Angioscopic Comparison of Neointimal Coverage Between Zotarolimus- and Sirolimus-Eluting Stents

Angioscopic evaluation after venous stents

BACKGROUND

Venous stenting is increasingly used to manage femoro-ilio-caval venous outflow obstruction/stenosis due to post-thrombotic syndrome. Although the safety, efficacy, and long-term patency of venous stents have been reported, re-interventions due to stent occlusion and in-stent restenosis (ISR) have also been reported. The mechanism of ISR and the in-stent neointimal growth after venous stenting remains unclear. We performed angioscopy to evaluate intraluminal details after venous stenting, allowing real-time direct visualization of the vessel lumen.

METHODS

Ten angioscopic procedures in four patients with post-thrombotic syndrome were performed. All evaluated vessels were stented iliac veins, and their native pathology was chronic post-thrombotic occlusion. Nine procedures in three patients underwent serial evaluation of the neointimal changes after stent implantation to study the natural time course of neointimal proliferation/coverage over the stent. The serial follow-up angioscopic evaluations were performed at the end of the venous stent deployment procedure, and at 6 months, 12 months, and 24 months. One procedure was performed 1 month after the stent implantation to evaluate ISR, which was observed at the first month of routine stent surveillance. A 5.7F angioscope was used to visualize the target veins. Continuous irrigation was used to displace blood and clear the visual field.

RESULTS

At 6 months after stent implantation, stent struts were covered by a thin neointima in two of the three patients. The struts were partially covered in one patient, but there was little neointimal growth overall. Neointimal coverage increased over time, and at 12 months stent struts in 2 patients were almost completely covered. There was no significant change between the 12 and 24 months after stent implantation. In the ISR case, angioscopy demonstrated an overgrown thickened neointima, and the stent struts were fully embedded and invisible in the entire stented area. No thrombus and no webs or trabeculae were found in the area evaluated as an ISR lesion.

CONCLUSIONS

At 6 months after stent placement, the stent struts were almost covered by a neointima. The stent struts were completely covered 1 year after stent implantation. Neointimal coverage was unchanged from the 1-year follow-up to the 2-year follow-up, suggesting that neointimal proliferation proceeded gradually with subsequent neointimal remodeling up to 1 year. The cause of ISR might be the overgrown thickened neointima rather than the formation of thrombosis.

Arterial Healing 10 Months After Implantation of an Ultrathin-Strut, Biodegradable-Polymer, Sirolimus-Eluting Stent - An Angioscopic Study

Background: The Orsiro^TM ultrathin-strut, biodegradable-polymer, sirolimus-eluting stent (O-SES) has specific characteristics regarding its components and has demonstrated comparable clinical outcomes compared with durable-polymer, drug-eluting stents (DES). However, arterial repair following deployment of the O-SES has not been elucidated to date.

Methods and Results: Using data from the Kansai Rosai Hospital database between November 2010 and September 2020, we analyzed coronary angioscopy (CAS) findings a mean (±SD) of 10±2 months after implantation of an O-SES, a durable-polymer everolimus-eluting stent (Xience^TM; X-EES), or a biodegradable-polymer everolimus-eluting stent (Synergy^TM; S-EES). Neointimal coverage (NIC), yellow color intensity of the stented segment, and the incidence of thrombus adhesion were compared between the O-SES (66 stents from 42 patients), X-EES (119 stents from 87 patients), and S-EES (132 stents from 88 patients). NIC was significantly thinner for the O-SES than S-EES (P<0.001), but was similar between the O-SES and X-EES (P=0.25). Yellow color intensity was significantly greater for the O-SES than X-EES (P<0.001), but similar between the O-SES and S-EES (P=0.51). The incidence of thrombus adhesions was similar in all 3 groups.

Conclusions: O-SES and X-EES resulted in similar inhibition of NIC and both resulted in a thinner NIC than with S-EES. In addition, O-SES exhibited a similar degree of thrombus adhesion as the other DES, suggesting similar thrombogenicity.

