Effects of balloon dilatation on ePTFE structural characteristics

Application of dual Willis covered stents in the management of large fusiform carotid aneurysms in a canine model

This study evaluates the efficacy of dual Willis covered stents for the treatment of large fusiform carotid aneurysms in a canine model. Carotid fusiform aneurysms >10 mm long were surgically created in 10 dogs and were then repaired using either single or dual covered stents. Clinical results were assessed by scheduled angiography and histological features by light and electron microscopy. Angiography immediately post-op and 6 months after surgery revealed aneurysm isolation rates of 60 and 20% for the single stent technique and 60 and 100% for the dual stent technique, respectively. The rate of complete obliteration of the aneurysm sac differed significantly between treatments ( P = 0.048). The dual stent technique also resulted in greater endothelialization. For large carotid fusiform aneurysms in a canine model, endovascular repair using dual Willis covered stents is technically feasible and more effectively obliterates the aneurysm sac than the use of a single stent.

Usefulness of balloon angioplasty for the right ventricle-pulmonary artery shunt with the modified Norwood procedure

OBJECTIVE

We sought to evaluate the efficacy of balloon angioplasty (BA) for severely desaturated patients due to a stenotic right ventricle (RV) to pulmonary artery (PA) shunt following modified Norwood procedure.

METHODS

Of 87 patients who underwent a Norwood procedure with the RV-PA shunt between February 1998 through March 2010, 22 (25%) patients underwent BA. The efficacy of BA was assessed by angiographic measurement of the changes in the internal diameters of the stenotic portions of the shunt, changes in arterial saturation and clinical outcomes.

RESULTS

BA was performed for stenotic RV-PA shunts following stage I palliation (n = 17, 77%), or those placed as an additional blood source (n = 5, 23%, 3 patients awaiting biventricular repair, 2 patients following stage II palliation). The location of the BA was at the distal anastomosis in 12 (54.5%), proximal anastomosis in 21 (95.4%) and in the mid-portion of the shunt in 11 (50%) cases. The diameters of these three shunt portions were measured from the anterior-posterior and lateral angiographic images, increasing significantly after BA (p < 0.0001) in all. Arterial saturation significantly improved after BA in all cases (66.5 ± 4.3% to 79.4 ± 3.4%, p < 0.0001). Freedom from reintervention was 100%. All patients underwent subsequent elective planned surgery at an appropriate age with no mortality.

CONCLUSIONS

A BA-alone strategy for a stenotic RV-PA shunt was effective for all three shunt portions, minimizing shunt-related premature surgical intervention.

Randomized evaluation of polytetrafluoroethylene-covered stent in saphenous vein grafts: the Randomized Evaluation of polytetrafluoroethylene COVERed stent in Saphenous vein grafts (RECOVERS) Trial

BACKGROUND

Treatment of lesions located in saphenous vein grafts (SVGs) is associated with increased procedural risk and a high rate of restenosis.

METHODS AND RESULTS

We conducted a randomized, multicenter trial to evaluate the usefulness of a polytetrafluoroethylene (PTFE)-covered stent compared with a bare stainless steel (SS) stent for prevention of restenosis and major adverse cardiac events (MACE) in patients undergoing SVG treatment. The primary end point was angiographic restenosis at 6 months. Secondary end points were 30-day and 6-month MACE rates, defined as the cumulative of death, myocardial infarction (MI), and target lesion revascularization. Between September 1999 and January 2002, 301 patients with SVG lesions were randomized to either the PTFE-covered JoStent coronary stent graft (PTFE group, n=156) or the SS JoFlex stent (control group, n=145). Angiographic and procedural success rates were similar between the 2 groups (97.4% versus 97.9% and 87.3% versus 93.8%, respectively). The incidence of 30-day MACE was higher in the PTFE group (10.9% versus 4.1%, P=0.047) and was mainly attributed to MI (10.3% versus 3.4%, P=0.037). The primary end point, the restenosis rate at 6-month follow-up, was similar between the 2 groups (24.2% versus 24.8%, P=0.237). Although the 6-month non-Q-wave MI rate was higher in the PTFE group (12.8% versus 4.1%, P=0.013), the cumulative MACE rate was not different (23.1% versus 15.9%, P=0.153).

