Smooth muscle-specific deletion of Ccn2 causes severe aorta malformation and atherosclerosis.

AIMS: Cellular Communication Network Factor 2 (CCN2) is a matricellular protein implicated in fibrotic diseases, with ongoing clinical trials evaluating anti-CCN2-based therapies. By uncovering CCN2 as abundantly expressed in non-diseased artery tissue, this study aimed to investigate the hypothesis that CCN2 plays a pivotal role in maintaining smooth muscle cell (SMC) phenotype and protection against atherosclerosis. METHODS AND RESULTS: Global- and SMC-specific Ccn2 knockout mouse models were employed to demonstrate that Ccn2 deficiency leads to SMC de-differentiation, medial thickening, and aorta elongation under normolipidemic conditions. Inducing hyperlipidemia in both models resulted in severe aorta malformation and a 17-fold increase in atherosclerosis formation. Lipid-rich lesions developed at sites of the vasculature typically protected from atherosclerosis-development by laminar blood flow, covering 90% of aortas, and extending to other vessels, including coronary arteries. Evaluation at earlier time points revealed medial lipid accumulation as a lesion-initiating event. Fluorescently labelled LDL injection followed by confocal microscopy showed increased LDL retention in the medial layer of Ccn2 knockout aortas, likely attributed to marked proteoglycan enrichment of the medial extracellular matrix. Analyses leveraging data from the Athero-Express study cohort indicated relevance of CCN2 in established human lesions, as CCN2 correlated with SMC marker transcripts across 654 transcriptomically profiled carotid plaques. These findings were substantiated through in situ hybridization showing CCN2 expression predominantly in the fibrous cap. CONCLUSIONS: This study identifies CCN2 as a major constituent of the normal artery wall, critical in regulating SMC differentiation and aorta integrity, and possessing a protective role against atherosclerosis development. These findings underscore the need for further investigation into the potential effects of anti-CCN2-based therapies on the vasculature.

A Single Injection of ADRCs Does Not Prevent AAA Formation in Rats in a Randomized Blinded Design.

There is a pressing need for alternative medical treatments for abdominal aortic aneurysms (AAAs). Mesenchymal regenerative cells derived from adipose tissue (ADRCs) have shown potential in modulating the inflammation and immune responses that drive AAA progression. We hypothesized that ADRCs could reduce inflammation and preserve vascular integrity, potentially slowing the progression of AAA. In our study, subcutaneous adipose tissue was harvested from male Sprague Dawley rats, from which ADRCs were isolated. AAA was induced in these rats using intraluminal porcine pancreatic elastase, followed by intravenous administration of either ADRCs (106 cells) or saline (0.1 mL). We monitored the progression of AAA through weekly ultrasound, and the rats were sacrificed on day 28 for histological analysis. Our results showed no significant difference in the inner abdominal aortic diameter at day 28 between the control group (172% ± 73%, n = 17) and the ADRC-treated group (181% ± 75%, n = 15). Histological analyses of AAA cross-sections also revealed no significant difference in the infiltration of neutrophils or macrophages between the two groups. Furthermore, the integrity and content of elastin in the tunica media were similar between groups. These findings indicate that a single injection of ADRCs does not inhibit the development of AAA in rats in a randomized blinded study.

Background, establishment and initial experiences of the Danish cardiovascular homograft biobank.

Odense University Hospital is a major tertiary vascular hospital in Scandinavia, performing approx. 200 aortic repairs annually. This article presents the rationale behind this endeavor and the early outcomes of the initial implantation of locally processed homografts. All patients receiving a homograft were identified from the established homograft biobank database and their medical records were reviewed after obtaining consent. All surgeons in charge of homograft implantations were semi structured interviewed regarding the harvesting procedure, the tools for detecting available homografts, their quality and delivery. The National board of Health approved the biobank fulling the EU Directive of Tissues and Cells after 18 months of preparation. From May 6, 2021, to March 1, 2023, 26 patients had a homograft implantation, with 7 for mycotic aneurysms, 10 for aorto-iliac graft infection, 6 for infra-inguinal graft infection, and 3 for graft infection in thoracic aorta. Six (23%) were emergently performed. Two (7.7%) died within 30 days postoperatively, both following in situ replacement of an infected aortoiliac graft, corresponding to a 20% mortality in this subgroup. The incidence of reinfections was 19.2%; one each in the mycotic aneurysm group, the aortoiliac graft infection group, and the thoracic graft infection group. After 90 days, two patients were diagnosed with aorto-enteric fistula. All involved surgeons could easily identify available suitable homografts, and within 2 h have homografts of acceptable quality and requested dimensions. The establishment of the Danish Cardiovascular Homograft Biobank was straightforward and effectively serves cardiovascular procedures performed 24/7. Additionally, the initial experiences seem comparable to others experiences.

