Effects of ticagrelor on neointimal hyperplasia and endothelial function, compared with clopidogrel and prasugrel, in a porcine coronary stent restenosis model

Clinical Outcomes of Ticagrelor in Korean Patients with Acute Myocardial Infarction without High Bleeding Risk

BACKGROUND

Although ticagrelor is known to increase the bleeding risk compared to clopidogrel in East Asian patients, its clinical benefits in patients with acute myocardial infarction (AMI) without high bleeding risk (HBR) remains unknown.

METHODS

A total of 7,348 patients who underwent successful percutaneous coronary intervention (PCI) from the Korea Acute Myocardial Infarction Registry-National Institute of Health (KAMIR-NIH), between November 2011 and December 2015, were divided into two groups according to the Academic Research Consortium for HBR criteria (KAMIR-HBR, 2,469 patients; KAMIR-non HBR, 4,879 patients). We compared in-hospital major adverse cardiovascular events (MACEs, defined as a composite of cardiac death, non-fatal myocardial infarction, or stroke), and the thrombolysis in myocardial infarction (TIMI) major bleeding between ticagrelor and clopidogrel in the KAMIR-HBR and the KAMIR-non HBR groups, respectively.

RESULTS

After propensity score matching, ticagrelor had a higher incidence of in-hospital TIMI major bleeding than clopidogrel in all patients (odds ratio [OR], 1.683; 95% confidence interval [CI], 1.010-2.805; P = 0.046) and the KAMIR-HBR group (OR, 3.460; 95% CI, 1.374-8.714; P = 0.008). However, there was no significant difference in in-hospital TIMI major bleeding between ticagrelor and clopidogrel in the KAMIR-non HBR group (OR, 1.436; 95% CI, 0.722-2.855; P = 0.303). No differences were observed in the cumulative incidences of in-hospital and 6-month MACEs between ticagrelor and clopidogrel in both groups.

CONCLUSIONS

The bleeding risk of ticagrelor was attenuated in Korean patients with AMI without HBR. Appropriate patient selection could reduce in-hospital bleeding complications associated with ticagrelor in Korean patients with AMI who underwent successful PCI.

The Effect of Platelet-Rich Plasma on Endothelial Progenitor Cell Functionality

Platelets mediate circulating endothelial progenitor cell (EPC) recruitment and maturation, participating in vascular repair, however the underlying mechanism(s) remain unclear. We investigated the effect of platelet-rich plasma (PRP) on the functionality of CD34⁺-derived late-outgrowth endothelial cells (OECs) in culture. Confluent OECs were coincubated with PRP under platelet aggregation (with adenosine diphosphate; ADP) and nonaggregation conditions, in the presence/absence of the reversible P2Y12 platelet receptor antagonist ticagrelor. Outgrowth endothelial cell activation was evaluated by determining prostacyclin (PGI₂) and monocyte chemoattractant protein-1 (MCP-1) release and intercellular adhesion molecule-1 (ICAM-1) membrane expression. Similar experiments were performed using human umbilical vein endothelial cells (HUVECs). Platelet-rich plasma increased ICAM-1 expression and PGI₂ and MCP-1 secretion compared with autologous platelet-poor plasma, whereas ADP-aggregated platelets in PRP did not exhibit any effect. Platelet-rich plasma pretreated with ticagrelor prior to activation with ADP increased all markers to a similar extent as PRP. Similar results were obtained using HUVECs. In conclusion, PRP induces OEC activation, a phenomenon not observed when platelets are aggregated with ADP. Platelet inhibition with ticagrelor restores the PRP capability to activate OECs. Since EPC activation is important for endothelial regeneration and angiogenesis, we suggest that agents inhibiting platelet aggregation, such as ticagrelor, may promote platelet-EPC interaction and EPC function.

