Coronary collateral function long after drug-eluting stent implantation

Dysregulated cellular metabolism in atherosclerosis: mediators and therapeutic opportunities

Accumulating evidence over the past decades has revealed an intricate relationship between dysregulation of cellular metabolism and the progression of atherosclerotic cardiovascular disease. However, an integrated understanding of dysregulated cellular metabolism in atherosclerotic cardiovascular disease and its potential value as a therapeutic target is missing. In this Review, we (1) summarize recent advances concerning the role of metabolic dysregulation during atherosclerosis progression in lesional cells, including endothelial cells, vascular smooth muscle cells, macrophages and T cells; (2) explore the complexity of metabolic cross-talk between these lesional cells; (3) highlight emerging technologies that promise to illuminate unknown aspects of metabolism in atherosclerosis; and (4) suggest strategies for targeting these underexplored metabolic alterations to mitigate atherosclerosis progression and stabilize rupture-prone atheromas with a potential new generation of cardiovascular therapeutics.

Endothelial Autophagy in Coronary Microvascular Dysfunction and Cardiovascular Disease

Coronary microvascular dysfunction (CMD) refers to a subset of structural and/or functional disorders of coronary microcirculation that lead to impaired coronary blood flow and eventually myocardial ischemia. Amid the growing knowledge of the pathophysiological mechanisms and the development of advanced tools for assessment, CMD has emerged as a prevalent cause of a broad spectrum of cardiovascular diseases (CVDs), including obstructive and nonobstructive coronary artery disease, diabetic cardiomyopathy, and heart failure with preserved ejection fraction. Of note, the endothelium exerts vital functions in regulating coronary microvascular and cardiac function. Importantly, insufficient or uncontrolled activation of endothelial autophagy facilitates the pathogenesis of CMD in diverse CVDs. Here, we review the progress in understanding the pathophysiological mechanisms of autophagy in coronary endothelial cells and discuss their potential role in CMD and CVDs.

Effects of clopidogrel vs. prasugrel vs. ticagrelor on endothelial function, inflammatory parameters, and platelet function in patients with acute coronary syndrome undergoing coronary artery stenting: a randomized, blinded, parallel study

AIMS

In a randomized, parallel, blinded study, we investigate the impact of clopidogrel, prasugrel, or ticagrelor on peripheral endothelial function in patients undergoing stenting for an acute coronary syndrome.

METHODS AND RESULTS

The primary endpoint of the study was the change in endothelium-dependent flow-mediated dilation (FMD) following stenting. A total of 90 patients (age 62 ± 9 years, 81 males, 22 diabetics, 49 non-ST elevation myocardial infarctions) were enrolled. There were no significant differences among groups in any clinical parameter. Acutely before stenting, all three drugs improved FMD without differences between groups (P = 0.73). Stenting blunted FMD in the clopidogrel and ticagrelor group (both P < 0.01), but not in the prasugrel group. During follow-up, prasugrel was superior to clopidogrel [mean difference 2.13, 95% confidence interval (CI) 0.68-3.58; P = 0.0047] and ticagrelor (mean difference 1.57, 95% CI 0.31-2.83; P = 0.0155), but this difference was limited to patients who received the study therapy 2 h before stenting. Ticagrelor was not significantly superior to clopidogrel (mean difference 0.55, 95% CI -0.73 to 1.82; P = 0.39). No significant differences were seen among groups for low-flow-mediated dilation. Plasma interleukin (IL)-6 (P = 0.02 and P = 0.01, respectively) and platelet aggregation reactivity in response to adenosine diphosphate (P = 0.002 and P = 0.035) were lower in the prasugrel compared to clopidogrel and ticagrelor group.

CONCLUSION

As compared to ticagrelor and clopidogrel, therapy with prasugrel in patients undergoing stenting for an acute coronary syndrome is associated with improved endothelial function, stronger platelet inhibition, and reduced IL-6 levels, all of which may have prognostic implications. This effect was lost in patients who received the study medication immediately after stenting.

EUDRACT-NO

2011-005305-73.

Prognostic impact of collaterals in patients with a coronary chronic total occlusion: A meta-analysis of over 3,000 patients

OBJECTIVES

To assess the prognostic implications of the degree of coronary collaterals on outcomes in patients with a CTO.

BACKGROUND

Coronary chronic total occlusions (CTO) are identified frequently in patients undergoing coronary angiography and have been associated with poorer prognosis. Whether the degree of coronary collaterals, the hallmark of CTOs impacts prognosis, is unknown.

METHODS

A search of EMBASE, MEDLINE, and Cochrane Library was conducted to identify studies reporting on coronary collaterals and risk of all-cause mortality, acute myocardial infarction (AMI) and successful percutaneous coronary intervention (PCI). Patients with Rentrop grade 0 or 1 collaterals were defined as poor collaterals, while Rentrop grade 2 or 3 were defined as robust collaterals.

RESULTS

Twelve studies with a total of 3,369 were included. Patients with robust collaterals did not have lower rates of AMI (OR: 0.89, 95%CI: 0.39-2.04) or lower rates of all-cause mortality (OR: 0.81, 95% CI: 0.42-1.58), however were more likely to have successful PCI (OR: 4.04, 95%CI: 1.10-14.85).

CONCLUSION

The presence of robust collaterals is not associated with lower rates of AMI or mortality, but does increase the likelihood of successful CTO PCI. These results have importance implications with respect to the indications for CTO PCI as well as selecting appropriate patients to undergo the procedure.

