Lessons learned in adopting endovascular techniques for treating abdominal aortic aneurysm

Aortic aneurysm surgery: problems and innovations

A long way was traveled since the first surgery was performed for the treatment of abdominal aortic aneurysm. Throughout this time, several innovations have been created in order to reduce the invasiveness of the surgical procedures and to improve their safety and durability. This review discusses the major and recent advances on aortic aneurysm interventions, including, the endovascular aortic repair, the laparoscopic aortic surgery, the conventional hybrid and endovascular techniques, combined laparoscopic and endovascular techniques, as well as future prospects for both thoracic and abdominal aorta. Faced with so many changes and developments, modern vascular surgeons must keep their minds open to innovations and should develop comprehensive training with different techniques, to provide the best therapeutic option for their patients.

Shape memory polymer foams for cerebral aneurysm reparation: effects of plasma sterilization on physical properties and cytocompatibility

Shape memory polyurethanes (SMPUs) represent promising candidate materials for aneurysm embolization, since they could enable clinical problems still associated with these clinical procedures to be overcome. In this work, we report on the characterization of physicochemical, thermomechanical and in vitro interface properties of two SMPU foams (Cold Hibernated Elastic Memory, CHEM), proposed as a material for embolization devices in minimally invasive procedures. Moreover, because device sterilization is mandatory for in vivo applications, effects on the properties of the foams after plasma sterilization were also evaluated. Both foams (CHEM 3520 and CHEM 5520) showed excellent shape recovery ability (recovery rate, R(r), up to 99%) in conventional shape recovery tests, performed at constant heating rate. Transition temperatures (T(trans)), determined by tandelta peaks in dynamic mechanical analysis (DMA), were 32.2 and 45.1 degrees C, for CHEM 3520 and 5520, respectively. The value of T(trans) affects shape memory ability in the recovery test at 37 degrees C, which simulates the behavior after implantation of the device: in fact, R(r) was significantly higher for lower T(trans) foam (R(r) approximately 82% and R(r) approximately 46%, respectively, for CHEM 3520 and CHEM 5520). After plasma sterilization performed by a Sterrad sterilization system, an increase in open porosity was observed: this is probably due to the sterilization cycle; however, no effects on shape recovery behavior were observed. Furthermore, plasma treatment had no significant effect on L929 cells in in vitro cytotoxicity tests, performed on cell culture medium extracts in contact with foams for up to 7 days. Moreover, direct cytocompatibility tests showed a good colonization and growth from L929 cells on CHEM foams, suggesting the effectiveness of an in vivo healing process. All these results seem to suggest that CHEM foams could be advantageously used for manufacturing devices for mini-invasive embolization procedures of aneurysms.

Systematic Review and Meta-analysis of 12 Years of Endovascular Abdominal Aortic Aneurysm Repair

BACKGROUND

Endovascular repair (ER) of abdominal aortic aneurysm (AAA) is a new technique, and reported rates of endoleak, conversion to open repair, rupture and mortality vary widely. The aim of this study was to estimate these rates from the published data, and examine how this has changed as more patients have undergone ER.

METHODS

A systematic review and meta-analysis of publications identified through searches of the electronic databases EMBASE and Medline. All publications quoting endoleak, conversion to open repair, rupture and mortality rates for a series of patients undergoing ER were included.

RESULTS

163 studies pertaining to 28,862 patients undergoing ER were identified as relevant for the review and meta-analysis. The pooled estimate for operative mortality was 3.3% (95% confidence interval 2.9 to 3.6%). The pooled estimate for type 1 endoleaks was 10.5% (95% confidence interval 9.0 to 12.1%), with an annual rate of 8.4% (95% confidence interval 5.7% to 12.2%). The pooled estimate of type 2,3 and 4 endoleaks was 13.7% (95% confidence interval 12.3 to 15.3%), with an annual rate of 10.2% (95% confidence interval 7.4% to 14.1%). The pooled estimate for primary conversion to open repair was 3.8% (95% confidence interval 3.2 to 4.4%), and for secondary conversion to open repair 3.4% (95% confidence interval 2.8 to 4.2%). The pooled estimate for post-operative rupture was 1.3% (95% confidence interval 1.1 to 1.7%), with an annual rupture rate of 0.6% (95% confidence interval 0.5% to 0.8%). Multivariate meta-regression analysis showed that rates of operative mortality, post-operative rupture and total number of endoleaks all fell significantly (p<0.05) over time.

