Nonsyndromic genetic predisposition to aortic dissection: a newly recognized, diagnosable, and preventable occurrence in families

Total aortic arch debranching with antegrade Thoracic Endovascular Aortic Repair (TEVAR) in acute non-A non-B aortic dissection

BACKGROUND

The surgical evaluation and management of non-A non-B aortic dissections, in the absence of ascending aortic involvement, remains a grey area. It is in these scenarios when thorough evaluation of patient/family history, clinical presentation, but also overall lifestyle, is of immense importance when determining an optimal intervention.

CASE PRESENTATION

We present a 38-year-old patient with a physically demanding lifestyle as a professional wrestler, uncontrolled hypertension due to history of medical non-adherence, and family history of aortic dissection who presented with acute non-A non-B aortic dissection. He was spared a total arch replacement by undergoing a hybrid approach of complete aortic debranching with antegrade Thoracic Endovascular Aortic Repair (TEVAR). The patient was able to benefit from reduced cardiopulmonary bypass (CPB) time, avoidance of aortic cross clamp, circulatory arrest, and hypothermic circulation.

CONCLUSIONS

This patient's unique composition of a physically demanding lifestyle, personal history of medical non-adherence, family history of aortic dissection, and clinical presentation required a holistic approach to understanding an ideal intervention that would be best suited long-term. Due to this contextualization, the patient was able to be spared a total arch replacement, or suboptimal medical management, by instead undergoing a hybrid-approach with total aortic arch debranching with antegrade TEVAR.

The Genetics of Thoracic Aortic Aneurysms and Dissection: A Clinical Perspective

Thoracic aortic aneurysm and dissection (TAAD) affects many patients globally and has high mortality rates if undetected. Once thought to be solely a degenerative disease that afflicted the aorta due to high pressure and biomechanical stress, extensive investigation of the heritability and natural history of TAAD has shown a clear genetic basis for the disease. Here, we review both the cellular mechanisms and clinical manifestations of syndromic and non-syndromic TAAD. We particularly focus on genes that have been linked to dissection at diameters <5.0 cm, the current lower bound for surgical intervention. Genetic screening tests to identify patients with TAAD associated mutations that place them at high risk for dissection are also discussed.

Size and dissection: what is the relation?

Thoracic aortic aneurysm is a complex disease. The consequences of such silent and indolent disease include acute aortic syndrome if not recognized early and treated appropriately. Aortic aneurysm size was a reliable clinical marker to aid clinical intervention; however, aneurysm growth is variable and is influenced by many factors such as age, presence of connective tissue disorders, genetic disorders, hypertension, inflammatory conditions of the aorta, autoimmune diseases, smoking, and history of previous cardiac surgery. Therefore, aortic size became a non-specific disease surrogate and prediction tool on outcome and intervention. In this review article, we examined the current literature for evidence about aneurysm size and its relation to type A aortic dissection.

The natural history of type B aortic dissection in patients with PRKG1 mutation c.530G>A (p.Arg177Gln)

OBJECTIVE

The c.530G>A (p.Arg177Gln) mutation in PRKG1 has been shown to be associated with thoracic aortic aneurysms and dissections. This rare mutation accounts for an estimated 1% of nonsyndromic heritable thoracic aortic disease. We sought to describe the clinical presentation of type B aortic dissection (TBAD), management, and outcomes in patients with this mutation.

METHODS

This is a descriptive multi-institutional retrospective study of patients from six families with the PRKG1 mutation. Patients with TBAD were selected for analysis. Demographics, family histories, TBAD management, and outcomes were reviewed.

RESULTS

Of the 29 individuals diagnosed with the PRKG1 mutation, 12 (41.3%) had TBAD (50% male, TBAD median age: 31 years [range, 16-58 years], median follow-up: 6 years [range, 3-15 years] after TBAD). All had a family history of aortic dissections and none had features of Marfan syndrome. The median size of the descending thoracic aorta (DTA) at TBAD was 4.1 cm (range, 3.8-5 cm). Most cases (9 acute TBAD, 1 incidental TBAD diagnosis during screening) were managed medically. One case had open DTA repair the acute phase. Repair for dissection-related aneurysmal degeneration was performed in seven cases (58.3%) in the chronic phase at a median of 2 years (range, 1-8 years) after TBAD. In four cases (33.3%), the DTA remained stable in size over a range of 1 to 7 years after TBAD. Type A aortic dissection subsequent to TBAD occurred in three cases (25%). There were four (33.3%) deaths in the series, all aortic related at a median age of 24 years (range, 19-43 years).

