Effect of ambrisentan on echocardiographic and Doppler measures from patients in China with pulmonary arterial hypertension.

BACKGROUND: We retrospectively evaluated the echocardiographic data of ambrisentan-treated patients with pulmonary arterial hypertension (PAH) (NCT01808313). METHODS: Change from baseline in right ventricle (RV) systolic function, right heart structure, and pulmonary artery systolic pressure (PASP) prognosis to Weeks 12 and 24 was evaluated by echocardiography. RESULTS: In the overall population, the mean tissue Doppler-derived tricuspid lateral annular systolic velocity (S') increased by 0.6 cm/s at both Weeks 12 (p < 0.001) and 24 (p = 0.004) and tricuspid annular plane systolic excursion increased by 0.13 cm at Week 12 and 0.15 cm at Week 24 (both p < 0.001). A marked decrease in transverse and longitudinal RV and RA diameter at Weeks 12 and 24 was observed. A significant decrease in diastolic eccentricity index at both Weeks 12 (-0.1; p = 0.02) and 24 (-0.1; p = 0.001). The decrease in PASP from baseline was significant at both Weeks 12 (-9.5 mmHg; p<0.001) and 24 (-7.6 mmHg; p<0.001), while a decrease in the estimated right atrium pressure was found to be significant at Week 24 (-0.8mmHg; p = 0.01). CONCLUSION: Significant improvements in a number of RV echocardiographic parameters were observed at Weeks 12 and 24 after ambrisentan treatment in patients with PAH.

NLRC3 inhibits PDGF-induced PASMCs proliferation via PI3K-mTOR pathway.

Few studies about nucleotide-oligomerization domain-like receptor subfamily C3 (NLRC3) in PASMCs have been conducted. This research aimed to investigate the role of NLRC3 on platelet-derived growth factor (PDGF)-induced proliferation of pulmonary artery smooth muscle cells (PASMCs) and its underlying mechanism. We found that the proliferation of PASMCs stimulated with PDGF decreased when phosphoinositide 3-kinase (PI3K) or mammalian target of rapamycin (mTOR) inhibitors pretreatment. Overexpression of NLRC3 inhibited the proliferation of PASMCs and the phosphorylation of PI3K and mTOR while knocking down NLRC3 reversed this effect. Targeted to PI3K or mTOR can also reverse the effect of NLRC3. Activation of PI3K increased the phosphorylation of mTOR while inhibition of PI3K reduced it. Our data suggest that PDGF can induce abnormal proliferation of PASMCs, and NLRC3 suppresses activation of the PI3K-mTOR signaling thus inhibits PASMCs proliferation. These findings unveiled the effect of NLRC3 as an inhibitor of the PI3K-mTOR pathway mediating protection against PASMCs proliferation.

Nucleolin promotes Ang II-induced phenotypic transformation of vascular smooth muscle cells by regulating EGF and PDGF-BB.

RNA-binding properties of nucleolin play a fundamental role in regulating cell growth and proliferation. We have previously shown that nucleolin plays an important regulatory role in the phenotypic transformation of vascular smooth muscle cells (VSMCs) induced by angiotensin II (Ang II). In the present study, we aimed to investigate the molecular mechanism of nucleolin-mediated phenotypic transformation of VSMCs induced by Ang II. Epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) inhibitors were used to observe the effect of Ang II on phenotypic transformation of VSMCs. The regulatory role of nucleolin in the phenotypic transformation of VSMCs was identified by nucleolin gene mutation, gene overexpression and RNA interference technology. Moreover, we elucidated the molecular mechanism underlying the regulatory effect of nucleolin on phenotypic transformation of VSMCs. EGF and PDGF-BB played an important role in the phenotypic transformation of VSMCs induced by Ang II. Nucleolin exerted a positive regulatory effect on the expression and secretion of EGF and PDGF-BB. In addition, nucleolin could bind to the 5' untranslated region (UTR) of EGF and PDGF-BB mRNA, and such binding up-regulated the stability and expression of EGF and PDGF-BB mRNA, promoting Ang II-induced phenotypic transformation of VSMCs.

NLRC3 inhibits MCT-induced pulmonary hypertension in rats via attenuating PI3K activation.