Spontaneous coronary collateral recruitment in patients with recurrent ST elevation myocardial infarction (STEMI)

The spontaneous recruitment of acute coronary collaterals in the setting of an ST elevation myocardial infarction (STEMI) is seen frequently in those patients undergoing primary percutaneous coronary intervention (pPCI) and is associated with improved clinical outcomes. However, it is unknown whether in patients who present with a recurrent STEMI, the degree of collateral recruitment remains the same as in the index procedure. We reviewed all patients presenting to our tertiary centre with a STEMI undergoing primary or rescue percutaneous coronary intervention (PCI) from July 2010 until December 2018. We identified patients who presented with a recurrent STEMI following their index procedure. We defined patients with poor collateral recruitment as Rentrop grade 0 or 1, whilst patients with robust collateral recruitment as Rentrop grade 2 or 3. Of the 1795 patients who were identified, there were 27 cases in 25 patients who presented with a repeat STEMI following their index procedure. The median time between cases was 12.8 days (IQR 2.3-589.5 days). Compared to the index case, there was no statistically significant difference in the degree of collateral recruitment in recurrent presentations (Z = - 0.378, p = 0.70). In those patients presenting more than 6 months following the index procedure, the median time between cases was 654.5 days (IQR 479.5-1151.9). There was no difference in the degree of collateral recruitment in recurrent presentations (Z = 0.000, p = 1.0). Cases which had poorer collateral recruitment in recurrent presentations were less likely to be current smokers (0% vs 50%, p < 0.001) and less likely to have diabetes (0% vs 27.3%, p < 0.05) The recruitment of spontaneous coronary collaterals remains constant in recurrent STEMI presentations suggesting an innate biological process rather than merely a manifestation of alteration of haemodynamic blood flow. Further investigations to identify these processes is required.

Restenosis after stenting in symptomatic vertebral arterial orifice disease and considerations for better outcome

We have performed stenting in 11 patients with symptomatic vertebral arterial orifice stenosis refractory to medical treatment or impairment in anterior circulation. Three of the 11 patients experienced asymptomatic severe in-stent restenosis or occlusion. Bare metal stents were used in those three patients, two of whom received revascularization therapy. Development of sufficient cervical collateral channels reconstituting the distal vertebral artery was the common feature in patients with asymptomatic in-stent restenosis. In selecting appropriate stents, consideration of mechanical strength and drug-eluting properties of a stent according to characteristics of the target vessel is important to reduce the risk of in-stent restenosis. Any decision to perform revascularization should be based on the presence of abundant cervical collaterals as well as clinical symptoms of vertebrobasilar ischemia.

Fatal derecruitment of occluded left anterior descending collaterals after left circumflex revascularization

Coronary arteries are not definitely functionally terminal arteries, as previously thought; indeed, they are linked and interconnected by a rich network of collaterals. Chronic total occlusions (CTOs) represent a subset of frequent lesions encountered in everyday catheterization laboratory practice, generally associated with a developed system of collateral connections. These latter have the capacity to prevent myocardial necrosis and may even uphold metabolic supply to the ischemic territory to maintain its contractile capacity. Authors have reported a rapid and progressive reduction of collateral function and their decline after antegrade flow restoration, resulting in higher myocardial susceptibility to ischemia in the CTO territory. Here, we report the case of a fatal derecruitment of collaterals for a left anterior descending CTO not reopened, after left circumflex subocclusion revascularization.

Collateral Circulation in Chronic Total Occlusions – an interventional perspective

Human coronary collaterals are inter-coronary communications that are believed to be present from birth. In the presence of chronic total occlusions, recruitment of flow via these collateral anastomoses to the arterial segment distal to occlusion provide an alternative source of blood flow to the myocardial segment at risk. This mitigates the ischemic injury. Clinical outcome of coronary occlusion ie. severity of myocardial infarction/ischemia, impairment of cardiac function and possibly survival depends not only on the acuity of the occlusion, extent of jeopardized myocardium, duration of ischemia but also to the adequacy of collateral circulation. Adequacy of collateral circulation can be assessed by various methods. These coronary collateral channels have been used successfully as a retrograde access route for percutaneous recanalization of chronic total occlusions. Factors that promote angiogenesis and further collateral remodeling ie. arteriogenesis have been identified. Promotion of collateral growth as a therapeutic target in patients with no suitable revascularization option is an exciting proposal.

Diagnosis and Evaluation of Stent Thrombosis with Optical Coherence Tomography

Stent thrombosis (ST) is a rare complication of percutaneous coronary interventions (PCI), especially with drug-eluting stents. ST presents as acute myocardial infarction requiring emergent repeat PCI; optimal reperfusion occurs in two-thirds of patients. As a result, ST has been associated with a high mortality rate and a high rate of recurrent thrombosis. We discuss the use of optical coherence tomography (OCT) for the diagnosis and evaluation of ST. OCT-guided ST management seems a feasible, safe, and appropriate approach. Intracoronary assesses the efficacy of coronary thrombus removal procedures and detects the prevalent stent-related factor that caused ST.

Effects of clopidogrel, prasugrel and ticagrelor on endothelial function, inflammatory and oxidative stress parameters and platelet function in patients undergoing coronary artery stenting for an acute coronary syndrome. A randomised, prospective, controlled study

INTRODUCTION

Particularly in the setting of acute coronary syndromes, the interplay between vascular and platelet function has been postulated to have direct clinical implications. The present trial is designed to test the effect of clopidogrel, prasugrel and ticagrelor on multiple parameters of vascular function, platelet aggregation, oxidative and inflammatory stress before and up to 4 weeks after coronary artery stenting.

