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Recent advances on the development of magnesium alloys for biodegradable implants.

Zinc is proposed as an exciting new biomaterial for use in bioabsorbable cardiac stents. Not only is zinc a physiologically relevant metal with behavior that promotes healthy vessels, but it combines the best behaviors of both current bioabsorbable stent materials: iron and magnesium. Shown here is a composite image of zinc degradation in a murine (rat) artery.

Zinc Exhibits Ideal Physiological Corrosion Behavior for Bioabsorbable Stents

Aims Treatment of elderly symptomatic patients with severe aortic stenosis and co-morbidities is challenging. Transcatheter aortic valve interventions [balloon valvuloplasty and transcatheter aortic valve implantation (TAVI)] are evolving as alternative treatment options to surgical valve replacement. We report the first results of the prospective multi-centre German Transcatheter Aortic Valve Interventions— Registry.

Methods and results Between January 2009 and December 2009, a total of 697 patients (81.4 ± 6.3 years, 44.2% males, and logistic EuroScore 20.5 ± 13.2%) underwent TAVI. Pre-operative aortic valve area was 0.6 ± 0.2 cm² with a mean transvalvular gradient of 48.7 ± 17.2 mmHg. Transcatheter aortic valve implantation was performed percutaneously in the majority of patients [666 (95.6%)]. Only 31 (4.4%) procedures were done surgically: 26 (3.7%) transapically and 5 (0.7%) transaortically. The Medtronic CoreValveTM prosthesis was used in 84.4%, whereas the Sapien EdwardsTM prosthesis was used in the remaining cases. Technical success was achieved in 98.4% with a post-operative mean transaortic pressure gradient of 5.4 ± 6.2 mmHg. Any residual aortic regurgitation was observed in 72.4% of patients, with a significant aortic insufficiency (≥Grade III) in only 16 patients (2.3%). Complications included pericardial tamponade in 1.8% and stroke in 2.8% of patients. Permanent pacemaker implantation after TAVI became necessary in 39.3% of patients. In-hospital death rate was 8.2%, and the 30-day death rate 12.4%.

Conclusion In this real-world registry of high-risk patients with aortic stenosis, TAVI had a high success rate and was associated with moderate in-hospital complications. However, careful patient selection and continued hospital selection seem crucial to maintain these results.

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Transcatheter aortic valve implantation: first results from a multi-centre real-world registry

BACKGROUND In patients with coronary artery disease who receive metallic drug-eluting coronary stents, adverse events such as late target-lesion failure may be related in part to the persistent presence of the metallic stent frame in the coronary-vessel wall. Bioresorbable vascular scaffolds have been developed to attempt to improve longterm outcomes. METHODS In this large, multicenter, randomized trial, 2008 patients with stable or unstable angina were randomly assigned in a 2:1 ratio to receive an everolimus-eluting bioresorbable vascular (Absorb) scaffold (1322 patients) or an everolimus-eluting cobalt–chromium (Xience) stent (686 patients). The primary end point, which was tested for both noninferiority (margin, 4.5 percentage points for the risk difference) and superiority, was target-lesion failure (cardiac death, target-vessel myocardial infarction, or ischemia-driven target-lesion revascularization) at 1 year. RESULTS Target-lesion failure at 1 year occurred in 7.8% of patients in the Absorb group and in 6.1% of patients in the Xience group (difference, 1.7 percentage points; 95% confidence interval, −0.5 to 3.9; P = 0.007 for noninferiority and P = 0.16 for superiority). There was no significant difference between the Absorb group and the Xience group in rates of cardiac death (0.6% and 0.1%, respectively; P = 0.29), targetvessel myocardial infarction (6.0% and 4.6%, respectively; P = 0.18), or ischemiadriven target-lesion revascularization (3.0% and 2.5%, respectively; P = 0.50). Device thrombosis within 1 year occurred in 1.5% of patients in the Absorb group and in 0.7% of patients in the Xience group (P = 0.13). CONCLUSIONS In this large-scale, randomized trial, treatment of noncomplex obstructive coronary artery disease with an everolimus-eluting bioresorbable vascular scaffold, as compared with an everolimus-eluting cobalt–chromium stent, was within the prespecified margin for noninferiority with respect to target-lesion failure at 1 year. (Funded by Abbott Vascular; ABSORB III ClinicalTrials.gov number, NCT01751906.)