Phosphoinositide 3-kinase (PI3K) activation plays a critical role in the pulmonary vascular remodeling of pulmonary hypertension (PH). The nucleotide-oligomerization domain (NOD)-like receptor subfamily C3 (NLRC3) inhibits proliferation and inflammation via PI3K signaling in cancer. We previously showed NLRC3 was significantly reduced in PH patients, but the mechanism of function remains unclear. This study aimed to determine the potential role of NLRC3 in PH. We found that NLRC3 was downregulated in the pulmonary arteries of PH animal models and platelet-derived growth factor-BB (PDGF-BB) stimulated pulmonary arterial smooth muscle cells (PASMCs). NLRC3 pretreatment reduced right ventricular systolic pressure, attenuated pulmonary vascular remodeling and RVHI, and ameliorated proliferation, migration, and inflammation. Monocrotaline (MCT)- and PDGF-BB-mediated PI3K activation were suppressed by NLRC3 pretreatment. 740Y-P decreased the effect of NLRC3. Collectively, NLRC3 protected against MCT-induced rat PH and PDGF-BB-induced PASMC proliferation, migration, and inflammation through a mechanism involving PI3K inhibition. NLRC3 may have a therapeutic effect on PH and provide a promising therapeutic strategy for PH.

Nucleolin promotes Ang II­induced phenotypic transformation of vascular smooth muscle cells via interaction with tropoelastin mRNA.

The current study aimed to clarify the role of nucleolin in the phenotypic transformation of vascular smooth muscle cells (VSMCs) and to preliminarily explore its underlying mechanism. The spatial and temporal expression patterns of nucleolin, and the effects of angiotensin II (Ang II) on the expression of VSMC phenotypic transformation markers, α­smooth muscle­actin, calponin, smooth muscle protein 22α and osteopontin were investigated. The effects of nucleolin on VSMC phenotypic transformation and the expression of phenotypic transformation­associated genes, tropoelastin, epiregulin and fibroblast growth factor 2 (b­FGF), were determined. Protein­RNA co­immunoprecipitation was used to investigate the potential target genes regulated by the nucleolin in phenotypic transformation of VSMCs. Finally, the stability of tropoelastin mRNA and the effects of nucleolin on the expression of tropoelastin were assayed. The results revealed that Ang II significantly promoted the phenotypic transformation of VSMCs. The expression of nucleolin was gradually upregulated in VSMCs treated with Ang II at different concentrations for various durations. Ang II induced nucleolin translocation from the nucleus to cytoplasm. Additionally, Ang II significantly promoted the phenotypic transformation of VSMCs. Overexpression and silencing of nucleolin regulated the expressions of tropoelastin, epiregulin and b­FGF. There was an interaction between tropoelastin mRNA and nucleolin protein, promoting the stability of tropoelastin mRNA and enhancing the expression of tropoelastin at the protein level. Upregulation of nucleolin had an important role in Ang II­induced VSMC phenotypic transformation, and its underlying mechanism may be through interacting with tropoelastin mRNA, leading to its increased stability and protein expression. The findings provide a new perspective into the regulatory mechanism of VSMC phenotypic transformation.

The effectiveness and safety of the RESTORE® drug-eluting balloon versus a drug-eluting stent for small coronary vessel disease: study protocol for a multi-center, randomized, controlled trial.

OBJECTIVE: Small coronary vessel disease (disease affecting coronary vessels with main branch diameters of ≤ 2.75 mm) is a common and intractable problem in percutaneous coronary intervention (PCI). This study was designed to test the theory that the effectiveness and safety of drug-eluting balloons for the treatment of de novo lesions in small coronary vessels are non-inferior to those of drug-eluting stents. METHODS: We designed a prospective, multicenter, randomized, controlled clinical trial aiming to assess the effectiveness and safety of the RESTORE® (Cardionovum, Bonn, Germany) drug-eluting balloon (DEB) versus the RESOLUTE® (Medtronic, USA) drug-eluting stent (DES) in the treatment of small coronary vessel disease. This trial started in August 2016. A total of 230 patients with a reference vessel diameter (RVD) ≥ 2.25 mm and ≤ 2.75 mm were randomly assigned to treatment with a DEB or a DES at a 1:1 ratio. The study was also designed to enroll 30 patients with an RVD ≥ 2.00 mm and ≤ 2.25 mm in the tiny vessel cohort. RESULTS: The key baseline data include demographic characteristics, relative medical history, baseline angiographic values and baseline procedural characteristics. The primary endpoint is in-segment diameter stenosis at nine months after the index procedure. Secondary endpoints include acute success, all-cause death, myocardial infarction, target vessel revascularization, target lesion revascularization and stent thrombosis. CONCLUSIONS: The study will evaluate the clinical efficacy, angiographic outcomes, and safety of DEBs compared to DESs in the treatment of de novo coronary artery lesions in small vessels.