Angioscopic assessments and clinical outcomes one year after polymer-free biolimus A9-coated coronary stent implantation

BACKGROUND

Polymer-free biolimus A9-coated coronary stent (DCS) has novel features which lead to the expectation of better arterial healing. However, comparisons of intravascular status between DCS and drug-eluting stents (DES), and robust real-word clinical assessments of DCS have been lacking to date.

METHODS

From September 2017 to September 2018, we evaluated the intra-vascular status of 74 DCS implanted in 55 lesions from 43 patients using coronary angioscopy (CAS) approximately one year after implantation from a cohort of 219 lesions in 158 patients. We set 239 second-generation durable-polymer DES (DP-DES) implanted in 211 lesions from 180 patients from a cohort of 2652 lesions in 1914 patients as the control. Angioscopic images were analyzed to determine (1) the dominant degree of neointimal coverage (NIC) over the stent; (2) the heterogeneity of NIC; (3) yellow color grade of the stented segment; and (4) the presence of intra-stent thrombus. The primary outcome was the incidence of thrombus and secondary outcomes were the other CAS findings, and the 1-year clinical outcomes which included target lesion revascularization (TLR) and major adverse cardiac events (MACE). To minimize inter-group differences in baseline characteristics, propensity score matching was performed for clinical outcomes.

RESULTS

Incidence of thrombus adhesion was similar in DCS and DP-DES groups (28.4% versus 22.6%, p=0.31). However, the dominant NIC grade was significantly higher in DCS (p<0.001), while NIC was more heterogeneous in DCS than in DP-DES (p=0.001). Maximum yellow color grade was similar (p=0.22). After propensity score matching, 202 lesion pairs from 146 patient pairs were retained for analysis. The cumulative incidence of TLR (4.6% versus 3.8%, p=0.38) and MACE (11.6% versus 11.7%, p=0.84) was similar for DCS and DP-DES.

CONCLUSIONS

DCS showed thrombus adhesion and clinical outcomes at 1 year similar to DP-DES. DCS can thus be used with similar safety and efficacy as DP-DES.

Angioscopic assessment of peri-stent contrast staining following drug-eluting stent implantation

BACKGROUND

Peri-stent contrast staining (PSS) has been recognized as a predictor of late stent thrombosis following drug-eluting stent (DES) implantation. However, the intravascular conditions at PSS sites remain unclear.

METHODS AND RESULTS

We evaluated 10 patients (median age 72 years, 80% male) with stable angina pectoris by coronary angioscopy. The patients had a total of 11 DES implantations (5 sirolimus-eluting stents; 4 paclitaxel-eluting stents; 2 everolimus-eluting stents) that showed PSS. Neointimal coverage (NIC), presence of thrombus, and yellow plaques underneath the stent were compared between PSS and non-PSS sites for each stent. NIC was graded as: grade 0, struts exposed; grade 1, struts bulging into the lumen, although covered; grade 2, struts embedded by neointima, but translucent; grade 3, struts fully embedded and invisible. Mean follow-up was 394±206 days (median: 289). NIC grade was lower at PSS sites (P=0.021) with 8 out of 11 stents (73%) having grade 0. Angioscopy detected a thrombus more frequently at PSS sites than at non-PSS sites (64% vs. 9%, P=0.012). Yellow plaques tended to be more significant at PSS sites than at non-PSS sites (82% vs. 45%, P=0.091).

CONCLUSIONS

The angioscopic findings suggest high thrombogenicity at PSS sites.

A higher colour grade yellow plaque was detected at one year after implantation of an everolimus-eluting stent than after a zotarolimus-eluting stent

OBJECTIVE

Neoatherosclerosis or atherosclerosis progression is one of the mechanisms of long-term stent failure. Yellow plaque detected by angioscopy has been associated with advanced atherosclerosis and the future risk of a coronary event. We compared the yellow colour of the stented segment between zotarolimus-eluting stents (ZES) and everolimus-eluting stents (EES) at 1 year after implantation.