Transplantation of cryopreserved cardiovascular homografts.

Due to degeneration, homografts were since the 1950s only used strictly for replacement of complex arterial segments and lesions incl. the aortic valve, replacement of infected arterial prostheses, and vascular access for patients on haemodialysis. During the 1990s, rate-differentiated freezing methods and anti-crystallization agents proved to prevent crystallisation, and more widespread use with expanded indications incl. coronary and lower limb bypasses began justified by promising midterm results. In 2021, the first Scandinavian homograft biobank was founded in Odense in Denmark. This review summarises the history and the experiences from this biobank.

Personalized Intervention Based on Early Detection of Atherosclerosis: JACC State-of-the-Art Review.

Cardiovascular disease (CVD) remains the leading cause of morbidity and mortality worldwide and challenges the capacity of health care systems globally. Atherosclerosis is the underlying pathophysiological entity in two-thirds of patients with CVD. When considering that atherosclerosis develops over decades, there is potentially great opportunity for prevention of associated events such as myocardial infarction and stroke. Subclinical atherosclerosis has been identified in its early stages in young individuals; however, there is no consensus on how to prevent progression to symptomatic disease. Given the growing burden of CVD, a paradigm shift is required-moving from late management of atherosclerotic CVD to earlier detection during the subclinical phase with the goal of potential cure or prevention of events. Studies must focus on how precision medicine using imaging and circulating biomarkers may identify atherosclerosis earlier and determine whether such a paradigm shift would lead to overall cost savings for global health.

Experimental comparative study of a novel drug-eluting arteriovenous graft in a sheep model.

Background: Arteriovenous (AV) grafts often develop severe complications of stenosis due to neointimal proliferation that occurs either at the venous anastomosis site or at the outflow receiving vein. This study compares primary patency during 12 months of follow up for a new experimental Biomodics© interpenetrating polymer network (IPN) drug-eluting graft prototype with state-of-the-art GORE® ACUSEAL (ACUSEAL) in an AV graft model in sheep. Methods and results: An end-to-end bypass from the common carotid artery to the jugularis vein was performed bilaterally in 12 sheep. The usage of ACUSEAL or the IPN, both 6.0 mm in diameter, was determined via randomization. The sheep were followed up every 4 weeks with ultrasonic duplex scanning to determine patency; the experienced observer was blinded to the randomization. One sheep died after 11 days, and the final sample accordingly consisted of 11 animals. When comparing neointimal hyperplasia after 12 months in the two grafts, Fisher's exact test showed a significant difference with none out of 11 in the IPN grafts and 9 out of 11 in the ACUSEAL graft (p < 0.001). However, the Biomodics© IPN exhibited severe deterioration over time. Conclusions: Almost all of the grafts occluded during the 12 months of follow up. Although the zwitterion-bounded interpenetrating drug eluting polymer network showed signs to impair neointimal hyperplasia and thrombosis, age-related degeneration hindered demonstrating a potential improvement in patency.

Exploring Drug Re-Purposing for Treatment of Abdominal Aortic Aneurysms: a Systematic Review and Meta-analysis.

OBJECTIVE: Large abdominal aortic aneurysms (AAAs) present a significant mortality risk. While numerous medical interventions have been proposed, no drugs have convincingly reduced AAA progression, rupture rates, or repair risk. This systematic review and meta-analysis aimed to assess the impact of re-purposed drugs or dietary supplements on slowing expansion rates, reducing the risk of rupture, or minimising the risk of repair for individuals with AAA. METHODS: A systematic search was conducted in five databases. Both observational studies and randomised controlled trials were included. Unpublished data from two screening trials were incorporated. Risk of bias was assessed using the Newcastle-Ottawa scale and revised Cochrane risk of bias tool. Meta-analyses were performed for each identified drug subclass and were stratified by overall risk of bias. Results were reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. RESULTS: Of 7 484 screened studies, 39 met the inclusion criteria. No studies on dietary supplements were included. A total of 84 cohorts were derived from the included studies, and twelve distinct drug groups underwent meta-analyses. Two drug groups, metformin and statins, were statistically significant in slowing AAA growth. No low risk of bias studies were included for these two drug groups, and the results had very high heterogeneity (I2 > 80%). Both groups had a GRADE certainty of very low. Metformin, excluding high risk of bias studies, presented an estimated mean growth difference of AAA diameter between users and non-users of -0.73 mm/year, whilst statins had an overall estimated mean difference of -0.84 mm/year. CONCLUSION: This systematic review and meta-analysis suggests that metformin and statins may provide some effect in slowing AAA progression. However, no definitive evidence was found for any of the investigated drugs included in this study. Further research is needed to identify effective medical treatments for AAA progression with more robust methodology.