NLRC3: A Novel Noninvasive Biomarker for Pulmonary Hypertension Diagnosis.

The nucleotide-oligomerization domain (NOD)-like receptor subfamily C3 (NLRC3) is a newly discovered and incompletely characterized member of the NLR family which negatively regulates inflammatory responses. Inflammation is considered a critical pathogenesis in pulmonary hypertension (PH). This is the first study to hypothesize that NLRC3 is closely correlated with PH. Total of 43 PH patients who were diagnosed by right heart catheterization (RHC) and 20 age-matched healthy control subjects were included. Echocardiographic variables and blood biochemical parameters were tested. Results of World Health Organization functional class (WHOFC), Borg dyspnea score and 6-minute walk tests (6MWT) were recorded. Mean pulmonary arterial pressure (mPAP) and pulmonary vascular resistance (PVR) were measured from RHC. Serum NLRC3 concentrations were detected by ELISA. ROC curve analysis was used to evaluate the diagnostic value of NLRC3 concentrations in PH. We found that serum NLRC3 concentration was significantly decreased in PH compared to the healthy control group. Serum NLRC3 concentration correlated negatively with mPAP and PVR. In addition, a negative correlation between serum NLRC3 concentration and WHOFC were detected. We proposed a cut-off value of 2.897ng/mL for serum NLRC3 concentration which was able to predict PH with 88% sensitivity and 85% specificity. In conclusion, NLRC3 concentrations in PH were significantly decreased, suggesting that NLRC3 may potentially be a diagnosis index and represent a prognostic factor for PH patients.

Impact of interaction between CYP1A1 genetic polymorphisms and smoking on coronary artery disease in the Han of China.

AIMS: To investigate the association of CYP1A1 genotype and additional gene-smoking interaction with coronary artery disease (CAD) risk based on a Chinese case-control study. METHODS: A total of 1862 participants (1134 men, 728 women) were selected, including 620 CAD patients and 1242 normal controls. Logistic regression was performed to investigate association of CYP1A1 genotype, gene-gene, and gene-smoking interaction with CAD. Generalized multifactor dimensionality reduction (GMDR) was used to screen the best gene-gene and gene-smoking interaction combination, cross-validation consistency, the testing balanced accuracy, and the sign test, to assess if each selected interaction was calculated. RESULTS: The carriers of homozygous mutant of rs4886605 polymorphism and heterozygous of rs4646903 are associated with increased CAD risk than those with wild-type homozygotes; OR (95% CI) was 1.98 (1.53-2.61) and 1.58 (1.24-1.96), respectively. The carriers of homozygous mutant of rs1048943 polymorphism is associated with decreased CAD risk than those with wild-type homozygotes, OR (95% CI) = 0.75 (0.60-0.93). GMDR model indicated a potential gene-gene interaction between rs4886605 and rs4646903 and a potential gene-smoking interaction between rs4886605 and smoking. Participants with rs4886605-CT or TT and rs4646903-TC or CC genotype have the highest CAD risk, compared to participants with rs4886605-CC and rs4646903-TT genotype; OR (95% CI) was 2.72 (2.03-3.61). In addition, we also found that smokers with rs4886605-CT or TT genotype have the highest CAD risk, compared to nonsmokers with rs4886605-CC genotype; OR (95% CI) was 3.07 (2.23-3.96). CONCLUSIONS: rs4886605 and rs4646903 are associated with increased CAD risk, but rs1048943 is associated with decreased CAD risk; we also found gene-gene interaction between rs4886605 and rs4646903 and gene-environment interaction between rs4886605 and smoking.

HIV protease inhibitors in pulmonary hypertension: rationale and design of a pilot trial in idiopathic pulmonary arterial hypertension.