CONCLUSIONS

The PRKG1 (p.Arg177Gln) mutation although rare is associated with nonsyndromic TBAD in young and middle-aged patients. Workup for this gene mutation should be included as part of the workup for TBAD etiology in relatively young patients and those with familial history of aortic dissections. Once diagnosed, testing of first-degree family members is warranted. In all individuals with a PRKG1 mutation, close follow-up for aortic root dilatation and hypertension control is essential to reduce the risk of type A or type B aortic dissection, and in cases of TBAD, to decrease the risk of dissection-related aneurysmal degeneration.

Postmortem genetic testing should be recommended in sudden cardiac death cases due to thoracic aortic dissection

BACKGROUND

Acute thoracic aortic dissections and ruptures, the main life-threatening complications of the corresponding aneurysms, are an important cause of sudden cardiac death. Despite the usefulness of the molecular diagnosis of these conditions in the clinical setting, the corresponding forensic field remains largely unexplored. The main goal of this study was to explore and validate a new massive parallel sequencing candidate gene​ assay as a diagnostic tool for acute thoracic aortic dissection autopsy cases.

MATERIALS AND METHODS

Massive parallel sequencing of 22 thoracic aortic disease candidate genes performed in 17 cases of thoracic aortic dissection using AmpliSeq and Ion Proton technologies. Genetic variants were filtered by location, type, and frequency at the Exome Aggregation Consortium and an internal database and further classified based on the American College of Medical Genetics and Genomics (ACMG) recommendations published in 2015. All prioritized results were confirmed by traditional sequencing.

RESULTS

From the total of 10 potentially pathogenic genetic variants identified in 7 out of the 17 initial samples, 2 of them were further classified as pathogenic, 2 as likely pathogenic, 1 as possibly benign, and the remaining 5 as variants of uncertain significance, reaching a molecular autopsy yield of 23%, approximately.

CONCLUSIONS

This massive parallel sequencing candidate gene approach proved useful for the molecular autopsy of aortic dissection sudden cardiac death cases and should therefore be progressively incorporated into the forensic field, being especially beneficial for the anticipated diagnosis and risk stratification of any other family member at risk of developing the same condition.

Whole exome sequencing for the identification of a new mutation in TGFB2 involved in a familial case of non-syndromic aortic disease

BACKGROUND

Non-syndromic aortic disease (NSAD) is a frequently asymptomatic but potentially lethal disease characterised by familial cases of thoracic aortic aneurysms and dissections. This monogenic but genetically heterogeneous condition is primarily inherited as an autosomal dominant disorder with low penetrance and variable expression. Mutations in ACTA2, TGFBR1, TGFBR2, MYH11, SMAD3, MYLK, and FBN1 genes have been described but still, there are many unresolved familial cases.

METHODS

The whole exome of two distantly related and affected members of a Spanish family with multiple cases of NSAD was analysed through 5500 SOLiD(™) System for the identification of shared and putative pathogenic variants.

RESULTS

A new mutation termed c.C1042T:p.R348C (NM_001135599.2) was identified in TGFB2, a gene located in an evolutionary highly conserved region (Chr1: 218,519,577-218,617,961) that has been recently connected to this disease. The analysis of other family members using capillary sequencing confirmed cosegregation of the mutation with the disease and its incomplete penetrance.

CONCLUSIONS

The repeated implication of TGFB2 in the development of thoracic aortic aneurysms and dissections suggests that this gene should be considered during genetic diagnosis of this disease. An accurate diagnosis of affected individuals and additional family members at risk allows for a personalised and more efficient gene-based follow-up and treatment. Finally, the reiterative presence of common musculoskeletal and craniofacial additional features in patients with TGFB2 mutations suggests the existence of a new yet undefined connective tissue syndrome responsible for not only aortic dilation, but also for the other extracardiac alterations present in the affected patients.