METHODS AND ANALYSIS

The study is designed as a three-arm, parallel design, randomised, investigator-blinded study. Patients with unstable angina or non-ST elevation myocardial infarction undergoing coronary intervention with a drug-eluting stent will be randomised to receive 600 mg clopidogrel, 60 mg prasugrel or 180 mg ticagrelor followed by oral therapy with the same drug. The primary endpoint of the trial is the impact of antiplatelet treatments on endothelial function as assessed by flow-mediated dilation at 1 day, 1 week and 1 month in patients who have undergone stenting. Secondary endpoints include the impact of study medications on parameters of macrovascular and microvascular function, platelet reactivity, oxidative and inflammatory stress. The study recruitment is currently ongoing and, after an interim analysis which was performed at 50% of the initially planned population, it is planned to continue until July 2015.

ETHICS AND DISSEMINATION

The protocol was approved by the local ethics committee. The trial will provide important pathophysiological insight on the relationship between platelet aggregation and endothelial function, two parameters that have been shown to influence patients' prognosis.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Identifier: NCT01700322; EudraCT-Nr.: 2011-005305-73. Current V.1.3, from 24 February 2014.

Contemporary analysis of incidence and outcomes of stent thrombosis presenting as ST elevation myocardial infarction in a primary percutaneous coronary intervention cohort

There are limited data about the effectiveness of primary percutaneous coronary intervention (PPCI) for stent thrombosis treatment. We aimed to evaluate the prevalence and outcomes of PPCI in patients with ST elevation acute myocardial infarction (STEMI) due to stent thrombosis, and comparing the outcomes with patients treated for de novo coronary thrombosis. This was an observational cohort study of 2,935 patients who underwent PPCI from 2003 to 2011 with follow-up for a median of 3.0 years (interquartile range 1.2 to 4.6). The primary end point was the first major adverse cardiac event (MACE) defined as death, nonfatal myocardial infarction, stroke, or target vessel revascularization. Stent thrombosis overall accounted for 6.6% (194 of 2,935) of all STEMIs with a proportion that increased over time (3.3% in 2004 to 9.4% in 2011). A total of 34.5% were early, 30.9% late stent thrombosis, and 34.5% were very late stent thrombosis. Indications for the original intervention were elective in 27.8%, after acute coronary syndrome (non-STEMI or unstable angina) in 21.1%, and after PPCI in 51.1%. Patients with stent thrombosis had higher rates of hypertension, hypercholesterolemia, diabetes, renal dysfunction, and previous myocardial infarction or coronary artery bypass surgery compared with patients with native artery occlusion. MACE rates were higher in patients with stent thrombosis compared with patients with native artery occlusions (40.9%, 95% confidence interval [CI] 31.1 to 50.6 vs 15.1%, 95% CI 12.5 to 18.3; p <0.0001). The poor outcome of stent thrombosis was particularly associated with early and late stent thromboses. Very late stent thrombosis appears to be a relatively less serious event, with similar outcomes to native vessel thromboses (MACE very late stent thrombosis 16.5%, 95% CI 8.2 to 28.6 vs native 15.1%, 95% CI 12.5 to 18.3, p = 0.245). In conclusion, stent thrombosis accounts for an increasing proportion of STEMI and is associated with worse outcomes compared with native artery occlusion.

Intra-individual head-to-head comparison of Sirolimus®- and Paclitaxel®-eluting stents for coronary revascularization. A randomized, multi-center trial

BACKGROUND

Despite the known effects of drug-eluting stents (DES), other cofactors attributed to patient characteristics affect their success. Interest focused on designing a study minimizing these factors to answer continuing concerns on the heterogeneity of response to different DESs. The study's aim was to investigate the feasibility and impact of an intra-individual comparison design in patients (pts) with two coronary artery stenosis treated with a Sirolimus- (SES) and a Paclitaxel- (PES) eluting stent.

METHODS AND RESULTS

The study was conducted as a prospective, randomized, multi-center trial in 112 pts who consented to treatment with a SES and a PES. Pts were eligible if they suffered from the presence of two single primary target lesions in two different native coronary arteries. Lesions were randomized to either SES or PES treatment. The primary endpoint was in-stent luminal late loss (LLL), as determined by quantitative angiography at 8 months; clinical follow up was obtained at 1, 8, and 12 months additionally. The LLL (0.13 ± 0.28 mm SES vs. 0.26 ± 0.35 mm PES, p=0.011) showed less neointima in SES. With a predefined cut-off criterion of 0.2mm difference in LLL, 53/87 pts SES and PES were similar effective. 34/87 pts had a divergent result, 26 pts had greater benefit from SES while 8 pts had greater benefit from PES. Overall, MACE (MI, TLR, and death) occurred in 19 (17%) pts. Based on lesion analysis of 108 lesions treated with SES and 110 lesions treated with PES, 5 (4.6%) lesions with SES and 3 (2.7%) lesions with PES required repeated TLR.

CONCLUSION

An intra-individual comparison design to assess differences in efficacy of different DESs is feasible, safe and achieves similar results to inter-individual studies. This study is among the first to show that failure of one DES does not necessarily implicate failure of another DES and vice versa.

The impact of the coronary collateral circulation on mortality: a meta-analysis

AIMS

The coronary collateral circulation as an alternative source of blood supply has shown benefits regarding several clinical endpoints in patients with myocardial infarction (MI) such as infarct size and left ventricular remodelling. However, its impact on hard endpoints such as mortality and its impact in patients with stable coronary artery disease (CAD) is more controversial. The purpose of this systematic review and meta-analysis was to explore the impact of collateral circulation on all-cause mortality.

