Susceptibility to acute thoracic aortic dissections in patients dying outside the hospital: an autopsy study

Unveiling cellular and molecular aspects of ascending thoracic aortic aneurysms and dissections

Ascending thoracic aortic aneurysm (ATAA) remains a significant medical concern, with its asymptomatic nature posing diagnostic and monitoring challenges, thereby increasing the risk of aortic wall dissection and rupture. Current management of aortic repair relies on an aortic diameter threshold. However, this approach underestimates the complexity of aortic wall disease due to important knowledge gaps in understanding its underlying pathologic mechanisms.Since traditional risk factors cannot explain the initiation and progression of ATAA leading to dissection, local vascular factors such as extracellular matrix (ECM) and vascular smooth muscle cells (VSMCs) might harbor targets for early diagnosis and intervention. Derived from diverse embryonic lineages, VSMCs exhibit varied responses to genetic abnormalities that regulate their contractility. The transition of VSMCs into different phenotypes is an adaptive response to stress stimuli such as hemodynamic changes resulting from cardiovascular disease, aging, lifestyle, and genetic predisposition. Upon longer exposure to stress stimuli, VSMC phenotypic switching can instigate pathologic remodeling that contributes to the pathogenesis of ATAA.This review aims to illuminate the current understanding of cellular and molecular characteristics associated with ATAA and dissection, emphasizing the need for a more nuanced comprehension of the impaired ECM-VSMC network.

The characteristics of thoracic aortic dissection in autopsy-diagnosed individuals: An autopsy study

Thoracic aortic dissection (TAD) is the most common cause of sudden cardiac death associated with aortic diseases. The age of TAD victims in forensic studies is significantly younger than hospitalized patients with TAD, while only a few studies have been conducted on autopsy-diagnosed TAD deceased. A retrospective study was conducted at the Medicolegal Center of Sun Yat-sen University from 1999 to 2019 to address the characteristics of TAD victims. A total of 200 deceased from spontaneous rupture of TAD were assessed, with 165 (82.5%) males and 175 (87.5%) Stanford type A deceased. Our main results showed that compared with patients with TAD diagnosed during their lifetime, individuals diagnosed with TAD until an autopsy showed an earlier onset (43.80 years old) and less accompanied hypertension (<50%). Sudden death was the initial symptom of 32 decedents. Instead of chest/back pain (40 decedents), abdominal pain (59 decedents) was the most common initial symptom, and 42 decedents presented with no accompanying pain. A higher proportion of abdominal pain and the painless symptom was associated with a higher risk of misdiagnosis. Women showed a more atypical clinical presentation and rapid progression than men. Younger decedents showed more pronounced left heart changes. The present study implicated the TAD individuals diagnosed until an autopsy as a particular entity, indicating the urgent need for further investigation on early diagnosis and pathogenesis of patients with TAD with atypical pain and painless or with younger age to reduce the burden of TAD-related sudden death.

A Systematic Review and Meta-analysis of the Incidence of Acute Aortic Dissections in Population-Based Studies

OBJECTIVE

To perform a systematic-review and meta-analysis of all population-based studies reporting on incidence of acute aortic dissections.

METHODS

We searched MEDLINE, EMBASE, CENTRAL and Open Grey databases from inception to August 2020 for population-based studies reporting on the incidence of AAD. A systematic review was conducted following the PRISMA guidelines using a registered protocol (CRD42020204007). Data was pooled using a random-effects model of proportions using Freeman-Tukey double arcsine transformation. The main outcome was the incidence of AAD. Secondary outcomes were incidence type A aortic dissections (TAAD) and type B aortic dissections (TBAD); incidence of aortic dissection repair and medical management and incidence of in-hospital mortality. In addition, we estimated the proportion of aortic dissection repair and mortality (in hospital, overall and specific mortality according to sub-type) among patients with AAD.