Platelet inhibition by ticagrelor is protective against diabetic nephropathy in mice

Diabetic nephropathy (DN) is a major complication of diabetes and is associated with high risk for cardiovascular mortality, which is partially related to elevated platelet activity. Platelets are also active players in inflammation and fibrosis. In this study, we examine the effect of ticagrelor-induced platelet inhibition on the development of DN. DN was induced by unilateral nephrectomy followed by streptozotocin injections for 5 days. Mice received ticagrelor (300 mg/kg) or vehicle every other day, for 16 weeks. Experimental groups: non-diabetic control, diabetic control, non-diabetic ticagrelor, and diabetic ticagrelor. Ticagrelor treatment in diabetic mice lowered urinary albumin excretion, it prevented diabetes-induced mesangial matrix expansion, podocyte effacement, and glomerular endothelial cell injury, which includes loss of endothelial fenestrations, ICAM-1 expression, and PECAM expression. In addition, ticagrelor treatment prevented collagen IV deposition and macrophage infiltration in the tubulointerstitium and these diabetic mice showed lower systemic and tubular inflammation and tubular apoptosis. This tubular protection is likely to be a result of protection to the glomerular endothelium by ticagrelor, which reduces albuminuria and albumin toxicity to the tubules and reduced tubular and interstitial inflammation and fibrosis. In conclusion, ticagrelor-induced platelet inhibition protects against renal injury in diabetic mice, likely by protecting the glomerular endothelial cells.

Carotid Stent Restenosis and Thrombosis in Rabbits: The Effect of Antiplatelet Agents

BACKGROUND

The purpose of the study was the comparative assessment of ticagrelor and clopidogrel effects on carotid post-balloon injury (PBI) and on post carotid artery stenting (CAS) rate of in-stent restenosis (ISR) and in-stent thrombosis in atherosclerotic rabbits.

METHODS

Forty-eight New Zealand white rabbits on high-fat diet were randomized into 4 groups: A1: PBI and clopidogrel (30 mg/kg/d), A2: PBI and ticagrelor (21 mg/kg twice daily), B1: PBI, CAS, and clopidogrel (30 mg/kg/d), B2: PBI, CAS, and ticagrelor (21 mg/kg twice daily). All rabbits received orally aspirin (10 mg/kg/d) and interventions were performed in their right carotid arteries (RCAs). Optical coherence tomography (OCT) and carotid angiography were performed at end point, while platelet aggregation and lipid profile were measured. After euthanasia both carotids were obtained for histological examination.

RESULTS

In B1 group, 3 rabbits presented thrombotic total occlusion of the stents, while none such episode was observed in B2 group. The neointimal areas in RCAs, calculated by OCT, did not differ between A1 and A2 groups, and between B1 and B2 groups (P > .05). From the histological findings, the intima/(media + intima) percentage (%) in RCAs of balloon-injured rabbits did not present any difference between groups (P = .812). Similarly, the immunohistochemically determined accumulation of endothelial cells and macrophages on vascular walls was equivalent between groups (P > .05).

CONCLUSION

Following carotid balloon injury and stenting, clopidogrel and ticagrelor did not show any differential effects on the extent of neointimal formation and ISR in atherosclerotic rabbits receiving aspirin. Three thrombotic stent occlusions were noted in the clopidogrel treatment group, but this finding was not statistically significant.

Platelets in In-stent Restenosis: From Fundamental Role to Possible Prognostic Application

BACKGROUND

Introduction of new generations of stents has decreased the percentage of patients experiencing in-stent restenosis (ISR) following the implantation of stent. However, a large number of patients are still afflicted with this phenomenon, which necessitates further study of ISR pathophysiology.

METHODS

Relevant English literature was searched up to 2018 and retrieved form the PubMed database and Google Scholar search engine. The following keywords were used: "In-stent restenosis", "Platelet", "Chemokine", "Inflammation", "Vascular smooth muscle cell" and "Neointima".

RESULTS

Previous studies have shown that ISR is a pathophysiologic response to damage of the artery wall after its elongation and separation of the atherosclerotic plaque. Development of neointimal hyperplasia (NIH) following this pathophysiologic response is a function of inflammation caused by platelets, monocytes, macrophages, and lymphocytes, as well as rapid migration and proliferation of generally quiescent cells in the median layer of the artery wall.