METHODS AND RESULTS

We searched MEDLINE, EMBASE, ISI Web of Science (2001 to 25 April 2011), and conference proceedings for studies evaluating the effect of coronary collaterals on mortality. Random-effect models were used to calculate summary risk ratios (RR). A total of 12 studies enrolling 6529 participants were included in this analysis. Patients with high collateralization showed a reduced mortality compared with those with low collateralization [RR 0.64 (95% confidence interval 0.45-0.91); P= 0.012]. The RR for 'high collateralization' in patients with stable CAD was 0.59 [0.39-0.89], P= 0.012, in patients with subacute MI it was 0.53 [0.15-1.92]; P= 0.335, and for patients with acute MI it was 0.63 [0.29-1.39]; P= 0.257.

CONCLUSIONS

In patients with CAD, the coronary collateralization has a relevant protective effect. Patients with a high collateralization have a 36% reduced mortality risk compared with patients with low collateralization.

Intravascular optical imaging technology for investigating the coronary artery

There is an ever-increasing demand for new imaging methods that can provide additional information about the coronary wall to better characterize and stratify high-risk plaques, and to guide interventional and pharmacologic management of patients with coronary artery disease. While there are a number of imaging modalities that facilitate the assessment of coronary artery pathology, this review paper focuses on intravascular optical imaging modalities that provide information on the microstructural, compositional, biochemical, biomechanical, and molecular features of coronary lesions and stents. The optical imaging modalities discussed include angioscopy, optical coherence tomography, polarization sensitive-optical coherence tomography, laser speckle imaging, near-infrared spectroscopy, time-resolved laser induced fluorescence spectroscopy, Raman spectroscopy, and near-infrared fluorescence molecular imaging. Given the wealth of information that these techniques can provide, optical imaging modalities are poised to play an increasingly significant role in the evaluation of the coronary artery in the future.

Advantages and disadvantages of biodegradable platforms in drug eluting stents

Coronary angioplasty with drug-eluting stent (DES) implantation is currently the most common stent procedure worldwide. Since the introduction of DES, coronary restenosis as well as the incidence of target vessel and target lesion revascularization have been significantly reduced. However, the incidence of very late stent thrombosis beyond the first year after stent deployment has more commonly been linked to DES than to bare-metal stent (BMS) implantation. Several factors have been associated with very late stent thrombosis after DES implantation, such as delayed healing, inflammation, stent mal-apposition and endothelial dysfunction. Some of these adverse events were associated with the presence of durable polymers, which were essential to allow the elution of the immunosuppressive drug in the first DES designs. The introduction of erodable polymers in DES technology has provided the potential to complete the degradation of the polymer simultaneously or immediately after the release of the immunosuppressive drug, after which a BMS remains in place. Several DES designs with biodegradable (BIO) polymers have been introduced in preclinical and clinical studies, including randomized trials. In this review, we analyze the clinical results from 6 observational and randomized studies with BIO polymers and discuss advantages and disadvantages of this new technology.

Safety and Efficacy of Clopidogrel before Surgery

Clopidogrel is an antiplatelet drug that is used in patients who have had previous cerebrovascular events, acute coronary syndromes, or who underwent percutaneous coronary interventions (PCI) with bare metal or drug-eluting stents. About 5% of patients who undergo PCI have to undergo non-cardiac surgery within 1 year of coronary stent implantation. Patients who receive clopidogrel may be at increased risk of bleeding complications during surgery. The risk of coronary thrombosis after non-cardiac surgery increases, especially when surgery is performed early after stenting, and particularly when antiplatelet agents are withdrawn before surgery. The decision to continue or withhold clopidogrel should reflect a balance of the consequences of perioperative hemorrhage versus the risk of perioperative vascular complications. Close communication among surgeons, anesthesiologists, and cardiologist is necessary to minimize both adverse cardiac risk and surgical risk in those patients.

Biolimus-eluting biodegradable polymer-coated stent versus bare metal stent in acute ST-elevation and non-ST elevation myocardial infarction: Justification for biodegradable polymer-coated stent in acute coronary syndrome (JANICE) registry

AIMS

We evaluated the efficacy and safety of a biolimus- eluting biodegradable polymer-coated stent (BES) in patients with ST-segment elevation and non ST-segment elevation acute myocardial infarction (AMI).

METHODS AND RESULTS

This was an observational study involving a single centre patient registry. We compared the rates of cardiac death, myocardial infarction, target vessel revascularization (TVR) and composite end point of cardiac death and myocardial infarction at 24 months in 106 patients who received BES versus 94 patients who received an otherwise similar bare metal stent (BMS) during percutaneous coronary intervention for AMI. There was no significant difference in the rate of cardiac death (0.9% versus 7.4%; P = 0.09), myocardial infarction (4.7% versus 3.2%; P = 0.69), stent thrombosis (0.9% versus 3.2%; P = 0.30) or cardiac death and myocardial infarction (5.7% versus 10.6%; P = 0.30) between the two groups. The rate of TVR was significantly higher in the BMS group (1.9% versus 8.5%; P = 0.04), with patients receiving BMS being four times more likely to require TVR.

CONCLUSION

The use of BES in selected patients with AMI appears to be safe and is associated with significantly reduced rate of TVR, when compared with an otherwise similar BMS.