We propose an exploratory clinical study, the first of its kind to our knowledge, to determine the safety and potential clinical benefit of the combination of the HIV protease inhibitors (HIV-PIs) saquinavir and ritonavir (SQV+RIT) in patients with idiopathic pulmonary arterial hypertension (IPAH). This study is based on evidence that (1) HIV-PIs can improve pulmonary hemodynamics in experimental models; (2) both Toll-like receptor 4 and high-mobility group box 1 (HMGB1) participate in the pathogenesis of experimental pulmonary hypertension; and (3) a high-throughput screen for inhibitors of HMGB1-induced macrophage activation yielded HIV-PIs as potent inhibitors of HMGB1-induced cytokine production. In this proposed open-label, pre-post study, micro, low, and standard doses of SQV+RIT will be given to IPAH patients for 14 days. Patients will receive follow-up for the next 14 days. The primary outcome to be evaluated is change in HMGB1 level from baseline at 14 days. The secondary outcome is changes in tumor necrosis factor α, interleukin 1ß, interleukin 6, C-reactive protein, pulmonary arterial pressure based on echocardiography parameters and New York Heart Association/World Health Organization functional class, and Brog dyspnea scale index from baseline at 14 days. Other secondary measurements will include N-terminal pro-brain natriuretic peptide, atrial natriuretic peptide, and 6-minute walk distance. We propose that SQV+RIT treatment will improve inflammatory disorders and pulmonary hemodynamics in IPAH patients. If the data support a potentially useful therapeutic effect and suggest that SQV+RIT is safe in IPAH patients, the study will warrant further investigation. (ClinicalTrials.gov identifier: NCT02023450.).

Vardenafil in pulmonary arterial hypertension: a randomized, double-blind, placebo-controlled study.

RATIONALE: Although the phosphodiesterase type 5 inhibitors sildenafil and tadalafil have demonstrated efficacy in patients with pulmonary arterial hypertension (PAH), monotherapy with these agents has not been conclusively shown to reduce clinical worsening events. OBJECTIVES: To evaluate the safety and efficacy of the phosphodiesterase type 5 inhibitor vardenafil in Chinese patients with PAH. METHODS: In a randomized, double-blind, placebo-controlled study, 66 patients with PAH were randomized 2:1 to vardenafil (5 mg once daily for 4 wk then 5 mg twice daily; n = 44) or placebo (n = 22) for 12 weeks. Patients completing this phase were then treated with open-label vardenafil (5 mg twice daily) for a further 12 weeks. MEASUREMENTS AND MAIN RESULTS: At Week 12, the mean placebo-corrected 6-minute walking distance was increased with vardenafil (69 m; P < 0.001), and this improvement was maintained for at least 24 weeks. Vardenafil also increased the mean placebo-corrected cardiac index (0.39 L·min(-1)·m(-2); P = 0.005) and decreased mean pulmonary arterial pressure and pulmonary vascular resistance (-5.3 mm Hg, P = 0.047; -4.7 Wood U, P = 0.003; respectively) at Week 12. Four patients in the placebo group (20%) and one in the vardenafil group (2.3%) had clinical worsening events (hazard ratio 0.105; 95% confidence interval, 0.012-0.938; P = 0.044). Vardenafil was associated with only mild and transient adverse events. CONCLUSIONS: Vardenafil is effective and well tolerated in patients with PAH at a dose of 5 mg twice daily.

[The efficacy and safety of bosentan therapy for Chinese patients with idiopathic pulmonary arterial hypertension: an open-label, prospective multicenter study].

OBJECTIVE: To investigate the efficacy, safety and tolerance of bosentan, a dual endothelin receptor antagonist, in Chinese patients with idiopathic pulmonary arterial hypertension (IPAH). METHODS: Totally 79 IPAH patients (hemodynamic criteria confirmed by right heart catheterization) were included in this open-label, prospective multicenter study. Patients received 62.5 mg of bosentan twice daily for the first 4 weeks, and then up-titrated to 125 mg twice daily for another 12 weeks. The primary end point was the change in exercise capacity showed by six-minute walk distance (6MWD) from baseline to 16 weeks. Secondary end points included the change in World Health Organization (WHO) functional class, Borg dyspnoea scale and systolic pulmonary artery pressure measured by echocardiography. RESULTS: The 6MWD increased from (343.7 ± 93.7) meters at baseline to (397.5 ± 104.4) meters after 16 weeks (P < 0.01), WHO functional class and Borg dyspnoea scale were also significantly improved after 16 weeks therapy compared to baseline levels (all P < 0.01). Furthermore, the systolic pulmonary artery pressure was significantly decreased from (97.8 ± 25.2) mm Hg (1 mm Hg = 0.133 kPa) to (92.8 ± 29.5) mm Hg (P < 0.05) after 16 weeks bosentan treatment. There was no patient withdrawal from this study for safety consideration. CONCLUSION: Bosentan therapy is well tolerated and can improve the exercise capacity and WHO functional class in Chinese IPAH patients.

