Abdominal aortic aneurysm screening guidelines: United States Preventative Services Task Force and Society for Vascular Surgery

An international, expert-based, Delphi consensus document on controversial issues in the management of abdominal aortic aneurysms

OBJECTIVE

As a result of conflicting, inadequate or controversial data in the literature, several issues concerning the management of patients with abdominal aortic aneurysms (AAAs) remain unanswered. The aim of this international, expert-based Delphi consensus document was to provide some guidance for clinicians on these controversial topics.

METHODS

A three-round Delphi consensus document was produced with 44 experts on 6 prespecified topics regarding the management of AAAs. All answers were provided anonymously. The response rate for each round was 100%.

RESULTS

Most participants (42 of 44 [95.4%]) agreed that a minimum case volume per year is essential (or probably essential) for a center to offer open or endovascular AAA repair (EVAR). Furthermore, 33 of 44 (75.0%) believed that AAA screening programs are (probably) still clinically effective and cost effective. Additionally, most panelists (36 of 44 [81.9%]) voted that surveillance after EVAR should be (or should probably be) lifelong. Finally, 35 of 44 participants (79.7%) thought that women smokers should (or should probably/possibly) be considered for screening at 65 years of age, similar to men. No consensus was achieved regarding lowering the threshold for AAA repair and the need for deep venous thrombosis prophylaxis in patients undergoing EVAR.

CONCLUSIONS

This expert-based Delphi consensus document provides guidance for clinicians regarding specific unresolved issues. Consensus could not be achieved on some topics, highlighting the need for further research in those areas.

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 β 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.

Fibromuscular Dysplasia and Abdominal Aortic Aneurysms Are Dimorphic Sex-Specific Diseases With Shared Complex Genetic Architecture

BACKGROUND

The risk of arterial diseases may be elevated among family members of individuals having multifocal fibromuscular dysplasia (FMD). We sought to investigate the risk of arterial diseases in families of individuals with FMD.

METHODS

Family histories for 73 probands with FMD were obtained, which included an analysis of 463 total first-degree relatives focusing on FMD and related arterial disorders. A polygenic risk score for FMD (PRSFMD) was constructed from prior genome-wide association findings of 584 FMD cases and 7139 controls and evaluated for association with an abdominal aortic aneurysm (AAA) in a cohort of 9693 AAA cases and 294 049 controls. A previously published PRSAAA was also assessed among the FMD cases and controls.

RESULTS

Of all first degree relatives of probands, 9.3% were diagnosed with FMD, aneurysms, and dissections. Aneurysmal disease occurred in 60.5% of affected relatives and 5.6% of all relatives. Among 227 female first-degree relatives of probands, 4.8% (11) had FMD, representing a relative risk (RR)FMD of 1.5 ([95% CI, 0.75-2.8]; P=0.19) compared with the estimated population prevalence of 3.3%, though not of statistical significance. Of all fathers of FMD probands, 11% had AAAs resulting in a RRAAA of 2.3 ([95% CI, 1.12-4.6]; P=0.014) compared with population estimates. The PRSFMD was found to be associated with an AAA (odds ratio, 1.03 [95% CI, 1.01-1.05]; P=2.6×10-3), and the PRSAAA was found to be associated with FMD (odds ratio, 1.53 [95% CI, 1.2-1.9]; P=9.0×10-5) as well.

CONCLUSIONS

FMD and AAAs seem to be sex-dimorphic manifestations of a heritable arterial disease with a partially shared complex genetic architecture. Excess risk of having an AAA according to a family history of FMD may justify screening in family members of individuals having FMD.

Impact of Implicit Abdominal Aortic Aneurysm Screening in the Veterans Affairs Health Care System Over 10 Years

Background

Abdominal aortic aneurysm (AAA) screening programs have been active in the United States since 2005, but are not the only way AAAs are detected. AAA management and outcomes have not been investigated broadly in the context of “implicit AAA screening,” whereby radiologic examinations not intended for focused screening can identify AAAs.

Methods and Results

We examined the association between imaging‐based AAA screening, both explicit and implicit, and various outcomes for ≈1.6 million veterans in the Veterans Affairs health care system from 2005 to 2015. Screened‐positive, screened‐negative, and unscreened veterans were identified in the overall cohort and within a subgroup of veterans aged 65 years in 2005. The yearly composite screening rate increased over 10 years, from 11.7% to 18.3%, whereas the screened‐positive rate decreased from 7.3% to 4.9%. Only 12.9% of screening examinations were explicit AAA screening ultrasounds. The subgroup’s composite screening rate was 74% within its 10‐year eligibility window, with implicit screening accounting for 91.8% of examinations. In the 2005 subgroup, all‐cause mortality and Charlson comorbidity scores were higher for veterans who underwent screening compared with those unscreened (31.2% versus 23.1% and 0.47 versus 0.25, respectively; P<0.001). AAA rupture rates were similar between those unscreened and screened‐negative individuals.

Conclusions

Accounting for both explicit and implicit screening, AAA screening in the Veterans Affairs population has moderate reach. Efforts to expand explicit AAA screening are not likely to impact either all‐cause mortality or AAA rupture on the population scale as significantly as a careful accounting for and use of implicit screening data.

