Conformation of Adjacent Self-expanding Stents: A Cross-Sectional In Vitro Study

Novel approach to treating calcified infrarenal aortic stenosis using intravascular lithotripsy without stenting

This case report presents the use of intravascular lithotripsy (IVL) in a 68-year-old woman with disabling bilateral claudication owing to a heavily calcified subocclusive stenosis of the infrarenal aorta. The patient had a history of tobacco use, dyslipidemia, and chronic obstructive pulmonary disease, with absent femoral pulses and severe arterial calcification. A 12-mm Shockwave L6 lithotripsy catheter was employed to treat the aortic lesion, resulting in a significant decrease in the aortic pressure gradient without the need for stenting. The patient experienced complete symptom resolution postoperatively, and at 1 month, follow-up imaging confirmed vessel patency with no sign of restenosis. IVL, used here as a standalone treatment, demonstrated effectiveness in modifying calcified plaques and restoring vessel compliance, offering a less complex and potentially more cost-effective alternative to stent grafting in calcified aortic lesions. This case highlights the potential of IVL as a safe and effective treatment option in select patients with calcified infrarenal aortic stenosis.

Role of intravascular ultrasound for the technical assessment of endovascular reconstruction of the aortic bifurcation

OBJECTIVE

The aim of this study was to evaluate the role of intravascular ultrasound (IVUS) for the technical assessment of kissing stents (KSs) and covered endovascular reconstruction of the aortic bifurcation (CERAB) in the treatment of aortoiliac obstructive disease involving the aortic bifurcation.

METHODS

We conducted a single-center retrospective review of patients undergoing endovascular treatment of severe aorto-iliac obstructive disease (2019-2023). IVUS was performed in patients treated by KSs or CERAB according to preoperative indications, in cases of moderate/severe calcifications, mural thrombus, total occlusions, and lesion extension towards the proximity of renal or hypogastric arteries. Indications for IVUS-guided intraoperative revisions were residual stenosis or compression >30%, incomplete stent-to-wall apposition, or flow-limiting dissection at the landing site. Follow-up assessment was performed at 6 and 12 months, and then yearly. Thirty-day outcomes and 2-year patency rates were evaluated. Logistic regression was used to identify factors associated with significant technical defects detected by IVUS needing intraoperative revision.

RESULTS

IVUS was used for the technical assessment of 102 patients treated by KSs (n = 57; 56%) or CERAB (n = 45; 44%) presenting with severe intermittent claudication (39%), rest pain (39%), or ischemic tissue loss (25%). Twenty-nine significant technical defects were identified by IVUS in 25 patients (25%) who then had successful intraoperative correction by additional ballooning (n = 23; 80%) or stenting (n = 6; 20%). Patients with a severely calcified chronic total occlusion (odds ratio, 1.85; 95% confidence interval, 1.01-5.27; P = .044) or severely calcified narrow aortic bifurcation with <12 mm diameter (odds ratio, 2.34; 95% confidence interval, 1.10-8.64; P = .032) were at increased risk for IVUS-guided intraoperative revision. There were no postoperative deaths and no major adverse events. Two-year primary patency was 100%.

CONCLUSIONS

IVUS was used for the technical assessment of KSs/CERAB in a selected cohort of patients with severe aorto-iliac obstructive disease. This allowed the identification and intraoperative correction of a significant technical defect not detected by completion angiogram in one-quarter of patients, achieving optimal 2-year results. IVUS assessment of KSs/CERAB may be considered especially in patients with a calcified total occlusion or narrow aortic bifurcation.

Mid-term Results of Endovascular Reconstruction of Aortic Bifurcation Using COVERA Stent Graft

INTRODUCTION

This article aims to evaluate the short-term and mid-term performance of a self-expanding covered stent (COVERA Plus, Bard Tempe, Arizona) during the treatment of Trans-Atlantic Inter-Society Consensus (TASC) C/D aortoiliac obstructive lesions involving the aortic bifurcation.

METHODS

A single-center retrospective review of all patients who underwent endovascular reconstruction of the aortoiliac bifurcation for obstructive disease, with the use of Covera, from January 2018 to March 2023. All patients received a postoperative CTA (computed tomography angiography) scan within 1 month from the intervention. Precision of deployment, stent conformation, and stent symmetry were evaluated at the arterial phase of the CTA. Early outcomes were technical success and freedom from open aortic reintervention and/or mortality. Late outcomes were primary and assisted primary patency rates and freedom from reintervention.