Danish men's experiences of cardiovascular screening and their views on preventive cardiovascular medication: A qualitative explorative nurse study.

OBJECTIVES: This study explored Danish men's experience of participating in a screening program for cardiovascular disease (CVD) and their perceptions of preventive medication for CVD before and after participation in the screening program. METHODS: An exploratory phenomenological-hermeneutical study. Fifteen men from a cardiovascular screening program for men aged 65-74 years participated. Semi-structured interviews were conducted before screening and one year later (2015-2017). The interviews were transcribed verbatim and analysed using Kvale and Brinkmann's approach to data analysis. RESULTS: Two main themes were identified: (i) seeking confirmation and control of health: familiarity with CVD; understanding the screening program; confirmation of health; perception of preventive medication, and (ii) sense of own health and prevention: experiences with the screening program; accept or denial of diagnosis and preventive medication. CONCLUSION: A minority of the men understood the nature of the diseases for which they were being examined. The invitation for screening and the outcome of the examinations must be communicated more skilfully. The health providers need to engage early in treatment after the screening and provide an individualised plan that addresses patients concerns and knowledge based on their needs.

Genome-wide association meta-analysis identifies risk loci for abdominal aortic aneurysm and highlights PCSK9 as a therapeutic target.

Abdominal aortic aneurysm (AAA) is a common disease with substantial heritability. In this study, we performed a genome-wide association meta-analysis from 14 discovery cohorts and uncovered 141 independent associations, including 97 previously unreported loci. A polygenic risk score derived from meta-analysis explained AAA risk beyond clinical risk factors. Genes at AAA risk loci indicate involvement of lipid metabolism, vascular development and remodeling, extracellular matrix dysregulation and inflammation as key mechanisms in AAA pathogenesis. These genes also indicate overlap between the development of AAA and other monogenic aortopathies, particularly via transforming growth factor ß signaling. Motivated by the strong evidence for the role of lipid metabolism in AAA, we used Mendelian randomization to establish the central role of nonhigh-density lipoprotein cholesterol in AAA and identified the opportunity for repurposing of proprotein convertase, subtilisin/kexin-type 9 (PCSK9) inhibitors. This was supported by a study demonstrating that PCSK9 loss of function prevented the development of AAA in a preclinical mouse model.

Cationic proteins from eosinophils bind bone morphogenetic protein receptors promoting vascular calcification and atherogenesis.

AIMS: Blood eosinophil count and eosinophil cationic protein (ECP) concentration are risk factors of cardiovascular diseases. This study tested whether and how eosinophils and ECP contribute to vascular calcification and atherogenesis. METHODS AND RESULTS: Immunostaining revealed eosinophil accumulation in human and mouse atherosclerotic lesions. Eosinophil deficiency in ΔdblGATA mice slowed atherogenesis with increased lesion smooth muscle cell (SMC) content and reduced calcification. This protection in ΔdblGATA mice was muted when mice received donor eosinophils from wild-type (WT), Il4-/-, and Il13-/- mice or mouse eosinophil-associated-ribonuclease-1 (mEar1), a murine homologue of ECP. Eosinophils or mEar1 but not interleukin (IL) 4 or IL13 increased the calcification of SMC from WT mice but not those from Runt-related transcription factor-2 (Runx2) knockout mice. Immunoblot analyses showed that eosinophils and mEar1 activated Smad-1/5/8 but did not affect Smad-2/3 activation or expression of bone morphogenetic protein receptors (BMPR-1A/1B/2) or transforming growth factor (TGF)-ß receptors (TGFBR1/2) in SMC from WT and Runx2 knockout mice. Immunoprecipitation showed that mEar1 formed immune complexes with BMPR-1A/1B but not TGFBR1/2. Immunofluorescence double-staining, ligand binding, and Scatchard plot analysis demonstrated that mEar1 bound to BMPR-1A and BMPR-1B with similar affinity. Likewise, human ECP and eosinophil-derived neurotoxin (EDN) also bound to BMPR-1A/1B on human vascular SMC and promoted SMC osteogenic differentiation. In a cohort of 5864 men from the Danish Cardiovascular Screening trial and its subpopulation of 394 participants, blood eosinophil counts and ECP levels correlated with the calcification scores of different arterial segments from coronary arteries to iliac arteries. CONCLUSION: Eosinophils release cationic proteins that can promote SMC calcification and atherogenesis using the BMPR-1A/1B-Smad-1/5/8-Runx2 signalling pathway.