RESULTS

Thirty-three studies were included. The pooled incidence of AADs was 4.8 per 100 000 individuals/year (95%CI: 3.6; 6.1). Incidence of TAAD was 3.0 per 100 000/year (95%CI: 1.8; 4.4) and incidence of TBAD was 1.6 per 100 000/year (95%CI: 1.1; 2.2). The incidence of AAD needing repair was 1.4 per 100 000/year (95%CI: 1.0; 2.0) [1.4 (95%CI: 1.2; 1.7) for TAAD and 0.4 (95%CI: 0.2; 0.7) for TBAD]. Incidence of medically managed AAD was 3.4 per 100 000/year (95%CI: 2.4; 4.5). Incidence of in-hospital death due to AAD was 1.3 per 100 000 individuals/year (95%CI: 0.9; 1.9); 1.0 (95%CI: 0.6; 1.4; I²97%) for TAAD and 0.3 for TBAD (95%CI: 0.2; 0.4; I²96%).

CONCLUSION

A global estimate regarding the incidence rate of acute aortic dissections was achieved. Incidence of acute aortic dissection varied significantly between study designs and geographical regions. More accurate information on acute aortic dissection epidemiology is crucial for public-health decisions, clinical understanding, and healthcare management.

Marfan syndrome

Marfan syndrome (MFS) is an autosomal dominant, age-related but highly penetrant condition with substantial intrafamilial and interfamilial variability. MFS is caused by pathogenetic variants in FBN1, which encodes fibrillin-1, a major structural component of the extracellular matrix that provides support to connective tissues, particularly in arteries, the pericondrium and structures in the eye. Up to 25% of individuals with MFS have de novo variants. The most prominent manifestations of MFS are asymptomatic aortic root aneurysms, aortic dissections, dislocation of the ocular lens (ectopia lentis) and skeletal abnormalities that are characterized by overgrowth of the long bones. MFS is diagnosed based on the Ghent II nosology; genetic testing confirming the presence of a FBN1 pathogenetic variant is not always required for diagnosis but can help distinguish MFS from other heritable thoracic aortic disease syndromes that can present with skeletal features similar to those in MFS. Untreated aortic root aneurysms can progress to life-threatening acute aortic dissections. Management of MFS requires medical therapy to slow the rate of growth of aneurysms and decrease the risk of dissection. Routine surveillance with imaging techniques such as transthoracic echocardiography, CT or MRI is necessary to monitor aneurysm growth and determine when to perform prophylactic repair surgery to prevent an acute aortic dissection.

COL5A1 Variants Cause Aortic Dissection by Activating TGF-β-Signaling Pathway

Background

Aortic dissection (AD) is one of the most life‐threatening cardiovascular diseases that exhibit high genetic heterogeneity. However, it is unclear whether variants within the COL5A1 gene can cause AD. Therefore, we intend to determine whether COL5A1 is a causative gene of AD.

Methods and Results

We performed targeted sequencing in 702 patients with unrelated sporadic AD and 163 matched healthy controls using a predesigned panel with 152 vessel matrix‐related genes. As a result, we identified that 11 variants in COL5A1 caused AD in 11 out of the 702 patients with AD. Furthermore, Col5a1 knockout (Col5a1^+/−) rats were generated through the CRISPR/Cas9 system. Although there was no spontaneous AD, electron microscopy revealed a fracture of elastic fibers and disarray of collagenous fibers in 6‐week‐old Col5a1^+/− rats, but not in WT rats (93.3% versus 0.0%, P<0.001). Three‐week‐old rats were used to induce the AD phenotype with β‐aminopropionitrile monofumarate for 4 weeks followed by angiotensin II for 72 hours. The β‐aminopropionitrile monofumarate and angiotensin II‐treated rat model confirmed that Col5a1^+/− rats had considerably higher AD incidence than WT rats. Subsequent mechanism analyses demonstrated that the transforming growth factor‐β‐signaling pathway was significantly activated in Col5a1^+/− rats.

Conclusions

Our findings, for the first time, revealed a relationship between variants in COL5A1 and AD via targeted sequencing in 1.57% patients with sporadic aortic dissection. The Col5a1 knockout rats exhibited AD after an intervention, indicating that COL5A1 is a causative gene of AD. Activation of the transforming growth factor‐β‐signaling pathway may be implicated in the pathogenesis of this kind of AD.

Left Ventricular Hypertrophy Is More Prevalent in Type B than Type A Aortic Dissection

OBJECTIVES

Several factors determining differences between types A and B aortic dissection (AD) have been reported; however, little data exist examining their differences in left ventricular hypertrophy (LVH). We compared the prevalence of LVH in patients with types A and B AD.

