Clinical and angiographic efficacy of a self-expanding nitinol stent in saphenous vein graft atherosclerotic disease: the Stent Comparative Restenosis (SCORES) Saphenous Vein Graft Registry

Very late stent thrombosis caused by rupture of lipid-laden neointima in a self-expanding coronary stent

A 60-year-old man was admitted to our hospital due to acute ST-segment elevation myocardial infarction. He had a history of self-expanding stent implantation in the proximal left anterior descending artery due to stable angina pectoris 7 years earlier. Emergent coronary angiography on admission showed occlusion in the distal portion of the previously stented segment, in which observation by optical coherence tomography revealed the existence of a remarkable proliferation of lipid-laden neointimal tissues with rupture and thrombus. This suggests that very late stent thrombosis in a self-expanding stent may occur through the process of atheromatous formation.

A comparison of the radial and the femoral approach in vein graft PCI. A retrospective study

BACKGROUND

Transradial PCI is a safe and effective method of percutaneous revascularization. However, there is limited data on the efficacy of the transradial approach for saphenous vein graft (SVG) PCI.

METHODS

We studied 334 patients who underwent SVG PCI between January 2000 and December 2003, and compared the radial (132 patients) and the femoral (202 patients) approach.

RESULTS

Mean EF (55.6+/-18.6% radial versus 58.1+/-16.8% femoral), lesion location (proximal, mid, distal: 22.6/50.6/26.7% versus 22.6/44.5/32.9% respectively) and lesion type (B1/B2/C: 3.4/4.1/92.5% versus 0.4/3.1/96.5%) were similar in both groups (P>0.05). Five patients had a failed radial attempt (3.8%) and were switched to the femoral approach. Mean fluoroscopy time (20.4+/-12.2 versus 18.4+/-10.2 min), procedural time (60.0+/-27.2 versus 61.6+/-24.9 min) and the use of contrast (223+/-91 versus 234+/-91 ml) IIB/IIIA inhibitors (27.2 versus 33.2%), and stenting (81.5 versus 81.3%) were similar in both groups, whereas 5 or 6 French sheaths were used more often in the radial group (83.4 versus 64.9%, P<0.01). Angiographic success (93.9 versus 92.9%), in hospital MACE (radial:5 MI (3.8%) versus femoral: 1 death (0.5%) and 7 MI (3.5%) and major vascular complications (0.7 versus 0.5%) were also similar.

CONCLUSIONS

The radial approach in SVG PCI is as fast and successful as the femoral.

Histopathologic evaluation of a novel‐design nitinol stent: the Biflex stent

BACKGROUND

Optimalization and improvement in stent material, stent design and deployment may alleviate the problem of restenosis after stenting. The Biflex stent is a novel-design stent made of nitinol; the vascular response after deployment in rabbit iliac arteries was evaluated.

METHODS AND RESULTS

Normocholesterolemic New Zealand white rabbits (n = 8) were used. Iliac arteries were randomized to receive either a stainless steel control stent or a nitinol stent and rabbits were euthanized at 30 days after implantation. All animals survived and there were no adverse events. Vessels were harvested and prepared for histopathologic analysis and histomorphometry. Stents were well opposed to the vessel wall and thrombi were absent. The lumen area and the area within the internal elastic lamina were significantly larger in the nitinol stent group as opposed to the control group (3.8 +/- 0.1 vs 3.3 +/- 0.1 mm, p = 0.009 and 4.6 +/- 0.1 vs 4.1 +/- 0.2 mm, p = 0.03, respectively). There were no differences in injury score, neointimal area, medial area, area within the external elastic lamina and amount of inflammatory cells. Staining for alpha-smooth muscle cell actin and endothelium did not show any differences between the two groups as assessed semiquantitatively.

CONCLUSION

This nitinol stent with a novel design demonstrated acceptable biocompatibility in iliac arteries of normocholesterolemic rabbits with minimal foreign-body reaction and minimal neointimal formation.

Clinical outcomes after percutaneous peripheral intervention for chronic total occlusion of superficial femoral arteries: comparison between self-expandable nitinol stent and stainless steel stent

BACKGROUND

It has been reported that nitinol stents provide higher patency in chronic phase than stainless steel stents after intervention to superficial femoral artery (SFA). However, there are few reports about stent patency for chronic total occlusion of SFA (SFA CTO).

OBJECTIVE

To compare clinical outcomes of self-expanding nitinol stents and stainless steel stents after percutaneous peripheral intervention (PPI) for SFA CTO.

