (n = 118) or ticagrelor-treated (n = 88) ACS patients following acute PCI. Cut-off values for high on-treatment residual ADP-inducible platelet reactivity (HRPR) were based on previous studies showing an association of test results with clinical outcomes.

RESULTS

Hyperuricemia was significantly associated with increased on-treatment residual ADP-inducible platelet reactivity in clopidogrel- and prasugrel-treated patients in univariate analyses and after adjustment for differences in patient characteristics by multivariate regression analyses. In contrast, ticagrelor-treated patients without and with hyperuricemia showed similar levels of on-treatment residual platelet reactivity to ADP. HRPR occurred more frequently in clopidogrel- and prasugrel-treated patients with hyperuricemia than in those with normal uric acid levels. In contrast, hyperuricemic patients receiving ticagrelor did not have a higher risk of HRPR compared with those with normal uric acid levels.

CONCLUSION

Hyperuricemia is associated with decreased platelet inhibition by thienopyridines but a normal response to ticagrelor. It remains to be established if lowering uric acid increases the antiplatelet effects of clopidogrel and prasugrel in hyperuricemic patients with HRPR.

Comparison of Light Transmission Aggregometry With Impedance Aggregometry in Patients on Potent P2Y12 Inhibitors

Since data on the agreement between light transmission aggregometry (LTA) and multiple electrode aggregometry (MEA) in patients on the more potent P2Y₁₂ inhibitors are missing so far, we investigated if the evaluation of the responsiveness to therapy by LTA can be replaced by MEA in 160 acute coronary syndrome (ACS) patients on dual antiplatelet therapy with aspirin and prasugrel or ticagrelor (n = 80 each). Cut-off values for high on-treatment residual platelet reactivity (HRPR) in response to adenosine diphosphate (ADP) or arachidonic acid (AA) were defined according to previous studies showing an association of HRPR with the occurrence of adverse ischemic outcomes. ADP- inducible platelet aggregation was 33% and 37% (P = 0.07) by LTA and 19 AU and 20 AU (P = 0.38) by MEA in prasugrel- and ticagrelor-treated patients, respectively. AA- inducible platelet aggregation was 2% and 3% by LTA and 15 AU and 16 AU by MEA, (all P ≥ 0.3) in patients on prasugrel and ticagrelor, respectively. By LTA, HRPR ADP and HRPR AA were seen in 5%/5% and in 4%/ 13% of patients receiving prasugrel- and ticagrelor, respectively. By MEA, HRPR ADP and HRPR AA were seen in 3%/ 25% and 0%/24% of prasugrel- and ticagrelor-treated patients, respectively. ADP-inducible platelet reactivity by MEA correlated significantly with LTA ADP in prasugrel-treated patients (r = 0.4, P < 0.001), but not in those receiving ticagrelor (r = 0.09, P = 0.45). AA-inducible platelet aggregation by LTA and MEA did not correlate in prasugrel- and ticagrelor-treated patients. Sensitivity/specificity of HRPR by MEA to detect HRPR by LTA were 25%/99% for MEA ADP and 100%/79% for MEA AA in prasugrel-treated patients, and 0%/100% for MEA ADP and 70%/83% for MEA AA in ticagrelor-treated patients. In conclusion, on-treatment residual ADP-inducible platelet reactivity by LTA and MEA shows a significant correlation in prasugrel- but not ticagrelor-treated patients. However, in both groups LTA and MEA revealed heterogeneous results regarding the classification of patients as responders or non-responders to P2Y₁₂ inhibition.

Ticagrelor Inhibits Toll-Like and Protease-Activated Receptor Mediated Platelet Activation in Acute Coronary Syndromes

Purpose

Since ticagrelor inhibits the cellular uptake of adenosine, thereby increasing extracellular adenosine concentration and biological activity, we hypothesized that ticagrelor has adenosine-dependent antiplatelet properties. In the current study, we compared the effects of ticagrelor and prasugrel on platelet activation in acute coronary syndrome (ACS).

Methods

Platelet surface expression of P-selectin and activated glycoprotein (GP) IIb/IIIa in response to adenosine diphosphate (ADP), the toll-like receptor (TLR)-1/2 agonist Pam3CSK4, the TLR-4 agonist lipopolysaccharide (LPS), the protease-activated receptor (PAR)-1 agonist SFLLRN, and the PAR-4 agonist AYPGKF were measured by flow cytometry in blood from 80 ticagrelor- and 80 prasugrel-treated ACS patients on day 3 after percutaneous coronary intervention. Residual platelet aggregation to arachidonic acid (AA) and ADP were assessed by multiple electrode aggregometry and light transmission aggregometry.

