Acute aortic syndrome: nationwide study of epidemiology, management, and outcomes.

BACKGROUND: Epidemiological studies on acute aortic syndrome (AAS) have relied largely on unverified administrative coding, leading to wide-ranging estimates of incidence. This study aimed to evaluate the incidence, management, and outcomes of AAS in Aotearoa New Zealand. METHODS: This was a national population-based retrospective study of patients presenting with an index admission of AAS from 2010 to 2020. Cases from the Ministry of Health National Minimum Dataset, National Mortality Collection, and the Australasian Vascular Audit were cross-verified with hospital notes. Poisson regression adjusted for sex and age was used to investigate trends over time. RESULTS: During the study interval, 1295 patients presented to hospital with confirmed AAS, including 790 with type A (61.0 per cent) and 505 with type B (39.0 per cent) AAS. A total of 290 patients died out of hospital between 2010 and 2018. The overall incidence of aortic dissection including out-of-hospital cases was 3.13 (95 per cent c.i. 2.96 to 3.30) per 100 000 person-years, and this increased by an average of 3 (95 per cent c.i. 1 to 6) per cent per year after adjustment for age and sex adjustment on Poisson regression, driven by increasing type A cases. Age-standardized rates of disease were higher in men, and in Maori and Pacific populations. The management strategies used, and 30-day mortality rates among patients with type A (31.9 per cent) and B (9.7 per cent) disease have remained constant over time. CONCLUSION: Mortality after AAS remains high despite advances over the past decade. The disease incidence and burden are likely to continue to increase with an ageing population. There is impetus now for further work on disease prevention and the reduction of ethnic disparities.

Common Designs of Custom-Made Fenestrated Arch Devices and Applicability of an Off-the-Shelf Design.

OBJECTIVES: To analyze device designs, similarities and overlaps of custom-made fenestrated arch endografts intended for mid/distal arch thoracic endovascular aortic repair. MATERIALS AND METHODS: A multicenter cross-sectional study analyzing custom-made anonymized graft plans was performed. Graft plans were included from a cohort of mid/distal aortic arch repairs using custom-made fenestrated aortic endografts treated at 8 centers. Grafts targeting >2 arteries were excluded. No patient/clinical data were analyzed. A descriptive analysis was performed followed by an analysis of overlap of the designs to reach a common design in which the greatest number of grafts would overlap. RESULTS: One hundred thirty-one graft plans were included. All grafts were custom-made grafts from the COOK Medical Fenestrated arch platform. Ninety-four (71.8%) had a scallop-and-single-fenestration design, 33 (25.2%) had a single fenestration and 4 (4.3%) a single scallop. For analysis purposes, these latter 4 grafts were excluded. Two main graft plans (Plans 1 and 2) were proposed after analysis with similar configuration (1 scallop with 30 mm width, 20 mm height, 12:00 position; 1 preloaded fenestration with 8 mm diameter, 26 mm from the top of the graft and 12:00 position; tapered, with a 193 mm length and 32 mm distal diameter) but with 2 different proximal diameters of 38 mm (Plan 1) and 44 mm (Plan 2), reaching an overall feasibility of 85.8% (n=109), being 47.2% (n=60) and 38.6% (n=49) for each design, respectively. CONCLUSION: The degree of overlap between the studied fenestrated and/or scalloped thoracic endovascular aneurysm repair (TEVAR) graft designs was high. Future studies analyzing these designs in a real-world cohort of patients are needed to further address off-the-shelf feasibility. CLINICAL IMPACT: In a multicenter study analyzing 127 fenestrated aortic arch endograft plans from 9 aortic centers, we found that the degree of overlap between the studied fenestrated and/or scalloped arch graft designs was high and that 2 proposed graft designs would be theoretically applicable in 85.8% of cases. Future studies analyzing these designs in a real-world cohort of patients are needed to further address off-the-shelf feasibility.

Mechanical aortic valve may no longer be a contraindication to inner branch aortic arch endografts.