METHODS AND RESULTS

Between April 2004 and August 2007, a total of 25 SFA CTO lesions (nitinol stent group, 13; stainless steel stent group, 12) in 21 patients were treated with PPI, all patients were followed clinically, and 21 lesions (nitinol, 9; stainless steel, 12) received follow-up angiography. There was no significant difference in baseline characteristics, mean stent diameter (7.3+/-0.7 mm vs. 6.9+/-1.2 mm, p=0.32), pre-ankle-brachial index (ABI), and Fontaine stage between groups. Mean occlusion length and stent length were significantly longer (129.5+/-54.9 mm vs. 39.0+/-20.6 mm, 250.8+/-90.0 mm vs. 145.2+/-64.6 mm, respectively, p<0.01) and number of stents was significantly larger (2.8+/-0.9 vs. 1.6+/-0.5, p<0.01) in the nitinol stent group. At follow-up, ABI was significantly lower (0.73+/-0.20 vs. 0.95+/-0.13, p=0.04), restenosis rate and target lesion revascularization was significantly higher (58.3% vs. 15.4%, p=0.03; 50.0% vs. 7.7%, p=0.02, respectively) in the stainless steel stent group.

CONCLUSION

Our study demonstrates the superiority of nitinol stent implantation compared with stainless steel stent implantation for SFA CTO.

Successful nitinol stent implantation in a large coronary aneurysm: post-interventional patency assessment by magnetic resonance imaging

Nitinol stents are thought to exhibit reduced occurrence of artifacts and may be suitable for magnetic resonance imaging (MRI) evaluation of stent localization and in-stent patency even in coronary-sized stent grafts. A 54-year-old male patient presented with a large coronary post-stenotic aneurysm of the right coronary artery (RCA) beside significant stenoses of the left circumflex coronary artery (LCX) and the left anterior descending coronary artery (LAD) with aneurysm formation. After implantation of stent grafts to the LAD and LCX, two polymermembrane-covered nitinol stent grafts were placed into the RCA. A control MR examination 7 days following the RCA intervention showed successful occlusion of the former aneurysm, no post-interventional endoleak, and bright signal within the stent indicating stent patency. Thus, coronary MRI after nitinol stent implantation in coronary aneurysms is feasible for post-interventional early imaging control at least as far as the exclusion of possible endoleaks is concerned.

Primary Patency of Long-Segment Self-Expanding Nitinol Stents in the Femoropopliteal Arteries

PURPOSE

To report a retrospective cohort study of nitinol stent implantation in patients at high risk for restenosis owing to long-segment (> or =10 cm) femoropopliteal disease.

METHODS

Sixty-five consecutive patients with peripheral artery disease underwent long-segment (> or =10 cm) femoropopliteal stent implantation using self-expanding nitinol stents after initial failure of plain balloon angioplasty (i.e., residual stenosis >30% or a flow-limiting dissection). Patients were followed for first occurrence of in-stent restenosis, defined as a >50% lumen diameter reduction by color-coded duplex sonography, with angiographic confirmation.

RESULTS

Cumulative median length of the stented segments was 16 cm (interquartile range [IQR] 12-25, absolute range 10-40) using up to 5 overlapping stents. During the median 8-month follow-up (IQR 6-11), no early thrombotic reocclusions occurred within 30 days, but 26 (40%) patients developed an in-stent restenosis. Cumulative freedom from restenosis at 6 and 12 months was 79% and 54% overall, respectively; at the same time periods, the rates were 84% and 71% in nondiabetic patients (n=41) versus 68% and 22% in diabetics (n=24) (adjusted hazard ratio 3.8, p=0.01). Cumulative stent length and number of implanted stents were not associated with restenosis.

CONCLUSION

Midterm restenosis after long-segment femoropopliteal stenting using self-expanding nitinol stents remains a major problem, particularly in patients with diabetes mellitus. The midterm results in nondiabetics are encouraging.

The Mechanism of In-Stent Restenosis in Radius Stent-An Experimental Porcine Study-

BACKGROUND

We investigated the mechanism of in-stent restenosis in radius stents in comparison to balloon-expandable stent (NIR stent) in pigs, with a focus on extracellular matrix (ECM).

