Clinical Implications of Platelet—Vessel Interaction

Effects of ticagrelor and prasugrel on coronary microcirculation in elective percutaneous coronary intervention

OBJECTIVE

To compare the effects of ticagrelor and prasugrel on absolute coronary blood flow (Q) and microvascular resistance (R) in patients with stable coronary artery disease (CAD) treated with elective percutaneous coronary intervention (PCI) (NCT05643586). Besides being at least as effective as prasugrel in inhibiting platelet aggregation, ticagrelor has been shown to have additional properties potentially affecting coronary microcirculation.

METHODS

We randomly assigned 50 patients to ticagrelor (180 mg) or prasugrel (60 mg) at least 12 hours before intervention. Continuous thermodilution was used to measure Q and R before and after PCI. Platelet reactivity was measured before PCI. Troponin I was measured before, 8 and 24 hours after PCI.

RESULTS

At baseline, fractional flow reserve, Q and R were similar in two study groups. Patients in the ticagrelor group showed higher post-PCI Q (242±49 vs 205±53 mL/min, p=0.015) and lower R values (311 (263, 366) vs 362 (319, 382) mm Hg/L/min, p=0.032). Platelet reactivity showed a negative correlation with periprocedural variation of Q values (r=-0.582, p<0.001) and a positive correlation with periprocedural variation of R values (r=0.645, p<0.001). The periprocedural increase in high-sensitivity troponin I was significantly lower in the ticagrelor compared with the prasugrel group (5 (4, 9) ng/mL vs 14 (10, 24) ng/mL, p<0.001).

CONCLUSIONS

In patients with stable CAD undergoing PCI, pretreatment with a loading dose of ticagrelor compared with prasugrel improves post-procedural coronary flow and microvascular function and seems to reduce the related myocardial injury.

Platelet reactivity and clinical outcomes following percutaneous coronary intervention in complex higher-risk patients

AIMS

To investigate the levels of platelet reactivity and the impact of high platelet reactivity (HPR) on long-term clinical outcomes of complex higher-risk and indicated patients (CHIP) with stable coronary artery disease (CAD) treated with elective percutaneous coronary intervention (PCI).

METHODS

We enrolled 500 patients undergoing elective PCI for stable CAD and treated with aspirin and clopidogrel. Patients were divided into four groups based on the presence of CHIP features and HPR. Primary endpoint was the occurrence of major adverse clinical events (MACE) at 5 years.

RESULTS

The prevalence of HPR was significantly greater in the CHIP population rather than non-CHIP patients (39.9% vs 29.8%, P = 0.021). Patients with both CHIP features and HPR showed the highest estimates of MACE (22.1%, log-rank P = 0.047). At Cox proportional hazard analysis, the combination of CHIP features and HPR was an independent predictor of MACE (hazard ratio 2.57, 95% confidence interval 1.30-5.05, P = 0.006).

CONCLUSION

Among patients with stable CAD undergoing elective PCI and treated with aspirin and clopidogrel, the combination of CHIP features and HPR identifies a cohort of patients with the highest risk of MACE at 5 years, who might benefit from more potent antiplatelet strategies.

Platelets and platelet extracellular vesicles in hemostasis and sepsis

Platelets, cell fragments traditionally thought of as important only for hemostasis, substantially and dynamically contribute to the immune system's response to infection. In addition, there is increasing evidence that externally active platelet entities, including platelet granules and platelet extracellular vesicles (PEVs), play a role not only in hemostasis, but also in inflammatory actions previously ascribed to platelets themselves. Given the functions of platelets and PEVs during inflammation and infection, their role in sepsis is being investigated. Sepsis is a condition marked by the dysregulation of the body's normal activation of the immune system in response to a pathogen. The mechanisms for controlling infection locally become detrimental to the host if they are applied systemically. Similar to cells traditionally ascribed to the immune system, including neutrophils, lymphocytes, and macrophages, platelets are instrumental in helping a host clear an infection, but are also implicated in the uncontrolled amplification of the immune response that leads to sepsis. Clearly, the function of platelets is more complicated than its simple structure and primary role in hemostasis initially suggest. This review provides an overview of platelet and platelet extracellular vesicle structure and function, highlighting the complex role platelets and PEVs play in the body in the context of infection and sepsis.

