Coronary Stent Thrombosis- Predictors and Prevention

Challenges and Advances in Interventional Cardiology for Coronary Artery Disease Management

The development of percutaneous coronary intervention (PCI) has been one of the greatest advances in cardiology and has changed clinical practice for patients with coronary artery disease (CAD). Despite continuous improvements in operators' experience, techniques, and the development of new-generation devices, significant challenges remain in improving the efficacy of PCI, including calcification, bifurcation, multivascular disease, stent restenosis, and stent thrombosis, among others. The present review aims to provide an overview of the current status of knowledge of endovascular revascularization in CAD, including relevant trials, therapeutic strategies, and new technologies addressing particular scenarios that can impact the prognosis of this vulnerable population.

Sutureless vascular anastomotic approaches and their potential impacts

Sutureless anastomotic devices present several advantages over traditional suture anastomosis, including expanded global access to microvascular surgery, shorter operation and ischemic times, and reduced costs. However, their adaptation for arterial use remains a challenge. This review aims to provide a comprehensive overview of sutureless anastomotic approaches that are either FDA-approved or under investigation. These approaches include extraluminal couplers, intraluminal devices, and methods assisted by lasers or vacuums, with a particular emphasis on tissue adhesives. We analyze these devices for artery compatibility, material composition, potential for intimal damage, risks of thrombosis and restenosis, and complications arising from their deployment and maintenance. Additionally, we discuss the challenges faced in the development and clinical application of sutureless anastomotic techniques. Ideally, a sutureless anastomotic device or technique should eliminate the need for vessel eversion, mitigate thrombosis through either biodegradation or the release of antithrombotic drugs, and be easily deployable for broad use. The transformative potential of sutureless anastomotic approaches in microvascular surgery highlights the necessity for ongoing innovation to expand their applications and maximize their benefits.

The Inhibitory Effect of Platelet Aggregation Ability Assessed by the Platelet Aggregatory Threshold Index in a Patient with Recurrent Stent Thrombosis

An 86-year-old man successfully underwent percutaneous coronary intervention (PCI), in which a drug-coated stent (DCS) was placed in the left anterior descending coronary artery. However, stent thrombosis occurred twice after eight and two months. After the second admission, the patient was tested for platelet aggregation activity using the platelet aggregation threshold index (PATI), and insufficient inhibition of platelet aggregation was observed. The patient's PATI improved to a satisfactory level using oral anticoagulants. At the six-month follow-up, clinical events were observed. Measuring the platelet aggregation ability can help clinicians understand the pathology of patients and determine treatment choices.

Five-year outcomes of double kissing mini-culotte stenting vs. mini-culotte stenting using drug-eluting stents for the treatment of true coronary bifurcation lesions

Objective

This study aimed to compare the clinical outcomes of double kissing mini-culotte (DKMC) stenting with those of mini-culotte (MC) stenting in treating patients with true coronary bifurcation lesions (CBLs) in the clinical real world.

Methods

This retrospective observational cohort study included 180 consecutive patients with true CBLs (Medina type 1,1,1; 1,0,1; 0,1,1). All eligible patients underwent coronary angiography and percutaneous coronary intervention with two-stent techniques in our hospital; among them, 97 received DKMC treatment and 83 MC treatment. The primary clinical endpoints were the major adverse cardiovascular events (MACE), which included cardiac death, myocardial infarction, and target vessel/lesion revascularization (TVR/TLR). The secondary endpoints were stent thrombosis, in-stent restenosis, and individual components of MACE.

Results

Quantitative coronary angiography analysis (at 5 years) revealed that late lumen loss (0.25 ± 0.41 mm vs. 0.14 ± 0.32 mm, P = 0.032) and segmental diameter restenosis of the side branch (27.84 ± 12.34% vs. 19.23 ± 9.76%, P = 0.016) were lower in the DKMC treatment group than that in the MC treatment group. Notably, compared to that in the MC treatment group, the cumulative event rate of MACE at 5 years (22.8% vs. 8.3%, P = 0.007) and TVR/TLR (17.7% vs. 6.3%, P = 0.018) was higher in the DKMC treatment group, driven mainly by TVR/TLR. Especially, the DKMC group was related to a significant reduction in the primary and secondary endpoints in high-risk patients.