Nicotine Administration Augments Abdominal Aortic Aneurysm Progression in Rats.

Inflammation and elastin degradation are key hallmarks in the pathogenesis of abdominal aortic aneurysms (AAAs). It has been acknowledged that activation of alpha7 nicotinic acetylcholine receptors (α7nAChRs) attenuates inflammation, termed the cholinergic anti-inflammatory pathway (CAP). Thus, we hypothesize that low-dose nicotine impairs the progression of elastase-induced AAAs in rats by exerting anti-inflammatory and anti-oxidative stress properties. Male Sprague-Dawley rats underwent surgical AAA induction with intraluminal elastase infusion. We compared vehicle rats with rats treated with nicotine (1.25 mg/kg/day), and aneurysm progression was monitored by weekly ultrasound images for 28 days. Nicotine treatment significantly promoted AAA progression (p = 0.031). Additionally, gelatin zymography demonstrated that nicotine significantly reduced pro-matrix metalloproteinase (pro-MMP) 2 (p = 0.029) and MMP9 (p = 0.030) activity in aneurysmal tissue. No significant difference was found in the elastin content or the score of elastin degradation between the groups. Neither infiltrating neutrophils nor macrophages, nor aneurysmal messenger RNA (mRNA) levels of pro- or anti-inflammatory cytokines, differed between the vehicle and nicotine groups. Finally, no difference in mRNA levels of markers for anti-oxidative stress or the vascular smooth muscle cells' contractile phenotype was observed. However, proteomics analyses of non-aneurysmal abdominal aortas revealed that nicotine decreased myristoylated alanine-rich C-kinase substrate and proteins, in ontology terms, inflammatory response and reactive oxygen species, and in contradiction to augmented AAAs. In conclusion, nicotine at a dose of 1.25 mg/kg/day augments AAA expansion in this elastase AAA model. These results do not support the use of low-dose nicotine administration for the prevention of AAA progression.

Arabic-speaking male immigrants' perceptions of preventive initiatives: An interview study.

BACKGROUND: Arabic-speaking men are a sparsely investigated population in health promotion and disease prevention. This may hamper their ability to achieve the highest obtainable health due to less accessibility and acceptability of preventive measures. AIM: We explored Arabic-speaking (Palestinian, Iraqi and Somali) male immigrants' perceptions of preventive initiatives in general and such initiatives for cardiovascular diseases (CVD) in particular to understand how to address inequalities in engagement in prevention. METHODS: This qualitative study employed content analysis of semistructured interviews with 60-66-year-old Arabic-speaking men living in Denmark. Supplementary, structured data, for example, health data, were collected. From June to August 2020, 10 men were interviewed. FINDINGS: Preventive initiatives were found ethically and culturally acceptable alongside personally and socially relevant; they were perceived as humanitarian and caring for the participants' health, respecting of their self-determination and enabling their empowerment. Thus, the participants entreated that their fellow countrymen be assisted in achieving the prerequisite coping capabilities to address inequality in access, perceived acceptance and relevance. This led us to define one main category 'Preventive initiatives - Caring and humanitarian aid empower us' with the underlying subcategories: 'We are both hampered and strengthened by our basic assumptions' and 'We need help to achieve coping capabilities enabling us to engage in preventive initiatives'. CONCLUSION: Prevention was perceived as acceptable and relevant. Even so, Arabic-speaking men may be a hard-to-reach group due to their basic assumptions and impaired capabilities for engaging in prevention. Addressing inequality in accessibility, acceptability and relevance in regard to prevention may be promoted through a person-centred approach embracing invitees' preferences, needs and values; and by strengthening invitees' health literacy through efforts at the structural, health professional and individual levels. PUBLIC CONTRIBUTION: This study was based on interviews. The interviewees were recruited as public representatives to assist us in building an understanding of Arabic-speaking male immigrants' perceptions of preventive initiatives in general and preventive initiatives for CVD in particular.