DESIGN

Cross-sectional study.

PATIENTS

Consecutive patients underwent angioscopic examination 1 year after the implantation of ZES (n=45) or EES (n=45) at a de novo native coronary lesion.

MAIN OUTCOME MEASURES

The maximum yellow colour grade (grade 0-3) of the stented segment, maximum and minimum neointima coverage grade (grade 0-2) and the presence of thrombus were examined. The neointima heterogeneity index was calculated as maximum - minimum coverage grade.

RESULTS

Maximum yellow colour grade was higher in EES than in ZES (1.3±0.9 vs 0.4±0.8, p<0.001) and maximum (2.0±0.2 vs 1.2±0.5, p<0.001) and minimum (1.5±0.6 vs 0.7±0.5, p<0.001) coverage grade was higher in ZES than in EES. The neointima heterogeneity index was not different between ZES and EES (0.4±0.5 vs 0.5±0.6, p=0.42). The incidence of thrombus was very low and was not different between ZES and EES (2% vs 4%, p=0.55).

CONCLUSIONS

Although both ZES and EES had good healing with homogeneous neointima coverage and a low incidence of thrombus, EES had more advanced atherosclerosis as shown by the presence of higher grade yellow plaque than ZES at 1 year after implantation.

Coronary stent thrombosis: current insights into new drug-eluting stent designs

The advances of interventional cardiology have been achieved by new device development, finding appropriate drug regimes, and understanding of pathomechanism. Drug-eluting stents (DES) implantation with dual anti-platelet therapy reduced revascularization without increasing mortality or myocardial infarction compared with bare-metal stenting. However, late-term stent thrombosis (ST) and restenosis limited its value and raised the safety concern. Main mechanisms of this phenomenon are impaired endothelialization and hypersensitivity reaction with polymer. The second generation DES further improved safety and/or efficacy by using thinner stent strut and biocompatible polymer. Recently, new concept DES with biodegradable polymer, polymer-free and bioabsorbable scaffold are under investigation in the quest to minimize the risk of ST.

Very late stent thrombosis at 2.5 years after sirolimus-eluting stent implantation with prior angioscopic image of culprit lesion: A case report

Although very late stent thrombosis after drug-eluting stent implantation is a critical event, its cause has not been clarified. This is the first report of a case with very late stent thrombosis after drug-eluting stent implantation for which prior angioscopic image of the culprit lesion is available. A 54-year-old Japanese male patient with stable angina who received implantation of sirolimus-eluting stent at the culprit lesion and 1-year follow-up angiographic and angioscopic examinations came back with chest pain at rest at 2.5 years after the stent implantation. Very late stent thrombosis was diagnosed by emergent angiographic and angioscopic examinations and was treated by zotarolimus-eluting stent. One-year angiographic and angioscopic follow-up examinations after zotarolimus-eluting stent were performed. Angioscopy revealed uncovered stent strut, yellow plaques, and thrombus at 1-year follow-up after sirolimus-eluting stent implantation, and it confirmed the thrombotic occlusion inside the sirolimus-eluting stent at the time of emergent catheterization. This is a case of very late stent thrombosis in the drug-eluting stent where uncovered stent strut, yellow plaques, and thrombus had been detected by angioscopy 1.5 years before the onset. Those thrombogenic sources might be the cause of stent thrombosis.