Results

ADP-induced platelet activation and aggregation, and AA-induced platelet aggregation were similar in patients on ticagrelor and prasugrel, respectively (all p ≥ 0.3). Further, LPS-induced platelet surface expression of P-selectin and activated GPIIb/IIIa did not differ significantly between ticagrelor- and prasugrel-treated patients (both p > 0.4). In contrast, Pam3CSK4-induced platelet surface expression of P-selectin and activated GPIIb/IIIa were significantly lower in ticagrelor-treated patients (both p ≤ 0.005). Moreover, SFLLRN-induced platelet surface expression of P-selectin and activated GPIIb/IIIa were significantly less pronounced in patients on ticagrelor therapy compared to prasugrel-treated patients (both p < 0.03). Finally, PAR-4 mediated platelet activation as assessed by platelet surface expression of activated GPIIb/IIIa following stimulation with AYPGKF was significantly lower in patients receiving ticagrelor (p = 0.02).

Conclusion

Ticagrelor inhibits TLR-1/2 and PAR mediated platelet activation in ACS patients more strongly than prasugrel.

α-Hydroxybutyrate dehydrogenase is associated with atherothrombotic events following infrainguinal angioplasty and stenting

Besides clinical characteristics, easy-accessible laboratory markers could be of value to refine risk stratification in peripheral artery disease. In the current study, we investigated whether α-hydroxybutyrate dehydrogenase (HBDH) is associated with atherothrombotic events in 83 stable patients undergoing infrainguinal angioplasty and stenting. The primary endpoint was defined as the composite of the first occurrence of nonfatal myocardial infarction, nonfatal stroke or transient ischemic attack and cardiovascular death within 2 years after angioplasty and stenting, and occurred in 6 patients (7.2%). HBDH levels at baseline were significantly higher in patients who subsequently developed the primary endpoint (126 U/L [116–137 U/L] vs. 105 U/L [95–120 U/L]; p = 0.04). ROC curve analysis revealed that HBDH could distinguish between patients without and with future atherothrombotic events. A HBDH concentration ≥ 115 U/L was identified as the best threshold to predict the composite endpoint, providing a sensitivity of 83.3% and a specificity of 71.4%, and was therefore defined as high HBDH. High HBDH was seen in 28 patients (33.7%). Ischemic events occurred significantly more often in patients with high HBDH than in patients with lower HBDH levels (5 vs. 1 patients, p = 0.007). In conclusion, HBDH is associated with the occurrence of atherothrombotic events after infrainguinal angioplasty with stent implantation. Future trials are warranted to study the predictive role of HBDH for ischemic outcomes and to investigate underlying mechanisms.

Protease-activated receptor-mediated platelet aggregation in acute coronary syndrome patients on potent P2Y12 inhibitors

BACKGROUND

Despite the increasing use of potent P2Y12 inhibitors, further atherothrombotic events still impair the prognosis of many acute coronary syndrome (ACS) patients. This may in part be attributable to intact platelet aggregation via the human thrombin receptors protease-activated receptor (PAR)-1 and PAR-4.

OBJECTIVE

We studied PAR mediated platelet aggregation in ACS patients following percutaneous coronary intervention (PCI) with stent implantation in a cross-sectional study.

METHODS

Platelet aggregation to ADP as well as to the PAR-1 agonist SFLLRN and the PAR-4 agonist AYPGKF was assessed by multiple electrode aggregometry in 194 ACS patients on dual antiplatelet therapy with aspirin and either prasugrel (n = 114) or ticagrelor (n = 80) 3 days after PCI.

RESULTS

Based on the consensus cutoff value, high on-treatment residual platelet reactivity to ADP (HRPR ADP) was observed in only 2 prasugrel-treated patients. Both patients with HRPR ADP had also a normal response to SFLLRN and AYPGKF. Among the 112 prasugrel-treated patients with adequate P2Y12 inhibition, 50 patients (45%) still had a normal response to SFLLRN, and 70 patients (63%) still had a normal response to AYPGKF. Among the 80 ticagrelor-treated patients with adequate P2Y12 inhibition, 25 patients (31%) still had a normal response to SFLLRN, and 50 (63%) still had a normal response to AYPGKF.

CONCLUSION

Normal platelet aggregation via PAR-1 and PAR-4 is preserved in many patients with adequate P2Y12 inhibition by prasugrel and ticagrelor. The present findings may at least in part explain adverse ischemic events despite potent P2Y12 inhibition.