METHODS

We retrospectively analyzed 334 patients with acute AD (227 type A; 107 type B). Concentric hypertrophy (CH; increased left ventricular mass index [LVMI] and relative wall thickness [RWT]) is one of four types of left ventricular (LV) geometry thought to be most associated with hypertension. We compared LVMI and the prevalence of CH in patients with types A or B AD. Multivariate logistic regression analyses of variables associated with type B AD were performed.

RESULTS

Comparing type A and B AD, LVMI (95 ± 26 vs.107 ± 28, p <0.001) and prevalence of CH (26% vs. 44%, p = 0.001) were higher in type B AD. In multivariate analysis, CH was an independent factor associated with type B AD (odds ratio: 2.62, confidence interval: 1.54-4.47, p <0.001).

CONCLUSIONS

Our data suggested LVH was more prevalent in type B than in type A AD. Considering LVH usually results from hypertension, patients with type B AD may be more affected by hypertension than those with type A.

Genetic aortic disease epidemiology, management principles, and disparities in care

Patients with syndromic and nonsyndromic heritable aortopathies (also known as genetic aortic disease) are a heterogeneous group of patients who present at younger ages with more rapid growth of aortic aneurysms and/or increased frequency of dissections compared with patients with atherosclerotic aortopathies. In this review, we describe the etiology, epidemiology, and appropriate care delivery for these conditions at each stage of management. Within each section, we discuss sex, gender, and race differences and highlight disparities in care and knowledge. We then discuss the role of the vascular team throughout the cycle of care and the evolving inclusion of patient input in research. This understanding is essential to the creation of effective health care policies that support equitable, appropriate, and patient-centered clinical practices.

Genetics of Thoracic and Abdominal Aortic Diseases

Dissections or ruptures of aortic aneurysms remain a leading cause of death in the developed world, with the majority of deaths being preventable if individuals at risk are identified and properly managed. Genetic variants predispose individuals to these aortic diseases. In the case of thoracic aortic aneurysm and dissections (thoracic aortic disease), genetic data can be used to identify some at-risk individuals and dictate management of the associated vascular disease. For abdominal aortic aneurysms, genetic associations have been identified, which provide insight on the molecular pathogenesis but cannot be used clinically yet to identify individuals at risk for abdominal aortic aneurysms. This compendium will discuss our current understanding of the genetic basis of thoracic aortic disease and abdominal aortic aneurysm disease. Although both diseases share several pathogenic similarities, including proteolytic elastic tissue degeneration and smooth muscle dysfunction, they also have several distinct differences, including population prevalence and modes of inheritance.

SMAD4 rare variants in individuals and families with thoracic aortic aneurysms and dissections

SMAD4 pathogenic variants cause juvenile polyposis (JPS) and hereditary hemorrhagic telangiectasia (HHT), and 40% of affected individuals also have thoracic aortic disease. At the same time, SMAD4 pathogenic variants have not been reported in thoracic aortic disease families without JPS-HHT. A SMAD4 heterozygous variant, c.290G>T, p.(Arg97Leu), not present in population databases and predicted to be damaging to protein function, was identified in a family with thoracic aortic disease and no evidence of HHT or JPS. Cellular studies revealed that the SMAD4 p.(Arg97Leu) alteration increased SMAD4 ubiquitination and 26S proteasome-mediated protein degradation. Smooth muscle cells (SMCs) infected with lentivirus expressing the SMAD4 p.(Arg97Leu) variant demonstrated reduced contractile protein gene expression when compared to that of wild-type SMAD4. In addition, two rare variants were identified in individuals with early age of onset of thoracic aortic dissection. These results suggest that SMAD4 rare missense variants can lead to thoracic aortic disease in individuals who do not have JPS or HHT.

Pathobiology of cardiovascular diseases: an update

This article introduces the Second Special Issue of Cardiovascular Pathology (CVP), the official journal of the Society for Cardiovascular Pathology (SCVP). This CVP Special Issue showcases a series of commemorative review articles in celebration of the 25th anniversary of CVP originally published in 2016 and now compiled into a virtual collection with online access for the cardiovascular pathology community. This overview also provides updates on the major categories of cardiovascular diseases from the perspective of cardiovascular pathologists, highlighting publications from CVP, as well as additional important review articles and clinicopathologic references.

