The amount of fibrinogen-positive platelets predicts the occurrence of in-stent restenosis

The impact of high on-treatment platelet reactivity and fibrinogen levels on ischemic events in patients with ST elevation myocardial infarction: a prospective observational study

BACKGROUND

After treatment, high residual platelet reactivity (HRPR) is considered as an essential risk factor for recurrent ischemic events.

AIM

To evaluate the impact of fibrinogen on HRPR after implantation of emergency drug-eluting stents (DES) in patients treated with aspirin and clopidogrel or ticagrelor due to ST-elevation myocardial infarction (STEMI) and to explore the predictive values of HRPR and fibrinogen for adverse ischemic events at 12 months.

METHOD

This single-center prospective observational study analyzed patients with STEMI who underwent primary percutaneous coronary intervention (PCI) with second-generation DES implantation from January 2017 to December 2018. Platelet reactivity was measured by thromboelastography (TEG) at 60-72 h after primary PCI. HRPR was defined as the adenosine diphosphate-induced maximum amplitude (MA_ADP) > 47 mm.

RESULTS

A total of 919 patients were analyzed, of which 512 (55.8%) received aspirin and clopidogrel and 406 (44.2%) received aspirin and ticagrelor. Elevated fibrinogen levels were associated with an increased prevalence of HRPR (P < 0.001). High fibrinogen (quartile IV, ≥ 410 mg/dL) was an independent risk factor for HRPR after multivariate regression (odds ratio 6.556, 95% confidence interval [CI]: 3.200-13.431, P < 0.001). When analyzed by Kaplan-Meier survival curves, the combination of high fibrinogen and HRPR was strongly predictive for ischemic major adverse cardiac events at 12 months compared to the group without HRPR and with low fibrinogen (hazard ratio 9.681, 95% CI: 4.467-20.98, log-rank P < 0.001). Similar results were confirmed in subgroups according to different dual antiplatelet therapies.

CONCLUSION

A combination of high fibrinogen and HRPR may identify recurrent adverse ischemic events over 12 months. Ticagrelor exhibited more potent platelet inhibition and a better prognosis than clopidogrel.

Enhanced biocompatibility of CD47-functionalized vascular stents

The effectiveness of endovascular stents is hindered by in-stent restenosis (ISR), a secondary re-obstruction of treated arteries due to unresolved inflammation and activation of smooth muscle cells in the arterial wall. We previously demonstrated that immobilized CD47, a ubiquitously expressed transmembrane protein with an established role in immune evasion, can confer biocompatibility when appended to polymeric surfaces. In present studies, we test the hypothesis that CD47 immobilized onto metallic surfaces of stents can effectively inhibit the inflammatory response thus mitigating ISR. Recombinant CD47 (recCD47) or a peptide sequence corresponding to the Ig domain of CD47 (pepCD47), were attached to the surfaces of both 316L-grade stainless steel foils and stents using bisphosphonate coordination chemistry and thiol-based conjugation reactions to assess the anti-inflammatory properties of CD47-functionalized surfaces. Initial in vitro and ex vivo analysis demonstrated that both recCD47 and pepCD47 significantly reduced inflammatory cell attachment to steel surfaces without impeding on endothelial cell retention and expansion. Using a rat carotid stent model, we showed that pepCD47-functionalized stents prevented fibrin and platelet thrombus deposition, inhibited inflammatory cell attachment, and reduced restenosis by 30%. It is concluded that CD47-modified stent surfaces mitigate platelet and inflammatory cell attachment, thereby disrupting ISR pathophysiology.

Macrophage-derived IL-18 and increased fibrinogen deposition are age-related inflammatory signatures of vascular remodeling

Aging has been associated with pathological vascular remodeling and increased neointimal hyperplasia. The understanding of how aging exacerbates this process is fundamental to prevent cardiovascular complications in the elderly. This study proposes a mechanism by which aging sustains leukocyte adhesion, vascular inflammation, and increased neointimal thickness after injury. The effect of aging on vascular remodeling was assessed in the rat balloon injury model using microarray analysis, immunohistochemistry, and LINCOplex assays. The injured arteries in aging rats developed thicker neointimas than those in younger animals, and this significantly correlated with a higher number of tissue macrophages and increased vascular IL-18. Indeed, IL-18 was 23-fold more abundant in the injured vasculature of aged animals compared with young rats, while circulating levels were similar in both groups of animals. The depletion of macrophages in aged rats with clodronate liposomes ameliorated vascular accumulation of IL-18 and significantly decreased neointimal formation. IL-18 was found to inhibit apoptosis of vascular smooth muscle cells (VSMC) and macrophages, thus favoring both the formation and inflammation of the neointima. In addition, injured arteries of aged rats accumulated 18-fold more fibrinogen-γ than those of young animals. Incubation of rat peritoneal macrophages with immobilized IL-18 increased leukocyte adhesion to fibrinogen and suggested a proinflammatory positive feedback loop among macrophages, VSMC, and the deposition of fibrinogen during neointimal hyperplasia. In conclusion, our data reveal that concentration changes in vascular cytokine and fibrinogen following injury in aging rats contribute to local inflammation and postinjury neointima formation.

