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The Outcomes of Endovascular Aneurysm Repair in Japan in 2017: A Report from the Japanese Committee for Stentgraft Management

Endovascular aortic repair (EVAR) was first approved in Japan a decade ago, and approximately 10,000 EVAR procedures are performed annually.1) The short-term outcomes of EVAR in Japan were reported to be acceptable; however, several issues were revealed. Half of the cases violated the instructions for use, and a quarter of post-EVAR aneurysm sacs dilated by more than 5 mm in 5 years.2) In addition, new devices have emerged, generating a learning curve for their use. Therefore, updating the realworld EVAR data from Japan will serve as a database for physicians to refer to during preoperative sizing or when considering procedural steps. This report demonstrated the number of EVAR procedures and the mortality and complication rates in 2017 in Japan using data from the Japanese Committee for Stentgraft Management (JACSM) nationwide registry, which includes outcome data for nearly all stent grafts shipped to Japan.2,3)


Introduction
Endovascular aortic repair (EVAR) was first approved in Japan a decade ago, and approximately 10,000 EVAR procedures are performed annually. 1) The short-term outcomes of EVAR in Japan were reported to be acceptable; however, several issues were revealed. Half of the cases violated the instructions for use, and a quarter of post-EVAR aneurysm sacs dilated by more than 5 mm in 5 years. 2) In addition, new devices have emerged, generating a learning curve for their use. Therefore, updating the realworld EVAR data from Japan will serve as a database for physicians to refer to during preoperative sizing or when considering procedural steps.
This report demonstrated the number of EVAR procedures and the mortality and complication rates in 2017 in Japan using data from the Japanese Committee for Stentgraft Management (JACSM) nationwide registry, which includes outcome data for nearly all stent grafts shipped to Japan. 2,3)

Database, exclusion criteria, and groups
The JACSM nationwide registry, including its foundation, structure, and quality control, has been previously described. 2,3) The JACSM, established in December 2006, is composed of 10 societies related to endovascular treatment and determined the practical standards for institutions and for practicing and supervising surgeons. Participating institutions are obligated to report data on EVAR and thoracic endovascular aortic repair (TEVAR), using a web-based case-registry form (http://www.stentgraft.jp/). Among 11,806 patients who underwent EVAR in 2017, 10,352 patients were analyzed after exclusion based on previous EVAR, failure of delivery, and missing data. The data of 10,339 patients were available at hospital discharge (511 and 9,828 patients in the rupture and non-rupture groups, respectively). Mortality, adverse events, including renal insufficiency and endoleaks, were observed in each group (Fig. 1).
This registry was conducted according to the principles of the Declaration of Helsinki, the International Conference on Harmonization, and Good Clinical Practice guidelines. The use of registry data was approved by the Institutional Review Board of the University of Tokyo Hospital (approval number: 2019306NI).

Type of data collected
Data regarding patient age, sex, aneurysm rupture, device usage, lesion for treatment, dissection, symptoms, pathogenesis, comorbidities, renal function, anatomy of the proximal and distal fixation, and preoperative aneurysm diameter were collected from the hospital database. Patient comorbidities included respiratory disorders, home oxygen therapy, hypertension (with medication), cerebrovascular disease, hemodialysis, coronary artery disease, diabetes mellitus, and a hostile abdomen. Renal function was determined using serum creatinine levels and the estimated glomerular filtration rate (eGFR).

Outcomes
The intraoperative rates of mortality, vascular injury, rupture, and endoleak were reported. Postoperative mortality and adverse events (migration, stenosis/occlusion, vascular injury, blood transfusion, infection, thromboembolism, renal insufficiency, cerebrovascular damage, paraplegia, rupture, wound trouble, and additional surgery) upon discharge from the hospital were also reported.
Categorical variables are presented as numbers and percentages, and continuous variables are presented as means±standard deviations.

Patient demographics
The mean patient age was 76.7±8.5 years. There were 1,920 females (18.5%), and the proportion differed between the rupture group (21.5%) and the non-rupture group (4.2%). EVAR was performed for a ruptured abdominal aortic aneurysm (AAA) in 5.0% of patients. The off-label use of the main body only or the leg only devices was 3.0% and 1.8%, respectively. Regarding etiology, most patients were diagnosed with degenerative (98.0%) and non-dissection (96.9%) conditions. Symptoms were present in 11.1% and more frequently in the rupture group (91.7%). Renal function was worse in the rupture group (eGFR: 47.5±22.2) than in the non-rupture group (eGFR: 57.7±19.6).
The mean aortic aneurysm diameter was 51.6±11.7 mm and was larger on average in the rupture group (66.5±17.3 mm). Regarding the landing zones, approximately 30 mm was secured in all groups at both the proximal and distal sites ( Table 1).

