Stent remodeling contributes to femoropopliteal artery restenosis: an intravascular ultrasound study

Carotid Artery Dynamics during Head Movements: A Reason for Concern with Regard to Carotid Stenting?

Purpose:

To evaluate carotid artery mobility patterns during head movements following carotid angioplasty/stenting (CAS).

Methods:

In 7 patients (all men; mean age 69 years, range 65–76) who had undergone unilateral CAS, 3D time-of-flight magnetic resonance angiography was performed, visualizing both carotid arteries in 5 different head positions (neutral, turned left and right, and bent forward and backward). Maximum intensity projection reconstructions were obtained to measure angulation at the proximal and distal stent junction. Configuration changes of the stented section of the carotid artery and the unstented contralateral artery were judged. Secondly, transverse sections at the level of the carotid bifurcation and at the skull base were used to calculate torsion shear in the common and internal carotid arteries (CCA, ICA) during turned left and right head position. Results were expressed as median (range).

Results:

In neutral head position, maximal angulation at the distal stent junction was 34.3° (32.3°–55.6°). With the head bent forward, this angulation changed to 47.6° (42.6°–85.2°, p=0.028) and when bent backward to 26.5° (25.0°–48.7°, p=0.027). In all patients, configuration changes of the stented sections were absent. The contralateral unstented side showed diffuse configuration changes without specific angulation at one location. With the head turned left and right, the CCA on the stented side was subjected to 28.6° (13.6°–53.7°) and 24.9° (2.0°–50.6°) of torsion shear, respectively. Torsion of the ICA was subsequently 18.1° (12.7°–40.5°) and 15.2° (2.9°–69.4°).

Conclusions:

Following carotid stenting, sharp ICA angulations that are aggravated by forward bending of the head occur at the distal stent junction. The stented section of the carotid artery shows complete lack of flexibility despite highly flexible features of the stents ex vivo. Both the CCA and ICA are subjected to considerable torsion shear with the head turned left and right. This shear is not accommodated by the current stent designs.

Deformation of Self-Expanding Stent-Grafts Complicating Endovascular Peripheral Aneurysm Repair

Purpose:

To demonstrate the deformation of self-expandable stents after endovascular repair of peripheral aneurysms.

Methods and Results:

The Corvita Endoluminal Graft was used to treat a traumatic false aneurysm of the right subclavian artery and a common iliac artery aneurysm in 2 patients. In the subclavian case, the stent-graft showed a “cigar-shaped” deformation with hemodynamically significant stenoses at the proximal and distal ends at 3 months. In the second case, the same type of deformity was noted only 1 day after implantation. Two months later, the stent-graft occluded, necessitating surgical repair.

Conclusions:

Both cases demonstrate the possibility of stent deformation of self-expanding stent-grafts implanted at arterial sites not subject to external compression.

Response of Renal and Femoropopliteal Arteries to Palmaz Stent Implantation Assessed with Intravascular Ultrasound

Purpose:

To establish the processes responsible for late lumen loss in renal and femoropopliteal Palmaz stents using intravascular ultrasound (IVUS).

Methods:

The first 7 consecutive patients treated with stents for renal (n = 4) and femoropopliteal (n = 3) arterial occlusive disease were studied with IVUS immediately after angiographically successful stent placement (< 10% residual stenosis) and periodically during follow-up. Images of both stent edges and the most stenotic site inside the stent at follow-up were matched to the same cross sections captured immediately after stent placement for quantitative analysis.

Results:

Late lumen loss in renal artery stents at 5 to 34 months was considerably less than in femoropopliteal stents (17% versus 62%, respectively). In the renal location, late lumen loss (3.0 ± 1.3 mm2) was due to neointimal hyperplasia, whereas stent area remained unchanged (3% decrease). Late lumen loss (7.4 ± 8.2 mm2) in femoropopliteal stents was due to neointimal hyperplasia and stent area reduction (26%). Overall, in both types of arteries, neointimal development and stent area reduction were larger at the most stenotic site than at the stent edges.