Plasma fibrinogen levels and restenosis after primary percutaneous coronary intervention

Plasma fibrinogen levels influence restenosis following elective percutaneous coronary intervention (PCI) for stable angina. It is unknown whether the same is true in the setting of primary PCI. The aim of the study was therefore to assess whether fibrinogen levels were associated to 6-month in-stent restenosis (ISR) in STEMI patients undergoing successful primary PCI. From January 2003 to October 2004, 267 patients were admitted to our Institution for STEMI and treated by primary PCI. Of these, 171 patients met the inclusion criteria and were enrolled in our study. Fibrinogen levels were assessed at admission, 12 h, 24 h, 48 h, 72 h following PCI and at discharge. Six-month angiographic follow-up was 100% complete. Subjects with 6-month ISR showed higher fibrinogen levels than patients without ISR. Patients in the upper fibrinogen tertile showed a higher 6-month incidence of symptoms and/or inducible myocardial ischemia (27.1% vs. 7.1%, P = 0.006) and a larger late lumen loss (1.3 ± 0.8 vs. 1.0 ± 0.9 mm, P = 0.049). Logistic regression analysis demonstrated a significant and independent association between fibrinogen levels and ISR. Our study suggests that increased plasma fibrinogen levels are related to ISR in STEMI patients undergoing primary PCI. Larger studies are warranted to assess the prognostic value of fibrinogen over harder end-points.

Doubling the clopidogrel dose in patients with reduced responsiveness to the standard dose is associated with a limited effectiveness as evaluated by impedance aggregometry

BACKGROUND

Different methods are available for quantifying platelet function inhibition. Measuring vasodilator-stimulated phosphoprotein (VASP) phosphorylation is currently the most specific method for assessing the clopidogrel effect. The aim of our study was to compare different tests in view of a clinically applicable bedside test. Further, we examined whether doubling the clopidogrel dose to 150mg/d in clopidogrel low-responder would lead to a reduction in platelet reactivity.

METHODS AND RESULTS

ADP-, ADP Hs-, and TRAP-induced platelet aggregation were measured by impedance aggregometry in 100 patients with CAD and 18 healthy controls. Moreover, platelet aggregation was assessed by flow cytometrical detection of VASP-phosphorylation and surface P-selectin in a subgroup of 34 patients and in healthy controls. Another 10 patients with CAD, identified as low-responder, were treated with a clopidogrel dose of 150mg/d. Thereafter, ADP-induced platelet aggregation was assessed by impedance aggregometry. Significant correlations were observed between ADP-induced platelet aggregation assessed by VASP-phosphorylation and by impedance aggregometry. Doubling the dose of clopidogrel to 150mg/d was associated with a reduction of ADP-induced platelet aggregation in only 60% of the patients.

CONCLUSIONS

Impedance aggregometry is a valuable bedside test to assess platelet function inhibition. Doubling the clopidogrel dose is not effective to reduce high on-treatment platelet reactivity in almost half of these patients, pointing to the need of a more powerful platelet inhibitor.

Endothelialization and in-stent restenosis on the surface of glycoprotein IIIa monoclonal antibody eluting stent

Since the percutaneous transtuminal coronary angioplasty was introduced into China in 1984, this procedure has become widely accepted as an important step in coronary revascularization. This study shows the effect of the monoclonal antibody (mAb) on the platelet glycoprotein IIIa receptor during endothelialization and in-stent restenosis by implanting the mAb-eluting stents into iliac arteries of rabbits. The hard tissue cross sections of the stent-implanted arterial segments were made by polymethylmethacrylate embedding. Arterial intima proliferation was observed and analyzed. The endothelialization of the stent surface was observed using scanning electron microscope, whereas the ultrastructure of the neointima was observed using transmission electron microscope. After one month of stent implantation, the surfaces of both groups were covered by intact endothelial layers, but the neointimal areas and the ratio of stenosis were significantly lesser in the mAb-eluting stent group (p < 0.01). After 3 months, the ratio of stenosis in the mAb-eluting stent group was 14.67 ± 0.79, whereas that of the bare stent group was 21.58 ± 1.76 (p < 0.01). Therefore, the mAb eluting from the stent surface has the potential to accelerate endothelialization, prevent thrombosis formation due to the interaction of stent with blood, and decrease the stenosis ratio by inhibiting neointima proliferation.