CONCLUSIONS

This study demonstrates a low mortality and a gradual reduction in vascular morbidity and mortality associated with endovascular repair since it was first introduced.

Secondary interventions following endovascular abdominal aortic aneurysm repair using current endografts. A EUROSTAR report

OBJECTIVE

The purpose of this study was to evaluate the need for secondary interventions after endovascular abdominal aortic aneurysm repair with current stent-grafts.

METHODS

Studied were data from 2846 patients treated from December 1999 until December 2004. The data were recorded from the EUROSTAR registry. The only patients studied were those with a follow-up of at least 12 months or until they had a secondary intervention within the first 12 months. The cumulative incidences of secondary transabdominal, extra-anatomic, and transfemoral interventions during follow-up (after the first postoperative month) were investigated.

RESULTS

A secondary intervention was performed in 247 patients (8.7%) at a mean of 12 months after the initial procedure within a follow-up period of a mean of 23 +/- 12 months. Of these, 57 (23%) transabdominal, 43 (16%) involved an extra-anatomic bypass, and 147 (60%) were by transfemoral approach. The cumulative incidence of secondary interventions was 6.0%, 8.7%, 12%, and 14% at 1, 2, 3, and 4 years, respectively. This corresponded with an annual rate of secondary interventions of 4.6%, which was remarkably lower than in a previously published EUROSTAR study of patients treated before 1999. Type I endoleaks (33% of procedures), migration (16%), and rupture (8.8%) were the most frequent reasons for secondary transabdominal interventions. Graft limb thrombosis was the indication for extra-anatomic bypass (60%). Type I endoleak (17%), type II endoleak (23%), device limb stenosis (14%), thrombosis (23%), and device migration (14%) were the most frequent reasons for secondary transfemoral interventions. Operative mortality was higher after secondary transabdominal interventions (12.3%, P = .007) compared with transfemoral interventions (2.7%). Overall survival was lower in patients with secondary transabdominal (P = .016) and extra-anatomic interventions (P < .0001) compared with patients without a secondary intervention.

CONCLUSION

Although the incidence of secondary interventions after endovascular aneurysm repair has substantially decreased in recent years, continuing need for surveillance for device-related complications remains necessary.

ENDOVASCULAR ABDOMINAL AORTIC ANEURYSM REPAIR: A 7 YEAR EXPERIENCE AT THE LAUNCESTON GENERAL HOSPITAL

BACKGROUND

To review our 7 year experience of endovascular abdominal aortic aneurysm repair (EVR) and to compare this to open repair (OR) during the same time period.

METHODS

One hundred and one EVR and 65 OR patients were studied. Parameters analysed included patient and procedure details, intensive care unit (ICU) and hospital admission time, and morbidity and mortality with particular emphasis on procedure-related problems.

RESULTS

Endovascular grafts were deployed with successful abdominal aortic aneurysm (AAA) exclusion in 100 patients. Primary technical success was achieved in 84%, clinical success in 86% and secondary success in 90% of cases. Complications occurred in 63% and 88% of EVR and OR patients, respectively. Early device-related complications occurred in 40 EVR patients (40%); 24 (60%) were corrected immediately by further stenting. Late device-related complications occurred in 15 EVR patients (15%); four (27%) required additional stenting. Most of the complications in the OR group were systemic (89%) resulting in longer ICU and hospital stays (median 48 vs 17 h and 13 vs 4 days for OR and EVR, respectively). Death within 30 days of the procedure occurred in three EVR patients. There was no perioperative mortality in the OR group.

