Taro Shimazaki

Thoracic endovascular aneurysm repair in Japan: Experience with fenestrated stent grafts in the treatment of distal arch aneurysms

OBJECTIVES In the West, stent grafts for endovascular repair of thoracic aortic aneurysms have been commercially available for several years, whereas in Japan, a manufactured stent graft was not approved for this application until March 2008. Nevertheless, endovascular thoracic intervention began to be performed in Japan in the early 1990s, with homemade devices used in most cases. Many researchers have continued to develop homemade devices. We have participated in joint design and assessment efforts with a stent graft manufacturer, focusing primarily on fenestrated stent grafts used in repairs at the distal arch, a site especially prone to aneurysm. METHODS From 1995 to February 2008, we performed about 1100 endovascular procedures to treat thoracic aortic aneurysms and 682 cases were performed at Tokyo Medical University. In 435 out of 682 the aneurysm was located in the area from the distal arch to the proximal descending aorta. Fenestrated stent grafts were inserted in 288 cases. Computed tomography scans were performed at 3, 6, and 12 months postoperatively and annually thereafter. RESULTS The initial success rate in the entire series was 95.2%. Complications included 26 cerebral infarctions (3.8%), six of which (0.9%) resulted in serious paralysis and changes in consciousness. Among patients who received fenestrated stent grafts, paraplegia occurred in 2.6%, aortic injury in 1.2%, and iliofemoral artery injury in 6.0%. No complications resulted from occlusion of aortic arch branches. At >/=2 years after intervention, aneurysm diameter was reduced in 62% of patients, 33% had no change, and 5% had a diameter enlargement. The stent graft complication rate during follow-up was 8.4%, the device fracture rate was 1.4%, and the device migration rate was 7%. The 5-year survival rate was 62.4%, with follow-up in 96.8% of the patients. CONCLUSION Endovascular repair has promising results in the descending thoracic aortic region, although some stent grafts and their delivery systems can still be improved. Additional commercial developments and available stent grafts designed for use in the distal arch are urgently needed.

Blood coagulation and fibrinolytic response after endovascular stent grafting of thoracic aorta.

OBJECTIVE Thrombosis is common in aneurysms immediately after stent-grafting, because of exclusion from systemic blood flow. We studied changes in blood coagulation and the fibrinolytic system in patients with thoracic aortic aneurysm or dissection after stent-grafting to examine risk for consumption coagulopathy. METHODS Thirty-one thoracic aortic aneurysms were treated with stent-grafting (aneurysm group), and 29 aortic dissections were treated with entry closure with stent-grafting (dissection group). The stent-graft was constructed from a self-expanding Z stent and thin-walled woven polyester fabric. Platelet count, fibrinogen, antithrombin III (AT III), and thrombin-AT III complex were assayed as markers of coagulation. Plasminogen, alpha(2)-plasmin inhibitor, alpha(2)-plasmin inhibitor-plasmin complex, fibrin degradation products fragment E (FDP-E), and fibrin degradation products d-dimer were monitored as markers of fibrinolysis. Blood samples were collected before surgery and on postoperative days 1, 3, 7, and 14. RESULTS In both groups platelet count significantly decreased on postoperative days 1 and 3, and increased on postoperative day 14. AT III significantly decreased on postoperative day 1, but recovered after postoperative day 7. FDP-E significantly increased on postoperative day 1 in both groups. There was significant correlation of aneurysm diameter with alpha(2)-plasmin inhibitor-plasmin complex, fibrin degradation products, and d-dimer in the dissection group on postoperative day 1. CONCLUSIONS Activation of coagulation and fibrinolysis was observed after stent-grafting to treat thoracic aortic aneurysm and aortic dissection. However, no patients exhibited consumption coagulopathy postoperatively. Therefore we believe there is little risk for consumption coagulopathy after stent-grafting.

Clinical results of endovascular stent graft repair for fifty cases of thoracic aortic aneurysms

Between February 1995 and December 1997, 50 cases (55 lesions) of thoracic aortic aneurysms including 20 cases of aortic dissections were treated with an endovascular technique using the stent grafts. All patients were treated in the operating room under general anesthesia and the stent grafts were implanted through 18 Fr. or 20 Fr. sheaths via femoral arteries under fluoroscopic guidance. The stent graft was composed of several units of self-expanding stainless-steel Z stents covered with an ultra-thin polyester fabric. Stent graft deployment was technically successful in 53 of 55 lesions (delivery success rate: 96.4%). Exclusion of the aneurysms and entry closing without endoleak were achieved within two weeks after the operation in 43 of 53 lesions (initial success rate: 81.1%). Endoleak was found in 10 lesions (minor endoleak: 8 and major endoleak: 2 lesions). Two patients died in the periopertive period of delivery failures as injury to external iliac artery and damage to the delivery sheath caused by tortuous and narrow access routes. Endovascular stent graft repair of thoracic aortic aneurysms is minimally invasive operation in comparison with conventional surgical graft replacement with extracorporeal circulation. These early results suggest that the stent graft repair is possibly safe and useful treatment for the patients of thoracic aortic aneurysms especially in high risk patients. However, careful long-term follow-up is necessary to prove the value and the effects of this endovascular treatment and improvement of the stent graft system and technical training of endovascular surgery for operators are required to reduce the delivery failure and to determine the stent graft repair is reliable treatment.

