Pressure rinsing of coronary stents immediately before implantation reduces inflammation and neointimal hyperplasia

Bench top evaluation and clinical experience with the Szabo technique: new questions for a complex lesion

BACKGROUND

The Szabo technique has been described as a method to ensure accurate ostial stent placement. We sought to investigate this novel technique in detail both in vitro and in vivo.

METHODS AND RESULTS

The technique was subjected to bench testing and also undertaken in 26 patients. Each step was recorded with cine angiography and the stents imaged by microcomputed tomography. The ostial LAD was treated in 81% and a DES was implanted in 92%. Angiographic success was 88.5% (one case of stent dislodgement). Repeat angiography was performed in 78% and restenosis observed in two patients. MACE rate at 15.5 ± 5.1 months was 13% (1 TLR, 1 MI, 1 cardiac death). Despite a seemingly excellent immediate angiographic result, we report one case of restenosis at follow up and one case of IVUS examination (performed in four patients) in which significant stent protrusion, into the proximal main vessel, was observed. In vitro bench testing confirmed a significant and asymmetric (carina side) stent protrusion into the main branch, with the last cell of the stent undergoing significant deformation.

CONCLUSIONS

The Szabo technique is not a precise technique to implant a stent at the level of the ostium. The proximal end of the stent undergoes significant and asymmetric deformation, protruding into main branch. Additional concerns with this complex technique include the potential for stent damage or contamination before implantation and the risk of stent dislodgement. We conclude that there are more disadvantages than benefits to this technique which only partially addresses the difficulties encountered in the treating ostial lesions.

Short-term effects of biocorrodible iron stents in porcine coronary arteries

BACKGROUND

Biocorrodible iron stents carry the potential to overcome limitations, such as chronic inflammation and premature recoil, posed by biodegradable polymer and magnesium alloy stents. This study aimed to test the safety and efficacy of biocorrodible iron stents in porcine coronary arteries.

METHODS

Iron stents and cobalt chromium stents were randomly deployed in the coronary arteries of juvenile domestic pigs. Animals were sacrificed at 28 days, and the vessels were fixed and processed for histochemistry.

RESULTS

At 28 days, iron stents started to show signs of degradation without evidence of stent particle embolization or thrombosis without traces of excess inflammation, or fibrin deposition. At 28 days, the surface of the iron stent struts was black to brown and the vascular wall adjacent to the iron stent had a brownish tinge. There were no statistically significant differences in any of the measured parameters between segments implanted with iron and cobalt chromium stents. There were also no adverse effects in the persistent areas.

CONCLUSION

The current study demonstrates that stents made of biocorrodible iron are safe. In some of the measured parameters, such as intimal thickness, intimal area, and percentage occlusion, there was a trend in favor of the iron stents.

Efficacy and safety of absorbable metallic stents with adjunct intracoronary beta radiation in porcine coronary arteries

BACKGROUND

Absorbable metallic stents (AMS) utilizing Mg alloy carry advantages over permanent metallic stents because of their potential to eliminate stent thrombosis, chronic inflammation, or artifacts with noninvasive imaging. These stents, however, are associated with a modest degree of late recoil and intimal hyperplasia. The aim of the study was to test whether adjunct vascular brachytherapy (VBT) compared to AMS alone can overcome these limitations.

METHODS

Juvenile domestic pig coronary arteries underwent implantation of either AMS (n = 11) with prior adjunct VBT utilizing Sr/Y-90 beta source seeds, with a dose of 24 Gy at 2 mm from the source, or AMS alone (n = 11). At 28 days following intravascular ultrasound, vessels were harvested and analyzed by histomorphometry.

RESULTS

Intravascular ultrasound analysis indicated that at follow-up, though statistically not significant, lumen and stent areas in the segments deployed with AMS following radiation were larger than those deployed with AMS alone (3.94 +/- 1.38 and 3.53 +/- 1.75 vs. 2.99 +/- 1.05 and 3.58 +/- 1.48). Extrastent plaque and intrastent plaque areas in the same segments were smaller (2.76 +/- 0.82 and 0.24 +/- 0.47 vs. 3.25 +/- 1.94 and 0.58 +/- 0.81). Morphometric data indicate that vessels in the VBT + AMS group showed characteristics of delayed healing and re-endothelialization. Neointimal area was significantly lower in the VBT + AMS group (0.49 +/- 0.34) compared to AMS (1.3 +/- 0.62, P = 0.001). Lumen area of the VBT + AMS was larger when compared with AMS alone (2.49 +/- 0.82 vs. 1.75 +/- 0.51, P = 0.02).