Conclusion

DKMC treatment was associated with less late lumen loss and restenosis in the side branch and a lower rate of cumulative MACE and TVR/TLR. DKMC treatment is more effective for treating true CBLs than MC treatment; however, these findings warrant further confirmation through a randomized clinical trial.

Effect of ticagrelor versus clopidogrel after implantation of drug-eluting stents guided by either intravascular ultrasound or angiography in patients with acute coronary syndrome-propensity score matching analysis

BACKGROUND

The effect of different dual antiplatelet therapies on thrombotic events on the background of intravascular ultrasound (IVUS) guidance is unclear. We investigated whether ticagrelor can provide any additional benefit to clopidogrel in reducing thrombotic events in acute coronary syndrome (ACS) treated with drug- eluting stent (DES), when guided by IVUS or not.

METHODS

A total of 5,666 ACS patients who underwent DES implantation and who were discharged on dual antiplatelet therapy were enrolled and grouped according to the use of IVUS or not. Each group was subdivided into two subgroups according to the type of P2Y12 inhibitor used after discharge. Propensity score matching (PSM) was used between the IVUS and no-IVUS groups. Covariate adjustment of Cox proportional hazards model was used between the ticagrelor and clopidogrel groups. Thrombotic event at 12 months was compared in groups separately.

RESULTS

After PSM, 12-month follow-up data were available for 1,174 patients. Major adverse cardiac events (MACE) were less frequent in the IVUS-guided group (2.2% vs. 4.3%, P = 0.081) with a trend toward statistical significance. Comparison of antiplatelet regimens revealed significantly fewer major adverse cardiac and cerebrovascular events (MACCE) with ticagrelor in the entire PSM cohort and angiography-guided subgroup (2.9% vs. 5.7%, P = 0.035; 3.1% vs. 6.4%, P = 0.020, respectively). Among patients in the IVUS-guided group the outcome was comparable (2.5% vs. 4.4%, P = 0.312). Ticagrelor was associated with increasing bleeding incidence in the entire PSM cohort (1.3% vs. 3.3%, P = 0.030), mainly due to Bleeding Academic Research Consortium type 2 bleeding (0.7% vs. 2.6%, P = 0.010). The results were consistent after covariate adjustment of Cox proportional hazards model.

CONCLUSION

The comparison of ischemic benefit between ticagrelor and clopidogrel was similar in patients receiving IVUS guidance during stent implantation, probably due to the precise implantation of IVUS. Multicenter, randomized studies should be performed to validate this conclusion.

Association of Periprocedural Inflammatory Activation With Increased Risk for Early Coronary Stent Thrombosis

BACKGROUND

Stent thrombosis is a rare but deleterious event. Routine coronary angiography with percutaneous coronary intervention (PCI) is often deferred in the presence of laboratory markers of acute inflammation to prevent complications. The aim of this study was to investigate whether an acute inflammatory state is associated with an increased risk of early stent thrombosis.

METHODS AND RESULTS

Within a prospective single-center registry, the association between preprocedural acute inflammatory activation, defined as C-reactive protein plasma levels >50 mg/L or a leukocyte count >12 g/L, and occurrence of early (≤30 days) stent thrombosis was evaluated. In total, 11 327 patients underwent PCI and of those, 6880 patients had laboratory results available. 49.6% of the study population received PCI for an acute coronary syndrome and 50.4% for stable ischemic heart disease. In patients with signs of acute inflammatory activation (24.9%), PCI was associated with a significantly increased risk for stent thrombosis (hazard ratio, 2.89; P<0.00001), independent of age, sex, kidney function, number and type of stents, presence of multivessel disease, choice of P2Y12 inhibitor, and clinical presentation. Elevated laboratory markers of acute inflammation were associated with the occurrence of stent thrombosis in both patients with acute coronary syndrome (hazard ratio, 2.63; P<0.001) and in patients with stable ischemic heart disease (hazard ratio, 3.57; P<0.001).

CONCLUSIONS

An acute inflammatory state at the time of PCI was associated with a significantly increased risk of early stent thrombosis. Evidence of acute inflammation should result in deferred PCI in elective patients, while future studies are needed for patients with acute coronary syndrome.