Conclusions:

These data suggest that there may be differences between renal and femoropopliteal arteries in the extent of hyperplastic response to stents.

Stent fracture in the brachiocephalic trunk

Stents are commonly used as a tool for revascularization of different vascular beds in the body. However, many pitfalls have been reported with their use, such as thrombosis, migration, restenosis or fractures. The latter have been strongly correlated to in-stent restenosis with long-term follow-up. We report a rare case of an early stent fracture in the brachiocephalic trunk with in-stent restenosis and recurrence of symptoms. To our knowledge there has been only one case report of a delayed brachiocephalic stent fracture in the English literature. We believe that our case is the first report of an early stent fracture in the brachiocephalic trunk.

Fractured Internal Carotid Artery Stent

Carotid artery stenting is gaining wider acceptance as an alternative option in the treatment of carotid artery stenosis. Conventional complications such as stroke and recurrent in-stent restenosis are well documented in the literature. However, we believe that carotid stent complications are underreported. The carotid artery segment has features that are relatively smilar to the femoropopliteal segment with respect to forces affecting the stented segment, which can contribute to stent complications such as fracture. In this article, we present a case of internal carotid artery stent fracture and thrombus formation after the patient was exposed to direct trauma to the chest and neck.

Carotid artery dynamics after carotid angioplasty and stenting

Carotid angioplasty and stenting (CAS) has emerged as an alternative treatment for carotid artery occlusive disease. As initial results in patients with an increased surgical risk appeared promising, the popularity of CAS has increased substantially over the last years and CAS has more often been advocated as an alternative to the gold standard, carotid endarterectomy (CEA). Several controlled trials comparing CAS with CEA are currently being conducted. However, long-term results of CAS are still sparse and several issues regarding the inherent differences between treatment modalities have not yet been elucidated. Interestingly, to date, very little attention has been directed towards the mobile features of the carotid artery and the implications of stent placement on carotid artery dynamics.

Impact of head movements on morphology and flow in the internal carotid artery after carotid angioplasty and stenting versus endarterectomy

OBJECTIVE

Because stents can cause vessel angulation during movement, we hypothesized that internal carotid artery (ICA) stents might lead to alterations of cerebropetal blood flow. This study assessed three-dimensional anatomy and volumetric flow rate (VFR) in the ICA in various head positions by comparing patients treated with carotid angioplasty and stenting (CAS) with patients treated with carotid endarterectomy (CEA).

METHODS

Three-dimensional time-of-flight magnetic resonance angiography and magnetic resonance flow quantification were performed on six subjects after CAS (median age, 70 years) and on six subjects after CEA (median age, 67 years). All investigations were performed in five head positions: neutral, bent forward, bent backward, and turned to the treated, ipsilateral side and to the contralateral side. Maximum-intensity projection reconstructions were obtained to measure maximal angulation of the ICA in the forward, backward, ipsilateral, and contralateral positions compared with neutral. Subsequently, the plane perpendicular to the ICA, 1 cm distal to the stent or 4 cm distal to the carotid bifurcation (CEA patients), was established. The VFR through this plane was measured for each position, and the forward, backward, ipsilateral, and contralateral positions were compared with neutral.

RESULTS

In CAS patients, there was a median change in ICA angulation of +10.2 degrees (interquartile range, +7.3 degrees to +17.9 degrees ) in the forward position, compared with +0.2 degrees (-1.0 degrees to +2.4 degrees ) in CEA patients ( P = .016). In all other head positions, there was no statistically significant difference in angulation change. There was no statistically significant difference in VFR change between groups in any of the head positions tested.

CONCLUSIONS

There was a significant increase in ICA angulation in CAS patients if the head was bent forward; this was not observed in CEA patients. This angulation change did not lead to significant acute changes in cerebropetal blood flow, but it might have chronic effects not yet tested.