Early Host Interactions That Drive the Dysregulated Response in Sepsis

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. While many individual cells and systems in the body are involved in driving the excessive and sometimes sustained host response, pathogen engagement with endothelial cells and platelets early in sepsis progression, are believed to be key. Significant progress has been made in establishing key molecular interactions between platelets and pathogens and endothelial cells and pathogens. This review will explore the growing number of compensatory connections between bacteria and viruses with platelets and endothelial cells and how a better understanding of these interactions are informing the field of potential novel ways to treat the dysregulated host response during sepsis.

Platelet reactivity and coronary microvascular impairment after percutaneous revascularization in stable patients receiving clopidogrel or prasugrel

BACKGROUND AND AIMS

Increased platelet reactivity (PR) associated with variable degree of coronary microvascular impairment has been reported in patients on clopidogrel after elective percutaneous coronary intervention (PCI). Prasugrel provides more potent platelet inhibition than clopidogrel, though it is unknown whether it might also prevent PCI-related platelet activation. In stable patients undergoing elective PCI, we compared: (1) the effects of prasugrel vs. clopidogrel on peri-procedural variations of PR and (2) the correlation of platelet inhibition potency with PCI-induced coronary microvascular impairment.

METHODS

Forty thienopyridine-naive patients were randomly assigned to a loading dose of either prasugrel 60 mg (n = 20) or clopidogrel 600 mg (n = 20) at least 12 h before PCI. At the time of PCI, we assessed adenosine diphosphate (ADP)-induced PR with the Multiplate Analyzer, and the pressure-derived index of microvascular resistance (IMR) in the treated coronary, both at baseline and post-procedure.

RESULTS

ADP-induced PR was significantly lower in the prasugrel compared with clopidogrel group both at baseline (16.0 ± 8.7 vs. 33.9 ± 18.0 aggregation units [AU], p < 0.001) and post-procedure (16.2 ± 9.0 vs. 39.0 ± 18.6 AU, p < 0.001). A significant peri-procedural increase in PR was observed in the clopidogrel group (p = 0.008), but not in the prasugrel group (p = 0.822). A significant correlation was found between IMR and PR both at baseline (r = 0.458, p = 0.003) and post-PCI (r = 0.487, p = 0.001).

CONCLUSIONS

A loading dose of prasugrel compared with clopidogrel is able to attenuate PCI-related increase in PR in patients with stable CAD undergoing PCI, which might contribute to the beneficial effect of this drug on peri-procedural coronary microvascular function.

Marker of Endothelial Dysfunction Asymmetric Dimethylarginine Is Elevated in HIV Infection but Not Associated With Subclinical Atherosclerosis

BACKGROUND

Cardiovascular disease contributes to excess morbidity and mortality in HIV infection, and endothelial dysfunction may contribute to this pattern. We aimed to determine the endothelial function in treated and untreated HIV-infected individuals and investigate potential associations with viral replication, immune activation, coagulation, platelet function, and subclinical atherosclerosis.

METHODS

Asymmetric dimethylarginine (ADMA, marker of endothelial dysfunction) and soluble CD14 (sCD14, marker of monocyte activation) were measured in plasma from two previously established cross-sectional cohorts: cohort A including 50 untreated and 50 antiretroviral therapy (ART)-treated HIV-infected individuals with previously assessed coagulation and platelet function and cohort B including 105 HIV-infected individuals on ART and 105 uninfected controls with previously assessed coronary artery calcium score, myocardial perfusion defects, and carotid intima-media thickness.

RESULTS

Concentrations of ADMA were higher in HIV-infected individuals compared with uninfected controls, and higher ADMA was found in ART-treated compared with untreated HIV-infected individuals. ADMA was associated with viral load, sCD14, D-dimer, and low CD4 T-cell count in untreated HIV infection. Only viral load remained significant in multivariate analyses. In ART-treated HIV-infected individuals, ADMA was not associated with coronary artery calcium score, myocardial perfusion defects, or intima-media thickness.

CONCLUSIONS

Evidence of endothelial dysfunction was found in HIV infection and in untreated compared with treated HIV infection. In untreated HIV infection, the main driver of endothelial dysfunction was viral replication. Importantly, in treated HIV infection, ADMA was not associated with subclinical atherosclerosis. Thus, our data question the potential of ADMA as a useful biomarker of early atherosclerosis in treated HIV infection.