CONCLUSION

After damage to the artery wall, platelets play an essential role in the incidence of NIH by contributing to inflammation and migration of vascular smooth muscle cells and extracellular matrix remodeling, especially via secretion of different chemokines; therefore, developing therapeutic strategies for platelet inhibition in a controlled manner could be the basis of preventive treatments in the near future. In this study, for the first time, we hypothesize that evaluation of platelet activity profile in patients before and after stent implantation may determine the prognosis and likelihood of ISR.

Beneficial Effects of Ticagrelor on Oxidized Low-Density Lipoprotein (ox-LDL)-Induced Apoptosis in Human Umbilical Vein Endothelial Cells

Background

Ticagrelor is the first oral anti-platelet agent which has direct anti-platelet aggregation effect by combining with ADP P2Y12 receptors in platelets. It has been approved to reduce the incidence of thrombus cardiovascular events in acute coronary syndrome patients. However, the effects of ticagrelor on endothelial apoptosis have not been investigated.

Material/Methods

Oxidized low-density lipoprotein (ox-LDL) was used to establish a human umbilical vein endothelial cell (HUVEC) apoptosis model. To investigate the effects of ticagrelor on endothelial apoptosis, the HUVECs were treated with different dose of ticagrelor. Apoptosis rates of HUVECs was evaluated by flow cytometry, and the expression levels of Akt, p-Akt, Bcl-2, Bax, caspase-3, endothelial nitric oxide synthase (eNOS), and nitric oxide (NO) concentration were assessed.

Results

After treatment with 50 ug/mL ox-LDL or 100 ug/mL ox-LDL, we found that the late apoptosis and necrosis rate and the expression levels of Bax and caspase-3 were significantly increased in HUVECs, whereas the expression levels of Akt, p-Akt, Bcl-2, eNOS, and NO were significantly decreased. Ticagrelor restored the apoptosis rate of ox-LDL-induced HUVECs in a dose-dependent manner. In addition, compared with ox-LDL group, ticagrelor treatment significantly increased the expression levels of Akt, p-Akt, Bcl-2, eNOS, and NO concentration, and significantly decreased the expression levels of Bax and caspase-3.

Conclusions

We found that ox-LDL induced significant apoptosis and necrosis in our model, which was dose-dependently improved by ticagrelor. These changes might be explained by alterations in apoptosis and antioxidant pathways.

Influence of Local Myocardial Infarction on Endothelial Function, Neointimal Progression, and Inflammation in Target and Non-Target Vascular Territories in a Porcine Model of Acute Myocardial Infarction

BACKGROUND

Patients with acute myocardial infarction (AMI) have worse clinical outcomes than those with stable coronary artery disease despite revascularization. Non-culprit lesions of AMI also involve more adverse cardiovascular events. This study aimed to investigate the influence of AMI on endothelial function, neointimal progression, and inflammation in target and non-target vessels.

METHODS

In castrated male pigs, AMI was induced by balloon occlusion and reperfusion into the left anterior descending artery (LAD). Everolimus-eluting stents (EES) were implanted in the LAD and left circumflex (LCX) artery 2 days after AMI induction. In the control group, EES were implanted in the LAD and LCX in a similar fashion without AMI induction. Endothelial function was assessed using acetylcholine infusion before enrollment, after the AMI or sham operation, and at 1 month follow-up. A histological examination was conducted 1 month after stenting.

RESULTS

A total of 10 pigs implanted with 20 EES in the LAD and LCX were included. Significant paradoxical vasoconstriction was assessed after acetylcholine challenge in the AMI group compared with the control group. In the histologic analysis, the AMI group showed a larger neointimal area and larger area of stenosis than the control group after EES implantation. Peri-strut inflammation and fibrin formation were significant in the AMI group without differences in injury score. The non-target vessel of the AMI also showed similar findings to the target vessel compared with the control group.

CONCLUSION

In the pig model, AMI events induced endothelial dysfunction, inflammation, and neointimal progression in the target and non-target vessels.