Everolimus-Eluting Bioresorbable Scaffolds for Coronary Artery Disease

The invention of balloon angioplasty as a percutaneous treatment for obstructive coronary disease by Andreas Gruntzig in 1977 was a huge leap forward in cardiovascular medicine and undoubtedly will always be remembered as a revolution in the field of revascularization. However, this technique was plagued by multiple problems, including the risk of acute vessel closure secondary to occlusive coronary dissection, sometimes necessitating emergency coronary artery bypass surgery.1,–,3 Although late luminal enlargement and vascular remodeling could take place, more often restenosis4,–,8 would occur instead. The restenosis would essentially be caused by constrictive remodeling9,–,13 and, to a lesser extent, by elastic recoil14 or the neointimal hyperplastic healing response.15,–,17

The advent of bare metal stenting (BMS) and the landmark Belgian-Netherlands Stent Study (BENESTENT) and Stent Restenosis Study (STRESS) trials have established BMS as the second revolution in interventional cardiology.18,19 This technology provided a solution to acute vessel occlusion by sealing the dissection flaps and preventing recoil. The rate of subacute occlusion was reduced to 1.5%, making emergency bypass surgery a rare occurrence. Restenosis rates were further reduced from 32% to 22% at 7 months, but this rate was still high, and neointimal hyperplasia inside the stent was even more prominent than with angioplasty, necessitating repeat treatment in numerous patients.18

Because the vessel was now caged with metal, late luminal enlargement and advantageous vascular remodeling could no longer occur. Another problem, namely late stent thrombosis (ST), was also first described.20 To solve the problem of in-stent restenosis, after the historic failure of brachytherapy to resolve this problem,21,22 drug-eluting stents (DES) were introduced. The first 45 patients implanted with the sirolimus-eluting Bx velocity stent (Cordis, Johnson …

Bioresorbable scaffold: The advent of a new era in percutaneous coronary and peripheral revascularization?

Objective: To observe and characterise vessel injury after stenting using optical coherence tomography (OCT), to propose a systematic OCT classification for periprocedural vessel trauma, to evaluate its frequency in stable versus unstable patients and to assess its clinical impact during the hospitalisation period. Setting: Stenting causes vessel injury. Design and interventions: All consecutive patients in whom OCT was performed after stent implantation were included in the study. Qualitative and quantitative assessment of tissue prolapse, intra-stent dissection and edge dissection were performed. Results: Seventy-three patients (80 vessels) were analysed. Tissue prolapse within the stented segment was visible in 78/80 vessels (97.5%). Median number of tissue prolapse sites was 8 (IQR 4-19), mean (SD) area 1.04 (0.9) mm2. Intra-stent dissection flaps were visible in 69/80 vessels (86.3%) (median number 3 (IQR 1.25-6), maximum flap length 450 (220) μm). Fifty-five out of 80 vessels (68.8%) showed dissection cavities (median number 2 (IQR 0-4.75), maximum depth 340 (170) μm). Edge dissection was visible in 20 vessels (mean (SD) length flap 744 (439) μm). The frequency of tissue prolapse or intra-stent dissection was similar in stable and unstable patients (95.6% vs 100%, p = 0.5 for tissue prolapse; 91.1% vs 82.9%, p = 0.3 for intra-stent dissection). There were no events during the hospitalisation period. Conclusions: OCT allows a detailed visualisation of vessel injury after stent implantation and enables a systematic classification and quantification in vivo. In this study, frequency of tissue prolapse or intra-stent dissections after stenting was high, irrespective of the clinical presentation of the patients, and was not associated with clinical events during hospitalisation.