CONCLUSION

VBT as an adjunct to AMS further reduces the intimal hyperplasia and improves the lumen area when compared to AMS alone but does not have any impact on late recoil.

The efficacy of nanoscale poly[bis(trifluoroethoxy) phosphazene] (PTFEP) coatings in reducing thrombogenicity and late in-stent stenosis in a porcine coronary artery model

OBJECTIVES

Previous experimental studies have demonstrated that poly[bis(trifluoroethoxy)phosphazene] (PTFEP) nanocoated stents have antithrombotic characteristics, reduce in-stent stenosis, prevent wall inflammation, and do not hamper endothelialization. This study was designed to validate these findings in a porcine coronary artery model.

MATERIALS AND METHODS

PTFEP-coated (n = 15) and bare stents (n= 13) were implanted in coronary arteries of 18 mini-pigs (4- and 12-week follow-up). Primary study endpoints were thrombogenicity and in-stent stenosis, secondary study endpoints were inflammatory response and re-endothelialization evaluated by quantitative angiography and light microscopy.

RESULTS

No thrombus deposition occurred on any stent. At 4 weeks follow-up, the bare stents (n = 4) had a significantly smaller neointimal area (1.93 vs. 3.20 mm(2), P = 0.009). At 12 weeks, PTFEP-coated stents (n = 11) had significantly superior results in almost all parameters: neointimal area (2.25 vs. 2.65 mm(2), P = 0.034), neointimal height (204.46 vs. 299.41 microm, P = 0.048), percentage stenosis (38.25 vs. 50.42%, P = 0.019), and inflammation score (0.12 vs. 0.30, P = 0.029). Complete re-endothelialization was seen in both stent types at both intervals.

CONCLUSION

At long-term follow-up, the superior results of PTFEP-coated stents were characterized by a noteworthy reduction of neointimal growth and inflammatory response.

Differential Response of Delayed Healing and Persistent Inflammation at Sites of Overlapping Sirolimus- or Paclitaxel-Eluting Stents

Background— Although effective coverage of challenging coronary lesions has warranted the use of overlapping drug-eluting stents, the histopathological response to stent overlap is unknown.

Methods and Results— The arterial reaction to overlapping Cypher or Taxus drug-eluting stents was examined in rabbits with bare metal stents, BxVelocity or Express, serving as controls. Single iliac artery balloon injury was followed by placement of 2 overlapping 3.0-mm-diameter drug-eluting stents or bare metal stents in 60 animals (mean length of overlap, 9.8±3.6 mm). Stented arteries were harvested at 28 and 90 days for histology. Overlapped segments exhibited delayed healing compared with proximal and distal nonoverlapping sites at 28 days. Overlapped segments in Taxus stents induced significantly more luminal heterophils/eosinophils and fibrin deposition than Cypher; peristrut giant cell infiltration, however, was more frequent in the latter. Overlapping bare metal stents also showed mild delayed healing compared with nonoverlapped segments, but not to the same extent as drug-eluting stents. Although neointimal thickness within the overlap was similar in 28- and 90-day Cypher stents, there was a significant increase with Taxus ( P =0.03).

Conclusions— Compared with bare metal stents, drug-eluting stents further delay arterial healing and promote inflammation at sites of overlap. Taxus stents induced greater fibrin deposition, medial cell loss, heterophils/eosinophils, and late neointimal hyperplasia. Patients receiving overlapping drug-eluting stents need more frequent follow-up than patients with nonoverlapping stents.

The influence of physical stent parameters upon restenosis

In this paper we examine whether the structure, geometry and dimensions of coronary stents influence the occurrence of restenosis. Whilst many consider these parameters to be less important since the advent of drug-eluting stents, this view reveals a poor appreciation of the technological development of stents over the last 18 years. Early 'slotted tube' stents were completely inflexible and posed major problems for delivery; and early 'coil' stents had poor radial strength, allowing considerable tissue prolapse. Nowadays, we are used to greatly improved physical stent parameters, which provide better deliverability, visibility, procedural success and scaffolding performance. Many of these physical parameters also impact upon restenosis, even in the current era of drug-eluting stent. In this paper we examine the contribution of mode of expansion (self vs. balloon-expandable), design (coil vs. tube), length and width to restenosis. We also consider the more subtle influence of advanced slotted tube vs. modular design, percent metal coverage, strut thickness, strut shape, surface smoothness and alloy composition.