Second- and third-generation drug-eluting coronary stents: progress and safety

Drug-eluting stents (DES) have revolutionized the treatment of coronary artery disease by reducing the rate of in-stent restenosis from 20-40% with bare-metal stent (BMS) to 6-8% with DES. However, with widespread use of DES, safety concerns have risen due to the observation of late stent thrombosis. With this in mind and better understanding of mechanism and pathophysiology of stent thrombosis, the technological platform, especially innovative anti-restenotic agents, polymeric coatings, and stent platforms, improved with newer DES. Two second-generation DES, the Endeavor zotarolimus-eluting stent (ZES) and the Xience-V everolimus-eluting stent (EES), have provided promising results in both randomized controlled trials (SPIRIT and ENDEAVOR) and registries (E-Five, COMPARE) compared with bare-metal stents (BMS) and first-generation DES. Newer third-generation stent technology, especially biodegradable polymers, polymer-free stents, and biodegradable stents on the basis of poly-L-lactide (PLLA) or magnesium, has been evaluated in preclinical and initial clinical trials. However, despite encouraging initial results, long-term data of large-scale randomized trials as well as registries comparing them to currently approved first- and second-generation DES are still lacking.

Drug-eluting coronary stents - focus on improved patient outcomes

The development of stent has been a major advance in the treatment of obstructive coronary artery disease since the introduction of balloon angioplasty. Subsequently, neointimal hyperplasia within the stent leading to in-stent restenosis emerged as a major obstacle in long-term success of percutaneous coronary intervention. Recent introduction of drug-eluting stents is a major breakthrough to tackle this problem. This review article summarizes stent technology, reviews progress of drug-eluting stents and discusses quality of life, patient satisfaction, and acceptability of percutaneous coronary intervention.

Possible role of damaged neoendothelial cells in the genesis of coronary stent thrombus in chronic phase. A dye staining angioscopic study

The mechanism(s) underlying formation of coronary stent thrombus (ST) in chronic phase is yet unclear. Endothelial cells are highly antithrombotic, therefore, it is conceivable that neoendothelial cells (NECs) covering stent struts are damaged and cause ST. This study was performed to examine the role of damaged NECs covering coronary stent struts in the genesis of occlusive or nonocclusive ST in chronic phase.(1) Forty-four patients with acute coronary syndrome (17 females and 27 males) underwent dye-staining coronary angioscopy, using Evans blue which selectively stains damaged endothelial cells, 6 months after bare-metal stent (BMS) deployment. Neointimal coverage was classified into not covered (grade 0), covered by a thin layer (grade 1), and buried under neointima (grade 2) groups. (2) In 7 beagles, the relationships between neointimal thickness and ST were examined 6 months after BMS deployment. (3) The NECs on the struts were stained blue in 4 of 25 patients with grade 2 and in 11 of 20 patients with grade 0/1 (P < 0.05). ST was observed in none of the former and in 5 of the latter (P < 0.05). (4) In beagles, neointimal coverage was grade 0/1 when neointimal thickness was 80.2 ± 40.0 µm, whereas grade 2 when thickness was 184 ± 59.4 µm. ST was observed in 9 of 15 struts with neointimal thickness within 100 µm and in one of 17 struts with thickness over 100 µm (P < 0.05). ST arose from damaged NECs covering the stent struts. NECs may have been damaged due to friction between them and struts due to thin interposed neointima which might have acted as a cushion, resulting in ST.

Improved late clinical safety with zotarolimus-eluting stents compared with paclitaxel-eluting stents in patients with de novo coronary lesions: 3-year follow-up from the ENDEAVOR IV (Randomized Comparison of Zotarolimus- and Paclitaxel-Eluting Stents in Patients With Coronary Artery Disease) trial

OBJECTIVES

The increased frequency of very late (>1 year) stent thrombosis (VLST) has raised concerns with regard to the safety of sirolimus-eluting stents and paclitaxel-eluting stents (PES).

BACKGROUND

Experimental and preliminary clinical findings with the zotarolimus-eluting stent (ZES) have suggested a favorable safety profile.

METHODS

The ENDEAVOR IV (Randomized Comparison of Zotarolimus- and Paclitaxel-Eluting Stents in Patients With Coronary Artery Disease) trial is a single-blind randomized ZES versus PES clinical trial in 1,548 patients with de novo native coronary lesions; the primary end point-9-month target vessel failure-was previously reported, annual clinical follow-up is planned for 5 years, and this report describes the 3-year outcomes.