Ticagrelor suppresses oxidized low‑density lipoprotein‑induced endothelial cell apoptosis and alleviates atherosclerosis in ApoE‑/‑ mice via downregulation of PCSK9

Although ticagrelor has been demonstrated to possess an anti-atherosclerosis (AS) effect, its underlying mechanism remains unclear. In the present study, it was investigated whether ticagrelor reduces oxidized low-density lipoprotein (ox-LDL)-induced endothelial cell apoptosis, an initial step for the development of AS, and alleviates AS in apolipoprotein-E-deficient (ApoE^−/−) mice by inhibiting the expression of proprotein convertase subtilisin/kexin type 9 (PCSK9). The human endothelial cell line EAhy926 was treated with ox-LDL, ox-LDL + ticagrelor (40 µmol/l) and ox-LDL + ticagrelor (60 µmol/l) for 24 h. Cell apoptosis was detected using Annexin V-fluorescein isothiocyanate/propidium iodide staining. The expression levels of PCSK9, apoptosis-associated proteins and signaling pathways were determined by reverse transcription-quantitative polymerase chain reaction and western blotting. ApoE^−/− mice fed a high-fat diet were used to induce an AS model. After 20 weeks, ApoE^−/− mice were randomly assigned to receive saline or ticagrelor intragastrically for 10 days. The formation of atherosclerotic plaques was detected by hematoxylin and eosin staining. The expression of PCSK9 in the arterial tissues was measured by immunohistochemistry. The results demonstrated that treatment with ticagrelor was able to decrease ox-LDL-induced apoptosis in a concentration-dependent manner (40 µmol/l vs. ox-LDL, 17.58±2.66 vs. 27.25±5.54%; 60 µmol/l vs. ox-LDL, 12.26±1.54 vs. 27.25±5.54%). The mRNA and protein expression level of PCSK9 significantly decreased following treatment with ticagrelor, accompanied with upregulation of B-cell lymphoma (Bcl) 2 and downregulation of Bcl-2 associated X, apoptosis regulator, caspase-3, p38, phosphorylated-(p) p38, p-c-Jun N-terminal kinases (JNK), p-extracellular signal-regulated kinases and the ratio of p-JNK to JNK. Histological analysis of arterial tissues revealed ticagrelor markedly decreased the atherosclerotic plaque area and inhibited the expression of PCSK9. The present results suggested that ticagrelor may alleviate AS via downregulation of PCSK9-mediated endothelial cell apoptosis, which may be JNK-dependent.

Endothelial Function: A Short Guide for the Interventional Cardiologist

An impaired function of the coronary endothelium is an important determinant of all stages of atherosclerosis, from initiation, to mediation of functional phenomena—such as spasm and plaque erosion, to atherothrombotic complications. Endothelial function is modified by therapies, including stent implantation. Finally, endothelial function changes over time, in response to physical stimuli and pharmocotherapies, and its assessment might provide information on how individual patients respond to specific therapies. In this review, we describe the role of the endothelium in the continuum of coronary atherosclerosis, from the perspective of the interventional cardiologist. In the first part, we review the current knowledge of the role of endothelial (dys)function on atherosclerotic plaque progression/instabilization and on the mechanisms of ischemia, in the absence of coronary artery stenosis. In the second part of this review, we describe the impact of coronary artery stenting on endothelial function, platelet aggregation, and inflammation.

Promoting vascular healing using nanofibrous ticagrelor-eluting stents

Objective

The current treatment of atherosclerotic coronary heart disease with limus-eluting stents can lead to incomplete endothelialization and substantial impairment of arterial healing relative to treatment with bare-metal stents. The sustained and local delivery of ticagrelor, a reversibly binding P2Y12 receptor inhibitor, using hybrid biodegradable nanofibers/stents, was developed to reduce neointimal formation and endothelial dysfunction.

Methods

In this investigation, a solution of ticagrelor, poly(D,L)-lactide-co-glycolide, and hexafluoro isopropanol was electrospun to fabricate ticagrelor-eluting nanofibrous drug-eluting stents. The in vitro and in vivo ticagrelor concentrations were measured using a high-performance liquid chromatography assay. The effectiveness of ticagrelor-eluting stents was examined relative to that of sirolimus-eluting stents.