CONCLUSION

Endovascular AAA repair can be undertaken successfully in a district general hospital. The majority of local and device-related complications can be corrected immediately, while those persisting beyond the initial procedure usually resolve spontaneously. EVR offers a minimally invasive approach to a problem that in the past has involved major surgery.

Endovascular treatment of abdominal aortic aneurysms

BACKGROUND

Endovascular treatment of abdominal aortic aneurysms is a rapidly evolving technique that has gained broad acceptance in the treatment of patients with abdominal aortic aneurysms.

METHODS

A review of the English literature was done to determine the short- and long-term outcomes of endovascular repair of abdominal aortic aneurysms. Reports of complications such as endoleak, graft migration, graft limb occlusion, aneurysm rupture, and aneurysm enlargement were evaluated.

RESULTS

Short-term results of endovascular repair of abdominal aortic aneurysms are excellent. The necessity for open conversions is less than 5%. The cumulative risk of aneurysm rupture is approximately 1% per year. The coverall incidence of graft limb occlusion was 2.8% in the follow-up period. The cumulative risk for a secondary procedure was 12% at 1 year, 24% at 2 years, and 35% at 3 years. Moderate and severe neck angulation was associated with an increased incidence of adverse events in the follow-up period. Endografts have the potential to become infected and develop aortoduodenal fistula. The treatment of ruptured aneurysms with endovascular grafts has been successful and a technique that is increasingly used.

CONCLUSION

Endovascular treatment of abdominal aortic aneurysm is an effective technique with excellent short-term results. The long-term results remain to be determined. Ongoing surveillance is necessary to avoid late complications of aneurysm rupture.

Endovascular Repair of the Abdominal Aortic Aneurysm

Since the early 1 990s, endovascular surgery has provided another treatment option for the management of abdominal aortic aneurysms. Its shorter postoperative recovery time, absence of an abdominal incision, and avoidance of aortic cross-clamping gives endovascular abdominal aortic aneurysm repair its appeal. New vascular grafts are being developed that may expand the number of eligible candidates. This less-invasive form of abdominal aortic aneurysm repair still provides the anesthesiologist with several challenges. The procedure has been performed under general anesthesia, regional anesthesia, and local anesthesia with monitored anesthesia care. The potential benefits of one anesthetic type over another for endovascular abdominal aortic aneurysm repair have not yet been fully explored. Several intraoperative complications, including acute aortic rupture and misdeployment of the stent graft, can necessitate conversion to an open laparotomy. Endovascular repair in the short term compares favorably to open surgical repair with a reduction in morbidity, blood loss, and hospital stay. Still, endovascular abdominal aortic aneurysm repair is a relatively new corrective modality, and long-term controlled trials comparing it with open repair have not yet been reported. As more research into the technique is performed, new strategies for endovascular abdominal aortic aneurysm repair may further increase the options available to patients.

Cold hibernated elastic memory foams for endovascular interventions

Cold hibernated elastic memory (CHEM) polyurethane-based foam is a new shape memory polymeric self-deployable structure. Standard cytotoxicity and mutagenicity tests were conducted on CHEM in vitro, to ensure biocompatibility before studying potential medical applications. In vivo, lateral wall aneurysms were constructed on both carotid arteries of eight dogs. Aneurysms were occluded per-operatively with CHEM blocks. In two dogs, CHEM embolization was compared with gelatin sponge fragment embolization. Internal maxillary arteries (Imax) were also occluded with CHEM using a 6F transcatheter technique. Angiography and pathology were used to study the evolution of aneurysms and Imax at 3 and 12 weeks. Imax embolized with CHEM foam remained occluded at 3 weeks. Most aneurysms embolized with CHEM showed a small residual crescent of opacification at initial angiography, but angiographic scores were significantly better at 3 weeks. Thick neointima formation over the CHEM at the neck of aneurysms was demonstrated at pathology. The foamy nature of CHEM favours the ingrowth of cells involved in neointima formation. New devices for endovascular interventions could be designed using CHEM's unique physical properties.