Redefining the histopathologic profile of acute aortic syndromes: Clinical and prognostic implications

The Cardiovascular Pathologist in the Aortic Team

Aortic diseases require a multidisciplinary management for diagnosis, treatment and follow-up with better outcomes in referral centers using a team-based approach. The setting up of a multi-disciplinary aortic team for the discussion of complex cases has been already proposed; it is also supported by the ACC/AHA. Surgeons and radiologists, more or less other physicians such as cardiologists, geneticists, rheumatologists/internal medicine specialists and pathologists are involved into such a team. The role of the cardiovascular pathologist is to examine the aortic specimens, to diagnose and classify the aortic lesions. Herein, the role of the pathologist in the aortic team is discussed and the pathobiology of aortic diseases is reviewed for reference by pathologists. The aortic specimens are mainly obtained from emergency or elective surgical procedures on the thoracic aorta, less frequently from organ/tissue (including cardiac or heart valve) donors, post-mortem procedures or abdominal aortic surgery. In the last decade, together with the progress of medical sciences, the histological definitions and classifications of the aortic pathology are undergoing thorough revisions that are addressed to an etiopathogenetic approach because of possible clinico-pathological correlations, therapeutic and prognostic impact. Pathologists may also have an important role in research and teaching. Therefore, histological analyses of the aortic specimens require adequate sample processing and pathologist expertise because histology contributes to definite diagnosis, correct management of patients and even (in genetic diseases) families, but also to research in the challenging field of aortopathies.

Insights From the Histopathologic Analysis of Acquired and Genetic Thoracic Aortic Aneurysms and Dissections

OBJECTIVE

The purpose of this study was to apply contemporary consensus criteria developed by the Society for Cardiovascular Pathology and the Association for European Cardiovascular Pathology to the evaluation of aortic pathology, with the expectation that the additional pathologic information may enhance the understanding and management of aortic diseases.

METHODS

A scoring system was applied to ascending aortic specimens from 42 patients with heritable thoracic aortic disease and known genetic variations and from 86 patients from a single year, including patients with known genetic variations (n = 12) and patients with sporadic disease (n = 74).

RESULTS

The various types of lesions of medial degeneration and the overall severity of medial degeneration overlapped considerably between those patients with heritable disease and those with sporadic disease; however, patients with heritable thoracic aortic disease had significantly more overall medial degeneration (P = .004) and higher levels of elastic fiber fragmentation (P = .03) and mucoid extracellular matrix accumulation (P = .04) than patients with sporadic thoracic aortic disease. Heritable thoracic aortic disease with known genetic variation was more prevalent in women than in men (27.2% vs 9.8%; P = .04), and women had more severe medial degeneration than men (P = .04). Medial degeneration scores were significantly lower for patients with bicuspid aortic valves than for patients with tricuspid aortic valves (P = .03).

CONCLUSION

The study's findings indicate considerable overlap in the pattern, extent, and severity of medial degeneration between sporadic and hereditary types of thoracic aortic disease. This finding suggests that histopathologic medial degeneration represents the final common outcome of diverse pathogenetic factors and mechanisms.

[Acute aortic syndrome]

Acute aortic syndrome embraces a group of heterogenous pathological entities involving the aortic wall with a common clinical profile. The current epidemiology, clinical presentation, diagnosis and treatment strategy are discussed in this review. Besides, the importance of multidisciplinary aortic teams, aortic centers and the implementation of an aortic code are emphasized.

Evidence Accumulates: Patients with Ascending Aneurysms Are Strongly Protected from Atherosclerotic Disease

Ascending thoracic aortic aneurysms may be fatal upon rupture or dissection and remain a leading cause of death in the developed world. Understanding the pathophysiology of the development of ascending thoracic aortic aneurysms may help reduce the morbidity and mortality of this disease. In this review, we will discuss our current understanding of the protective relationship between ascending thoracic aortic aneurysms and the development of atherosclerosis, including decreased carotid intima-media thickness, low-density lipoprotein levels, coronary and aortic calcification, and incidence of myocardial infarction. We also propose several possible mechanisms driving this relationship, including matrix metalloproteinase proteins and transforming growth factor-β.