OBJECTIVES: The presence of a mechanical aortic valve has been a contraindication to the use of an arch branch aortic endograft due to the risk of damaging the valve, resulting in acute aortic regurgitation, or a trapped endograft. METHODS: We present a 67-year-old woman, with a background of Marfan's syndrome and a previous Bentall's procedure, who presented with a symptomatic enlarging aortic arch and descending thoracic aortic aneurysm, with a type 1A endoleak. RESULTS: Using an inner branch arch endograft (Cook Medical, Bloomington, Indiana), the nose cone of the delivery system was passed laterally through the semi-circular aperture of the mechanical aortic valve to facilitate deployment just distal to the coronary buttons. CONCLUSIONS: With advancement of endovascular technology, techniques and experience, endovascular aortic arch repair in the presence of a mechanical aortic valve is feasible.

Novel modification of a branched arch endograft with a retrograde left common carotid branch for acute pseudoaneurysm post type A repair.

OBJECTIVE: Pseudoaneurysm formation post type A aortic dissection repair is rare. Revision surgical repair is challenging, with a risk of death from haemorrhage. METHODS: We present a 56-year-old man who presented with a rapidly enlarging distal ascending aortic anastomotic pseudoaneurysm following a recent ascending and hemiarch replacement for acute type A aortic dissection. RESULTS: A tight kink in the ascending aortic graft precluded an endovascular repair utilizing two antegrade branches, and so a novel custom-made 3 inner branched aortic endograft was designed, with an antegrade brachiocephalic inner branch and retrograde left common carotid and subclavian artery inner branches. The patient required an angioplasty to dilate the kinked/coarcted surgical graft, but made an uneventful recovery. CONCLUSION: An aortic arch inner branch design with an antegrade brachiocephalic branch but retrograde left common carotid and left subclavian branches was feasible and may prove particularly useful when there is limited space in the ascending aorta.

Particle Image Velocimetry Evaluation of Hemodynamics Proximal to the Kissing Stent Configuration in the Aorto-Iliac Bifurcation.

PURPOSE: The kissing stent (KS) method is low-risk compared with open surgery techniques. It is often used to treat aorto-iliac occlusive disease (AIOD). Deployment of the KS geometry has a high technical success rate. However, stent patency reduces in the first 5 years potentially due to deleterious flow behavior. Potentially harmful hemodynamics due to the KS were investigated in vitro. METHODOLOGY: A compliant phantom of the aorto-iliac bifurcation was manufactured. Two surrogate stent-grafts were deployed into the phantom in the KS configuration to investigate effects of the presence of the stents, including the compliance mismatch they cause, on the hemodynamics proximal and distal to the KS. The investigation used pulsatile flow through a flow circuit to simulate abdominal aortic flow. Particle image velocimetry (PIV) was used to quantify the hemodynamics. RESULTS: PIV identified peak proximal and distal velocity in vitro was 0.71 and 1.40m·s-1, respectively, which were within physiological ranges. Throughout systole, flow appeared normal and undisturbed. A lumen wall collapse in the sagittal plane formed during late systole and continued to early diastole proximal to the aorto-iliac bifurcation, distal to the inlet stent position. The wall collapse led to disturbed flow proximal to the stented region in early diastole producing potential recirculation zones and abnormal flow patterns. CONCLUSION: The normal systolic flow behavior indicates the KS configuration is unlikely to cause an inflammatory response of the arterial walls. The collapse has not been previously identified and may potentially cause long-term patency reduction. It requires further investigation. CLINICAL IMPACT: The role of this article is to provide further insight into the haemodynamic behavior through a stented aorto-iliac artery. The results of this investigation will improve the understanding of the effects that using the kissing stent method may have on a patient and help to identify high risk regions that may require more detailed monitoring. This paper also develops the in vitro modelling techniques that will enable further research that cannot be carried out within patients.

Review of the Development of Hemodynamic Modeling Techniques to Capture Flow Behavior in Arteries Affected by Aneurysm, Atherosclerosis, and Stenting.