Relation of Neutrophil to Lymphocyte Ratio With Periprocedural Myocardial Damage in Patients Undergoing Elective Percutaneous Coronary Intervention

Neutrophil to lymphocyte ratio (NLR) has been proposed as a marker of cardiovascular risk. The potential relation between NLR and periprocedural myocardial damage after percutaneous coronary intervention (PCI) is unclear. We enrolled 502 consecutive patients with stable coronary artery disease undergoing elective PCI. Blood samples were drawn in all patients at baseline, 6 hours, and 24 hours after PCI for complete blood cell count and cardiac biomarkers (creatine kinase-MB and troponin T [Tn-T]) assessment. NLR was calculated as the ratio between the absolute number of neutrophil over the absolute number of lymphocyte. Periprocedural myocardial infarction (PMI) was defined according to the 2012 universal definition of myocardial infarction. In the overall population, a significant postprocedural increase in NLR was observed (3.255 [2.763 to 3.995] at baseline, 4.430 [3.390 to 6.020] at 6 hours, 4.720 [3.940 to 5.750] at 24 hours, p <0.0001). PMI occurred in 33 patients (6.6%). Baseline NLR was similar in patients with and without PMI (3.250 [2.820 to 3.885] vs 3.260 [2.750 to 4.000], p = 0.898); however, patients who developed PMI showed significantly higher NLR both at 6 hours (5.750 [4.360 to 9.095] vs 4.370 [3.370 to 5.950], p <0.001) and 24 hours (5.180 [4.440 to 8.065] vs 4.670 [3.920 to 5.710], p = 0.003). Among patients who developed PMI, periprocedural NLR increase showed a moderate positive correlation with both creatine kinase-MB (rho = 0.377, p = 0.031) and troponin T increase (rho = 0.506, p = 0.003). In conclusion, preprocedural NLR values do not impact on the occurrence of PMI during elective PCI; however, PCI procedures induce a significant increase in NLR that seems to be proportional to the magnitude of periprocedural myocardial damage.

α2A-Adrenergic receptor polymorphism potentiates platelet reactivity in patients with stable coronary artery disease carrying the cytochrome P450 2C19*2 genetic variant

OBJECTIVE

Platelet α2A-adrenergic receptors (ARs) mediate platelet aggregation in response to sympathetic stimulation. The 6.3-kb variant of α2A-AR gene is associated with increased epinephrine-induced platelet aggregation in healthy volunteers. The cytochrome P450 2C19*2 (CYP2C19*2) loss-of-function allele influences P2Y12-mediated platelet inhibition and hence the rate of major adverse cardiovascular events. We assessed the influence of 6.3-kb α2A-AR gene variant on platelet aggregation and its interaction with CYP2C19*2 loss-of-function allele in patients with stable angina on aspirin and clopidogrel (dual antiplatelet therapy).

APPROACH AND RESULTS

Aggregation to 5 increasing doses of epinephrine (from 0.156 to 10 μmol/L) was assessed in aggregation units by Multiplate Analyzer and platelet reactivity in P2Y12 reactivity units and % inhibition by VerifyNow P2Y12 assay before percutaneous revascularization. Gene polymorphisms were analyzed with TaqMan Drug Metabolism assay. Of 141 patients, aggregation was higher in 6.3-kb carriers (n=52) when compared with wild types (n=89) at all epinephrine doses (P<0.05) apart from 10 μmol/L (P=0.077). Percentage inhibition was lower (P=0.048) in 6.3-kb α2A-AR carriers. Percentage inhibition was lower (P=0.005) and P2Y12 reactivity units was higher (P=0.012) in CYP2C19*2 allele carriers. Higher P2Y12 reactivity units (P=0.037) and lower percentage inhibition (P=0.009) were observed in carriers of both 6.3-kb α2A-AR variant and CYP2C19*2 allele when compared with wild-type or with either mutation on its own.

CONCLUSIONS

The 6.3-kb α2A-AR variant is associated with increased platelet reactivity to epinephrine and has an additive effect along with CYP2C19*2 loss-of-function allele on P2Y12-mediated platelet responses in patients with stable angina on dual antiplatelet therapy.