Midterm follow-up of balloon-expandable ePTFE endografts in the femoropopliteal segment

PURPOSE

To evaluate the midterm clinical outcome of patients treated with a balloon-expandable polytetrafluoroethylene (ePTFE) endograft for long-segment occlusive disease of the femoropopliteal segment.

METHODS

Eighty-nine patients (68 men; median age 69 years, range 43-81) with disabling claudication (n=73) or critical ischemia (n=16) were treated with an ePTFE endograft (mean length 29 cm) for 7 stenosis (mean length 9 cm) and 82 occlusions (mean length 19 cm) in the femoropopliteal segment. The follow-up protocol included Doppler ankle-brachial pressure measurement and duplex scanning or angiography of the endograft at 6-month intervals. Primary and secondary patency rates were analyzed.

RESULTS

At the last examination, the endograft was patent in 52 patients (median 17 months, range 7-50) and occluded in 35 (median 7 months, range 0-40); 2 patients died of nonvascular causes with a patent endograft at 6.5 and 7 months. At follow-up, the primary and secondary endograft patency rates were 71% and 83% at 6 months, 57% and 69% at 1 year, 45% and 49% at 2 years, and 30% and 44% at 3 years, respectively.

CONCLUSIONS

The midterm success of this new ePTFE endograft is limited; therefore, the device needs to be refined if this minimally invasive technique is to compete with conventional bypass surgery.

Intravascular ultrasound evidence for stabilization of compensatory enlargement of the femoropopliteal segment after endograft placement

PURPOSE

To document whether the vasodilatory response seen at the anastomotic segment 6 months after placement of a balloon-expandable endograft in the femoropopliteal segment progresses between 6 and 24 months.

METHODS

Twelve patients (9 men; median age 65 years, range 47-75) treated with an investigational polytetrafluoroethylene (PTFE) endograft for obstructive disease of the femoropopliteal segment were studied with intravascular ultrasound (IVUS) immediately after placement and at 6 months (first follow-up period) and 24 months (second follow-up period). Matched IVUS cross sections derived from the endograft and the anastomotic segment were analyzed for changes in lumen (LA), vessel (VA), and plaque areas (PLA).

RESULTS

Five patients had complete IVUS surveillance at both the first (mean 8 months, range 7-9) and second (mean 25 months, range 23-26) follow-up periods; 1 patient was lost to follow-up during the second interval, and another 6 were excluded owing to graft occlusion (n = 4) or no IVUS surveillance available (n = 2) during the second follow-up period. Matched IVUS cross sections derived from the endograft showed no significant change in LA during both follow-up periods (-8% and +1%, respectively). There was no evidence for intimal hyperplasia or endograft recoil. During both follow-up periods, IVUS cross sections derived from the anastomotic segment revealed significant increases in LA (+37% and +8%, respectively) and VA (+26% and +6%, respectively) (both p < 0.05). The change in PLA during both follow-up periods was not significant (+13% and +3%, respectively).

CONCLUSIONS

The PTFE endograft seems to inhibit both intimal hyperplasia and constrictive remodeling. The short-term (6-month) vascular dilatory response seen at the anastomotic segment tends to stabilize at 2 years. Therefore, this endovascular anastomosis acts as an "ideal" end-to-end anastomosis.

Vascular response in the femoropopliteal segment after implantation of an ePTFE balloon-expandable endovascular graft: an intravascular ultrasound study

PURPOSE

To use intravascular ultrasound (IVUS) to document changes in vascular dimensions after placement of a balloon-expandable endograft.

METHODS

Thirteen patients (9 men; mean age 62 years, range 47-75) treated with an investigational polytetrafluoroethylene endograft for obstructive disease of the femoropopliteal segment were studied with IVUS immediately after endograft implantation and at follow-up. Corresponding IVUS cross sections were analyzed for changes in lumen, vessel, and plaque areas seen inside the endograft, in the anastomotic segment, and in the remote arterial segment.