Cardiovascular diseases (CVDs) are the leading cause of death in the developed world. CVD can include atherosclerosis, aneurysm, dissection, or occlusion of the main arteries. Many CVDs are caused by unhealthy hemodynamics. Some CVDs can be treated with the implantation of stents and stent grafts. Investigations have been carried out to understand the effects of stents and stent grafts have on arteries and the hemodynamic changes post-treatment. Numerous studies on stent hemodynamics have been carried out using computational fluid dynamics (CFD) which has yielded significant insight into the effect of stent mesh design on near-wall blood flow and improving hemodynamics. Particle image velocimetry (PIV) has also been used to capture behavior of fluids that mimic physiological hemodynamics. However, PIV studies have largely been restricted to unstented models or intra-aneurysmal flow rather than peri or distal stent flow behaviors. PIV has been used both as a standalone measurement method and as a comparison to validate the CFD studies. This article reviews the successes and limitations of CFD and PIV-based modeling methods used to investigate the hemodynamic effects of stents. The review includes an overview of physiology and relevant mechanics of arteries as well as consideration of boundary conditions and the working fluids used to simulate blood for each modeling method along with the benefits and limitations introduced.

An open approach to a ruptured common iliac artery aneurysm with resultant ilio-iliac arteriovenous fistula.

OBJECTIVE: Presentations of a spontaneous ilio-iliac arteriovenous fistula are considered a rare occurrence and warrant urgent intervention. They are usually a result following trauma, previous surgery or uncommonly from a ruptured aneurysm. METHOD: We describe a case of a patient presenting with general malaise who examined to have a pulsatile abdominal mass with an associated bruit. He was found to have an ilio-iliac arteriovenous fistula secondary to a ruptured iliac aneurysm that was treated successfully with open surgical repair. RESULT: The patient was brought forward for open surgical repair due to haemodynamic instability as well as likely predicted difficulties with endovascular repair. Intra-operatively, his sigmoid colon was adherent to the aneurysm prompting the need for a Hartmann's procedure to allow for better visualisation of the aneurysm. A combination of external digital compression and Prolene suture was used to close the arteriovenous fistula. CONCLUSION: Open surgical repair of an ilio-iliac arteriovenous fistula secondary to a ruptured iliac aneurysm appears to be safe and feasible approach. The advancement of medical technology does open up the possibility of an endovascular approach; however, in a small subset of patients, open repair would appear to be better.

Use of the Off-the-Shelf t-Branch Device to Treat an Acute Type Ia Endoleak in a Symptomatic Juxtarenal Abdominal Aortic Aneurysm.

PURPOSE: To report the use of the off-the-shelf Zenith t-Branch Thoracoabdominal Endovascular Graft for the treatment of a symptomatic acute type Ia endoleak subsequent to previous infrarenal bifurcated endovascular aneurysm repair. CASE REPORT: A 72-year-old man presented 4 years after implantation of an Anaconda stent-graft with sac expansion and type II endoleak, which was treated over the next 18 months with repeated coil and glue embolization of the leak and sac. Six months after the last attempt, imaging disclosed a new type Ia endoleak. Sac enlargement became symptomatic, and emergent treatment was performed using the off-the-shelf Zenith b-Branch device. The 4 visceral arteries were bridged with Fluency stent-grafts. The Anaconda stent-graft precluded the use of a standard Zenith universal distal body bifurcated device below the t-Branch graft, so a reversed tapered 16×20×82-mm iliac limb was placed to bridge the t-Branch to the larger Anaconda limb; the smaller 12-mm contralateral Anaconda limb was occluded. The procedure was concluded with a femorofemoral bypass. At 10 months after the procedure, the patient is well; the sac diameter has decreased, and there is no endoleak on imaging. CONCLUSION: The multibranched Zenith t-branch device may be useful in treating proximal endoleaks in bifurcated stent-grafts.

A 12-year experience in the management of blunt thoracic aortic injury in Otautahi Christchurch.