Identifying the Incidence, Predictors, Outcomes, and Prevention of Stent Thrombosis (ST) in Post-percutaneous Coronary Revascularization Patients With Drug-Eluting Stents (DES): A Systematic Review

Stent thrombosis (ST) is a rare but catastrophic event to happen to a stented coronary artery. The incidence of ST has greatly been reduced after the advent of modern drug-eluting stent (DES) implants, which have become the most preferred treatment option in the stenting category for coronary artery disease (CAD). Although the risk reduction by newer category implant provides substantial benefits, the possibility of thrombosis still exists mostly during the early stage of DES implantation. The development of ST after percutaneous coronary intervention (PCI) can be predicted by multiple factors, but advancements in early diagnostic techniques and modified stent types have greatly reduced the occurrence of this complication. Mortality, which is one of the complications of ST, is primarily influenced by patient-related factors such as incomplete treatment duration of dual antiplatelet therapy (DAPT). The duration of DAPT after DES implantation in patients with acute coronary syndrome (ACS) is determined based on individual characteristics, mainly considered in view of bleeding or ischemia risk. Risk evaluation systems like DAPT/precise-DAPT scores help tailor and personalize the duration of DAPT for each individual patient. This systematic review contains pertinent articles extracted from the PubMed database. We retrieved articles from various study categories, encompassing publications from the period spanning 2014 to 2022. Our analysis highlighted results from studies investigating different aspects contributing to ST development. The most favorable prevention option was the use of customized DAPT intervention based on patient-specific predictable factors. Several complications associated with ST were identified, including recurrent ST, major adverse cardiovascular events (MACE) encompassing all-cause mortality (including cardiac and non-cardiac mortality), cerebrovascular accidents (CVA) or transient ischemic attacks (TIA), hospitalization due to heart failure, and myocardial infarction requiring revascularization. Mortality was also observed as a significant outcome. The umbrella term of ST includes multiple causative factors. Although DES has improved patient survival rates vastly with its usage, careful risk factor assessment and required follow-up, in each individual being stented, further guarantee a more promising reduction in late adverse outcomes.

Concurrent Pacemaker Lead Perforation and Subacute Coronary Stent Thrombosis: A Case Report

Stent thrombosis and lead perforation are important differentials for patients presenting with chest pain following recent coronary stent insertion and pacemaker insertion. In this report, we describe an unusual case of a 78-year-old male who presented with sharp chest pain one week after admission for posterior ST-elevation myocardial infarction (STEMI) and subsequent Mobitz type II block, for which he received primary percutaneous coronary intervention (PPCI) to the left circumflex artery (LCx) and dual chamber permanent pacemaker (PPM) insertion. Computed tomography (CT) chest and CT coronary angiogram (CTCA), respectively, showed he had concurrent lead perforation and stent thrombosis. On balance, the cause of chest pain was likely lead perforation. This diagnosis was reached by having a high index of suspicion for both of these important post-procedure complications and investigating appropriately.

Prolonged dual antiplatelet therapy after drug-eluting stent implantation improves long-term prognosis for acute coronary syndrome: five-year results from a large cohort study

BACKGROUND

To investigate the most appropriate dual antiplatelet therapy (DAPT) duration for patients with acute coronary syndrome (ACS) after drug-eluting stent (DES) implantation in the largest cardiovascular center of China.

METHODS

We enrolled 5,187 consecutive patients with ACS who received DES from January to December 2013. Patients were divided into four groups based on DAPT duration: standard DAPT group (11-13 months, n=1,568) and prolonged DAPT groups (13-18 months [n=308], 18-24 months [n=2,125], and >24 months [n=1,186]). Baseline characteristics and 5-year clinical outcomes were recorded.

RESULTS

Baseline characteristics were similar across the four groups. Among the four groups, those with prolonged DAPT (18-24 months) had the lowest incidence of major adverse cardiovascular and cerebrovascular events (MACCEs) (14.1% vs. 11.7% vs. 9.6% vs. 24.2%, P<0.001), all-cause death (4.8% vs. 3.9% vs. 2.1% vs. 2.6%, P<0.001), cardiac death (3.1% vs. 2.6% vs. 1.4% vs. 1.9%, P=0.004), and myocardial infarction (MI) (3.8% vs. 4.2% vs. 2.5% vs. 5.8%, P<0.001). The incidence of bleeding was not different among the four groups (9.9% vs. 9.4% vs. 11.0% vs. 9.4%, P=0.449). Cox multivariable analysis showed that prolonged DAPT (18-24 months) was an independent protective factor for MACCEs (hazard ratio [HR] 0.802, 95% confidence interval [CI] 0.729-0.882, P<0.001), all-cause death (HR 0.660, 95% CI 0.547-0.795, P<0.001), cardiac death (HR 0.663, 95% CI 0.526-0.835, P<0.001), MI (HR 0.796, 95% CI 0.662-0.957, P=0.015), and target vessel revascularization (HR 0.867, 95% CI 0.755-0.996, P=0.044). Subgroup analysis for high bleeding risk showed that prolonged DAPT remained an independent protective factor for all-cause death and MACCEs.

