Takafumi Akai

Inverse association between the existence of coronary artery disease and progression of abdominal aortic aneurysm.

OBJECTIVES A strong degree of co-existence between coronary artery disease (CAD) and abdominal aortic aneurysm (AAA) is widely acknowledged, however, it remains to be elucidated whether the existence of CAD is associated with an accelerated expansion rate of AAA. Also, the relationship between preoperative CAD and postoperative major adverse cardiovascular events (MACE) has not been examined in Japanese patients. The aim of this study was to investigate the deleterious effects of CAD on the progression of AAA and the onset of postoperative MACE after elective AAA repair. METHODS AND RESULTS A retrospective cohort study of 665 consecutive Japanese patients who underwent elective surgical repair for infrarenal AAA at 2 high-volume Tokyo hospitals from 2003 through 2010 was performed. Preoperative CAD was shown to be a significant determinant of postoperative MACE (HR 2.29; 95%CI, 1.12-4.66; p=0.02). In the analysis of 510 patients for whom there were at least 2 follow-up CT scans of the size of their AAA before repair, the existence of CAD was shown to be inversely associated with the accelerated expansion rate of AAA. CONCLUSION This study on the patients undergone elective repair for infrarenal AAA identified an inverse association between the existence of CAD and progression of AAA as well as the significant impact of preoperative CAD on the occurrence of postoperative MACE after elective AAA repair.

Long-Term Results of Treatment for Critical Limb Ischemia.

From 2001 to 2012, arterial reconstruction was performed in 306 out of 497 limbs (62%) with critical limb ischemia. The reasons for non-vascularization include high operative risk (36%), extended necrosis or infection (20%), and technical issues (15%). Cumulative patency and limb salvage in collagen disease were significantly worse compared to arteriosclerosis obliterans. Cumulative limb salvage, amputation free survival (AFS), and major adverse limb event and perioperative death (MALE + POD) in patients with end-stage renal disease (ESRD) were significantly worse compared to patients without ESRD, but not significant with regards to graft patency. Our finding suggests that aggressive arterial reconstruction provides satisfactory long-term results in critical limb ischemia so long as case selection for revascularization is properly made. (This article is a translation of J Jpn Coll Angiol 2014; 54: 5-11.).

Development of an Image-Based Modeling System to Investigate Evolutional Geometric Changes of a Stent Graft in an Abdominal Aortic Aneurysm

BACKGROUND Quantification of geometric changes of the stent graft (SG) in abdominal aortic aneurysm has been required for follow up of endovascular aneurysm repair (EVAR). The aim was to develop an image-based modeling system (V-Modeler) to investigate these changes over time. METHODS AND RESULTS: V-Modeler was applied to investigate the migration of the SG. Three sets of computed tomography images were taken at 3 different times: (1) 5 days after the implantation; (2) 7 months later when the unilateral leg migrated upward; and (3) 10 months later when the limb had migrated into the common iliac aneurysm resulting in a type 1b endoleak. A spline function was used to represent the center lines of the SG to track its evolutional geometric changes in a three-dimensional manner. The characteristics of vascular geometry, as well as the SG geometry using geometric parameters such as length, curvature, torsion, angle of tangent vector (ATV), and migrated length, was evaluated. It was observed that the strong peak of the curvature in the distal area appeared, and a conversion of the torsion disappeared chronologically. CONCLUSIONS The V-Modeler was developed, which not only can extract vascular geometry but also can identify geometric parameter, such as curvature, torsion, and ATV, to predict adverse events following EVAR.

Acute aortic occlusion in a patient with chronic paralysis due to spinal cord injury: a case report

Patients with spinal cord injury experience changes in the cardiovascular system and a high morbidity associated with peripheral artery disease. We report a case of acute aortic occlusion in a patient with chronic paralysis due to spinal cord injury. A 65-year-old man with chronic paralysis due to spinal cord injury developed mottling of the right extremity. Because of the complete tetraplegia, the patient had no subjective symptoms. Computed tomography revealed occlusion of the infrarenal abdominal aorta. An emergency thromboembolectomy established adequate blood flow, and the postoperative course was uneventful. The loss of muscle mass might be an advantage in avoiding ischemia reperfusion syndrome. Early detection of acute aortic occlusion and immediate reperfusion are primarily important, but patients with chronic paralysis present a risk of delay in detection, diagnosis, and treatment of acute aortic occlusion because of motor or sensory deficits. Although rare, it is necessary to consider acute aortic occlusion in the case of acute limb ischemia in patients with chronic paralysis due to spinal cord injury.