The Management of Antiplatelet Therapy in Patients With Coronary Stents Undergoing Noncardiac Surgery

Whereas the development of coronary stents has been a major breakthrough in the treatment of coronary artery disease, stent thrombosis, associated with myocardial infarction and death, has introduced a new challenge in the care of patients with coronary stents undergoing noncardiac surgery. This review presents the authors’ recommendations regarding the optimal management of such patients. Elective surgery should be postponed for at least 6 weeks and optimally 3 months for a bare-metal stent and at least 1 year for a drug-eluting stent. On the other hand, managing a patient undergoing non-elective surgery is more difficult and necessitates a case-by-case assessment of bleeding risk versus thrombotic risk based on patient comorbidities, type of stents present, details of the coronary intervention, and type of surgical procedure. Patients with a risk of bleeding that outweighs the risk of stent thrombosis should discontinue at least clopidogrel, whereas all other patients should continue dual antiplatelet therapy throughout the perioperative period.

Coronary microvascular function in early chronic kidney disease

BACKGROUND

coronary microvascular dysfunction may underlie the high cardiovascular risk associated with chronic kidney disease (CKD), but the effects of CKD on coronary microvasculature function remain uncertain.

METHODS AND RESULTS

we assessed myocardial blood flow changes in mild-to-moderate CKD and analyzed the association between creatinine clearance (CrCl) and peak myocardial blood flow and coronary flow reserve (CFR) measured as the ratio of stress to rest perfusion at baseline and at 1 year in 435 nondiabetic individuals who underwent quantitative rest and pharmacological stress positron emission tomography imaging. At baseline, CFR was significantly associated with CrCl (β per 10 mL/min increase, 0.07; P=0.001). Factors such as age and blood pressure accounted for this association, and it was not significant in adjusted analyses (β=-0.02, P=0.53). Peak flow was not associated with CrCl in either crude or adjusted analyses (β per 10 mL/min=-0.02 mL/min per g, P=0.29). Although change in peak flow at 1 year was similar in patients with and without CKD, CrCl was a strong and independent predictor of a higher rate of change in CFR, with a loss of 0.11 CFR units/y (95% confidence interval, 0.01 to 0.20) for each 10 mL/min drop in CrCl (P=0.03).

CONCLUSIONS

these findings demonstrate that mild-to-moderate CKD is not independently associated with a reduction in peak myocardial flow or CFR and suggests that microvascular changes are unlikely to explain the high cardiovascular mortality in mild to moderate CKD. Loss of CFR, however, may accelerate in mild to moderate CKD. Further studies are needed to determine whether these changes lead to more significant reductions that may reduce peak flows and CFR and contribute to cardiovascular risk in more severe CKD.

Drug-eluting versus bare-metal stent for treatment of saphenous vein grafts: a meta-analysis

BACKGROUND

Saphenous vein grafts develop an aggressive atherosclerotic process and the efficacy of drug eluting stents (DES) in treating saphenous vein graft (SVG) lesions has not been convincingly demonstrated. The aim of this study was to review and analyze the current literature for controlled studies comparing DES versus bare metal stents (BMS) for treatment of SVG stenoses.

METHODOLOGY/PRINCIPAL FINDINGS

We searched several scientific databases and conference proceedings up to March 15, 2010 for controlled studies comparing target vessel revascularization (TVR) between DES and BMS. Summary odds ratios (OR) for the primary endpoint TVR and secondary endpoints infarction, stent thrombosis and death were calculated using random-effect models. A total of 29 studies (3 randomized controlled trials RCT) involving 7549 (202 in RCT) patients were included. The need for target vessel revascularization in the DES group tended to be lower compared to BMS for the 3 RCT (OR 0.50 [0.24-1.00]; p = 0.051) and for observational studies (0.62 [0.49-0.79]; p<0.001). There was no significant difference in the risk for myocardial infarction in the RCT (OR 1.25 [0.22-6.99]; p = 0.250) but a lower risk for DES based on the observational studies 0.68 [0.49-0.95]; p = 0.023. The risk for stent thrombosis was found to be non-different in the RCT (OR 0.78 [0.03-21.73], p = 0.885) while it was in favor of DES in the observational studies (0.58 [0.38 - 0.84]; p<0.001). The mortality was not significantly different between DES and BMS in the RCT's (OR 2.22 [0.17 - 29.50]; p = 0.546) while the observation studies showed a decreased mortality in the DES group (0.69 [0.55-0.85]; p<0.001).

CONCLUSION

DES may decrease TVR rate in treatment of SVG stenoses. No differences in reinfarction rate, stent thrombosis or mortality was found between the DES and BMS groups in the RCT's while the observational data showed lower risk for myocardial infarction, stent thrombosis and death in the DES group. This may be a result of patient selection bias in the observational studies or represent a true finding that was not the detected in the RCT analysis due to limited statistical power.

Short-term exercise training prevents micro- and macrovascular disease following coronary stenting

The purpose of this study was to determine the effects of exercise on coronary blood flow and macrovascular atherosclerosis in response to stent deployment. Male Yucatan swine were placed on a control diet (C); on a high-fat/cholesterol diet (hypercholesterolemic; H); or on a high-fat/cholesterol diet and aerobically exercise trained (HX) starting after 36 wk on the diet. All pigs underwent coronary angiography and intravascular ultrasound (IVUS) guided placement of a bare metal stent in the circumflex coronary artery after 40 wk on diets and 3 wk later pigs underwent repeat angiography and IVUS and coronary blood flow (CBF) measurement. Average peak velocity (APV) was measured under basal conditions and in response to intracoronary application of the endothelium-independent vasodilator adenosine and the endothelium-dependent vasodilator bradykinin. There was a similar approximately 8-fold increase in total cholesterol in H and HX compared with control. Baseline CBF was increased above control and H in HX (P<0.05). At all doses adenosine-induced CBF was impaired in H, but preserved in HX. Similarly, bradykinin-induced CBF was impaired in H vs. control, yet was potentiated in HX. Microvessel density was decreased in H and preserved in HX vs. control. Native atheroma in HX was lower relative to H and control, while in-stent stenosis in HX was not different from H. Hyperlipidemia-induced microvascular dysfunction after stent deployment may be a result of reduction in microvessel density. This is the first report that short-term exercise training near the time of stenting prevents stent-induced microvascular dysfunction and attenuates native atheroma independent of changes in plasma cholesterol in this porcine model.