BACKGROUND: Blunt thoracic aortic injury (BTAI) is associated with a high mortality and is the second most common cause of death from trauma. The approach to major trauma, imaging technology and advancement in endovascular therapy have revolutionised the management of BTAI. Endovascular therapy has now become the gold standard technique replacing surgery with its high mortality and morbidity in unstable patients. We aim to assess the outcomes following management of BTAI. METHOD: This is a retrospective study of all patients with BTAI between 1 January 2010 and 1 January 2022. Data were obtained from electronic health records. The grading of BTAI severity was done based on the Society of Vascular Surgery (SVS) Criteria. RESULTS: Fifty patients were included in the study analysis. The most common cause of BTAI was due to high-speed motor vehicle accidents (MVA) (36 patients, 72%). Grade 1 and grade 3 BTAI injuries were mostly encountered in 40% and 30% of the study cohort, respectively. Twenty-three patients (46%) underwent thoracic endovascular aortic repair (TEVAR). There was no secondary aortic re-intervention, conversion to open surgery or aortic-related deaths at 30 days or at most recent follow-up. CONCLUSION: Management of BTAI in our centre compares well with currently published studies. Long-term studies are warranted to guide clinicians in areas of controversy in BTAI management.

Analysis of Flow Through Extra-Anatomic Bypasses Between Supra-Aortic Branches Using Particle Image Velocimetry (PIV).

Supra-aortic extra-anatomic debranch (SAD) are prosthetic surgical grafts used to revascularize head and neck arteries that would be blocked during a surgical or hybrid procedure used in treating ascending and arch of the aorta pathologies. However, bypassing the supra-aortic arteries but not occluding their orifice might introduce potential for competitive flow that reduces bypass patency. Competitive flow within the bypasses across the supra-aortic arteries has not previously been identified. This research identified haemodynamics due to prophylactic inclusion of bypasses from the brachiocephalic artery (BCA) to the left common carotid artery (LCCA), and from the LCCA to left subclavian artery (LSA). Four model configurations investigated the risk of competitive flow and the necessity of intentionally blocking the proximal LSA and/or LCCA. Particle image velocimetry (PIV) was used to assess haemodynamics in each model configuration. We found potential for competitive flow in the BCA-LCCA bypass when the LSA was blocked, in the LSA-LCCA bypass, when the LCCA alone or LCCA and LSA were blocked. Flow stagnated at the start of systole within the RCCA-LCCA bypass, along with notable recirculation zones and reciprocating flow occurring throughout systolic flow. Flow also stagnated in the LCCA-LSA bypass when the LCCA was blocked. There was a large recirculation in the LCCA-LSA bypass when both the LCCA and LSA were blocked. The presence of competitive flow in all other configurations indicated that it is necessary to block or ligate the native LCCA and LSA once the debranch is made and the thoracic endovascular aortic repair (TEVAR) completed.

Segmental arterial mediolysis after fenestrated endovascular abdominal aortic aneurysm repair-A rare complication.

Segmental arterial mediolysis (SAM) is a rare, noninflammatory, nonatherosclerotic condition that occurs commonly in mesenteric vessels. There are no known predisposing risk factors to the development of SAM. We present a case of a 67-year-old woman who presented with abdominal pain 2 days following discharge after an elective endovascular abdominal aortic intervention. Repeat imaging 2 days after readmission showed the presence of multiple new aneurysms involving the mesenteric vasculature. She underwent attempted endovascular embolization of the largest aneurysm. The postmortem and histopathologic examinations confirmed the diagnosis of SAM.

A glimpse into the incidence and mortality of aortic dissection in Aotearoa New Zealand.

