Genetic screening in heritable thoracic aortic disease—rationale, potentials and pitfalls

Clinical effectiveness of genetic testing guidelines in patients with thoracic aortic aneurysms

OBJECTIVE

To analyze the effectiveness of the current genetic testing guidelines for patients with thoracic aortic aneurysms.

METHODS

We evaluated genetic tests for thoracic aortic disease (TAD) from 2012 to 2023 in patients aged 18 and older with a thoracic aorta diameter greater than 4 cm. Mutation rates were compared by American College of Cardiology/American Heart Association testing criteria met by patients: age younger than 60 years, syndromic features of connective tissue diseases (CTDs), family history, or none. Results were classified as pathogenic, variants of uncertain significance (VUS), or negative. Genes tested were analyzed in 2 categories: primary (strongly associated with heritable diseases) or secondary (less strongly associated).

RESULTS

In total, 1034 patients were included: 42.4% aged younger than 60 years, 19.1% with syndromic features of CTD, 41.8% with family history, and 30.7% meeting no criteria. Overall, 3.97% had pathogenic mutations, and 27.27% had VUS. Mutation rates were greatest in patients with syndromic features of CTD (13.2%), followed by patients aged younger than 60 years (5.48%), with a family history (4.63%), and with no criteria met (2.21%). Primary genes had pathogenic mutation rates of 3.29% and VUS rates of 12.19%. Secondary genes had lower pathogenic rates (0.68%) but greater VUS (17.5%). Mutation rates in primary genes peaked at 22% in patients meeting all criteria, whereas those younger than 60 years without family history or syndromic features of CTD had the lowest rate (0.54%).

CONCLUSIONS

Refining genetic testing guidelines to incorporate multiple patient criteria could enhance risk stratification and support informed decision-making in genetic testing for TAD. Limiting testing to genes strongly associated with TAD could lower VUS rates.

Practice Patterns and Barriers to Vascular Genetic Testing Among Vascular Surgeons

INTRODUCTION

Engaging patients living with or at risk of aortic dissection via the Aortic Dissection Collaborative, physician education in vascular genetics was identified as a research priority. We surveyed vascular surgeons to characterize practice patterns, motivations, and barriers regarding aortopathy genetic testing.

METHODS

An anonymous 27-question survey was distributed on social media platforms between November and December 2022. Domains included demographics, vascular genetic education, testing attitudes and utilization, and experience in treating patients with genetic vascular aortopathies. The analysis included summary statistics and unpaired t-test to compare responses by interest in incorporating testing and practice type.

RESULTS

A total of 171 vascular surgeons from 15 countries responded to the survey (23% trainees). Over half received vascular genetics education during training (59%), and most (86%) were interested in incorporating genetic testing into their practice. Academic surgeons were more likely to have cared for a patient with a known genetic aortopathy over the past year than surgeons in hospital-based and private practices (83% vs. 56% vs. 27%; P < 0.01), to have ever made a referral to a medical geneticist (78% vs. 51% vs. 9%; P < 0.01), and have access to genetic counselors or geneticists (66% vs. 46% vs. 0%; P < 0.01). Barriers to genetic testing were rated as more significant by surgeons in nonacademic practices, with top barriers being insurance coverage of testing, cost of genetic testing, and access to genetic counselors. Evidence-based professional society guidelines were the strongest rated motivating factor for testing incorporation among respondents.

CONCLUSIONS

Vascular surgeon attitudes are not major barriers to incorporating genetic testing for patients with aortopathies; however, practical challenges regarding genetic testing and counseling are barriers to implementation especially for vascular surgeons in nonacademic practices. Future efforts should focus on evidence-based society guidelines, continuing medical education to increase adoption, and facilitating access to genetic counseling.

Contributions of Germline and Somatic Mosaic Genetics to Thoracic Aortic Aneurysms in Nonsyndromic Individuals

BACKGROUND

Thoracic aortic aneurysm (TAA) is associated with significant morbidity and mortality. Although individuals with family histories of TAA often undergo clinical molecular genetic testing, adults with nonsyndromic TAA are not typically evaluated for genetic causes. We sought to understand the genetic contribution of both germline and somatic mosaic variants in a cohort of adult individuals with nonsyndromic TAA at a single center.