CONCLUSION

For patients with ACS after DES, appropriately prolonging the DAPT duration may be associated with a reduced risk of adverse ischemic events without increasing the bleeding risk.

An Uncommon Case of Acute Coronary Stent Thrombosis

Coronary stent thrombosis is an uncommon complication of percutaneous coronary intervention, which can result in myocardial infarction and often death. We present a case of acute stent thrombosis in a patient with newly diagnosed triple vessel coronary artery disease occurring within less than an hour of stent placement along with a review of the literature.

Roles and current applications of S-nitrosoglutathione in anti-infective biomaterials

Bacterial infections can compromise the physical and biological functionalities of humans and pose a huge economical and psychological burden on infected patients. Nitric oxide (NO) is a broad-spectrum antimicrobial agent, whose mechanism of action is not affected by bacterial resistance. S-nitrosoglutathione (GSNO), an endogenous donor and carrier of NO, has gained increasing attention because of its potent antibacterial activity and efficient biocompatibility. Significant breakthroughs have been made in the application of GSNO in biomaterials. This review is based on the existing evidence that comprehensively summarizes the progress of antimicrobial GSNO applications focusing on their anti-infective performance, underlying antibacterial mechanisms, and application in anti-infective biomaterials. We provide an accurate overview of the roles and applications of GSNO in antibacterial biomaterials and shed new light on the avenues for future studies.

Subacute stent thrombosis with spontaneously resolved secondary thrombi in paroxysmal nocturnal hemoglobinuria: a case report

Background

Stent thrombosis (ST) is a serious complication; however, a method to prevent ST in patients with thrombophilic diseases has not been established.

Case presentation

We report a case of subacute ST in a patient with paroxysmal nocturnal hemoglobinuria (PNH) who was receiving continuous heparin treatment in addition to the usual dual antiplatelet therapy for contrast defects at the proximal site of the occluded right coronary artery and the proximal site of the left circumflex artery. Despite the resolution of thrombi in secondary lesions, subacute ST occurred. After percutaneous coronary intervention for ST, triple therapy, including oral anticoagulation for PNH-related thrombosis, was initiated. The patient subsequently underwent craniotomy hematoma removal for hemorrhagic cerebral infarction.

Conclusions

Reported cases of ST in patients with PNH are very few, and this case adds evidence with respect to antithrombotic therapy in patients with thrombotic tendencies. Both thrombosis and bleeding should be considered when administering antithrombotic therapy to patients with thrombotic diseases. If there are specific treatments for thrombophilic diseases, they should be initiated early.

Efficacy and safety of tirofiban bridge as an alternative to suspension of dual antiplatelet therapy in patients undergoing surgery: a systematic review

Use of a tirofiban bridge is an alternative to simply withdrawing dual antiplatelet therapy prior to operating on patients at high risk of stent thrombosis and bleeding. We aimed to evaluate the efficacy and safety of this protocol in patients undergoing surgery within 12 months of a percutaneous coronary intervention involving stenting. We performed a systematic review based on searches of the PubMed, Web of Science, Cochrane, Embase, Lilacs, and Scielo databases and of the references of relevant articles on the topic. Five of the 107 studies identified were included after application of eligibility criteria and analysis of methodological quality, totaling 422 patients, 227 in control groups. Notwithstanding the limitations reported, four of the five studies included indicate that the tirofiban bridge technique is effective for reducing adverse cardiac events and is safe in terms of not interfering with the risk of hemorrhagic events or bleeding. However, randomized clinical trials are needed to provide robust evidence.