Results

Adequate ticagrelor levels were detected for four weeks in vitro. Less HES5-positive labeling was found near the ticagrelor-eluting stented vessels (0.33±0.12) than close to the sirolimus-eluting stented vessels (0.57±0.15) (p<0.05). Four weeks after deployment, the ticagrelor-eluting stent also exhibited an up-regulated local expression of SOD1 in the stenting area (p<0.001). The ticagrelor-eluting stent substantially preserved endothelial function and re-endothelialization, minimized inflammatory responses, and inhibited neointimal hyperplasia.

Conclusion

Ticagrelor-eluting stents may provide an alternative route for treating patients at a high risk of bleeding to preserve endothelial recovery and to reduce smooth muscle proliferation.

No Differences in Levels of Circulating Progenitor Endothelial Cells or Circulating Endothelial Cells Among Patients Treated With Ticagrelor Compared With Clopidogrel During Non- ST -Segment-Elevation Myocardial Infarction

Background

Ticagrelor use during acute coronary syndromes demonstrated a decrease in all‐cause mortality in the PLATO (Platelet Inhibition and Patient Outcomes) trial. This effect has been attributed to a non–platelet‐derived improvement in endothelial function. The aim of this study was to determine differences in the number of endothelial progenitor cells and/or circulating endothelial cells found in peripheral blood in patients treated with either ticagrelor or clopidogrel during non–ST‐segment–elevation myocardial infarction.

Methods and Results

In this multicenter, randomized study (NCT02244710), patients were considered for inclusion after non–ST‐segment–elevation myocardial infarction whenever they were P2Y₁₂‐inhibitor naïve. Ticagrelor and clopidogrel were allocated at a 1:1 ratio. Blood samples for determining endothelial progenitor cells and circulating endothelial cells were extracted before the antiplatelet loading dose, 48 hours after presentation of index symptoms, and 1 month after the event. A multichannel cytometer was used for optimal cell characterization. A total of 96 patients fulfilled the inclusion criteria. Circulating endothelial cell levels corrected by white blood cells were as follows at baseline, 48 hours, and 1 month: 44 (28–64), 50 (33–63), and 38 (23–62) cells/mL, respectively, for clopidogrel and 38 (29–60), 45 (32–85), and 35 (24–71) cells/mL, respectively, for ticagrelor (P=0.6). Endothelial progenitor cell levels were 29 (15–47), 27 (15–33), and 18 (10–25) cells/mL, respectively, for clopidogrel and 20 (11–33), 22 (12–32), and 18 (11–29) cells/mL, respectively, for ticagrelor (P=0.9). No differences in intraindividual changes were found.

Conclusions

Patients treated with ticagrelor during non–ST‐segment–elevation myocardial infarction, in comparison to clopidogrel, showed similar levels of endothelial progenitor cells and circulating endothelial cells. These data suggest that the endothelial protective effect mediated by ticagrelor is not related to bone marrow physiology modulation.

Clinical Trial Registration

URL: https://www.clinicaltrials.gov. Unique identifier: NCT02244710.

Interaction between platelets and endothelium: from pathophysiology to new therapeutic options

Platelets were traditionally considered to purely have a role in the maintenance of haemostasis. Recently their role in vasomotor function, inflammation and atherosclerosis has been very well-recognized. Endothelium which was originally considered as a simple passive barrier, it is now viewed as an organ whose normal functioning is crucial for maintaining vascular health. When endothelial balance is disturbed, vascular disease initiates. Platelet interactions with endothelium have an important contribution in this process. Low-grade inflammation, endothelial dysfunction, and platelet hyper-reactivity are all independently associated with an increased risk of cardiovascular events. Older antiplatelet agents like aspirin and clopidogrel and newer more potent agents like prasugrel and ticagrelor have been proven effective in all the clinical spectrum of coronary artery disease patients. Current antiplatelet medications and especially newer generation P2Y12 inhibitor ticagrelor, offer clinical benefits not only due to their well-recognized antithrombotic effect, but also via the attenuation of platelet inflammatory action, impediment of P2Y12 activation effects in other cells and through other complex and sometimes undefined pathways. Future research is expected to better define platelet-endothelium interactions and the multiple impact of current antiplatelet therapy on them.

Does Ticagrelor Improve Endothelial Function?