Biomechanical Analysis of an Aortic Aneurysm Model and Its Clinical Application to Thoracic Aortic Aneurysms for Defining “Saccular” Aneurysms

Background We aimed to develop a simple structural model of aortic aneurysms using computer‐assisted drafting (CAD) in order to create a basis of definition for saccular aortic aneurysms. Methods and Results We constructed a simple aortic aneurysm model with 2 components: a tube similar to an aorta and an ellipse analogous to a bulging aneurysm. Three parameters, including the vertical and horizontal diameters of the ellipse and the fillet radius, were altered in the model. Using structural analysis with the finite element method, we visualized the distribution of the maximum principal stress (MPS) in the aortic wall and identified the area(s) of prominent stress. We then selected patients with thoracic aortic aneurysms in whom the aneurysm expansion rates were followed up and applied the theoretical results to the raw imaging data. The maximum MPS drastically increased at areas where the aspect ratio (vertical/horizontal) was <1, indicating that “horizontally long” hypothetical ellipses should be defined as “saccular” aneurysms. The aneurysm expansion rate for the patients with thoracic aneurysms conforming to these parameters was significantly high. Further, “vertically long” ellipses with a small fillet might be candidates for saccular aneurysms; however, the clinical data did not support this. Conclusions Based on the biomechanical analysis of a simple aneurysm model and the clinical data of the thoracic aortic aneurysms, we defined “horizontally long” aortic aneurysms with an aspect ratio of <1 as “saccular” aneurysms.

Original Homebuilt Off-the-Job Training System for Vascular Surgeons: System Analysis and Assessment

Objective: We assessed the effectiveness and appropriateness of our original off-the-job training (Off JT) system using data acquired from recruited medical students and doctors. Materials and Methods: We presented our original homebuilt Off JT system, which is simple and inexpensive. In our unique system, we performed anastomosis at the bottom of a plastic pot, which mimics the actual open surgical procedure at a deep site. There were four evaluation points: (A) operating time, (B) performance of anastomosis by semi-automatically analyzing the image with the coefficient of variation (standard deviation/length) of the “bite” and the “pitch,” (C) scoring of the total surgical skill evaluated by the trainers according to the Operative Performance Rating System (OPRS), and (D) the relationship of these three factors (A, B, and C). Results: The procedural time and coefficient of variation of the bite and pitch decreased and the OPRS score increased after training. There was a strong correlation between procedural time, anastomotic performance, and OPRS score. Conclusion: The effectiveness of our original homebuilt system was shown by reduced procedural time, improved anastomotic quality, and increased OPRS score.

Theoretical mechanism of temporary renal function improvement after abdominal aortic aneurysm surgery

Abstract We evaluated the effects of changes in blood flow due to abdominal aortic aneurysm (AAA) surgery by using a simple zero-dimension model and applied theoretical values to clinical data. The zero-dimension electronic circuit model and diagram of blood flow distribution were created by setting the resistance of the aorta, bilateral iliac arteries, renal arteries, and aneurysm. Resistance of the aneurysm and resistance of the aorta before surgery were compared with that of the aorta after surgery. We set the radius length of each anatomical parameter to calculate theoretical values. Renal flow increased 13.4% after surgery. Next, we analyzed contrast-enhanced computed tomography data of 59 patients who underwent AAA surgery. A total of 19 patients were treated with a Y graft and 7 patients were treated with a straight graft during open surgery. However, 33 patients were treated with a bifurcated stent graft. A significant linear relationship between the increased estimated glomerular filtration rate (eGFR) ratio and the decreased aneurysm ratio was found only for the straight graft group. Using a circuit model, renal blood flow theoretically increased after AAA surgery. Clinically, there was a correlation between volume regression and eGFR improvement only in the limited AAA group.