Aortic dilatation in children with systemic hypertension

The aim of the study was to determine the presence of aortic dilatation in hypertensive children, the prevalence of which is 4% to 10% in hypertensive adults. Prospectively enrolled multiethnic children, untreated for their hypertension, underwent an echocardiogram to exclude congenital heart disease and evaluate for end-organ damage and aortic size. The aorta was measured in the parasternal long-axis view at three levels: the sinus of Valsalva, supra-tubular junction, and the ascending aorta. Aortic dilatation was determined by z-score >2 at any one of the levels measured. Hypertension was defined as blood pressure above the 95th percentile based on the Fourth Working Group criteria confirmed by 24-hour ambulatory blood pressure monitoring. Among 142 consecutive hypertensive children (median age, 14 years; 45% females) aortic dilatation was detected in 2.8% (95% confidence interval, 1%-7%; median age, 16 years; 100% females). Children with aortic dilatation, when compared with those without, had significantly more aortic valve insufficiency (P = .005) and left ventricular hypertrophy (P = .018). Prevalence of aortic dilatation was 2.8% and was associated with significantly more aortic insufficiency and left ventricular hypertrophy in comparison to those without aortic dilatation.

A case of acute aortic dissection presenting with chest pain relieved by sublingual nitroglycerin

Acute aortic dissection is an uncommon disorder which can have fatal results in the event of treatment delay or misdiagnosis. This case examines a 77-year-old woman presenting with chest pain relieved by nitroglycerin. She was referred to the emergency room with clinical suspicion of acute coronary syndrome (ACS). However, she was later diagnosed with acute aortic dissection and an emergency operation was performed with successful recovery. Aortic dissection may manifest in various ways depending on the site involved and may mimic other disorders such as ACS or pulmonary embolism. Therefore, clinicians must always be aware of aortic dissection and its different clinical manifestations must be understood.

High-density oligonucleotide-based resequencing assay for mutations causing syndromic and non-syndromic forms of thoracic aortic aneurysms and dissections

Thoracic aortic aneurysm and dissection is associated with increasing mortality rate that may occur as part of a syndrome or as an isolated familial condition. Several genes have been implicated in causing TAAD, though an appropriate genetic test for their parallel testing is not yet available. Herein, we describe the novel 117-kb "MFSTAAD chip" that may help to understand the genetic basis of TAAD. A custom duplicate resequencing assay was developed to cover eight genes previously described in TAAD; FBN1, TGFBR1&2, COL3A1, MYH11, ACTA2, SLC2A10 and NOTCH1. GSEQ and SeqC software were used for data analysis. The analytical sensitivity of the assay was validated by the recognition of 182 known mutations (153 point mutations, 21 deletions, 7 insertions and 1 duplication) and a cohort of 28 patients were selected to determine the mutation yield, whereby 18 of them were previously negative for mutations in the genes FBN1 and TGFBR2. The assay had significantly higher sensitivity for point mutations (100%) and the largest deletion of 16 bp was detectable through a decline in the hybridization strength. The overall analytical sensitivity was 85%. Mutation testing of 28 unrelated TAAD patients revealed 4 known and 6 possibly pathogenic mutations with a mutation yield of 32%. The MFSTAAD chip is an alternative tool to next-generation sequencing that allows parallel analysis of several genes on a single platform. Refinements in the probe design and data analysis software will increase the analytical sensitivity of insertions and deletions making this assay even more applicable for clinical testing.

Novel genetic mechanisms for aortic aneurysms

Aortic aneurysms occur in the thoracic and abdominal sections of the aorta and are a deadly late-age-at-onset disease with complex pathobiology. Currently, the number of published genome-wide analyses including microarray-based expression profiling, DNA linkage studies, and genetic association studies is still limited and it is difficult to make generalizations about the disease pathogenesis or genetic risk factors contributing to aortic aneurysms, but it appears that thoracic aortic aneurysms differ in many ways from abdominal aortic aneurysms. Characterization of diseases at the molecular level is likely to lead to more accurate diagnoses and the use of "genomic nosology" of disease. The biggest future challenge will be to translate the genomic information to the clinic and improve our understanding of the disease processes, help us to develop better diagnostic tools, and lead to the design of new ways to manage aortic aneurysms in the era of personalized medicine.

Gene expression signature in peripheral blood detects thoracic aortic aneurysm

Background

Thoracic aortic aneurysm (TAA) is usually asymptomatic and associated with high mortality. Adverse clinical outcome of TAA is preventable by elective surgical repair; however, identifying at-risk individuals is difficult. We hypothesized that gene expression patterns in peripheral blood cells may correlate with TAA disease status. Our goal was to identify a distinct gene expression signature in peripheral blood that may identify individuals at risk for TAA.