Ticagrelor is a P2Y12 receptor antagonist with proven clinical benefit in patients with acute coronary syndrome. Apart from its principal antiplatelet action, pleiotropic effects have been implicated in the clinical profile of ticagrelor, including a potentially beneficial impact on endothelial function. In light of the common presence and prognostic value of endothelial dysfunction in patients with coronary artery disease, several clinical studies have investigated the postulated effect of ticagrelor on endothelial function, yielding conflicting results. Limitations of the relevant studies as well as substantial differences in patient population, study design, and methods may account for these controversial findings. Most of these studies, however, support a beneficial impact of ticagrelor on endothelial function, which seems to be significant in the higher risk patients. In order to elucidate this effect, further research efforts should aim to clarify how quickly does endothelial function respond to ticagrelor, how sustained this response is during the dosing intervals and in the long term, which mechanisms are implicated, and whether this pleiotropic action is clinically significant. Future studies should include larger and diverse populations of patients, assess endothelial function at several time points after treatment initiation, and use multiple methods of endothelial function measurement, while implementing strict methodology. Nevertheless, the extent of the clinical benefit of ticagrelor attributable to actions beyond its potent and consistent antiplatelet effect remains uncertain.

Ticagrelor protects against AngII-induced endothelial dysfunction by alleviating endoplasmic reticulum stress

Ticagrelor has been reported to decrease cardiovascular mortality compared with clopidogrel. This benefit cannot be fully explained by the more efficient platelet inhibition. Many studies demonstrated that ticagrelor improved endothelial function, leaving the mechanism elusive though. The present study aims to investigate whether ticagrelor protects against endothelial dysfunction induced by angiotensinII (AngII) through alleviating endoplasmic reticulum (ER) stress. Male Sprague Dawley rats were infused with AngII or vehicle and administrated with ticagrelor or vehicle for 14 days. Reactive oxygen species (ROS) was detected. Aortas from normal mice were incubated with endoplasmic reticulum stress inducer tunicamycin with or without ticagrelor. Vasorecactivity was measured on wire myography. Rat aortic endothelial cells (RAECs) were pretreated with ticagrelor followed by AngII or tunicamycin. Endothelial nitric oxide synthase (eNOS) phosphorylation and ER stress markers were determined by western blotting. Impaired endothelial function, induction of ER stress, reduced eNOS phosphorylation and elevated ROS generation was restored by ticagrelor treatment in vivo. In addition, tunicamycin induced endothelial dysfunction was improved by ticagrelor. In vitro, the induction of ER stress and inhibited eNOS phosphorylation in REACs exposed to AngII as well as tunicamycin was reversed by co-culturing with ticagrelor. In conclusion, ticagrelor protects against AngII-induced endothelial dysfunction via alleviating ER stress.

Ticagrelor Improves Endothelial Function by Decreasing Circulating Epidermal Growth Factor (EGF)

Ticagrelor is one of the most powerful P2Y₁₂ inhibitor. We have recently reported that, in patients with concomitant Stable Coronary Artery Disease (SCAD) and Chronic Obstructive Pulmonary Disease (COPD) undergoing percutaneous coronary intervention (PCI), treatment with ticagrelor, as compared to clopidogrel, is associated with an improvement of the endothelial function (Clinical Trial NCT02519608). In the present study, we showed that, in the same population, after 1 month treatment with ticagrelor, but not with clopidogrel, there is a decrease of the circulating levels of epidermal growth factor (EGF) and that these changes in circulating levels of EGF correlate with on-treatment platelet reactivity. Furthermore, in human umbilical vein endothelial cells (HUVEC) incubated with sera of the patients treated with ticagrelor, but not with clopidogrel there is an increase of p-eNOS levels. Finally, analyzing the changes in EGF and p-eNOS levels after treatment, we observed an inverse correlation between p-eNOS and EGF changes only in the ticagrelor group. Causality between EGF and eNOS activation was assessed in vitro in HUVEC where we showed that EGF decreases eNOS activity in a dose dependent manner. Taken together our data indicate that ticagrelor improves endothelial function by lowering circulating EGF that results in the activation of eNOS in the vascular endothelium.

