Late angiographic follow-up after Palmaz-Schatz stent implantation

Two-year follow-up intravascular ultrasound analysis after bare metal stent implantation in 120 lesions

The objective of this study was to examine long-term changes after bare metal stent implantation in a relatively large number of patients. There are few reports of intravascular ultrasound (IVUS) studies performed on stented and nonstented (reference) segments beyond 6 months after bare metal stenting. Using IVUS, we evaluated serial changes in stented and reference segments between 6 and 24 months after stent implantation in 110 patients with 120 lesions. Serial IVUS images were acquired at five equidistant intrastent sites and at two different reference segment sites. Measurements were made of the external elastic membrane (EEM), stent, lumen, and intimal hyperplasia (IH = stent - lumen) area. For the whole patient group, between 6 and 24 months, the mean IH area in stented segments decreased from 2.6 +/- 1.0 to 2.3 36+/- 0.9 mm2 (P < 0.001), and the mean lumen area increased from 6.2 +/- 2.0 to 6.5 +/- 1.9 mm2 (P < 0.001). The mean IH area decreased in 91 lesions (76%) and increased in 29 lesions (24%) between 6 and 24 months. There were no significant changes in EEM or lumen area in the reference segments. Late angiographic restenosis (diameter stenosis > or = 50%) occurred in three lesions between 6 and 24 months. A late target lesion revascularization was performed for one lesion. In the period of time between 6 and 24 months after stenting, IH regression occurred in most (76%) stent lesions, resulting in late lumen increase. However, IH progression was observed in 24% of in-stent lesions. No significant changes of EEM or lumen area occurred in the reference segments.

Can we prevent in-stent restenosis?

Nowadays stent placement has replaced balloon angioplasty as the most commonly performed percutaneous coronary interventional procedure, mainly because of its better acute and chronic outcome. As a result, in-stent restenosis (ISR) has become a widespread problem. The incidence of ISR varies from 10% to 50% and depends on the absence or presence of several risk factors, such as small vessel size, longer lesions, and diabetes. Intravascular ultrasound studies have demonstrated that ISR is mainly caused by neointimal proliferation; consequently, this pathologic process has become the target of many preventive and therapeutic approaches. This article provides an overview of such management strategies, highlighting the rather disappointing experiences with mechanical and systemic drug therapies; the relative merits and disadvantages of intracoronary radiation; and the exciting yet realistic promise, embodied by the recent advancements in drug-eluting stent technology, of potentially eradicating ISR in the near future.

Relationship between blood flow, thrombus, and neointima in stents

PURPOSE

To establish a relationship between flow, acute thrombus formation, and late intimal hyperplasia in arterial stents.

MATERIALS AND METHODS

To compare short-term stent patency in the canine femoral artery with normal flow to that in the opposite femoral artery with restricted flow, 24 dogs were subdivided in four groups: groups 1 (no intravenous heparin) and 2 (intravenous heparin) had unilateral flow restriction by surgically created stenosis, downstream of a Palmaz stent. Group 3 (no intravenous heparin) and 4 (intravenous heparin) had sham surgical exposure of the corresponding arterial segment, without flow restriction. Thrombocyte activity over the stent segment was evaluated for 3 hours after stent placement with nuclear scanning, after administration of indium-111-labeled platelets. To evaluate long-term stent patency in relationship to arterial flow, 14 additional dogs were subjected to long-term observation. Matched, symmetrically implanted femoral stents with normal and restricted flow, were explanted at 1, 12, and 24 weeks for histologic analysis and comparative measurement of neointimal thickness. Angiographic studies were performed before and after nuclear scanning in the short-term study group and before explant in the long-term animal group.

RESULTS

In the short-term, groups 2 and 4 showed neither increased platelet uptake nor angiographically demonstrable thrombus. Group 1 had increased platelet uptake and occlusive or subocclusive angiographic thrombus. Group 3 had increased platelet uptake and angiographic thrombus in one instance. In the long-term, stents with flow restriction had significantly greater neointimal formation in comparison with unrestricted stents. Histologic studies suggested that the stent neointima resulted from progressive replacement of stent thrombus.

CONCLUSION

Regardless of flow condition, intravenous heparinization is necessary to prevent thrombus formation in the stent lumen. Within the experimental parameters of this study, low flow and absent heparinization consistently lead to stent thrombosis. Stent implantation under low flow is associated with increased neointima formation. It is not known whether this is preventable by antithrombotic medication.

First clinical experience with the premounted balloon-expandable serpentine stent: acute angiographic and intermediate-term clinical results

The beStent-Artist coronary stent is a newly developed, stainless steel coronary stent with a serpentine tubular design and terminal stent markers, premounted on a semicompliant balloon. During this pilot evaluation we aimed to test the acute clinical and angiographic results, short-term (30 days) and 6-month clinical results. A total of 57 stents were used to treat 43 lesions in 40 patients. Deployment strategy included predilatation, stent deployment, balloon repositioning to match the distal end of the balloon to the distal stent marker, and subsequent 12-14 atm postdilatation. There were two cases of stent dislodgment, but no procedural complications. In four cases, stent recrossing with another balloon was necessary. In two of these cases, distal dissections were observed and treated with another stent. The minimal lumen diameter (MLD) increased from 0.84+/0.52 mm at baseline to 2.7+/-0.62 mm at the end of the procedure (a corresponding decrease in diameter stenosis from 78.6 > 16.4 to 18.2+/-10.7%). The acute gain was 1.89+/-0.61mm. No adverse events occurred by 30 days. During six months, 7/40 (18.5%) of patients required target vessel revascularization due to in-stent restenosis. In summary, the premounted beStent-Artist can be delivered and deployed with favorable immediate results and high success rate with favorable long-term recurrent event rates.

Coronary artery stenting: indications and cost implications

The practice of coronary stenting is evolving rapidly, with new stent designs, deployment techniques, and adjunctive therapy. In many respects, clinical practice is changing in advance of the availability of supporting data. The consistent excellent angiographic result with stent deployment exceeds that achieved by any other previous interventional device, and the extent to which this accounts for the exponential increase in stent utilization cannot be accurately determined but is undoubtedly considerable. Controlled randomized trials have confirmed that stent deployment is superior to balloon angioplasty in certain lesion subsets or clinical scenarios. These include focal de novo native vessel lesions, lesions with late recoil after balloon angioplasty, acute closure after balloon angioplasty, and proximal left anterior descending coronary artery lesions. In addition, observational data is persuasive in focal coronary saphenous vein graft lesions and aorto-ostial lesions. On the other hand, the evidence supporting the use of stents strictly to improve on a suboptimal result, possibly the most frequent indication, is indirect and circumstantial. Stents are expensive, but it was anticipated that with the reduction in restenosis not only would they be cost-effective but also ultimately would reduce costs. This hope has not as yet been realized. However, there is little question that the introduction of intracoronary stents has been the most significant and exciting development since the introduction of percutaneous revascularization almost 20 years ago. It has revitalized the field.