Prediction of spinal cord ischemia with a retrievable stent graft on endovascular treatment for a case of thoracic aortic aneurysm

Multiple aortic aneurysms in Behçets disease were repaired with transluminaly placed endovascular stent grafts. Before deploying the stent graft device for permanent implantation for the saccular aneurysm located in the descending thoracic aorta, from which feeding arteries for the spinal cord possibly branched, a retrievable stent graft was inserted and evoked spinal cord potential (ESP) were monitored in order to predict spinal cord ischemia. The original retrievable stent graft, constructed of a self-expandable Z-shaped stainless steel stent covered with e-PTFE, can be easily withdrawn into a 18 Fr. sheath after deployment. Blood flow into intercostal arteries branching from that part of the descending aorta where the permanent stent graft is planned to be implanted, is intercepted by the retrievable stent graft. A change of ESP during the temporary implantation of the device indicates that spinal cord ischemia would be caused by permanent implantation of the stent graft. In this case, no change of ESP was observed and the patient showed no postoperative paraplegia. The retrievable stent graft was useful for prediction of spinal cord ischemia before endoluminal stent graft repair of the descending aortic aneurysm. However, the device is not flexible enough to fit a severely tortuous aorta, therefore we are obliged to select patients to some extent. Further improvement of the device is required to make prediction of spinal cord ischemia with the retrievable stent graft possible in all cases.

Celiac artery coverage after occlusion test during endovascular stent grafting for thoracoabdominal aortic aneurysm

Previous investigators have reported favorable results with endovascular repair of thoracoabdominal aortic aneurysms by occlusion of the celiac artery (CA). Verification of collateral blood flow to the CA, however, is important to prevent postprocedural ischemic changes in the liver, stomach, and intestines. We describe the use of a CA occlusion test to investigate the collateral blood flow from the superior mesenteric artery (SMA) to the CA in a patient undergoing endovascular stent grafting for a thoracic and thoracoabdominal aortic aneurysm.

Endovascular stent graft repair for thoracic aortic aneurysms: the history and the present in Japan.

Stent-grafts for endovascular repair of thoracic aortic aneurysms have been commercially available for more than ten years in the West, whereas, in Japan, a manufactured stent-graft was not approved for the use until March 2008. Nevertheless, endovascular thoracic intervention began to be performed in Japan in the early 1990s, with homemade devices used in most cases. Many researchers have continued to develop their homemade devices. We have participated in joint design and assessment efforts with a stent-graft manufacturer, focusing primarily on fenestrated stent-grafts used in repairs at the distal arch, a site especially prone to aneurysm. In March 2008, TAG (W.L. Gore & Associates, Inc., Flagstaff, Arizona, USA) was approved as a stent graft for the thoracic area first in Japan, which was major turning point in treatment for thoracic aortic aneurysms. Subsequently, TALENT (Medtronic, Inc., Minneapolis, Minnesota, USA) was approved in May 2009, and TX2 (COOK MEDICAL Inc., Bloomington, Indiana, USA) in March 2011. Valiant as an improved version of TALENT was approved in November 2011, and TX2 Proform as an improved version of TX2 began to be supplied in October 2012. These stent grafts are excellent devices that showed good results in Western countries, and marked effectiveness can be expected by making the most of the characteristics of each device. A clinical trial in Japan on Najuta (tentative name) (Kawasumi Labo., Inc., Tokyo, Japan) as a line-up of fenestrated stent grafts that can be applied to distal arch aneurysms showing a high incidence, and allow maintenance of blood flow to the arch vessel was initiated. This trial was completed, and Najuta has just been approved in January of 2013 in Japan, and further development is expected. In the U.S., great efforts have recently been made to develop and manufacture excellent stent grafts for thoracic aneurysms, and rapid progress has been achieved. In particular, in the area of the aortic arch, in which we often experience aneurysmal change, but there are no commercially available devices which are urgently needed. Companies are competing keenly to develop devices. To our knowledge, more than 4 manufacturers are involved in the development of functionally new stent grafts in this area. The introduction of branched stent grafts may not be faraway.