RESULTS

The ZES compared with PES reduced target vessel failure (12.3% vs. 15.9%, hazard ratio [HR]: 0.76, 95% confidence interval [CI]: 0.58 to 1.00, p = 0.049), myocardial infarctions (MI) (2.1% vs. 4.9%, HR: 0.44, 95% CI: 0.25 to 0.80, p = 0.005), and cardiac death plus MI (3.6% vs. 7.1%, HR: 0.52, 95% CI 0.32 to 0.82, p = 0.004). Although the overall 3-year rate of Academic Research Consortium definite/probable stent thrombosis did not differ significantly (1.1% vs. 1.7%, HR: 0.67, 95% CI 0.28 to 1.64, p = 0.380), VLST (between 1 and 3 years) was significantly reduced in ZES patients (1 event vs. 11 events; 0.1% vs. 1.6%, HR: 0.09, 95% CI: 0.01 to 0.71, p = 0.004). Ischemia-driven target lesion revascularization at 3 years was similar with ZES versus PES (6.5% vs. 6.1%, HR: 1.10, 95% CI: 0.73 to 1.65, p = 0.662).

CONCLUSIONS

Three-year follow-up results from the ENDEAVOR IV trial indicate similar antirestenosis efficacy but improved clinical safety associated with ZES compared with PES, due to significantly fewer peri-procedural and remote MIs associated with fewer VLST events. (A Randomized, Controlled Trial of the Medtronic Endeavor Drug [ABT-578] Eluting Coronary Stent System Versus the Taxus Paclitaxel-Eluting Coronary Stent System in De Novo Native Coronary Artery Lesions; NCT00217269).

Angioscopic Evaluation of Neointimal Coverage of Coronary Stents

Drug-eluting stents (DES) reduce coronary restenosis significantly; however, late stent thrombosis (LST) occurs, which requires long-term antiplatelet therapy. Angioscopic grading of neointimal coverage of coronary stent struts was established, and it was revealed that neointimal formation is incomplete and prevalence of LST is higher in DES when compared to bare-metal stents. It was also observed that the neointima is thicker and LST is less frequent in paclitaxel-eluting and zotarolimus-eluting stents than in sirolimus-eluting stents. Many new stents were devised and they are now under experimental or clinical investigations to overcome the shortcomings of the stents that have been employed clinically. Endothelial cells are highly anti-thrombotic. Neo-endothelial cell damage is considered to be caused by friction between the cells and stent struts due to the thin neointima between them which might act as a cushion. Therefore, development of a DES that causes an appropriate thickness (around 100 μm) of the neointima is a potential option with which to prevent neo-endothelial cell damage and consequent LST while preventing restenosis.

Late safety, efficacy, and cost-effectiveness of a zotarolimus-eluting stent compared with a paclitaxel-eluting stent in patients with de novo coronary lesions: 2-year follow-up from the ENDEAVOR IV trial (Randomized, Controlled Trial of the Medtronic Endeavor Drug [ABT-578] Eluting Coronary Stent System Versus the Taxus Paclitaxel-Eluting Coronary Stent System in De Novo Native Coronary Artery Lesions)

OBJECTIVES

The aim of this study was to assess, after 2 years of follow-up, the safety, efficacy, and cost-effectiveness of a zotarolimus-eluting stent (ZES) compared with a paclitaxel-eluting stent (PES) in patients with native coronary lesions.

BACKGROUND

Early drug-eluting stents were associated with a small but significant incidence of very late stent thrombosis (VLST), occurring >1 year after the index procedure. The ZES has shown encouraging results in clinical trials.

METHODS

The ENDEAVOR IV trial (Randomized, Controlled Trial of the Medtronic Endeavor Drug [ABT-578] Eluting Coronary Stent System Versus the Taxus Paclitaxel-Eluting Coronary Stent System in De Novo Native Coronary Artery Lesions), a randomized (1:1), single-blind, controlled trial (n = 1,548) compared ZES versus PES in patients with single de novo coronary lesions. Two-year follow-up was obtained in 96.0% of ZES and 95.4% of PES patients. The primary end point was target vessel failure (TVF), and safety end points included Academic Research Consortium-defined stent thrombosis. Economic end points analyzed included quality-adjusted survival, medical costs, and relative cost-effectiveness of ZES and PES.