Left ventricular hypertrophy is a possible biomarker for early mortality after type B aortic dissection

OBJECTIVE

Data regarding the cardiac abnormalities associated with Stanford type B aortic dissection (TBAD) and whether these abnormalities are related to outcomes are limited. We describe the prevalence of cardiac abnormalities in patients with TBAD as detected by echocardiography.

METHODS

This retrospective review included patients with TBAD presenting between 1990 and 2016. Echocardiograms performed within 6 weeks of acute TBAD were reviewed. Cardiac function, valve abnormalities, and stigmata of hypertensive heart disease including left ventricular hypertrophy (LVH) were ascertained. Characteristics of patients who did and did not receive echocardiograms were compared. Outcomes of patients with and without evidence of LVH on echocardiography were also compared.

RESULTS

Of 239 patients with TBAD, 90 had echocardiograms performed within 6 weeks of acute TBAD (74% male; mean age, 57.8 ± 13.2 years). Echocardiograms were obtained at a median of 2 days (range, 0-41 days) from acute TBAD. Patients who had echocardiograms were more likely to present with malperfusion (28% vs 14%; P < .01) and had a trend toward increased operative repair during the subacute phase (17.4% vs 9.5%; P = .07) compared with patients who did not receive an echocardiogram. A majority of patients (57%) had at least mild LVH, including 39% of patients without a prior diagnosis of hypertension. Fibrocalcific changes associated with hypertension, including aortic sclerosis and mitral annular calcification, were noted in 40% and 11% of the patients, respectively. Among patients with LVH, there was a trend toward higher all-cause mortality (35% vs 23%; P = .21) and a younger age at death (58 ± 14 years vs 66 ± 13 years; P = .19) despite a similar age at TBAD onset. In a multivariable analysis controlling for age, sex, and admission estimated glomerular filtration rate, LVH independently predicted all-cause mortality (hazard ratio, 2.38; 95% confidence interval, 1.02-5.56; P = .04).

CONCLUSIONS

LVH and other findings of hypertensive heart disease are common in patients with TBAD. LVH predicted all-cause mortality after TBAD in this small group of patients. Further exploration of the relationship between the chronic effects of hypertension and using LVH as an objective biomarker to risk stratify patients with TBAD and long-term outcomes after TBAD is warranted.

Therapeutics Targeting Drivers of Thoracic Aortic Aneurysms and Acute Aortic Dissections: Insights from Predisposing Genes and Mouse Models

Thoracic aortic diseases, including aneurysms and dissections of the thoracic aorta, are a major cause of morbidity and mortality. Risk factors for thoracic aortic disease include increased hemodynamic forces on the ascending aorta, typically due to poorly controlled hypertension, and heritable genetic variants. The altered genes predisposing to thoracic aortic disease either disrupt smooth muscle cell (SMC) contraction or adherence to an impaired extracellular matrix, or decrease canonical transforming growth factor beta (TGF-β) signaling. Paradoxically, TGF-β hyperactivity has been postulated to be the primary driver for the disease. More recently, it has been proposed that the response of aortic SMCs to the hemodynamic load on a structurally defective aorta is the primary driver of thoracic aortic disease, and that TGF-β overactivity in diseased aortas is a secondary, unproductive response to restore tissue function. The engineering of mouse models of inherited aortopathies has identified potential therapeutic agents to prevent thoracic aortic disease.

Perspectives on the revised Ghent criteria for the diagnosis of Marfan syndrome

Three international nosologies have been proposed for the diagnosis of Marfan syndrome (MFS): the Berlin nosology in 1988; the Ghent nosology in 1996 (Ghent-1); and the revised Ghent nosology in 2010 (Ghent-2). We reviewed the literature and discussed the challenges and concepts of diagnosing MFS in adults. Ghent-1 proposed more stringent clinical criteria, which led to the confirmation of MFS in only 32%–53% of patients formerly diagnosed with MFS according to the Berlin nosology. Conversely, both the Ghent-1 and Ghent-2 nosologies diagnosed MFS, and both yielded similar frequencies of MFS in persons with a causative FBN1 mutation (90% for Ghent-1 versus 92% for Ghent-2) and in persons not having a causative FBN1 mutation (15% versus 13%). Quality criteria for diagnostic methods include objectivity, reliability, and validity. However, the nosology-based diagnosis of MFS lacks a diagnostic reference standard and, hence, quality criteria such as sensitivity, specificity, or accuracy cannot be assessed. Medical utility of diagnosis implies congruency with the historical criteria of MFS, as well as with information about the etiology, pathogenesis, diagnostic triggers, prognostic triggers, and potential complications of MFS. In addition, social and psychological utilities of diagnostic criteria include acceptance by patients, patient organizations, clinicians and scientists, practicability, costs, and the reduction of anxiety. Since the utility of a diagnosis or exclusion of MFS is context-dependent, prioritization of utilities is a strategic decision in the process of nosology development. Screening tests for MFS should be used to identify persons with MFS. To confirm the diagnosis of MFS, Ghent-1 and Ghent-2 perform similarly, but Ghent-2 is easier to use. To maximize the utility of the diagnostic criteria of MFS, a fair and transparent process of nosology development is essential.