BACKGROUND: Aortic dissection is a lethal medical diagnosis associated with high morbidity and mortality. Currently published studies have noted a rising incidence of aortic dissection globally as well as a downward trend in mortality secondary to aortic dissection. There remains no nationally available study here in Aotearoa New Zealand looking into the incidence and mortality of aortic dissection. METHOD: A retrospective observational study was performed using data extracted from the Manatu Hauora - Ministry of Health National Minimum Dataset (NMDS) from 1 July 2001 to 30 June 2021. Diagnosis of aortic dissection was based on the ICD-10 version 2 code for aortic dissection (I7100). Population-based statistics were obtained from Statistics New Zealand. RESULT: A total of 4,737 patients were included in the study over the 20-year period. The incidence rate of aortic dissection in Aotearoa New Zealand is rising and the current median incidence rate is 4.99 per 100,000 per annum. The mortality rate from aortic dissection is slowly decreasing in Aotearoa New Zealand and the current median mortality rate is 2.19 per 100,000 per annum. CONCLUSION: There appears to be a rise in the incidence of aortic dissection in Aotearoa New Zealand and a decrease in the mortality rate.

PIV Analysis of Haemodynamics Distal to the Frozen Elephant Trunk Stent Surrogate.

PURPOSE: The Frozen Elephant Trunk (FET) stent is a hybrid endovascular device that may be implemented in the event of an aneurysm or aortic dissection of the aortic arch or superior descending aorta. A Type 1B endoleak can lead to intrasaccular flow during systole and has been identified as a known failure of the FET stent graft. The purpose was to develop in-vitro modelling techniques to enable the investigation of the known failure. METHODS: A silicone aortic phantom and 3D printed surrogate stent graft were manufactured to investigate the haemodynamics of a Type 1B endoleak. Physiological pulsatile flow dynamics distal to the surrogate stent graft were investigated in-vitro using Particle Image Velocimetry (PIV). RESULTS: PIV captured recirculation zones and an endoleak distal to the surrogate stent graft. The endoleak was developed at the peak of systole and sustained until the onset of diastole. The endoleak was asymmetric, indicating a potential variation in the phantom artery wall thickness or stent alignment. Recirculation was identified on the posterior dorsal line during late systole. CONCLUSIONS: The identification of the Type 1B endoleak proved that in-vitro modelling can be used to investigate complex compliance changes and wall motions. The recirculation may indicate the potential for long term intimal layer inflammatory issues such as atherosclerosis. These results may aid future remediation techniques or stent design. Further development of the methods used in this experiment may assist with the future testing of stents prior to animal or human trial.

In vitro pulsatile flow study in compliant and rigid ascending aorta phantoms by stereo particle image velocimetry.

The aorta is a high risk region for cardiovascular disease (CVD). Haemodynamic patterns leading to CVD are not well established despite numerous experimental and numerical studies. Most overlook effects of arterial compliance and pulsatile flow. However, rigid wall assumptions can lead to overestimation of wall shear stress; a key CVD determinant. This work investigates the effect of compliance on aortic arch haemodynamics experiencing pulsatility. Rigid and compliant phantoms of the arch and brachiocephalic branch (BCA) were manufactured. Stereoscopic particle image velocimetry was used to observe velocity fields. Higher velocity magnitude was observed in the rigid BCA during acceleration. However, during deceleration, the compliant phantom experienced higher velocity. During deceleration, a low velocity region initiated and increased in size in the BCA of both phantoms with irregular shape in the compliant. At mid-deceleration, considerably larger recirculation was observed under compliance compared to rigid. Another recirculation region formed and increased in size on the inner wall of the arch in the compliant during late deceleration, but not rigid. The recirculation regions witnessed identify as high risk areas for atherosclerosis formation by a previous ex-vivo study. The results demonstrate necessity of compliance and pulsatility in haemodynamic studies to obtain highly relevant clinical outcomes.

Timeliness and outcomes of carotid endarterectomy for symptomatic carotid artery stenosis: a single centre audit.