Survival of Chinese patients with pulmonary arterial hypertension in the modern treatment era.

BACKGROUND: In a previous study of Chinese patients with idiopathic pulmonary arterial hypertension (IPAH) in the nontargeted therapy era (defined as the time before 2006 when new pulmonary arterial hypertension-specific drugs were not available in China), we reported 1- and 3-year survival estimates of only 68% and 39%, respectively. However, it is not yet known whether the survival of patients with pulmonary arterial hypertension is improved in the modern treatment era (defined in China as after 2006). METHODS: A retrospective cohort study was undertaken in 276 consecutive patients with newly diagnosed incident IPAH and connective tissue disease-related pulmonary arterial hypertension (CTDPAH) who were referred between 2007 and 2009. Baseline characteristics and survival rates in the two groups were compared. RESULTS: The 1- and 3-year survival estimates were 92.1% and 75.1%, respectively, in patients with IPAH, and 85.4% and 53.6%, respectively, in patients with CTDPAH. Patients with CTDPAH had a significantly lower mean pulmonary artery pressure, more pericardial effusion, and more severe impairment of the diffusion capacity of the lung for carbon monoxide than patients with IPAH. A diagnosis of CTDPAH, World Health Organization functional class III or IV, single-breath diffusion capacity of the lung for carbon monoxide < 80% predicted, and the presence of pericardial effusion were independent predictors of mortality. The 1- and 3-year survival rates of male patients were 93.5% and 77.5%, respectively, in those with IPAH, and 71.1% and 47.4%, respectively, in those with CTDPAH. CONCLUSIONS: The survival rates of patients with pulmonary arterial hypertension have improved in China in the modern treatment era, despite the high costs of treatment and financial constraints. However, the survival rates of patients with CTDPAH are inferior to those of patients with IPAH. Our study also indicates poorer survival rates in male patients with CTDPAH.

[Effects of intracoronary diltiazem on no-reflow phenomenon after emergent percutaneous coronary intervention in patients with acute myocardial infarction].

OBJECTIVE: To assess the effects of intracoronary diltiazem on no-reflow phenomenon of infarct-related artery (IRA) after emergent percutaneous transluminal coronary angioplasty or/and intracoronary stenting (PTCA/Stenting) in the patients with acute myocardial infarction (AMI). METHODS: We studied 34 AMI patients with no-reflow phenomenon of IRA after emergent PTCA/Stenting between January 1999 and August 2005. Urokinase-treated group (n=16) was given intracoronary urokinase 30,0000 - 50,0000 units within 15 - 30 minutes between January 1999 and April 2002 while diltiazem-treated group (n=18) was given intracoronary diltiazem 0.5 - 2 mg within 10 - 30 minutes between May 2002 and August 2005. Fifteen minutes later, coronary arteriography (CAG) was performed and the thrombolysis in myocardial infarction (TIMI) flow grade was measured. RESULTS: No apparent change of TIMI flow grade was found between pre-administration and post-administration of intracoronary urokinase, but TIMI flow grade was significantly improved after intracoronary diltiazem (P<0.01). TIMI flow grade of diltiazem-treated group was significantly higher than that of urokinase-treated group after the administration (P<0.05). The percentage of the patients who reached TIMI flow grade 3 after the intracoronary administration was higher in the diltiazem-treated group than that in the urokinase-treated group (P<0.01). CONCLUSION: The intracoronary administration of diltiazem 0.5~2mg can effectively improve the no-reflow phenomenon after emergent PTCA/Stenting in patients with AMI.

[Formation and function of coronary collateral circulation and their influencing factors].