RESULTS

The TVF at 2 years was similar in ZES and PES patients (11.1% vs. 13.1%, p = 0.232). There were fewer myocardial infarctions (MIs) in ZES patients (p = 0.022), due to fewer periprocedural non-Q-wave MIs and fewer late MIs between 1 and 2 years. Late MIs were associated with increased VLST (PES: 6 vs. ZES: 1; p = 0.069). Target lesion revascularization was similar comparing ZES with PES (5.9% vs. 4.6%; p = 0.295), especially in patients without planned angiographic follow-up (5.2% vs. 4.9%; p = 0.896). The cost-effectiveness of ZES and PES was similar.

CONCLUSIONS

After 2 years of follow-up, ZES demonstrated efficacy and cost-effectiveness comparable to PES, with fewer MIs and a trend toward less VLST. (The ENDEAVOR IV Clinical Trial: A Trial of a Coronary Stent System in Coronary Artery Lesions; NCT00217269).

Intracoronary thrombus formation after drug-eluting stents implantation: optical coherence tomographic study

BACKGROUND

Intracoronary thrombus formation after drug-eluting stent (DES) implantation is not sufficiently evaluated.

METHODS

Optical coherence tomography (OCT) was performed in 226 patients (total DES n = 244, sirolimus-eluting stent [SES] n = 95, paclitaxel-eluting stent [PES] n = 62, zotarolimus-eluting stent [ZES] n = 87) after implantation (mean 11 months, range 3-66 months). Using OCT, we investigated the incidence and determinants of intracoronary thrombus.

RESULTS

Intracoronary thrombus was detected in 35 (14%) cases (27 SES [28%], 7 PES [11%], and 1 ZES [1%], P < .001) and was associated with longer stent, smaller stent diameter, and stents at bifurcation lesions. More uncovered stent struts (26 +/- 23 vs 8 +/- 17, P < .001) and malapposed stent struts (6 +/- 14 vs 2 +/- 6, P < .001) were also associated with intracoronary thrombus. Multiple logistic regression analysis found the following determinants of intracoronary thrombus: stent length > or =28 mm (odds ratio [OR] 7.31, 95% CI 1.79-29.86, P = .01), stent diameter <3.0 mm (OR 4.38, 95% CI 1.38-13.97, P = .01), and > or =8 uncovered struts in each stent (OR 3.29, 95% CI 1.07-10.17, P = .04).

CONCLUSIONS

Length, size, and types of DES may be more important than clinical factors in intracoronary thrombus formation after DES implantations.

Coronary angioscopic evaluation for serial changes of luminal appearance after pharmacological and catheter interventions

Although preventive pharmacological therapies effectually reduce the risk of cardiovascular events, acute coronary syndrome (ACS) remains a leading cause of morbidity and mortality in our country, Japan. Disruption of atherosclerotic vulnerable plaques and flow-limiting thrombus formation in non-stent segments of native coronary arteries are considered a main mechanism of ACS. In addition, stent thrombosis originating from implanted metallic coronary stents, so-called vulnerable stents, occasionally appears as ACS in the clinical settings. Coronary angioscopy is a unique imaging modality permitting direct visualization of luminal structures, such as atherosclerotic plaque, thrombus, stent struts, and proliferating neointima. On the basis of accumulated angioscopic findings, intense yellow plaques and stents without neointimal coverage are considered vulnerable plaques and vulnerable stents, respectively. In contrast, morphological disappearance of vulnerable plaques or vulnerable stents by pharmacological and trans-catheter therapies imply stabilization of the plaques or stents. Hence, angioscopic assessment for vulnerability (or stability) of atherosclerotic plaques and implanted stents might be useful for risk classification in the future events of ACS. To evaluate serial changes of coronary lumen after pharmacological and catheter interventions using angioscopy might also provide important information on potential benefits and surrogate endpoints of the therapies and on patients' management.