Gender-specific Predicted Normal Aortic Size and Its Consequences of the Population-Based Prevalence of Abdominal Aortic Aneurysms.

BACKGROUND: To investigate if a relative-size-index of the abdominal aortic diameter influences the prevalence estimates of abdominal aortic dilatations compared to absolute diameters. METHODS: Cross-sectional study. Participants from the Viborg Vascular Screening Trial, Viborg Women Cohort, and the Viborg Screening Program. Through multivariate linear regression analyses, 2 gender-specific prediction-equations were developed based upon body-surface area and age. The definitions of absolute and relative size of aortic ectasies were 25-29 mm and 1.25-1.49× individual-predicted size (IPS), abdominal aortic aneurysm (AAA) 30 mm and 1.5× IPS, and large repair-recommendable AAA ≥55 mm or ≥ 2.75× IPS, respectively. RESULTS: Nineteen thousand two hundred and sixty nine males (69.6 years) and 2,426 females (67.1 years) attended the population- and ultrasound-based screening studies for AAA. The mean peak systolic abdominal anterior-posterior inner to inner diameter was 19.1 mm (±5.3 mm) and 16.6 mm (±2.8 mm) (P < 0.001) in males and females, respectively. Body surface area showed the strongest correlation with aortic diameters in both males (r = 0.19, P < 0.001) and females (r = 0.17, P < 0.001). Age correlated significantly with size, but only in males (r = 0.03, P < 0.001). The prevalence in men of absolute size-defined and relative size index-defined screening-detected aortic ectasies, AAAs and repair-recommendable AAAs were: 5.9% and 9.5% (P < 0.001), 3.3% and 4.2% (P < 0.001) and 9.9% and 15.2% (P = 0.004), respectively. Prevalence in females of absolute-size-defined and relative-size-index-defined screening-detected aortic ectasies, AAAs and repair-recommendable AAAs were 1.2% and 5.8% (P < 0.001), 0.5% and 1.3% (P = 0.003) and 0.0% and 23.1% (P = 0.553), respectively. CONCLUSIONS: Despite statistical differences, ultrasound-based absolute diameters to detect AAA seem acceptable in men. In females, poor agreements were noticed concerning all 3 categories of aneurysms, indicating that the current absolute diagnostic cut-points do not reflect female anatomy.

Effects of Vitamin K2 and D Supplementation on Coronary Artery Disease in Men: A RCT.

Background: Extent and progression of coronary artery calcification (CAC) are strong predictors of myocardial infarction and mortality. Objectives: This study aims to investigate if vitamin K2 and D supplementation can reduce CAC progression. Methods: A total of 389 participants were randomized to supplementation with vitamin K2 (720 µg/day) and D (25 µg/day) vs placebo in a multicenter double-blinded randomized controlled trial. The primary endpoint (progression of aortic valve calcification) has been reported. This study reports CAC progression in participants with no ischemic heart disease. CT scans were performed at baseline, 12, and 24 months. ΔCAC and coronary plaque volume were evaluated in the entire group and in 2 subgroups. A safety endpoint was the composite of myocardial infarction, coronary revascularization, and all-cause mortality. Results: In total, 304 participants (male, mean age 71 years) were identified. The intervention and placebo group both increased in mean CAC scores from baseline to 24-month follow-up (Δ203 vs Δ254 AU, P = 0.089). In patients with CAC scores ≥400 AU, CAC progression was lower by intervention (Δ288 vs Δ380 AU, P = 0.047). Plaque analyses showed no significant difference in progression of noncalcified plaque volume (Δ-6 vs Δ46 mm3, P = 0.172). Safety events were fewer in participants receiving supplementation (1.9% vs 6.7%, P = 0.048). Conclusions: Patients with no prior ischemic heart disease randomized to vitamin K2 and D supplementation had no significant reduction in mean CAC progression over a 2-year follow-up compared to placebo. Although the primary endpoint is neutral, differential responses to supplementation in those with CAC scores ≥400 AU and in safety endpoints are hypothesis-generating for future studies.

Clinical Characteristics, Incidences, and Mortality Rates for Type A and B Aortic Dissections: A Nationwide Danish Population-Based Cohort Study From 1996 to 2016.