METHODS AND RESULTS

Radius (n = 4) or NIR (n = 4) stents were implanted in the left coronary arteries of miniature pigs. Quantitative coronary ultrasound (QCU) was performed before, immediately after, and at 1 and 4 weeks after the implantation. The stented-coronary arteries were harvested at 4 weeks after the implantation followed by immunohistochemical, histological, reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR studies. In QCU, mean luminal areas at 4 weeks did not differ between both groups, whereas the mean stent area and neointimal area were significantly greater in the radius (p < 0.01). The immunohistochemical study revealed a significantly decreased number of neointimal macrophages and neovascularizations (p < 0.05, p < 0.01, respectively), and a stronger expression of tenascin-C in the radius. The histological study showed a larger ECM area and less neointimal cell density in the radius than in the NIR. The RT-PCR and real-time PCR analysis revealed an enhanced expression of tanascin-C mRNA in the radius than in the NIR.

CONCLUSIONS

Increased production of ECM, especially tenascin-C, played a greater role in the neointimal formation in the radius stent than inflammation.

Feasibility, safety, and preliminary efficacy of a novel ePTFE-covered self-expanding stent in saphenous vein graft lesions: The Symbiot II trial

Compared with percutaneous interventions in native coronary arteries, revascularization of saphenous vein graft (SVG) lesions is associated with increased rates of immediate and long-term major adverse cardiac events (MACE). The Symbiot II trial was a multicenter prospective study designed to evaluate the feasibility and safety of a novel self-expanding polytetrafluoroethylene (ePTFE)-covered stent in the treatment of de novo and restenotic SVG lesions. The primary endpoint was MACE through 30 days postprocedure. Successful Symbiot stent deployment was achieved in 75 of 77 patients (97.4%) with SVG lesions < or = 35 mm in length (visual assessment). The procedural success rate (defined as < 30% residual stenosis at the target site and no clinical complications) was 83%, and all study device procedures provided grade 3 TIMI flow postprocedure. Within the first 30 days postprocedure, four patients (5.2%) experienced MACE (defined as death, Q-wave or non-Q-wave myocardial infarction, and clinically driven target vessel revascularization), of whom three patients (3.9%) experienced periprocedural non-Q-wave myocardial infarction. No subacute stent thrombosis was observed over the 6-month follow-up period. No relevant luminal loss at the target site (mean, 0.3 +/- 0.9 mm) was observed in the 58 patients (77.3% of enrolled patients) who underwent quantitative coronary angiography at 6 months. The incidences of binary in-stent restenosis, in-segment restenosis, and target vessel failure (defined as acute and late-term MACE through 6 months postprocedure) were low (7.0%, 8.6%, and 14.3%, respectively). The Symbiot self-expanding ePTFE membrane-covered stent was associated with a high procedural success rate (97.4%), low incidences of MACE at 30 days (5.2%) and 6 months (14.3%), suggesting that it is safe and effective in the treatment of SVG disease.

Primary Patency of Femoropopliteal Arteries Treated with Nitinol versus Stainless Steel Self-expanding Stents: Propensity Score–adjusted Analysis

PURPOSE

To evaluate, in a propensity score-adjusted analysis, the intermediate-term primary patency rates associated with nitinol versus stainless steel self-expanding stent placement for treatment of atherosclerotic lesions in femoropopliteal arteries.

MATERIALS AND METHODS

The authors analyzed the clinical and imaging data of 175 consecutive patients with peripheral artery disease and either intermittent claudication (n = 150) or critical limb ischemia (n = 25) who underwent femoropopliteal artery implantation of nitinol (n = 104) or stainless steel (n = 123) stents in a nonrandomized setting. The stents were placed owing to either significant residual stenosis (ie, >30% lumen diameter reduction) or flow-limiting dissection after initial balloon angioplasty of the femoropopliteal artery. Patients were followed up for a median period of 9 months (mean, 13 months; range, 6-66 months) for the detection of a first in-stent restenosis, defined as a greater than 50% lumen diameter reduction that was seen at color-coded duplex ultrasonography and confirmed at angiography.

RESULTS

Cumulative patency rates at 6, 12, and 24 months were 85%, 75%, and 69%, respectively, after nitinol stent placement versus 78%, 54%, and 34%, respectively, after stainless steel stent placement (P =.008, log-rank test). There were no statistically significant differences in associated patency among the three different nitinol stents used (P =.72, log-rank test). Multivariate Cox proportional hazard analysis, in which the effect of propensity to receive a nitinol stent was considered, revealed a significantly reduced risk of restenosis with the nitinol stents compared with the risk of restenosis with the stainless steel stents (adjusted hazard ratio, 0.44; 95% confidence interval: 0.22, 0.85; P =.014).

CONCLUSION

Nitinol stents are associated with significantly improved primary patency rates in femoropopliteal arteries compared with stainless steel stents. Randomized controlled trials are needed to confirm these results.