Methods and Findings

Whole genome gene expression profiles from 94 peripheral blood samples (collected from 58 individuals with TAA and 36 controls) were analyzed. Significance Analysis of Microarray (SAM) identified potential signature genes characterizing TAA vs. normal, ascending vs. descending TAA, and sporadic vs. familial TAA. Using a training set containing 36 TAA patients and 25 controls, a 41-gene classification model was constructed for detecting TAA status and an overall accuracy of 78±6% was achieved. Testing this classifier on an independent validation set containing 22 TAA samples and 11 controls yielded an overall classification accuracy of 78%. These 41 classifier genes were further validated by TaqMan® real-time PCR assays. Classification based on the TaqMan® data replicated the microarray results and achieved 80% classification accuracy on the testing set.

Conclusions

This study identified informative gene expression signatures in peripheral blood cells that can characterize TAA status and subtypes of TAA. Moreover, a 41-gene classifier based on expression signature can identify TAA patients with high accuracy. The transcriptional programs in peripheral blood leading to the identification of these markers also provide insights into the mechanism of development of aortic aneurysms and highlight potential targets for therapeutic intervention. The classifier genes identified in this study, and validated by TaqMan® real-time PCR, define a set of promising potential diagnostic markers, setting the stage for a blood-based gene expression test to facilitate early detection of TAA.

Litigation in Nontraumatic Aortic Diseases – A Tempest in the Malpractice Maelstrom

OBJECTIVES

Physicians are vulnerable to highly litigated thoracic aortic diseases. On the basis of a review of litigated cases, we aim to determine legally protective strategies for physicians and methods to improve treatment.

METHODS

Thirty-three nontraumatic, thoracic aorta-related legal cases were analyzed.

RESULTS

Twenty-three patients (69.7%) had dissections (21 ascending, 2 descending), 8 (24.2%) had aneurysms and 2 had miscellaneous other phenomena (1 coarctation and 1 iatrogenic descending aortic rupture). The adverse event was death in 30 (90.9%) patients and paraplegia or stroke in 3 (9.1%). Allegations included: failure/delay in diagnosis (19), delay in surgery (4), error in surgical technique (5), failure to prevent paraplegia (2) and miscellaneous (3). Medical treatment was retrospectively judged suboptimal in 22 cases (66.6%) for reasons consonant with allegations.

CONCLUSIONS

Aortic disease can be diagnostically elusive, as 'the great masquerader'. Emergency physicians must maintain a high index of suspicion for aneurysm and dissection. The D-dimer test can effectively rule out aortic dissection. 'Triple rule-out' CT scans should be performed liberally. CT scan readers must remember to evaluate the aorta. Operating room administrators must be aware that postponing a scheduled thoracic aortic case may result in interim rupture and consequent litigation. With virulent thoracic aortic diseases, adverse outcome itself does not imply substandard care.

Biglycan deficiency causes spontaneous aortic dissection and rupture in mice

BACKGROUND

For the majority of cases, the cause of spontaneous aortic dissection and rupture is unknown. An inherited risk is associated with Marfan syndrome, Ehlers-Danlos syndrome type IV, and loci mapped to diverse autosomal chromosomes. Analysis of pedigrees however has indicated that it may be also inherited as an X-linked trait. The biglycan gene, found on chromosome X in humans and mice, encodes a small leucine-rich proteoglycan involved in the integrity of the extracellular matrix. A vascular phenotype has never been described in mice deficient in the gene for small leucine-rich proteoglycans. In the breeding of BALB/cA mice homozygous for a null mutation of the biglycan gene, we observed that 50% of biglycan-deficient male mice died suddenly within the first 3 months of life.

METHODS AND RESULTS

Necropsies revealed a major hemorrhage in the thoracic or abdominal cavity, and histology showed aortic rupture that involved an intimal and medial tear as well as dissection between the media and adventitia. By transmission electron microscopy and biomechanical testing, the aortas of biglycan-deficient mice showed structural abnormalities of collagen fibrils and reduced tensile strength. Similar collagen fibril changes were observed in male as well as in female biglycan-deficient mice, which implies a role of additional determinants such as gender-related response to stress in the development of this vascular catastrophe only in male mice.