RESULTS

A mean 6-month (range 1.5-9) follow-up was completed in 12 patients. Matched IVUS cross sections derived from within the endograft (n = 12) and at the endograft edges (n = 23) showed no change in lumen area (LA) in 17, reduction in 11, and dilatation in 7. Median changes within the endograft (+3%) were not significant (p = 0.28) and no neointima was found. Cross sections obtained at the anastomotic segment revealed a significant increase in LA (85%, p < 0.001), which was associated with a significant increase in both vessel area (VA) (42%, p < 0.001) and plaque area (PLA) (15%, p = 0.003) area. In the remote arterial segment, the change in LA was minimal (6%, p = 0.07), as were changes in the VA (9%, p = 0.04) and PLA (10%, p = 0.07).

CONCLUSIONS

Following endograft placement, luminal changes within the endograft, at the endograft edges, and at the remote arterial segments were minimal. Intimal hyperplasia was not observed in the endograft. The distinct LA increase at the anastomotic segments was determined by the extent of VA and PLA change.

Physical properties of endovascular stents: an experimental comparison

PURPOSE

Different endovascular stent types (AVE Bridge, AVE Bridge X, Memotherm, Palmaz Large, Palmaz Medium, Palmaz-Schatz Long-Medium, Perflex, S.MA.R.T., Symphony, and Wall-stent) of 4 cm length and 8 mm diameter were subjected to standardized physical tests.

MATERIALS AND METHODS

The metal mass of each stent was assessed by weighing. The balloon-expandable stents were pneumatically tested for hoop strength. In self-expanding stents, radial resistive force and chronic outward force were determined with use of a loop test. Stent delivery system pushability was assessed in a crossover model. Stent radiopacity was analyzed quantitatively.

RESULTS

The hoop strength of the balloon-expandable stents ranged from 15.8 N/cm (Perflex) to 28.9 N/cm (AVE Bridge X). The stent weight increased with greater hoop strength (Perflex, 0.046 g/cm vs. AVE Bridge X, 0.061 g(cm). The self-expanding stents had a radial resistive force between 0.39 N/cm (Wallstent) and 1.7 N/cm (Smart). The flexible balloon-expandable stents showed pushability values between 0.13/N (AVE Bridge) and 0.20/N (Perflex). The self-expanding stents had flexibilities between 0.13/N (Memotherm) and 0.24/N (Symphony). Radiopacity assessed with use of a phantom simulating the iliac region ranged from 92 (Palmaz Large) to 115 (AVE Bridge) on a 256-point gray scale (0 = black, 256 = white).

CONCLUSIONS

There is no stent with ideal physical properties. However, depending on the characteristics of the arterial lesion to be treated, the most appropriate stent can be chosen.

Response of renal and femoropopliteal arteries to Palmaz stent implantation assessed with intravascular ultrasound

PURPOSE

To establish the processes responsible for late lumen loss in renal and femoropopliteal Palmaz stents using intravascular ultrasound (IVUS).

METHODS

The first 7 consecutive patients treated with stents for renal (n = 4) and femoropopliteal (n = 3) arterial occlusive disease were studied with IVUS immediately after angiographically successful stent placement (< 10% residual stenosis) and periodically during follow-up. Images of both stent edges and the most stenotic site inside the stent at followup were matched to the same cross sections captured immediately after stent placement for quantitative analysis.

RESULTS

Late lumen loss in renal artery stents at 5 to 34 months was considerably less than in femoropopliteal stents (17% versus 62%, respectively). In the renal location, late lumen loss (3.0 +/- 1.3 mm2) was due to neointimal hyperplasia, whereas stent area remained unchanged (3% decrease). Late lumen loss (7.4 +/- 8.2 mm2) in femoropopliteal stents was due to neointimal hyperplasia and stent area reduction (26%). Overall, in both types of arteries, neointimal development and stent area reduction were larger at the most stenotic site than at the stent edges.