Optical coherence tomography evaluation of zotarolimus-eluting stents at 9-month follow-up: comparison with sirolimus-eluting stents

OBJECTIVE

To evaluate the vascular response at 9 months after zotarolimus-eluting stent (ZES; Endeavor) implantation using optical coherence tomography (OCT). These findings were compared with those after implantation of a sirolimus-eluting stent (SES; Cypher Select).

DESIGN

Cross-sectional observational study with prospective OCT registry.

SETTING

Nine months after ZES or SES implantation.

PATIENTS AND METHODS

A total of 68 patients (32 ZES and 36 SES) underwent OCT at 9 months after stent implantation. The neointima hyperplasia (NIH) thickness inside each strut and percentage of NIH area at every 1 mm cross section were measured.

MAIN OUTCOME MEASUREMENT

The degree of neointimal coverage and the prevalence of malapposition at 9 months after ZES and SES implantation using OCT.

RESULTS

The mean (SD) NIH thickness (251.2 (110.0) mum vs 85.5 (53.3) mum, p<0.001) and percentage of NIH area (27.9 (9.1)% vs 11.2 (7.1)%, p<0.001) were significantly greater in ZES than in SES. The prevalence of uncovered strut as well as malapposed strut was significantly lower in ZES than in SES (0.3% vs 12.3%, p<0.001 and 0.08% vs 2.6%, p<0.001). Thrombus was not observed in ZES (0.0% in ZES vs 27.8% in SES, p = 0.001).

CONCLUSIONS

Neointimal coverage in ZES was almost complete and malapposition was very rare at 9-months' follow-up.

Late stent thrombosis, endothelialisation and drug-eluting stents

Drug-eluting stents (DES) significantly reduce the risk of restenosis after percutaneous coronary revascularisation, but an increased risk of late stent thrombosis (LST) has been put forward as a major safety concern. Meta-analysis of clinical trials, however, does not support this caveat. Even so, many interventional cardiologists think that LST is associated with DES and related to delayed endothelialisation. This hypothesis is based on autopsy studies and clinical intracoronary angioscopy. In autopsy studies, differences between endothelialisation of DES and baremetal stents (BMS) have been reported. Most preclinical studies, however, have failed to show any significant differences in endothelialisation between DES and BMS. Our own studies, using the porcine coronary artery model, also suggest that DES show no differences in re-endothelialisation. However, DES do delay vascular healing and induce endothelial dysfunction. This paper will review clinical and animal studies which consider re-endothelialisation and LST. (Neth Heart J 2009;17:177-81.).

The molecular mechanisms of congenital hypofibrinogenaemia

Congenital hypofibrinogenaemia is characterized by abnormally low levels of fibrinogen and is usually caused by heterozygous mutations in the fibrinogen chain genes (alpha, beta and gamma). However, it does not usually result in a clinically significant condition unless inherited in a homozygous or compound heterozygous state, where it results in a severe bleeding disorder, afibrinogenaemia. Various protein and expression studies have improved our understanding of how mutations causing hypo- and afibrinogenaemia affect secretion of the mature fibrinogen molecule from the hepatocyte. Some mutations can perturb chain assembly as in the gamma153 Cys-->Arg case, while others such as the Bbeta Leu-->Arg and the Bbeta414 Gly-->Ser mutations allow intracellular hexamer assembly but inhibit protein secretion. An interesting group of mutations, such as gamma284 Gly-->Arg and gamma375 Arg-->Trp, not only cause hypofibrinogenaemia but are also associated with liver disease. The nonexpression of these variant chains in plasma fibrinogen is due to retention in the endoplasmic reticulum, which in turn leads to hypofibrinogenaemia.