Underutilization of Guideline-based Abdominal Aortic Aneurysm Screening in an Academic Health System

OBJECTIVES

The US Preventive Services Task Force (USPSTF) recommends a 1-time screening for AAA with ultrasonography in men aged 65-75 who have ever smoked. Our objectives were to identify the AAA screening rates in a large academic health system and assess factors associated with receipt of screening.

METHODS

Data were extracted from electronic health record data from the Duke University Health System and the US Census Bureau. Index screening eligibility date was defined as the 65^th birthdate for male patients with a history of smoking. Patients with an index screening eligibility date between 1/1/2016 and 12/31/2018 were included in the study population and followed through 12/31/2019. Screened patients were identified by procedure codes for ultrasonography, CT or MRI.

RESULTS

Among 6,682 eligible patients who turned 65 years old between 1/1/2016 and 12/31/2018 with at least 1 year of follow-up, only 463 (6.9%) received AAA screening during the study period. The odds of receiving AAA screening within 1 year of index eligibility were 27% lower for Black patients compared to whites [OR=0.73, 95% CI (0.58,0.93)]. Patients who visited a PCP or had hypertension had 75% and 41% greater odds of receiving screening, respectively [OR 1.75, 95% CI (1.36,2.25)] and [OR 1.41 95% CI (1.11,1.80)] compared with patients who did not. Among 4,580 men with 2 years of follow-up, AAA screening rate increased to 13.0%. Patients who visited a PCP had 64% greater odds of receiving screening within 2 years of index eligibility compared to those who did not [OR=1.64, 95% CI (1.30,2.06)].

CONCLUSION

Screening for AAA per USPSTF guidelines is underutilized with evidence of a racial disparity. Although PCP visit is the most consistent predictor of screening, provider screening rates are low.

Abdominal aortic aneurysms

Abdominal aortic aneurysms (AAA) are prevalent among older adults and can cause significant morbidity and mortality if not addressed in a timely fashion. Their etiology remains the topic of continued investigation. Known causes include trauma, infection, and inflammatory disorders. Risk factors include cigarette smoking, advanced age, dyslipidemia, hypertension, and coronary artery disease. The pathophysiology of the disease is related to an initial arterial insult causing a cascade of inflammation and extracellular matrix protein breakdown by proteinases leading to arterial wall weakening. When identified early, aneurysms must be monitored for size, growth rate, and other factors which could increase the risk of rupture. Factors predisposing to rupture include size, active smoking, rate of growth, aberrant biomechanical properties of the aneurysmal sac, and female sex. Medical management includes the control of risk factors that may prevent growth, stabilize the aneurysm, and prevent rupture. Surgical management prevents rupture of high risk aneurysms, most commonly predicted by size. Less frequently, surgical management is required when the aneurysm has ruptured. Surgery involves a multidisciplinary approach to evaluate the patient's risk profile and to develop an operative plan involving either an endovascular or an open surgical repair. The patient must be carefully monitored post-operatively for complications and, in the case of endovascular repairs, for endoleaks. AAA management has evolved rapidly in recent years. Technical and technological advances have transformed the diagnosis and treatment of this disease.

Validation of natural language processing to determine the presence and size of abdominal aortic aneurysms in a large integrated health system

OBJECTIVE

Previous studies of the natural history of abdominal aortic aneurysms (AAAs) have been limited by small cohort sizes or heterogeneous analyses of pooled data. By quickly and efficiently extracting imaging data from the health records, natural language processing (NLP) has the potential to substantially improve how we study and care for patients with AAAs. The aim of the present study was to test the ability of an NLP tool to accurately identify the presence or absence of AAAs and detect the maximal abdominal aortic diameter in a large dataset of imaging study reports.

METHODS

Relevant imaging study reports (n = 230,660) from 2003 to 2017 were obtained for 32,778 patients followed up in a prospective aneurysm surveillance registry within a large, diverse, integrated healthcare system. A commercially available NLP algorithm was used to assess the presence of AAAs, confirm the absence of AAAs, and extract the maximal diameter of the abdominal aorta, if stated. A blinded expert manual review of 18,000 randomly selected imaging reports was used as the reference standard. The positive predictive value (PPV or precision), sensitivity (recall), and the kappa statistics were calculated.

RESULTS

Of the randomly selected 18,000 studies that underwent expert manual review, 48.7% were positive for AAAs. In confirming the presence of an AAA, the interrater reliability of the NLP compared with the expert review showed a kappa value of 0.84 (95% confidence interval [CI], 0.83-0.85), with a PPV of 95% and sensitivity of 88.5%. The NLP algorithm showed similar results for confirming the absence of an AAA, with a kappa of 0.79 (95% CI, 0.799-0.80), PPV of 77.7%, and sensitivity of 91.9%. The kappa, PPV, and sensitivity of the NLP for correctly identifying the maximal aortic diameter was 0.88 (95% CI, 0.87-0.89), 88.8%, and 88.2% respectively.

CONCLUSIONS

The use of NLP software can accurately analyze large volumes of radiology report data to detect AAA disease and assemble a contemporary aortic diameter-based cohort of patients for longitudinal analysis to guide surveillance, medical management, and operative decision making. It can also potentially be used to identify from the electronic medical records pre- and postoperative AAA patients "lost to follow-up," leverage human resources engaged in the ongoing surveillance of patients with AAAs, and facilitate the construction and implementation of AAA screening programs.