Histopathological Gap in Aortic Diseases: A Prospective Analysis

Aortic dissection (AD) is a critical cardiovascular condition with the potential for devastating consequences. This study evaluated the histological changes in the aorta wall in patients with AD and aortic aneurysm (AA) who received surgical aortic replacement. Histopathological data showed that modifications of the media layer (p = 0.0197), myxomatous aspect (p = 0.0001), and subendothelial layer degeneration (p = 0.0107) were more frequently seen in AA versus AD samples. Patients with AA were approximately twice as likely to develop histological changes than those with AD (p = 0.0037). Patients with moderate or severe medial degeneration had a higher chance of developing AD (p = 0.0001). Because the histopathological score proved to be a predictor of both in-hospital and overall mortality, its evaluation should become the standard of care in any patients who undergo aortic replacement. Individualized postoperative management might be influenced by the histopathological aspect of the aortic layer.

Clinical and imaging differences between Stanford Type B intramural hematoma-like lesions and classic aortic dissection

BACKGROUND

Intramural hematoma (IMH) and Aortic dissection (AD) have overlapping features. The aim of this study was to explore the differences between them by comparing the clinical manifestations and imaging features of patients with acute Stanford type B IMH-like lesions and acute Stanford type B AD (ATBAD).

METHODS

This study retrospectively analysed the clinical and computed tomography angiography (CTA) imaging data of 42 IMH-like lesions patients with ulcer-like projection (ULP) and 38 ATBAD patients, and compared their clinical and imaging features.

RESULTS

(1) The IMH-like lesions patients were older than the ATBAD patients (64.2 ± 11.5 vs. 50.9 ± 12.2 years, P < 0.001). The D-dimer level in the IMH-like lesions group was significantly higher than that in the ATBAD group (11.2 ± 3.6 vs. 9.2 ± 4.5 mg/L, P < 0.05). The incidence rate of back pain was significantly higher in the ATBAD group than in the IMH-like lesions group (71.1% vs. 26.2%, P < 0.05). (2) The ULPs of IMH-like lesions and the intimal tears of ATBAD were concentrated in zone 4 of the descending thoracic aorta. The ULPs of IMH-like lesions and the intimal tears of ATBAD were mainly in the upper quadrant outside the lumen (64.3% vs. 65.8%, P > 0.05). (3) The maximum diameter of the ULPs in IMH-like lesions was smaller than that of the intimal tears in ATBAD (7.4 ± 3.4 vs. 10.8 ± 6.8 mm, P = 0.005). The lumen compression ratio in the ULPs plane and the maximum compression ratio of the aortic lumen in the IMH-like lesions group were smaller than that in the ADBAD group (P < 0.05). Fewer aortic segments were involved in IMH-like lesions patients than in ATBAD patients (5.6 ± 2.2 vs. 7.1 ± 1.9 segments, P < 0.005). The IMH-like lesions group had less branch involvement than that of the ATBAD group (P < 0.001).

CONCLUSION

The degree of intimal tears, lumen compression ratio, extent of lesion involvement, and impact on branch arteries in ATBAD are more severe than that of IMH-like lesions. But for the ULPs of IMH-like lesions and intimal tears of ATBAD, they have astonishing similarities in the location of the partition and the lumen quadrant, we have reason to believe that intimal tear is the initial factor in the pathogenesis of this kind of disease, and their clinical and imaging manifestations overlap, but the severity is different. Concerning similarities between these two conditions, these two may be a spectrum of one disease.

Thoracic Aorta: Anatomy and Pathology

The aorta is the largest elastic artery in the human body and is classically divided into two anatomical segments, the thoracic and the abdominal aorta, separated by the diaphragm. The thoracic aorta includes the aortic root, the ascending aorta, the arch, and the descending aorta. The aorta's elastic properties depend on its wall structure, composed of three distinct histologic layers: intima, media, and adventitia. The different aortic segments show different embryological and anatomical features, which account for their different physiological properties and impact the occurrence and natural history of congenital and acquired diseases that develop herein. Diseases of the thoracic aorta may present either as a chronic, often asymptomatic disorder or as acute life-threatening conditions, i.e., acute aortic syndromes, and are usually associated with states that increase wall stress and alter the structure of the aortic wall. This review aims to provide an update on the disease of the thoracic aorta, focusing on the morphological substrates and clinicopathological correlations. Information on anatomy and embryology will also be provided.