BACKGROUND: Population-based epidemiologic studies of aortic dissections (ADs) are needed. This study aimed to report clinical characteristics, incidences, and mortality rates for adult patients admitted to Danish hospitals with type A AD (TAAD) or type B AD (TBAD) from 1996 through 2016. METHODS: We conducted a nationwide, population-based register study. All cases of AD registered with International Classification of Diseases, Tenth Revision codes in the Danish National Patient Registry at time of admission to a hospital with available medical records underwent validation. Data were merged between nationwide health registries including the cause of death registry. Patients with validated AD were matched 1:10 on sex and age with patients with hypertension from the general Danish population. RESULTS: Of 5018 registered cases of AD, 4183 cases underwent review and 3023 (60.2%) were validated as AD. After exclusions, the distribution of validated TAAD and TBAD was 1620 (60.5%) and 1059 (39.5%; P<0.001), 67.5% and 67.0% of patients were men, and mean ages at dissection were 63.5±12.9 and 67.5±12.2 years (P<0.001), respectively. The most prevalent comorbidities for TAAD were hypertension (55.2%), thoracic aortic aneurysms (14.6%), and chronic obstructive pulmonary disease (13.1%); for TBAD, the most prevalent comorbidities were hypertension (64.1%), aortic aneurysms at any location (7.5% to 12.0%), and chronic obstructive pulmonary disease (15.7%). The overall mean annual incidence rate was 4.2/100 000 patient-years. Incidence was significantly higher for TAAD (2.2/100 000) compared with TBAD (1.5/100 000; P<0.001). The 30-day mortality rates for validated TAAD and TBAD were 22.0% and 13.9% (P<0.001), respectively, with no significant changes over time or between sexes. Adjusted 5-year overall mortality rates for TAAD and TBAD were hazard ratio 3.2 (2.9 to 3.5; P<0.001; aortic-related cause of death, 57.0%) and hazard ratio 2.1 (1.9 to 2.4; P<0.001; aortic-related cause of death, 42.8%), respectively, compared with the general hypertensive population. Among patients who survived 30 days from dissection, the adjusted 5-year overall mortality rates were hazard ratio 1.1 (1.0 to 1.3; P=0.12; aortic-related cause of death, 23.2%) and hazard ratio 1.4 (1.2 to 1.6; P<0.001; aortic-related cause of death, 25.6%) for TAAD and TBAD, respectively. CONCLUSIONS: Hypertension, aortic aneurysms, and chronic obstructive pulmonary disease were the most prevalent comorbidities. The 30-day mortality frequencies were consistent over time with no significant differences between sexes. The 5-year mortality rate was higher for TAAD than TBAD. If the patient survived 30 days from dissection, the mortality rate for patients with TAAD was comparable with that of the general hypertensive population, but the mortality rate was significantly higher in patients with TBAD.

Ultra-low-dose non-contrast CT and CT angiography can be used interchangeably for assessing maximal abdominal aortic diameter.

Background: Routine CT scans may increasingly be used to document normal aortic size and to detect incidental abdominal aortic aneurysms. Purpose: To determine whether ultra-low-dose non-contrast CT (ULDNC-CT) can be used instead of the gold standard CT angiography (CTA) for assessment of maximal abdominal aortic diameter. Materials and Methods: This retrospective study included 50 patients who underwent CTA and a normal-dose non-contrast CT for suspected renal artery stenosis. ULDNC-CT datasets were generated from the normal-dose non-contrast CT datasets using a simulation technique. Using the centerline technique, radiology consultants (n = 4) and residents (n = 3) determined maximal abdominal aortic diameter. The limits of agreement with the mean (LOAM) was used to access observer agreement. LOAM represents how much a measurement by a single observer may plausibly deviate from the mean of all observers on the specific subject. Results: Observers completed 1400 measurements encompassing repeated CTA and ULDNC-CT measurements. The mean diameter was 24.0 and 25.0 mm for CTA and ULDNC-CT, respectively, yielding a significant but minor mean difference of 1.0 mm. The 95% LOAM reproducibility was similar for CTA and ULDNC-CT (2.3 vs 2.3 mm). In addition, the 95% LOAM and mean diameters were similar for CTA and ULDNC-CT when observers were grouped as consultants and residents. Conclusions: Ultra-low-dose non-contrast CT exhibited similar accuracy and reproducibility of measurements compared with CTA for assessing maximal abdominal aortic diameter supporting that ULDNC-CT can be used interchangeably with CTA in the lower range of aortic sizes.