Early, Subacute Coronary Stent Thrombosis: A Complication of COVID-19 Infection

Soon after it was discovered in Wuhan, China, in December 2019, coronavirus disease 2019 (COVID-19) blow-out very fast and became a pandemic. The usual presentation is respiratory tract infection, but cardiovascular system involvement is sometimes fatal and also a serious personal and health care burden. We report a case of a 57-year-old man who was admitted with anterior wall acute myocardial infarction secondary to early coronary stent thrombosis and associated with COVID-19 infection. He was managed with primary coronary angioplasty and discharged home. Procoagulant and hypercoagulability status associated with severe acute respiratory syndrome coronavirus 2 infection is the most likely culprit. Choosing aggressive antithrombotic agents after coronary angioplasty to prevent stent thrombosis during the COVID-19 pandemic may be the answer but could be challenging.

Coronary In-Stent Restenosis: Predictors and Treatment

BACKGROUND

Despite the use of modern drug-eluting stents (DES), in-stent restenosis (ISR) may still occur in as many as 2-10% of percutaneous coronary interventions (PCI) in certain lesion/patient subsets. ISR causes increased morbidity after stent implantation; acute myocardial infarction is a frequent correlate to a clinical ISR, arising in 5-10% of cases. Compared to de novo stenosis, patients with ISR also present more frequently with symptoms of unstable angina pectoris (45% versus 61%). In this article, we discuss the risk factors for ISR and the corresponding diagnostic measures and effective treatment strategies.

METHODS

This review is based on pertinent publications retrieved by a selective search in PubMed, with special attention to current international guidelines and specialist society recommendations.

RESULTS

The type of implanted stent, the presence of diabetes mellitus, previous bypass surgery, and small vessel caliber are predictors for ISR. In their guidelines, the European specialist societies (ESC/EACTS) recommend repeated PCI with DES implantation or drug-coated balloon (DCB) angioplasty as the methods of choice for the treatment of ISR. This approach is supported by evidence from meta-analyses. The RIBS-IV trial showed that revascularization treatment of the target lesion is needed less often after everolimus-eluting stent (EES) implantation than after DCB dilatation (11 [7.1%] versus 24 [15.6%]; p = 0.015; hazard ratio: 0.43; 95% confidence interval: [0.21; 0.87]).

CONCLUSION

Because the pathogenesis of ISR is multifactorial, differentiated risk stratification is necessary. The identification of patient-, stent-, and lesion-related predictors is particularly important, as the most effective way to combat ISR is to prevent it.

The Pivotal Role of Effective Communication in Patient Care: A Case of Coronary Stent Thrombosis

Myocardial infarction is a significant cause of morbidity and mortality worldwide, resulting in millions of percutaneous coronary interventions being performed yearly. Coronary artery stents are, however, at risk of thrombosis, with a significant mortality rate. Stent thrombosis is, however, preventable using dual antiplatelets, barring other procedural or unique personal predisposing characteristics. Good communication with patients is indispensable in ensuring adherence to dual antiplatelet therapy, protecting the patient from stent thrombosis. This paper presents a patient who discontinued his dual antiplatelet therapy prematurely and developed stent thrombosis within a week after discharge, highlighting the importance of good communication in promoting adherence to an agreed management plan.

Inhibition of Platelet Aggregation After Coronary Stenting in Patients Receiving Oral Anticoagulation

BACKGROUND

Approximately 18% of patients with atrial fibrillation undergo a percutaneous coronary intervention (PCI) to treat coronary heart disease. Pharmacological anticoagulation in patients with atrial fibrillation and PCI involves a trade-off of potential ischemic and hemorrhagic complications.

METHODS

This review is based on pertinent publications that were retrieved by a selective literature search, including current guidelines and recommendations.

RESULTS

Dual antiplatelet therapy (DAPT) with acetylsalicylic acid (ASA) and a P2Y12 inhibitor protects against stent thrombosis, but not against thromboembolic stroke. In contrast, oral anticoagulation does provide effective prevention against stroke during atrial fibrillation. Combining DAPT with oral anticoagulation (triple therapy) over the long term, as has been recommended to date, carries an elevated risk of hemorrhage. In a randomized controlled trial, 44% of patients with atrial fibrillation receiving triple therapy sustained a hemorrhagic event, compared to 19.4% of patients receiving dual therapy. A meta-analysis has shown that clinically relevant hemorrhage is less common under combined treatment with one of the new oral anticoagulants (NOAC) and a single antiplatelet drug than under triple therapy including a vitamin K antagonist (hazard ratio, 0.56; 95% confidence interval 0.39; 0.80]), but no significant difference was found with respect to stent thrombosis, myocardial infarction, or overall mortality.