Intraoperative data
Intraoperative death occurred in 13 patients (0.1%), 10 of whom were in the rupture group. The rate of intraoperative vascular injury was 1.7%, the rupture rate was 0.1%, and additional procedures were required in 15.5% of cases. Intraoperative endoleak occurred in 566 patients ( Table 2).

Postoperative data
The overall in-hospital mortality rate was 1.2%, with 12.5% of deaths occurring in the rupture group and 0.6% in the non-rupture group. The duration of postoperative hospitalization was 10.0±9.6 days in the non-ruptured group and long in the rupture group (21.3±19.3 days). Renal insufficiency occurred in 3.2% of all patients, and 11.2% of these patients were in the rupture group. Blood transfusion was required in 33.3% and 3.9% of patients in the rupture and non-rupture groups, respectively.

Causes of death
Intraoperative rupture, hemorrhage, and systemic circulatory failure were the most common causes of intraoperative death, accounting for six and two patients in the rupture and non-rupture groups, respectively. During hospitalization, infection or sepsis was the most common cause of death in the non-rupture group (n=11). The next most common causes were pneumonia and respiratory  failure (n=10), followed by disseminated intravascular coagulation and multiple organ failure (n=8), arrhythmia, low output syndrome, and heart failure (n=7). Multiple thromboembolisms occurred in five cases, and vascular-related complications, including thoracic aortic aneurysm rupture and aortic dissection, occurred in four cases ( Table 4).

Discussion
The JACSM registry began in July 2006 after the approval of the stent graft device in Japan, and data input and storage have been transferred from the JACSM database to the National Clinical Database since January 2016.
The analysis with the data through 2015 was published previously. 2) The 2016 annual data were reported on the JACSM website, and the committee decided to publish data annually henceforth. In this study, patients were divided into the rupture and non-rupture groups because of the high mortality and morbidities of ruptured AAA cases. The backgrounds of these groups were too different to match; therefore, we did not compare the outcomes of these groups statistically. It will be necessary to perform a similar study in groups that can be matched so that statistical analyses can be used to confirm our observations. The mortality of ruptured AAAs varied widely among previous studies, possibly due to selection bias between      5) A lower mortality rate was reported in a group of high-volume centers (21.2%) 6) and in a risk-stratified analysis. 7) Although our study used more recent registry data, the mortality rate of 14.2% was considered low, particularly in the rupture group (5%). This could potentially be accounted for if operators only select patients whose anatomy was feasible for EVAR. The outcomes of EVAR for ruptured AAAs were considered acceptable in the current EVAR situation. The mortality of the non-rupture group was 0.6%, which was lower than the rate between 2006 and 2015 (1.0%). 2) Technological advancements in the available devices and improved technical skills likely contributed to the low mortality rate.
The proportion of females was high in the rupture group, which could correlate with higher aneurysm rupture and expansion rates in women compared with that in men. 8,9) Although there were other differences between the rupture and non-rupture groups, including decreased renal function, larger aneurysm diameter, and more symptoms in the rupture group, these results were reasonable and expected.
The presence of endoleaks was different intraoperatively than at hospital discharge. The rate of type 1 endoleak decreased at discharge. Although type 1 endoleak should be treated intraoperatively if possible, minor leakage, such as a sleeve leak could be expected to thrombose after the operation.
The duration of postoperative hospitalization was similar in both groups and considered long. In EVAR trial 1, the average length of postoperative stay was 6.9 days. 10) The longer stay might be derived from a difference in the health insurance system in each country. In the future, the duration can potentially be shortened in our country by using percutaneous EVAR or intraoperative evaluation with cone-beam computed tomography.
The main causes of death were respiratory and cardiovascular events. The rate of preoperative morbidities potentially affects the causes of death. Surveillance and careful perioperative treatment for comorbidities are likely to be important for the improvement of EVAR outcomes.
The mortality and morbidities of EVAR were acceptable in both rupture and non-rupture groups. The outcomes of the non-rupture group improved compared with that of the previous report with data from 2006 to 2015, possibly due to improvements in devices and operators skills.