Emerging drugs for coronary restenosis: the role of systemic oral agents the in stent era

Introduction of drug eluting stents (DES) during percutaneous coronary interventions significantly reduces the rate of angiographic restenosis, target lesion and vessel revascularization. In spite of these benefits, other clinical hard end points such as death or myocardial infarction were not reduced and, furthermore, new concerns associated with the presence of late and very late stent thrombosis have been raised. The requirement of long-term dual antiplatelet therapy is another limitation associated with DES. Conversely, in this decade, other options to DES have been simultaneously discussed in observational and randomized studies. Several registries and randomized trials using the systemic approach with anti-inflammatory, immunosuppressive or antiplatelet therapies have been identified and discussed in this manuscript. In spite of all randomized studies with oral therapies in the bare metal stent (BMS) era demonstrating positive reductions in coronary restenosis, this practice has not been introduced clinically. Furthermore, a recent randomized trial comparing oral sirolimus plus BMS versus DES demonstrated that the first approach was cost saving and of comparable efficacy to DES. Conclusive evidence of high incidence of late and very late stent thrombosis with DES, together with clinical limitations for its widespread use, has opened up a large opportunity to search for alternative therapies in coronary restenosis prevention.

The stent-eluting drugs sirolimus and paclitaxel suppress healing of the endothelium by induction of autophagy

Clinical studies have indicated that the stent-eluting drugs sirolimus and paclitaxel impact restenosis; however, it is still elusive how these drugs affect the vascular endothelium at the molecular and cellular levels. The purpose of this study was to determine whether sirolimus and paclitaxel induce molecular and cellular alterations in the vascular endothelium. Endothelial regrowth was assessed in human aortic endothelial cells and rat aortic endothelium. Molecular and cellular alterations were analyzed in human aortic endothelial cells by Western blot analysis, transmission electron microscopy, and immunofluorescence staining. Green fluorescent protein-LC3 mice were used to analyze autophagic endothelium. Here, we show that sirolimus and paclitaxel differentially induce self-digesting autophagy in vascular endothelial cells with changes in expression of LC3B, p53, and Bcl-2, considerably suppressing re-endothelialization and revascularization. These results suggest that phenotypic alteration in the endothelium by sirolimus or paclitaxel might affect the rates of late stent thrombosis, myocardial infarction, and mortality.

Perioperative handling of patients on antiplatelet therapy with need for surgery

The widespread use of metal stents and drug-eluting stents has shown the extent to which patients with unstable coronary perfusion depend on antiplatelet drugs, and how their risk of late thrombosis depends on the long-term use of agents such as clopidogrel. It has also been shown that the risk of surgical bleeding, if antiplatelet drugs are continued, is lower than that of coronary thrombosis if they are withdrawn. Thus, except for low-risk settings, the practice of withdrawing antiplatelet drugs 5-10 days prior to surgical procedures should be changed. The following suggestions are meant to provide a guideline in this respect. Most of the current surgical procedures may be performed while on low-dose aspirin treatment. Except when bleeding may occur in closed spaces (e.g. intracranial surgery, spinal surgery in the medullary canal, surgery of the posterior chamber of the eye) or where excessive blood loss is expected, where only clopidogrel should be discontinued; in all other cases the surgical procedures should be carried out in the presence of dual antiplatelet agents (if prescribed). Aspirin may be discontinued only in subjects at low risk of thrombosis, and at high risk of intraoperative bleeding. Operations associated with an expected excessive blood loss should be postponed unless vital. When prescribed for acute coronary syndrome or during stent re-endothelialization, clopidogrel should not be discontinued before a noncardiac procedure. For elective procedures, surgery should be postponed until the end of the indication for clopidogrel. After the operation, clopidogrel should be resumed within the 12-24 h. Cardiac procedures should be postponed for at least 4 days after clopidogrel withdrawal. The thrombotic risk of preoperative withdrawal of antiplatelet drugs overwhelms the benefit of regional or neuraxial blockade. Antiplatelet treatment replacement by heparin or low-molecular weight heparin does not provide protection against the risk of coronary artery or stent thrombosis. Haemostasis requires that at least 20% of circulating platelets have a normal function. As the effects of antiplatelet agents are not reversible by other drugs, fresh platelets are the only manner to rapidly restore normal haemostasis. Aprotinin decreases postoperative bleeding and transfusion rates in patients undergoing CABG and on clopidogrel during the days preceding surgery.

