Optimal deployment of third-generation stents: an intravascular ultrasound assessment

First-in-Man Trial of SiO2 Inert-Coated Bare Metal Stent System in Native Coronary Stenosis - The AXETIS FIM Trial

BACKGROUND

A novel bare metal stent with an SiO2coating was developed to prevent excessive neointimal hyperplasia by inertization of the metallic stent surface. The efficacy of the device was demonstrated in a preclinical model. The aim of this first-in-man trial was to assess the safety and feasibility of the new device.

METHODS AND RESULTS

This prospective non-randomized single-arm trial was designed to enroll 35 patients with a de novo coronary lesion. Quantitative coronary angiography and optical coherence tomography (OCT) were performed at the baseline procedure and at the 6-month follow-up. Stent implantation was performed with OCT guidance according to optimal stent implantation criteria. The trial was terminated upon the advice of the data safety monitoring board after enrolling 14 patients due to the high incidence of re-intervention. Optimal OCT implantation criteria were achieved in only 8.3% of lesions. At 6 months, angiographic in-stent late lumen loss as the primary endpoint was 0.77±0.44 mm, and binary restenosis occurred in 33.3% of lesions. At the 6-month OCT, neointimal volume obstruction was 32.8±15.6% with a neointimal thickness of 237±117 µm. At 12 months, the device-oriented composite endpoint (defined as cardiac death, target vessel myocardial infarction, and clinically indicated target lesion revascularization rate) was 33.3%.

CONCLUSIONS

In contrast with the preclinical study, the Axetis stent did not efficiently suppress neointimal hyperplasia in humans in this trial.

Discrepancy between morphologic and functional criteria of optimal stent deployment using intravascular ultrasound and pressure derived myocardial fractional flow reserve

BACKGROUND

Pressure derived myocardial FFR, a functional index of epicardial stenosis has been proposed for the assessment of optimal stent deployment. The following study evaluated the potential of serial fractional flow reserve (FFR) measurements in comparison to the 'gold standard' intravascular ultrasound (IVUS) for optimal stent deployment and its long-term outcome.

METHODS

35 patients with a single de novo lesion underwent PTCA followed by stent implantation with an initial inflation pressure of 12 atm. If optimal stent expansion using IVUS-criteria were not fulfilled, re-dilatation at 16 atm as well as additional inflations with larger balloon sizes were performed to reach the procedural end-point. IVUS and FFR were performed after each dilatation (n = 136). Angiography was repeated after 6 months.

RESULTS

In 30 pts who fulfilled IVUS criteria, mean lumen area (2.9+/-1.3 mm2) increased after PTCA and stent implantation to 10.0+/-3.0 mm2. In six pts, optimum stent deployment according to a value of FFR0.94 was not reached. Four of six pts reached the IVUS criteria at 12 atm and two pts at 16 atm, respectively. Positive and negative predictive values of FFR were 26 and 64%. Three of the 30 pts (10%) revealed a restenosis at three months follow-up. One of these restenosis was seen in a patient with a post-procedural FFR<0.94.

CONCLUSIONS

FFR was not valid to predict optimal stent expansion according to IVUS criteria but could delineate under-expanded stents despite a reasonable angiographic appearance. Morphologic (IVUS) and functional criteria (FFR) for optimal stent deployment revealed a comparably low restenosis rate.

Impact of a prolonged delivery inflation time for optimal drug-eluting stent expansion

PURPOSE

We examined the importance of prolonged inflation time for optimal sirolimus-eluting stent (SES) or paclitaxel-eluting stent (PES) expansion.

METHODS

Eighty-one de novo lesions deployed single SES or PES between April 2007 and March 2008 were divided into four groups; group 1: 21 SES deployed at 20 atm x 60 sec, group 2: 20 SES deployed with 2-step inflation at 20 atm x 60 sec following 20 atm x 20 sec, group 3: 20 PES deployed same as group 1, group 4: 20 PES deployed same as group 2. The minimal lumen diameter (MLD) and stent expansion ratio (SER; stent cross- sectional area at lesion/balloon cross-sectional area which was calculated according to the compliance chart at the same atmosphere as stent deployment) were compared between group 1 and group 2 in SES, between group 3 and group 4 in PES.

RESULTS

The MLD of post 60 sec was significantly higher than that of post 20 sec (2.84 +/- 0.28 mm in group 1, 2.76 +/- 0.33 mm in group 2 vs. 2.54 +/- 0.33 mm in group 2; P = 0.003, 0.045, respectively and 2.94 +/- 0.28 mm in group 3, 3.00 +/- 0.34 mm in group 4 vs. 2.69 +/- 0.35 mm in group 4; P = 0.022, 0.007, respectively). The SER of post 60 sec was significantly higher than that of post 20 sec (79.3% +/- 8.5% in group 1, 80.8% +/- 7.8% in group 2 vs. 71.1% +/- 10.2% in group 2; P = 0.014, 0.011, respectively and 81.1% +/- 7.9% in group 3, 84.3% +/- 9.9% in group 4 vs. 72.6% +/- 10.5% in group 4, P = 0.011, 0.001, respectively).

CONCLUSION

The prolonged delivery inflation for 60 sec may result in a more optimal stent expansion. It is therefore considered to be a useful method for deploying drug-eluting stent.

Incidence of stent under-deployment as a cause of in-stent restenosis in long stents

Although stent under-deployment (SU) has been associated with increased risk of in-stent restenosis, little data have been reported on the incidence of SU in patients presenting with clinical in-stent restenosis. In 59 patients referred for vascular brachytherapy and showing angiographic in-stent restenosis, we sought (1) to determine the incidence of SU using standard intravascular ultrasound (IVUS) criteria (2) to evaluate the effects of repeat angioplasty on further stent expansion. Stented length was 32+/-17 mm and diameter stenosis was 75+/-14%. Before re-intervention, the incidence of reduced absolute values of minimal stent cross-sectional area (MSCSA) varied from 69% (< or =8 mm2) to 15% (< or =5 mm2). After re-intervention, the incidence decreased to 24% (< or =8 mm2) (p = 0.0001) and 0% (< or =5 mm2) (p = 0.005). Before re-intervention, SU as assessed by relative criteria varied from 21% (80% mean reference lumen area or 90% minimum distal reference lumen area) to 28% (100% minimum reference lumen area). After re-intervention, the incidence of SU varied from 7% (90% minimum distal reference lumen area) (p = 0.0001 vs. pre) to 24% (55% mean reference EEM area) (p = ns). No change in strut apposition (97% pre vs. 100% post) nor in symmetry index (100% pre vs. post) was noted. From all criteria, the 90 and 100% minimum reference lumen area criteria were the most altered by repeat balloon dilatation, 21% pre vs. 7% post and 28% pre vs. 11% post, respectively. In conclusion, among patients presenting with severe angiographic in-stent restenosis, a significant number showed signs of SU whose incidence varied according to applied criteria. Significant stent re-expansion can be obtained following IVUS-guided repeat angioplasty irrespective of initial SU criteria.