METHODS AND RESULTS

One hundred eighty-one consecutive patients <60 years who presented with nonsyndromic TAA at the Massachusetts General Hospital underwent deep (>500×) targeted sequencing across 114 candidate genes associated with TAA and its related functional pathways. Samples from 354 age- and sex-matched individuals without TAA were also sequenced, with a 2:1 matching. We found significant enrichments for germline (odds ratio [OR], 2.44, P=4.6×10-6 [95% CI, 1.67-3.58]) and also somatic mosaic variants (OR, 4.71, P=0.026 [95% CI, 1.20-18.43]) between individuals with and without TAA. Likely genetic causes were present in 24% with nonsyndromic TAA, of which 21% arose from germline variants and 3% from somatic mosaic alleles. The 3 most frequently mutated genes in our cohort were FLNA (encoding Filamin A), NOTCH3 (encoding Notch receptor 3), and FBN1 (encoding Fibrillin-1). There was increased frequency of both missense and loss of function variants in TAA individuals.

CONCLUSIONS

Likely contributory dominant acting genetic variants were found in almost one quarter of nonsyndromic adults with TAA. Our findings suggest a more extensive genetic architecture to TAA than expected and that genetic testing may improve the care and clinical management of adults with nonsyndromic TAA.

Cellular, Molecular and Clinical Aspects of Aortic Aneurysm-Vascular Physiology and Pathophysiology

A disturbance of the structure of the aortic wall results in the formation of aortic aneurysm, which is characterized by a significant bulge on the vessel surface that may have consequences, such as distention and finally rupture. Abdominal aortic aneurysm (AAA) is a major pathological condition because it affects approximately 8% of elderly men and 1.5% of elderly women. The pathogenesis of AAA involves multiple interlocking mechanisms, including inflammation, immune cell activation, protein degradation and cellular malalignments. The expression of inflammatory factors, such as cytokines and chemokines, induce the infiltration of inflammatory cells into the wall of the aorta, including macrophages, natural killer cells (NK cells) and T and B lymphocytes. Protein degradation occurs with a high expression not only of matrix metalloproteinases (MMPs) but also of neutrophil gelatinase-associated lipocalin (NGAL), interferon gamma (IFN-γ) and chymases. The loss of extracellular matrix (ECM) due to cell apoptosis and phenotype switching reduces tissue density and may contribute to AAA. It is important to consider the key mechanisms of initiating and promoting AAA to achieve better preventative and therapeutic outcomes.

Prevalence of Genetic Variants and Deep Phenotyping in Patients with Thoracic Aortic Aneurysm and Dissection: A Cross-Sectional Single-Centre Cohort Study

BACKGROUND

There is a paucity of evidence on people with thoracic aortic aneurysm and dissection. We aimed to determine the prevalence of genetic variants and their associations with phenotypes.

METHODS

In this cross-sectional single-centre cohort study of consecutive patients who underwent endovascular or open-surgical repair of thoracic aortic aneurysm and dissection, genetic analysis was performed using four-stage Next Generation Sequencing, and findings were confirmed with Sanger sequencing. We collected personal and family history on comorbidities, clinical examination, anthropometrics, skeletal deformities, joint function, and ophthalmological measures. Cardiovascular risk and phenotype scores were calculated.

RESULTS

Ninety-five patients were eligible (mean age 54 ± 9 years, 70% males, 56% aortic dissection). One-fifth had a family history of aortic disease. Furthermore, 95% and 54% had a phenotype score of ≤5 and ≤2, respectively. There were no significant differences in the distribution of phenotype characteristics according to age, sex, aortic pathology, or performed invasive procedures. Genetic variants of uncertain significance were detected in 40% of patients, with classic mutations comprising 18% of all variants. We observed no significant association with cardiovascular and phenotype scores but with higher joint function scores (p = 0.015).

CONCLUSION

Genetic variants are highly present in clinically relevant aortic pathologies. Variants appear to play a larger role than previously described. The different variants do not correlate with specific phenotypes, age, pathology, sex, or family history.