Redox-dependent mechanisms in coronary collateral growth: the "redox window" hypothesis

This review addresses the complexity of coronary collateral growth from the aspect of redox signaling and introduces the concept of a "redox window" in the context of collateral growth. In essence, the redox window constitutes a range in the redox state of cells, which not only is permissive for the actions of growth factors but also amplifies their actions. The interactions of redox-dependent signaling with growth factors are well established through the actions of many redox-dependent kinases (e.g., Akt and p38 mitogen-activated protein kinase). The initial changes in cellular redox can be induced by a variety of events, from the oxidative burst during reperfusion after ischemia, to recruitment of various types of inflammatory cells capable of producing reactive oxygen species. Any event that "upsets" the normal redox equilibrium is capable of amplifying growth. However, extremes of the redox window, oxidative and reductive stresses, are associated with diminished growth-factor signaling and reduced activation of redox-dependent kinases. This concept of a redox window helps to explain why the clinical trials aimed at stimulating coronary collateral growth, the "therapeutic angiogenesis trials," failed. However, understanding of redox signaling in the context of coronary collateral growth could provide new paradigms for stimulating collateral growth in patients.

The effect of intended duration of clopidogrel use on early and late mortality and major adverse cardiac events in patients with drug-eluting stents

BACKGROUND

The optimal duration of clopidogrel use for prevention of stent thrombosis with drug-eluting stent (DES) use is uncertain. Our objective was to determine whether the planned duration of clopidogrel at the time of percutaneous coronary intervention affected patient outcomes.

METHODS

We analyzed data from 2,980 patients who underwent percutaneous coronary intervention in the Melbourne Interventional Group registry who had 12-month follow-up. We compared outcomes at 30 days and 12 months according to planned duration of clopidogrel use.

RESULTS

Twelve-month mortality was significantly lower in patients with a DES with a longer (>or=12 months) planned duration of clopidogrel when compared with a shorter (<or=6 months) planned duration (2.8% vs 5.3%, P = .012). However, myocardial infarction, target-vessel revascularization, and overall major adverse cardiac events were similar in the longer- and shorter-duration clopidogrel strategies. In contrast, in patients receiving a bare-metal stent, mortality at 12 months was similar among the clopidogrel-duration strategies. Kaplan-Meier analysis demonstrated improved cumulative survival with planned clopidogrel use of >or=12 months (log rank P = .017), and the propensity score-adjusted odds ratio was 0.59 (95% confidence interval 0.35-0.99, P = .04). Premature cessation of clopidogrel in DES patients was documented in 5.2% of patients alive at 30-day follow-up, and these patients had increased 12-month mortality (10.6% vs 1.4%, P < .0001) and major adverse cardiac events (22.4% vs 12.0%, P = .005).

CONCLUSIONS

These data suggest that in patients treated with DES, longer (>or=12 months) planned duration of clopidogrel results in reduced 12-month mortality and that premature cessation of clopidogrel results in significantly higher event rates. Randomized studies are urgently needed to address this issue.

Effectiveness of primary percutaneous coronary interventions for stent thrombosis

There are very few (and conflicting) data about the effectiveness of primary percutaneous coronary interventions (PCIs) for stent thrombosis (ST) treatment. We sought to evaluate the prevalence, efficacy, and outcomes of primary PCI in patients with ST-elevation acute myocardial infarction (STEMI) due to ST in 2,464 consecutive patients treated by primary PCI. ST was the cause of STEMI in 67 patients (3%). Patients with ST showed a lower rate of significant collateral circulation (0% vs 6%, p = 0.034) and a higher peak creatine kinase value (2,678 +/- 3,221 vs 2,375 +/- 2,189 U/L, p = 0.003) compared with the other 2,397 patients with STEMI. PCI was successful in 64 patients (96%) in the ST group and consisted of additional stenting (78%) or only balloon angioplasty (22%). Abciximab and rheolytic thrombectomy were used in 75% and 31% of patients, respectively. Procedure (39 +/- 26 vs 32 +/- 19 minutes, p = 0.0001) and fluoroscopy (13 +/- 10 vs 10 +/- 8 minutes, p = 0.0001) times were longer, and contrast medium amount (221 +/- 89 vs 194 +/- 103 ml, p = 0.034) larger in patients with ST compared with patients with de novo STEMI. Six-month death (12% vs 8%, p = 0.216) and nonfatal reinfarction (10% vs 1%, p = 0.0001) rates were higher in patients with ST compared with those without. At 6-month angiographic follow-up (n = 1,843 of 2,269), the restenosis/reocclusion rate was 54% versus 17% (p = 0.0001) in patients with and without ST. In conclusion, the prevalence of primary PCI for ST is low. Additional stenting with or without thrombectomy is effective in restoring vessel patency in patients with ST, but restenosis and reocclusion are frequent. ST treated with successful PCI is associated with a large infarct and poor outcome.

Negative Inotropic Effect of Rapamycin on Isolated Human Cardiomyocytes

Rapamycin is an increasingly important immunosuppressive drug and reduces restenosis after coronary stenting, but its effects on cardiac contractility are largely unknown. We investigated the acute inotropic effects of rapamycin on isolated human cardiomyocytes. Cardiomyocytes were enzymatically isolated from right atrial appendages obtained during routine coronary artery bypass surgery. Cell morphology was examined by confocal microscopy. Cell contraction was recorded after electrical stimulation. Rapamycin elicited a concentration-dependent decrease in fractional cell shortening ranging from 14.3 ± 2.6% at 10−8 M rapamycin to 26.4 ± 4.2% at 10−5 M. Rapamycin also caused a concentration-dependent decrease in diastolic cell length. Contractile performance of isolated cardiomyocytes was well preserved, as evidenced by the profound positive inotropic effects of high extracellular calcium concentration and the β-adrenoreceptor agonist isoproterenol. The acute negative inotropic effect of rapamycin on human cardiomyocytes might be due to altered calcium homeostasis through the binding of rapamycin to FKBP12.6 and its regulatory function on the ryanodine receptor, with increased calcium leakage from the sarcoplasmic reticulum.