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Optical coherence tomography assessment of the acute effects of stent implantation on the vessel wall: a systematic quantitative approach

Aims: Multimodality imaging of the first-in-man trial using a fully resorbable everolimus-eluting scaffold (BVS, Abbott Vascular, Santa Clara, CA, USA) demonstrated at two years the bioresorption of the device while preventing restenosis. Nevertheless, the long-term safety and efficacy of this novel therapy remain to be documented. Methods and results: The ABSORB trial completed in July 2006 at four clinical sites in Europe and New Zealand the enrolment of 30 patients with a single de novo native coronary artery lesion. The major clinical endpoint was ischaemia-driven major adverse cardiac events (ID-MACE) defined as a composite of cardiac death, myocardial infarction, or ischaemia-driven target lesion revascularisation. Clinical follow-up was available in 29 patients since one patient withdrew consent. At 46 days, one patient experienced a single episode of chest pain and underwent a diagnostic optical coherence tomography and subsequently a target lesion revascularisation with slight troponin rise after the procedure. At 3-year the hierarchical ID-MACE of 3.4% remained unchanged. Clopidogrel therapy was discontinued in all but one patient. There has been no stent thrombosis reported. Two non-cardiac deaths were reported; one from duodenal perforation, the other from Hodgkin disease. Two patients underwent non-ischaemia driven target vessel revascularisation. Conclusions: Three-year clinical results have demonstrated a sustained low MACE rate (3.4%) without any late complication such as stent thrombosis.

Three-year results of clinical follow-up after a bioresorbable everolimus-eluting scaffold in patients with de novo coronary artery disease: the ABSORB trial.

Fully bioabsorbable scaffolds (BRS) are a novel approach that provides transient vessel support with drug delivery capability without the long-term limitations of the metallic drug-eluting stents (DES), such as permanent caging with or without malapposition. The technology has the potential to overcome many of the safety concerns associated with metallic DES, and possibly even convey further clinical benefit. Although the technology is still in its infancy, several devices have been tested in clinical trials and the initial results have been very promising. This review will discuss the emerging need for BRS, the theoretical advantages of this new technology over current generation metallic DES and review the status of the currently available BRS. In addition, we will discuss the ideal duration of bioresorption, the proven and potential clinical benefits and future perspectives of this rapidly progressing technology.

Bioresorbable scaffold technologies.

Background: Anecdotal evidence suggests that transcatheter aortic valve implantation (TAVI) is being used beyond pre-market label indications. Methods: To assess the frequency and outcomes associated with “off-label” use of TAVI, we conducted a retrospective study, examining adherence to patient selection criteria in 63 patients undergoing implantation with the 18F CoreValve ReValving System (CRS). Label status (on-label vs off-label) was determined by following (1) inclusion/exclusion criteria indicated in the 18F CRS safety and efficacy trial and (2) a patient selection matrix indicating anatomical boundaries to guide patient selection. Off-label use was defined as the presence of at least one exclusion criterion or “non-acceptable” criteria based on the patient selection matrix. Results: Off-label implantation was identified in 42 patients (67%)—40% had one, 19% had two and 8% had three or more off-label criteria. Baseline demographics were similar between the groups except for a higher logistic EuroSCORE in the on-label group (19.8 (11.2) vs 14.5 (7.3), p = 0.029). There was no significant difference in the procedural success rates between the on-label and off-label groups (91% vs 95%, respectively, p = 0.47). The frequency of angiographic moderate-severe aortic regurgitation, post-implant dilatation or implantation of a second valve was also similar between the groups. At 30 days, the cumulative death rate was 10%; there were four deaths in the “on-label” and three deaths in the “off-label” group. Conclusion: In this study we found that “off-label” implantation of the CRS was common. Further studies are needed to evaluate the consequences of “label status” for patients undergoing TAVI.

https://heart.bmj.com/content/heartjnl/96/1/19.full.pdf

Y Onuma

Papers

Bioresorbable scaffold: The advent of a new era in percutaneous coronary and peripheral revascularization?

Optical coherence tomography assessment of the acute effects of stent implantation on the vessel wall: a systematic quantitative approach

Three-year results of clinical follow-up after a bioresorbable everolimus-eluting scaffold in patients with de novo coronary artery disease: the ABSORB trial.

Bioresorbable scaffold technologies.

Adherence to patient selection criteria in patients undergoing transcatheter aortic valve implantation with the 18F CoreValve ReValving System.