Influence of Local Myocardial Damage on Index of Microcirculatory Resistance and Fractional Flow Reserve in Target and Nontarget Vascular Territories in a Porcine Microvascular Injury Model

OBJECTIVES

The aim of this study was to investigate the influence of microvascular damage in one vessel territory on invasively measured physiological parameters in the other vessel, using a porcine microvascular damage model.

BACKGROUND

Although fractional flow reserve (FFR)-guided decision-making for the nonculprit stenosis in patients with acute myocardial infarction has been reported to be better than angiography-guided revascularization, there have been debates regarding the influence of microvascular dysfunction on measured FFR in nonculprit vessels.

METHODS

In Yorkshire swine, microvascular damage was induced with selective intracoronary injection of microspheres (100 μm × 10⁵ each) into the left anterior descending artery (LAD). Coronary stenosis was created in both the LAD and the left circumflex artery (LCx) using balloon catheters. Coronary physiological changes were assessed with index of microcirculatory resistance (IMR) and FFR at baseline and at each subsequent injection of microsphere up to a fifth dose in both the LAD and LCx. Measurements were repeated 5 times at each stage, and a total of 424 measurements were made in 12 Yorkshire swine models.

RESULTS

The median area stenosis in LAD and LCx was 48.1% (interquartile range: 40.8% to 50.4%) and 47.9% (interquartile range: 31.1% to 62.9%), respectively. At baseline, FFR in the LAD was lower than that in the LCx (0.89 ± 0.01 and 0.94 ± 0.01; p < 0.001). There was no difference in the IMR (18.4 ± 5.8 U and 17.9 ± 1.2 U; p = 0.847). With repeated injections of microspheres, IMR in LAD was significantly increased, up to 77.7 ± 15.7 U (p < 0.001). Given the same stenosis, FFR in the LAD was also significantly increased, up to 0.98 ± 0.01 along with IMR increase (p < 0.001). Conversely, IMR and FFR were not changed in the LCx throughout repeated injury to the LAD territory (p = 0.105 and p = 0.286 for IMR and FFR, respectively). The increase in LAD IMR was mainly driven by the increase in hyperemic mean transit time (p < 0.001).

CONCLUSIONS

In Yorkshire swine models, local microvascular damage increased both FFR and IMR in a vessel supplying target myocardial territory. However, IMR and FFR were maintained in the other vessel. These physiological results in swine support the concept that FFR measurement might provide useful information for evaluating nonculprit lesions in clinical settings involving significant acute myocardial injury.

Comparison of the 9-month intra-stent conditions and 2-year clinical outcomes after Resolute zotarolimus-eluting stent implantation between 3-month and standard dual antiplatelet therapy

BACKGROUND

The use of short-duration dual antiplatelet therapy (DAPT) remains controversial. To investigate efficacy and safety of short-duration DAPT, we performed a detailed comparison of intra-stent conditions by optical coherence tomography (OCT) after second-generation drug-eluting stent implantation with short-term and standard DAPT.

METHODS AND RESULTS

Eighty-two consecutive patients with stable angina pectoris who received Resolute zotarolimus-eluting stents (R-ZESs; Medtronic Cardiovascular, Santa Rosa, CA, USA) were enrolled. Patients were assigned to 3-month (3M group: 41 patients) and standard (standard group: 41 patients) DAPT. In the 3M group, clopidogrel was discontinued 3 months after stent implantation. In the standard group, DAPT was maintained until follow-up OCT. At 9 months, neointimal proliferation was significantly larger in the 3M group, but there were no significant between-group differences in the proportion of uncovered and malapposed strut. The prevalence of abnormal intra-stent tissue (AIT) at 9 months was equivalent between groups. A multiple regression analysis revealed malapposition at 9 months as the strongest independent predictor of AIT at 9 months, and the prevalence of AIT was not associated with DAPT duration. Over 2 years, cardiac events were equal between groups; however, major bleeding was higher tendency in the standard group than in the 3M group.

CONCLUSION

This OCT study indicated that reducing DAPT's duration may provide acceptable arterial healing in patients with implanted R-ZESs.