CONCLUSIONS

The spontaneous death of biglycan-deficient male mice from aortic rupture implicates biglycan as essential for the structural and functional integrity of the aortic wall and suggests a potential role of biglycan gene defects in the pathogenesis of aortic dissection and rupture in humans.

Familial thoracic aortic aneurysms and dissections--incidence, modes of inheritance, and phenotypic patterns

BACKGROUND

We examined the genetic nature and phenotypic features of thoracic aortic aneurysms (TAAs) and dissections in a large cohort of patients.

METHODS

Interviews were conducted with 520 patients with TAAs and their pedigrees were compiled to identify family members with aneurysms. Study patients were divided into three groups: 101 non-Marfan patients, in 88 pedigrees, had a family pattern for TAA (familial group), 369 had no family pattern (sporadic group), and 50 had Marfan syndrome (MFS). We determined incidence of familial clustering, age at presentation, rate of aneurysm growth, incidence of hypertension, correlation of aneurysm sites among kindred, and pedigree inheritance patterns.

RESULTS

An inherited pattern for TAA was present in 21.5% of non-MFS patients. The predominant inheritance pattern was autosomal dominant (76.9%), with varying degrees of penetrance and expressivity. The familial TAA group was significantly younger than the sporadic group (p < 0.0001), but not as young as the MFS group (p < 0.0001) (mean ages, 58.2 versus 65.7 versus 27.4 years). Among all 197 probands and kindred with aneurysm, 131 (66.5%) had TAA, 49 (24.9%) had abdominal aortic aneurysm (AAA), and 17 (8.6%) had cerebral or other aneurysms. Ascending aneurysm paired most commonly with ascending, and descending with abdominal. Abdominal aortic aneurysms (AAAs) and hypertension were more often associated with descending than with ascending TAAs (p < 0.001). Aortic growth rate was highest for the familial group (0.21 cm/y), intermediate for the sporadic group (0.16 cm/y), and lowest for the Marfan group (0.1 cm/y; p < 0.01).

CONCLUSIONS

TAAs are frequently familial diseases. The predominant mode of inheritance is autosomal dominant. Familial TAAs have a relatively early age of onset. Aneurysms in relatives may be seen in the thoracic aorta, the abdominal aorta, or the cerebral circulation. Screening of first-order relatives of probands with TAA is essential. Familial TAAs tend to grow at a higher rate, exemplifying a more aggressive clinical entity.

Heritable Disorders Predisposing to Aortic Dissection

Heritable disorders of connective tissue often predispose patients to aortic pathology and in particular aortic dissection. The Marfan syndrome, vascular Ehlers-Danlos syndrome, familial forms of thoracic aortic aneurysms or aortic dissection, and bicuspid aortic valve are all examples of heritable disorders that have associated defects affecting the integrity of the aortic wall, posing a risk of both aneurysmal dilation and dissection. The purpose of this review was to outline the phenotypes of the heritable syndromes that predispose to aortic dissection, present a guideline to their management and surveillance, and to offer insight into some of the surgical pitfalls that occur when repairing ascending aortic dissections in these types of patients.

Newly mapped gene for thoracic aortic aneurysm and dissection

Thoracic aortic aneurysm and dissection (TAAD) is associated with high mortality and medical expense. These poor outcomes are preventable by surgical repair; however, identifying at-risk individuals is difficult. Researchers are actively surveying the human genome (the repository of human genes) to characterize the genetic determinants of TAAD by identifying chromosomal regions likely to harbor such predisposing genes. In previous studies, investigators identified genetic markers shared by a subset of families who were ascertained to have the disease, which clustered into 2 chromosomal regions: 5q13-q15 (TAAD1) and 11q23.2-q24 (familial aortic aneurysm [FAA1]). In a subsequent study, a third chromosomal region at 3p24-25 (TAAD2) was found to contribute to TAAD in a 4-generation, 52-member family that displayed little evidence of sharing either the TAAD1 or FAA1 regions. Although additional regions of the genome may contribute to TAAD, investigators are focusing their efforts on identifying the actual genes and the specific mutations that participate in the disease process. The goal of these endeavors is to develop screening tests to identify individuals at risk for familial TAAD. This genetic discovery has significant clinical implications because high-risk individuals and families can be closely monitored and can benefit from preventative surgical repairs.