RESULTS

During the study period, 35 patients underwent primary endovascular treatment of obstructive lesions involving the aortic bifurcation with parallel COVERA stents. Aortoiliac lesions were classified as TASC-IIC in 23 (65.7%) patients and TASC D in 12 (34.2%). Median follow-up was 49 months (interquartile [IQR]: 18-60). Overall survival was 97.1% (95% confidence interval [CI]=91-100) at 60 months. During follow-up, there were one early stent stenosis, treated with an angioplasty and stent relining with an estimated primary patency at 60 months of 97.1% (95% CI=94-100) and a primary-assisted patency of 100%. Estimated freedom from all types of reinterventions at 60 months was 94.3% (95% CI=89-99.3).

CONCLUSIONS

The new self-expanding covered Bard COVERA Plus stent used for endovascular treatment of TASC C/D aorto iliac disease proved to be safe and feasible with high technical procedural success rates. Comparison with other types of stents is necessary to further assess the role of the COVERA Plus stent in aortic bifurcation repair.

CLINICAL IMPACT

This study investigates the safety and feasibility of the new self-expanding covered Bard Covera Plus stent used for endovascular treatment of TASC C/D aorto iliac disease. The retrospective analysis of 35 patients highlights high technical success and primary patency rate at 60 months. The geometric analysis also helped to underline how this stent can be used precisely in particular conditions. These findings suggest the need for further research to compare COVERA with other types of stents in aortic bifurcation repair.

The Geometry of Y-Stent Configurations Used for Wide-Necked Aneurysm Treatment: Analyzing Double-Barrel Stents In Vitro Using Flat-Panel Computed Tomography

BACKGROUND

Stent-assisted coil embolization of wide-necked bifurcation aneurysms often employs a Y configuration stent. A similar stent configuration, termed kissing/double-barrel (KDB), is used often at the aortoiliac bifurcation. Studies of KDB stents in aortoiliac disease show that rates of thromboembolic complications vary with the cross-sectional geometry of the stent pair, a function of the radial crush resistive force of each stent. We assessed cross-sectional geometry of intracranial stent pairs in an in vitro model of the basilar artery using flat-panel computed tomography.

METHODS

In a silicone model of a wide-necked basilar tip aneurysm, 6 simulated KDB stent deployment trials were performed using combinations of 5 stents (Enterprise 1, Enterprise 2, Neuroform Atlas, LVIS, LVIS Jr.). Flat-panel computed tomography reconstructions were used to assess cross-sectional stent geometry. Relative conformability, defined by ovalization and D-ratio, radial crush resistive force (predicted vs. actual), and radial mismatch fraction were compared by stent type (braided vs. laser-cut).

RESULTS

Several distinct forms of cross-sectional stent geometry were observed. Braided stents had lower ovalization and D-ratio (P = 0.015) than laser-cut stents. The Neuroform Atlas/LVIS combination yielded the lowest radial mismatch fraction (19.7% vs. mean 44.3% ± 0.7%). Braided stents tended to have a deployed stent radius closer to the expected (nominal) diameter (i.e., higher relative crush resistive force) than laser-cut stents (measured vs. nominal diameter discrepancy +38.6% ± 21.1% vs. -10.7% ±16.1%, P = 0.14).

CONCLUSIONS

In constant anatomy, cross-sectional geometry of the KDB stent configuration will vary depending on the design and structure of the stents employed.

In vivo geometry of the kissing stent and covered endovascular reconstruction of the aortic bifurcation configurations in aortoiliac occlusive disease

Objectives

Various configurations of kissing stent (KS) configurations exist and patency rates vary. In response the covered endovascular reconstruction of the aortic bifurcation configuration was designed to minimize mismatch and improve outcome. The aim of the current study is to compare geometrical mismatch of kissing stent with the covered endovascular reconstruction of the aortic bifurcation configuration in vivo.

Methods

Post-operative computed tomographic data and patient demographics from 11 covered endovascular reconstruction of the aortic bifurcation and 11 matched kissing stent patients were included. A free hand region of interest and ellipse fitting method were applied to determine mismatch areas and volumes. Conformation of the stents to the vessel wall was expressed using the D-ratio.