Bicuspid aortic valve: inter-racial difference in frequency and aortic dimensions

OBJECTIVES

The objective of this study was to examine the similarities and differences in Caucasian (C) and African-American (AA) patients with bicuspid aortic valve (BAV) with respect to morphology, severity of aortic stenosis/insufficiency, and aortic dilation.

BACKGROUND

BAV is a common congenital valve abnormality, accounting for a large number of valve replacements.

METHODS

A total of 229 patients with the diagnostic code BAV were identified retrospectively from our computerized adult echocardiographic database, which consists of 91,896 studies performed at the University of Chicago Medical Center from 1998 to 2009, representing 40,878 patients. Of those, 183 patients with BAV were included in this retrospective BAV single-center cohort study and reanalyzed with a comprehensive assessment of aortic dimensions, aortic valve morphology and function, clinical cardiovascular risk factors, and patient characteristics.

RESULTS

Of the 183 patients with BAV, 138 were C and 45 were AA. Our echocardiographic database encompasses approximately 65% AA, 31% C, and 4% other races, for an estimated frequency of BAV in AA patients of 0.17% and a frequency in C patients of 1.1% (p = 0.001). There were no significant inter-racial differences regarding sex, height, weight, hyperlipidemia, diabetes, tobacco use, cardiac medications, and left ventricular ejection fraction. The AA cohort was older (age 50 ± 17 years vs. 43 ± 17 years, p < 0.05) and had a higher prevalence of hypertension (51% vs. 24%, p < 0.05). After adjusting for comorbidities, aortic dimensions were larger in C (C vs. AA: annulus, 2.4 ± 0.4 vs. 2.1 ± 0.4 cm; sinuses of Valsalva, 3.4 ± 0.7 vs. 3.1 ± 0.6 cm; sinotubular junction, 3.0 ± 0.6 vs. 2.6 ± 0.5 cm; and ascending aorta, 3.5 ± 0.7 vs. 3.2 ± 0.5 cm; all p values <0.05).

CONCLUSIONS

This is the first study to report racial differences among patients with BAV with reduced aortic dimensions in AA patients despite the presence of more risk factors, suggestive of marked heterogeneity in the BAV population and indicating race as a potential disease modifier in BAV.

Is Race Determination in the Medicolegal Setting Important?

Racial designations have evolved over the years to accommodate the changes in our population demographics. The Federal Office of Management and Budget (OMB) has developed Federal Standards to assist with the uniform documentation and reporting of race and ethnicity. A minimum of five defined categories currently exist for race (American Indian or Alaska Native, Asian, Black or African American, Native Hawaiian or Other Pacific Islander and White). Ethnicity is separated into either Hispanic origin or Non-Hispanic origin. Current death certificates allow for the selection of one or more races; however, only one ethnicity may be chosen. Race of unknown decedents is either based subjectively on the observer's opinion or, in severely decomposed or skeletal remains, by anthropological analysis utilizing sound statistical methodology. If the data and statistical analysis suggest a good classification, the race determination will be correct more often than not. Information obtained from the National Missing and Unidentified Persons System (NamUs) indicates that absence of race determination does not hinder the identification potential. Mortality rates, life expectancy, disease risk and causes of death are often disaggregated by race and/or ethnicity. Differences in the presentation, etiology and outcomes of many diseases have been based on race and ethnicity data. Uniform collection of this data is the key to its importance. Medical examiners, coroners and others tasked with examination of decedents should utilize the defined categories set forth in the OMB Revised Standards for race and ethnicity documentation.