CONCLUSION

After coronary stent implantation, dual therapy with a NOAC and a P2Y12 inhibitor is recommended, subsequent to triple therapy given only during the peri-interventional period.

A Comparison of Safety and Effectiveness Between Wingspan and Neuroform Stents in Patients With Middle Cerebral Artery Stenosis

Background: Percutaneous transluminal angioplasty and stenting with the Wingspan stent has proven safe and effective in patients with middle cerebral artery stenosis (MCAS), but the off-label use of the Neuroform stent might be an alternative treatment. This study aimed to compare the safety and effectiveness of the above two intracranial stents in patients with MCAS. Methods: We retrospectively analyzed consecutive patients with symptomatic MCAS who had been treated with the Neuroform EZ or the Wingspan stent. A propensity score was generated to control for differences in baseline characteristics. The endpoints were the rate of peri-procedural complications within 30 days after stenting, the in-stent restenosis rate, and any target-vessel-related stroke or deaths during follow-up. Results: After matching for propensity score, the peri-procedural complication rate in the Wingspan group was 7.4% compared with 5.6% in the Neuroform group (p = 1.00), while the follow-up in-stent restenosis rates were 23.3 vs. 14.3%, respectively (p = 0.41). In the restenosis group, the patients tended to be younger (p < 0.01) and the degree of artery stenosis before stenting was higher (p < 0.01). Conclusion: This study indicated that in patients with symptomatic MCAS, Neuroform EZ stents are an alternative to Wingspan. Moreover, younger age and higher degree of artery stenosis before stenting might be a risk factor of in-stent restenosis.

Early stent thrombosis confirmed in a cancer patient receiving regorafenib, despite triple antithrombotic therapy: a case report

Background

While developments in oncology have lengthened survival in patients with cancer, such patients often develop cardiovascular diseases. Thus, percutaneous coronary intervention (PCI) is frequently undertaken in them. Although stent thrombosis remains a fatal complication in stent-based PCI, worldwide consensus panels tend to recommend shorter duration of dual-antiplatelet therapy. This is based on its clinical efficacy that has resulted from technological innovation. However, there is insufficient discussion on the risk of stent thrombosis in cancer patients with coronary artery disease, especially in those undergoing chemotherapeutic regimens that have a risk for thrombosis, such as regimens with the anti-vascular endothelial growth factor. Presented here is a case of early stent thrombosis that occurred in a cancer patient on regorafenib, despite the administration of triple antithrombotic therapy.

Case presentation

A 66-year-old Japanese male patient received regorafenib for metastatic colorectal carcinoma and apixaban for deep vein thrombosis. Coronary angiography revealed severe stenosis in the proximal left anterior descending artery. A sirolimus-eluting stent was implanted, without malapposition and under-expansion, under intravascular ultrasound guidance while administering a triple antithrombotic therapy (aspirin: 100 mg/day, prasugrel: 3.75 mg/day, and apixaban: 5 mg/day). However, he was admitted to the hospital for exacerbation of heart failure 1 month after PCI. Coronary angiography revealed contrastive defects in the previous stent. Optical frequency domain imaging confirmed stent thrombosis. PCI was successfully performed with perfusion balloon long-inflation. Antithrombotic therapy was enhanced (aspirin: 100 mg/day, ticagrelor: 120 mg/day, and apixaban: 10 mg/day) and regorafenib was discontinued permanently. While ischemic events did not occur thereafter, the patient died due to metastatic carcinoma progression.

Conclusions

This case suggests that anti-vascular endothelial growth factor might contribute to early stent thrombosis, despite triple antithrombotic therapy. Further discussion is needed on the surveillance and management of cancer patients with coronary artery disease receiving chemotherapy, which carries a risk of thrombosis.

Vascular Wall Reactions to Coronary Stents-Clinical Implications for Stent Failure

Coronary stents belong to the most commonly implanted devices worldwide. A number of different types of stent exist, with very different mechanical and biochemical characteristics that influence their interactions with vascular tissues. Inappropriate inflammatory reactions are the major cause of the two major complications that follow implantation of stents in a percentage as high as 5-20%. It is therefore important to understand these reactions and how different they are among different generations of stents.