Antiplatelet therapy in the era of drug-eluting stents: current and future perspectives

The use of drug-eluting stents (DESs) dramatically reduced in-stent restenosis. However, the increasing use of these stents has raised concern about their potential thrombogenicity. Indeed, the particularity of DES thrombosis compared with bare metal stent thrombosis is a high rate of late thrombosis. Antiplatelet therapy is efficient in preventing DES thrombosis. However, this therapy could be optimized and may be improved in the future. This article will review the mechanisms and the epidemiology of stent thrombosis. Then, we will summarize the antiplatelet therapeutic strategies used to prevent stent thrombosis and especially DES-associated thrombosis. Finally, we will present some data with regard to potential advantages and pitfalls in DES thrombosis prevention using novel antiplatelet agents currently under development, as well as future stent designs with improved healing properties.

Neointimal expression of rapamycin receptor FK506-binding protein FKBP12: postinjury animal and human in-stent restenosis tissue characteristics

Despite excellent clinical results for sirolimus (rapamycin)-eluting stents, the exact mechanisms of antirestenotic activity and affected cellular targets are incompletely understood. Therefore, we determined the presence and tem- porospatial expression pattern of FKBP12, the primary intracellular receptor of rapamycin, in rat carotid arteries after balloon injury, as well as in human in-stent restenosis and primary stable coronary atheroma. FKBP12 expression was assessed by immunohistochemistry. Rat carotid arteries revealed maximal expression in 57.7 +/- 4.0% of neointimal cells at day 7. A large proportion of these FKBP12+ cells showed luminally confined co-expression with dendritic cell markers. Despite a considerably thicker neointima at day 28, presence of FKBP12 decreased (8.5 +/- 1.9%, p = 0.02) with a scattered pattern in luminal and deep neointima. Likewise, human in-stent restenosis atherectomy specimens (time after stent implantation 2-12 months) revealed a comparable extent of cellular rapamycin receptor expression (9.3 +/- 1.0%) that significantly differed from that found in primary stable atheroma (1.3 +/- 0.4%, p < 0.001). In conclusion, the rapamycin receptor is predominantly present during early neointima formation, while mature neointimal atheromas show a relatively low expression without confinement to luminal areas. Co-expression of FKBP12 and dendritic cell markers suggests that dendritic cells may be another important target for early and long-term rapamycin effects.

Perioperative antiplatelet therapy: the case for continuing therapy in patients at risk of myocardial infarction

Recent clinical data show that the risk of coronary thrombosis after antiplatelet drugs withdrawal is much higher than that of surgical bleeding if they are continued. In secondary prevention, aspirin is a lifelong therapy and should never be stopped. Clopidogrel is regarded as mandatory until the coronary stents are fully endothelialized, which takes 3 months for bare metal stents, but up to 1 yr for drug-eluting stents. Therefore, interruption of antiplatelet therapy 10 days before surgery should be revised. After reviewing the data on the use of antiplatelet drugs in cardiology and in surgery, we propose an algorithm for the management of patients, based on the risk of myocardial ischaemia and death compared with that of bleeding, for different types of surgery. Even if large prospective studies with a high degree of evidence are still lacking on different antiplatelet regimens during non-cardiac surgery, we propose that, apart from low coronary risk situations, patients on antiplatelet drugs should continue their treatment throughout surgery, except when bleeding might occur in a closed space. A therapeutic bridge with shorter-acting antiplatelet drugs may be considered.

A new intra-arterial delivery platform for pro-arteriogenic compounds to stimulate collateral artery growth via transforming growth factor-beta1 release

OBJECTIVES

The purpose of this study was to develop a cytokine-eluting stent to stimulate collateral artery growth (arteriogenesis) in the peripheral circulation of the rabbit via local transforming growth factor (TGF)-beta1 release.

BACKGROUND

The stimulation of arteriogenesis with cytokines is a potential new treatment option for patients suffering from vascular occlusive diseases. However, the lack of a delivery platform for continuous intra-arterial application of pro-arteriogenic compounds has hampered the clinical implementation of this promising therapeutic strategy.

METHODS

Different polymer coatings were tested regarding their suitability for cytokine release. Fifty-four rabbits underwent implantation of bare-metal stents (BMS), polymer-only coated stents (PDLLA), polymer-coated TGF-beta1-eluting stents (TGF) in the iliac artery, or bolus infusion of TGF-beta1 and subsequent femoral artery ligation. Collateral artery growth was assessed with fluorescent microspheres, angiography, and histological quantification of the proliferation marker Ki67. In-stent neointima formation was measured in histological sections of plastic-embedded stents.

RESULTS

A TGF-beta1-loaded coating based on poly(D,L-lactide) released up to 2.4 microg active TGF-beta1 over a period of 24 h. Perfusion measurements revealed a significant increase in collateral conductance after TGF-beta1 stent implantation compared with the control groups ([ml/min/100 mm Hg] BMS: 47.8 +/- 2.5; PDLLA: 44.1 +/- 3.9; TGF: 91.3 +/- 32.6). Bolus infusion of TGF-beta1 had no effect. Collateral arteries showed a higher proliferation activity in the TGF-treated group. At 7 days, no significant difference in in-stent neointima formation was observed.

CONCLUSIONS

We first describe the use of a cytokine-releasing stent to stimulate collateral artery growth. These results show that intra-arterial cytokine-releasing devices might serve as a novel platform for the delivery of compounds affecting biological processes downstream of the site of implantation.