OBJECTIVE: To clarify the formation and function of coronary collateral circulation (CCC) in coronary artery disease (CAD) patients with severe coronary artery stenosis and their influencing factors. METHODS: Coronary angiography was performed on 266 CAD patients with severe coronary stenosis. CCC formation was evaluated by Rentrop rating on those 266 patients and 401 severe stenosis arteries; while in CCC formed patients, CCC function was evaluated by Werner collateral collection (CC) rating. The formation, function of CCC and their influencing factors were analyzed and compared. RESULTS: CCC formation in those severe stenosis coronary arteries was related to the severity of coronary stenosis: the forming rate of CCC was 42.6% in vessels with 90%-94% stenosis (Group A), 56.9% with 95%-99% stenosis (Group B) and 93.0% with 100% stenosis (Group C) (p <0 .01). Between CCC forming and non-forming groups, there was no significant difference in age, gender, incidence of MI, hypertension and diabetes, history of smoking and serum levels of HDL-C and LDL-C (P > 0.05). In the CCC formation group, serum HDL-C level was the highest in the CC Grade 2 group (according to Werner function rating) and the lowest in the CC Grade 0 group (P < 0.05). Whereas, LDL-C level was the lowest in the CC Grade 2 group and the highest in the CC Grade 0 group (P < 0.05). CONCLUSION: Severity of coronary stenosis was the major influencing factor in CCC formation and function, and the rate of CCC formation increased with the exacerbation of coronary stenosis. Serum HDL-C and LDL-C level had no relationship with CCC formation, but related to CCC function. Better CCC function was found in patients with high level of HDL-C whereas the patients with high level of LDL-C had spoiled CCC function.

[Effects of nitroglycerin on plasma calcitonin gene-related peptide and endothelin in congestive heart failure].

OBJECTIVE: To investigate the plasma calcitonin gene-related peptide (CGRP) and endothelin (ET) levels and the effects of nitroglycerin on CGRP and ET in congestive heart failure (CHF), and to make clear the mechanism of nitroglycerin in vasodilation and cardiac protection. METHODS: The fast blood samples were taken from the peripheral vein of 40 volunteers and 40 CHF patients to estimate the basal level of CGRP and ET. Infusion of nitroglycerin of 25 to 50 micrograms/min started in the forearm vein of CHF patients. Blood samples were taken at the end of the 1 hour infusion and (12 +/- 2) days of nitroglycerin treatment. Plasma concentrations of CGRP and ET were measured by radioimmunoassay. RESULTS: In patients with CHF before the treatment, the plasma concentration of CGRP was significantly lower than that in the controls (P < 0.001), but the concentration of ET significantly higher than that in the controls (P < 0.001). During the nitroglycerin treatment, the plasma concentration of CGRP significantly increased (P < 0.001), whereas the concentration of ET significantly decreased (P < 0.01). The mean arterial pressure significantly decreased (P < 0.001). CONCLUSION: Nitroglycerin can increase the peripheral plasma CGRP level and decrease the concentration of ET when treating CHF. Intravenous nitroglycerin may be beneficial to the improvement of abnormal haemodynamics and neurohormonal derangement.

Comparison of the self-expanding Radius stent and the balloon-expandable Multilink stent for elective treatment of coronary stenoses: a serial analysis by intravascular ultrasound.

We compared the outcome of the self-expanding Radius stent and the balloon-expandable Multilink stent serially by angiography and intravascular ultrasound. Successful stent deployment was achieved in 66 lesions of 56 stable angina patients (34 lesions with Radius stents and 32 lesions with Multilink stents). At follow-up, there were no significant differences in minimal lumen diameter or percent diameter stenosis between the groups, nor in restenosis rates, although the Radius stent group rate was slightly lower (23.5% vs. 31.3%). In the Radius stent group, stent cross-sectional area (CSA) increased gradually after implantation until the 6-month follow-up (8.37 +/- 1.83 to 10.16 +/- 2.59 mm(2); n = 15), giving a larger CSA (P = 0.03) than the Multilink stent group, which decreased (9.00 +/- 2.05 to 8.27 +/- 2.15 mm(2); n = 17). The lumen CSA was also slightly larger (6.82 +/- 3.06 vs. 5.84 +/- 1.85 mm(2); P = 0.29) in the Radius stent group. These findings indicated that the Radius stent enlarged progressively after implantation, which might be useful for prevention of restenosis.