CONCLUSIONS

The study did not demonstrate a difference in restenosis rate and 6-month clinical outcome between the PTFE-covered stent and the SS stent for treatment of SVG lesions. However, a higher incidence of nonfatal myocardial infarctions was found in patients treated with the PTFE-covered stent.

Unsuccessful long-term outcome after treatment of a vein graft false aneurysm with a polytetrafluoethylene-coated Jostent

We describe a case in which a stented ulcerated plaque in an old vein graft ruptured to a huge false aneurysm. By the use of a PTFE-coated Jostent, the false aneurysm could be percutaneously closed. However, 6 months later, a new false aneurysm, probably due to focal perforation of the covered Jostent, developed.

Coronary stent grafts covered by a polytetrafluoroethylene membrane

In a prospective observational study, 40 patients were treated with coronary stent grafts covered by a polytetrafluoroethylene membrane. These devices may be regarded as therapy of choice for acute coronary rupture; treatment of conventional in-stent restenosis was not associated with a favorable outcome, whereas the promising results in degenerated vein grafts warrant a randomized, controlled trial.

Polytetrafluoroethylene-encapsulated stent-grafts: use in experimental abdominal aortic aneurysm

PURPOSE

To evaluate expanded polytetrafluoroethylene (ePTFE) encapsulated stents for the treatment of aortic aneurysms with emphasis on the blood and tissue-material interactions.

MATERIALS AND METHODS

Experimental aortic aneurysms were created in dogs by enlarging the aortic lumen with an abdominal fascial patch. Twenty animals underwent endoluminal repair after allowing the surgically created aneurysm to heal for 2 months prior to transluminal aneurysmal exclusion. The device used consisted of an 8-cm-long ePTFE encapsulated stent graft. The animals were killed in groups at 1 week and at 1, 2.25, 6, and 12 months. Specimens were processed for histologic and luminal surface studies.

RESULTS

Before the animals were killed, aortography demonstrated two thrombosed aortae in the 6-month group and two endoleaks in the 12-month group. Endothelialized neointima extended into the proximal and distal portions of the prosthetic lumen, with minimal cell coverage in the center of the graft. The overall percent surface area covered by endothelialized neointima was 22% +/- 6% at 6 months and 18% +/- 10% by 1 year (P = .75). Histologic examination demonstrated minimal tissue penetration into the ePTFE.

CONCLUSION

Transluminal exclusion of abdominal aortic aneurysms by encapsulated stent-graft is easily accomplished. With this device, tissue coverage and penetration of the stent graft is limited and does not tend to increase with time.

Healing response associated with balloon-dilated ePTFE

Deployment of endovascular grafts composed of a metallic stent surrounded by expanded polytetrafluoroethylene (ePTFE) stretches the polymer beyond its original dimensions, altering the structural characteristics of the ePTFE. We hypothesized this structural modification would alter the healing response associated with the implant. In this study, 4 mm i.d. of ePTFE (30 microns internodal distance) vascular grafts were balloon dilated using angioplasty balloons having final diameters of 6 (1.5X), 8 (2X), 10 (2.5X), 12 (3X), and 18 (4.5X) mm. Following balloon dilatation of the ePTFE, a circular punch (6 mm in diameter) was used to prepare polymer samples for implantation. The ePTFE circular patches were implanted within subcutaneous tissue and epididymal fat pads of male Sprague-Dawley rats. After 5 weeks, the implants were removed and analyzed for fibrous capsule formation, inflammation, and neovascularization associated with the material. Histological analysis revealed the formation of fibrous capsules only with control subcutaneous implants. The inflammatory response associated with subcutaneously implanted ePTFE was decreased significantly following balloon dilatation to at least 2.5 times the original diameter of the graft. In contrast, ePTFE implanted within adipose tissue demonstrated a significantly greater inflammatory response following balloon dilatation when compared to control implants. Only ePTFE balloons dilated to 6 mm and implanted within adipose tissue demonstrated neovascularization to any extent. These data suggest the structural modifications incurred by ePTFE following balloon dilatation dramatically affect the inflammatory response associated with an implant. Therefore, polymeric materials used for endovascular graft technology require designs that consider changes in polymer healing inherent to device design.