CONCLUSIONS

These data suggest that there may be differences between renal and femoropopliteal arteries in the extent of hyperplastic response to stents.

Deformation of self-expanding stent-grafts complicating endovascular peripheral aneurysm repair

PURPOSE

To demonstrate the deformation of self-expandable stents after endovascular repair of peripheral aneurysms.

METHODS AND RESULTS

The Corvita Endoluminal Graft was used to treat a traumatic false aneurysm of the right subclavian artery and a common iliac artery aneurysm in 2 patients. In the subclavian case, the stent-graft showed a "cigar-shaped" deformation with hemodynamically significant stenoses at the proximal and distal ends at 3 months. In the second case, the same type of deformity was noted only 1 day after implantation. Two months later, the stent-graft occluded, necessitating surgical repair.

CONCLUSIONS

Both cases demonstrate the possibility of stent deformation of self-expanding stent-grafts implanted at arterial sites not subject to external compression.

Incidence, time-of-onset, and anatomical distribution of recurrent stenoses after remote endarterectomy in superficial femoral artery occlusive disease

PURPOSE

The incidence, time-of-onset, and anatomical distribution of recurrent stenoses after remote endarterectomy in superficial femoral artery (SFA) occlusive disease were studied.

METHODS

Patients undergoing SFA remote endarterectomy procedures were examined with duplex surveillance. Patients were examined at 6 weeks, 3, 6, 9, and 12 months, and then annually. Recurrent stenosis was defined as a peak systolic velocity ratio of 2.5 or higher. Duplex results were also compared with clinical and hemodynamic changes.

RESULTS

Restenoses were identified in 46 of 101 (46%) limbs treated after a mean interval of 5.8 months (range, 1 to 18 months). These 46 limbs formed the base of this study. The median follow-up period was 25 months. Thirty-eight (83%) of all restenoses were detected within 1 year. The lesions were located within the entire SFA and were not specifically related to the adductor canal or distal stented region only. Multiple stenoses were found in 21 limbs. Only 10 (22%) restenoses were correlated with worsening of clinical symptoms, change of ankle-brachial index, or both. Ten of 23 cases (43%) of nonrevised restenoses progressed to occlusion. These 10 occlusions occurred in all patients with restenosis that developed within the first year. Nonrevised late restenoses (more than 1 year) were not associated with any reocclusion.

CONCLUSION

Recurrent stenoses after SFA remote endarterectomy were noticed in 46 of 101 (46%) limbs. Most restenoses (83%) developed within the first year. In the nonrevised group, time-of-onset restenosis (less than 1 year) was correlated with a higher risk for occlusion ( P =.02). The location of restenoses were found without any anatomical site of preference along the entire endarterectomized SFA segment.

Endovascular stent-grafts for aneurysms of the femoral and popliteal arteries

Our objective was to investigate the preliminary use of endovascular stent-grafts for the treatment of femoropopliteal artery aneurysm. Ten patients with an aneurysm of the femoropopliteal artery referred for endovascular treatment were investigated. The series consisted of patients with a true aneurysm of the superficial femoral artery (n = 2); a true aneurysm of the popliteal artery (n = 4); an aneurysmal dilatation of a Biograft bypass (n = 2); a false aneurysm of the superficial femoral aneurysm (n = 1); and a false aneurysm of a composite bypass (n = 1). In 8 of the 10 patients the stent-graft was composed of one or more Palmaz stents sutured to an ePTFE tube graft; in the other 2 patients a venous covering was used in combination with Palmaz stents. The procedure was guided by angiography and intravascular ultrasound. The results of our investigation showed that endovascular stent-grafting of aneurysms of the femoropopliteal artery is a feasible but experimental technique that should be restricted to a selected group of patients.