Clinical results of acute closing aortic dissection

The therapeutic outcomes of 43 patients with acute closing aortic dissection treated during the past 10 years were evaluated. The patients consisted of 30 men and 13 women with a mean age of 65 +/- 9 years. Ten were classified as Stanford type A, and the remaining 33 as type B. During follow-up (6 to 120 months; average 55 months), recanalization and an enlarged ulcer-like projection (ULP) were observed in 5 and 2 type a patients. Although recanalization was not observed in type B patients, enlarged ULP was observed in 10 of them, in 6 of whom developed aneurysm. During the follow-up period, ULP was observed at 30 sites in 26 patients. Monitoring the change in ULP over time showed that the ascending and the proximal descending aorta frequently tended to be enlarged and progressed to aorta frequently tended to be enlarged and progressed to aneurysm. Surgery was performed in 3 patients with recanalization, 5 with enlarged ULP, and 3 with atheroscloerotic aortic aneurysm. Although one patient died of cerebral complications, the other 10 patients showed favorable postsurgical courses. Among 8 patients who died, the actuarial survival rate was favorable, being 96, 91 and 83% at 1, 3 and 5 years. However, the survival rate free from complications related to aortic dissection, defined as rupture, ercanalization, enlarged ULP and aneurysmal change, was 78, 58 and 54% at 1, 3 and 5 years, indicating that aortic dissection-related complications are likely to develop within 3 years. This being the case, conservative therapy may be selected for closing aortic dissection when there are no serious complications in the acute phase. However, closely following patients with diagnostic imaging techniques is essential as there may be complications such as recanalization or enlarged ULP. Such complications should be surgically treated because they may affect long-term prognosis.

Evaluation of thrombogenicity by indium-111 platelet scintigraphy in endografting for abdominal aortic aneurysms.

Obstruction of the endograft limb by thrombosis has often been reported and may cause fatal complications such as leg necrosis or myonephropathic metabolic syndrome. The purpose of this study was to evaluate endograft antithrombogenicity by indium-111 platelet scintigraphy. Seventeen patients with abdominal aortic aneurysms were treated by endografting. Thirteen patients were treated with conventional open surgery using an artificial graft. The endograft was constructed from a self-expanding Z-shaped stent and woven polyester fabric. Autologous platelets labeled with indium-111 were injected at 2 weeks postoperatively. At 24 hours and 72 hours postinjection, the ratio of scintillation count of the endograft or graft to that of the native artery was calculated to assess platelet deposition. The normalization ratio was calculated as follows: (scintillation count per pixel of endograft or graft/circumference)/(scintillation count per pixel of the native femoral artery). Platelet factor 4 and beta-thromboglobulin were measured to evaluate the systemic platelets activity at 2 weeks postoperatively. There was no significant difference in platelet counts or labeling efficiency between the groups. The ratio was significantly higher in the endografting group than in the open surgery group at 72 hours postinjection (2.5-0.7 vs 3.9-1.1, P<.001). There was no significant difference in platelet factor 4 and beta-thromboglobulin between the groups. Although there was no difference in systemic platelet activity, endografting was associated with lower antithrombogenicity. It remains unclear whether lower antithrombogenicity causes thromboembolism as a complication of the procedure. The authors recommend the administration of antiplatelet drugs to prevent endograft obstruction in patients with very narrow iliac arteries.

Pleural Effusion after Endovascular Grafting for Aortic Dissection.

慢性期の偽腔開存型大動脈解離に対するステントグラフト内挿術後の胸水貯留について検討した.16例についてCTより術前胸水ありをP群,術前胸水はなく術後胸水出現ありをE群,出現なしをN群と分類した.各群間で年齢,動脈最大径,手術施行時期,術後の発熱期間,白血球数,CRP,呼吸器合併症を比較した.P群は4例,E群は4例,N群は8例であった.P群の胸水は術後も不変であった.年齢,動脈最大径,手術施行時期,白血球数,CRP値およびそれらの推移は各群で差がなかった.発熱期間はE群とN群,E群とP群の間で有意差を認めた.全例で呼吸器合併症はなかった.本法が原因とみられる胸水貯留は25%あり,発熱が遷延化したが呼吸器合併症はなかった.本法の呼吸機能に与える影響は比較的低いものと考える.

A Case of Complete Thrombotic Occlusion by Endovascular Stent Grafting for Anastomosis Leakage after Aortic Arch Replacement of Stanford Type A Dissecting Aortic Aneurysm.

症例は60歳女性. 突然の胸背部痛で発症した早期閉塞型 Stanford A型大動脈解離と診断され, 保存的治療を行っていた. 発症後約2カ月で再び胸背部痛が出現し, 解離腔の再開通と診断され, elephant trunk を併用した弓部全置換術を行った. 術後のDSAにて, 人工血管末梢吻合部より解離腔へ造影剤の漏出を認め, 1カ月後にステントグラフト内挿術を施行した. 解離腔は血栓化し早期離床が可能であった.