BACKGROUND: For patients presenting with symptomatic internal carotid artery stenosis, carotid endarterectomy (CEA) surgery is recommended to be performed generally within a 48-hr to 14-day window. This study aimed to assess timeliness of delivery, and outcomes, of CEA surgery in a tertiary vascular centre. METHOD: Patients with symptomatic internal carotid artery stenosis who underwent CEA between 1 June 2014 and 31 June 2017 were identified and data were obtained from hospital records. The timeline of their journey from presentation to surgery was then mapped together with their outcomes. RESULTS: One hundred and seventy-two cases were included in the study. Overall, the median time from development of presenting symptoms to surgery was 9 days and 119 (69%) cases were operated on within 14 days. The median time from development of presenting symptoms to ultrasound imaging was 2 days and the median time from symptoms to vascular referral was also 2 days. There were no deaths, strokes or transient ischaemic attacks within 30 days of CEA. At 1 year, survival was 100% but 15 (8.7%) had experienced at least one transient ischaemic attack or stroke. In the 53 cases operated upon beyond 14 days the dominant cause of delay in 32 (60%) was accessing surgery after review by the vascular service. CONCLUSION: The aim of delivering CEA within 14 days of developing relevant symptoms was achieved in most cases with good outcomes. Nevertheless, points of delay in the patient journey that could be targeted for future quality improvement were identified.

A Review of Arterial Phantom Fabrication Methods for Flow Measurement Using PIV Techniques.

Cardiovascular diseases (CVD) are the leading cause of morbidity and mortality in the western world. In the last three decades, fluid dynamics investigations have been an important component in the study of the cardiovascular system and CVD. A large proportion of studies have been restricted to computational fluid dynamic (CFD) modeling of blood flow. However, with the development of flow measurement techniques such as particle image velocimetry (PIV), and recent advances in additive manufacturing, experimental investigation of such flow systems has become of interest to validate CFD studies, testing vascular implants and using the data for therapeutic procedures. This article reviews the technical aspects of in-vitro arterial flow measurement with the focus on PIV. CAD modeling of geometries and rapid prototyping of molds has been reviewed. Different processes of casting rigid and compliant models for experimental analysis have been reviewed and the accuracy of construction of each method has been compared. A review of refractive index matching and blood mimicking flow circuits is also provided. Methodologies and results of the most influential experimental studies are compared to elucidate the benefits, accuracy and limitations of each method.

Increased nitric oxide production during acute rejection in kidney transplantation: a useful marker to aid in the diagnosis of rejection.

BACKGROUND: The diagnosis of acute rejection (AR) relies on biopsy (Bx), with all the noninvasive tests failing to show satisfactory predictive value. Nitric oxide (NO) has been shown to play a role in AR. The aim of this study is to analyze the relationship between NO and (1) biopsy-proven allograft rejection and (2) other reasons of allograft dysfunction. PATIENTS AND METHODS: Fifty consecutive renal allograft recipients ages 23-72 yrs who were transplanted were prospectively recruited. Blood samples were collected for 3 months. Endogenous serum nitrate (SNO(3)) levels were measured with Griess reagent in 1178 samples. Biopsies were performed as clinically indicated. Tacrolimus levels, urinary cultures, and renal function tests were done as per unit protocol. RESULTS: Fifty recipients (mean+/-SD age 45.2+/-2.18 yrs, 24 men and 6 women) underwent 68 biopsies. Forty-five Bx (66.2%) showed AR in 19 recipients (mean age 47+/-8) and 23 (33.8%) Bx in 13 recipients (mean age 43+/-12) showed no AR. SNO(3) in AR was (73+/-8.89 micromol/L) compared with negative Bx (45+/-4.5 micromol/L; P<0.05). There was also a significant difference in SNO(3) during AR and other causes of allograft dysfunction; delayed graft function (54+/-7.8 micromol/L), urinary tract infection (44+/-2.9 micromol/L), tacrolimus toxicity (51+/-2.86 micromol/L), and increase in serum creatinine (44+/-2.36 micromol/L). CONCLUSION: There is a significant increase of serum nitrate with episodes of acute rejection compared with other causes of renal dysfunction. SNO(3) can therefore aid in the diagnosis of acute rejection.