Results

Patients were mostly treated for Rutherford category 2 and 3 (64%) with a lesion classification of TASC C and D in 82%. Radial mismatch area and volume for the covered endovascular reconstruction of the aortic bifurcation group was significantly lower compared to the kissing stent configuration (P < 0.05). The D-ratio did not significantly differ between groups. Measurements were performed with good intra-class correlation. There were no significant differences in the post-procedural aortoiliac anatomy.

Conclusions

The present study shows that radial mismatch exists in vivo and that large differences in mismatch exist, in favour of the covered endovascular reconstruction of the aortic bifurcation configuration. Future research should determine if the decreased radial mismatch results in improved local flow profiles and subsequent clinical outcome.

Geometrical consequences of kissing stents and the Covered Endovascular Reconstruction of the Aortic Bifurcation configuration in an in vitro model for endovascular reconstruction of aortic bifurcation

OBJECTIVE

Kissing stents (KS) are commonly used to treat aortoiliac occlusive disease, but patency results are often lower than those of isolated stents. The Covered Endovascular Reconstruction of the Aortic Bifurcation (CERAB) technique was recently introduced to reconstruct the aortic bifurcation in a more anatomical and physiological fashion. The aim of this study is to compare the geometrical consequences of various stent configurations in vitro.

METHODS

Anatomic vessel phantoms of the aortoiliac bifurcation were created to accommodate stent configurations. Self-expandable nitinol KS, balloon-expandable covered KS, and two versions of the CERAB configuration were deployed, one with the iliac legs positioned inside the tapered part of the aortic cuff (1) and one with the legs deployed above this level (2). Computed tomography data were obtained to assess the geometry. The conformation ratio (D-ratio) was calculated by use of the ratio of the major and minor axes. The proximal mismatch area, mean mismatch area, and total mismatch volume were calculated.

RESULTS

The highest D-ratios were observed in the nitinol KS and the CERAB configuration, implying an ideal "double-D" shape. The proximal and mean mismatch areas were four- to sixfold lower in the CERAB (1) configuration when compared with nitinol KS and CERAB (2), respectively, whereas the covered KS had the highest mismatch area. Nitinol and covered KS had the largest mismatch volume, whereas the mismatch volume was the lowest in the CERAB (1) configuration.

CONCLUSIONS

Although nitinol self-expandable stents have a high stent conformation, the lowest radial mismatch was found in the CERAB (1) configuration, supporting the hypothesis that the CERAB configuration is the most anatomical and physiological reconstruction of the aortic bifurcation. Within the CERAB configuration, the two limbs are ideally positioned inside the tapering portion of the cuff, minimizing mismatch.

T-stenting with small protrusion technique (TAP-stenting) for stenosed aortoiliac bifurcations with small abdominal aortas: an alternative to the classic kissing stents technique

PURPOSE

To report the feasibility and midterm results of aortic bifurcation reconstruction in patients with small abdominal aortas using commercially available stents applied in a modified T-stenting technique adapted from coronary angioplasty.

METHODS

Twenty-three patients (16 men; mean age 52.4 years) with lower limb ischemia (Fontaine stage IIb or III) and distal abdominal aortas <14 mm in diameter were treated for 39 common iliac artery and 16 aortic stenotic lesions involving the aortic bifurcation. A large, self-expanding stent was implanted from the lower aorta to one iliac branch, followed by deployment of a balloon-expandable stent in the contralateral iliac artery such that its proximal edge protruded a few millimeters through the struts of the self-expanding stent into the aorta [TAP (T And Protrude)-stenting technique]. Follow-up clinical, Doppler ultrasound, and computed tomography examinations were scheduled for each patient.

RESULTS

Angiographic success was obtained in all 23 patients, who received 23 self-expanding aortomonoiliac stents (mean diameter 13.5 mm) and 22 balloon-expandable stents (mean diameter 8.14 mm) in the contralateral iliac branch. No complications were reported. At a mean 16.3-month follow-up (range 2-60), clinical and ankle-brachial index (0.6±0.2 at baseline versus 1.04±0.1, p<0.01) improvement was observed in all patients. All stents were patent (patency rate 100%). Two late technical failures of the contralateral stent were observed (incomplete dilation requiring angioplasty and incomplete protrusion without any hemodynamic impact).

CONCLUSION

The TAP-stenting technique adapted to the aortoiliac bifurcation appears to be feasible, with satisfactory early and midterm patency rates in patients with small abdominal aortas. Larger series with longer follow-up times are necessary.