Histopathological findings of diseased ascending aortae with clinicopathological correlation - A single-centre study of 160 cases

The most common reason for ascending aorta resection is an aneurysm or dissection. Aortic dissection is a life-threatening condition in which an aneurysm is a crucial risk factor. The essential criteria for aneurysm resection include the diameter, genetic predisposition, and aortic valve disease. This study aimed to compare the histological findings in aneurysms and dissections and correlate them with clinical parameters to determine whether histopathological findings correspond with the current clinical approach. A total of 160 ascending aorta surgical specimens, separate or with an aortic valve, were collected and divided into four groups: aneurysm-tricuspid (n = 40; median 67 y), aneurysm-malformed (n = 68; median 50 y), dissection-tricuspid (n = 48; median 65.5 y), and dissection-malformed (n = 4; median 52.5 y). Male preponderance was observed in all groups; the youngest patients were in the aneurysm-malformed group. None of the specimens showed normal aortic histology. The most common finding in the aortic samples was medial degeneration, which was the most severe and most common in dissection. The mildest findings were found in the aneurysm-malformed group. Atherosclerosis was predominant and most severe in the aneurysm-tricuspid group, while only mild in both dissection groups, suggesting its protective effect against this complication. Chronic aortitis was the least common pathology, found only in the aneurysm-tricuspid group. The aortic valve was resected and examined simultaneously with the ascending aorta in 76 cases, most commonly in the aneurysm-malformed group (n = 53). Myxoid degeneration was the major finding in the tricuspid aortic valves, with calcifications in the malformed. Comparing the histopathological results with the clinical aspects, aneurysms with a malformed aortic valve seem to be managed appropriately, with the findings not reaching the severity as in patients with a tricuspid valve. In contrast, in patients with a tricuspid valve, there were more dissections than aneurysms, with a significant subset of aneurysms showing histological findings almost identical to those of dissections. Supported by histological findings, patients with a diseased ascending aorta and tricuspid aortic valve represent an underdiagnosed risk group that would benefit from earlier diagnosis and intervention to prevent dissection. There is a need to find a marker for dissection risk other than the aortic diameter.

Acute aortic syndromes: An internist's guide to the galaxy

Acute aortic syndromes (AASs) are severe conditions defined by dissection, hemorrhage, ulceration or rupture of the thoracic aorta. AASs share etiological and pathophysiological features, including long-term aortic tissue degeneration and mechanisms of acute aortic damage. The clinical signs and symptoms of AASs are unspecific and heterogeneous, requiring large differential diagnosis. When evaluating a patient with AAS-compatible symptoms, physicians need to integrate clinical probability assessment, bedside imaging techniques such as point-of-care ultrasound, and blood test results such as d-dimer. The natural history of AASs is dominated by engagement of ischemic, coagulative and inflammatory pathways at large, causing multiorgan damage. Medical treatment, multiorgan monitoring and outcome prognostication are therefore paramount, with internal medicine playing a key role in non-surgical management of AASs.

Aortic Cellular Diversity and Quantitative Genome-Wide Association Study Trait Prioritization Through Single-Nuclear RNA Sequencing of the Aneurysmal Human Aorta

BACKGROUND

Mural cells in ascending aortic aneurysms undergo phenotypic changes that promote extracellular matrix destruction and structural weakening. To explore this biology, we analyzed the transcriptional features of thoracic aortic tissue.

METHODS

Single-nuclear RNA sequencing was performed on 13 samples from human donors, 6 with thoracic aortic aneurysm, and 7 without aneurysm. Individual transcriptomes were then clustered based on transcriptional profiles. Clusters were used for between-disease differential gene expression analyses, subcluster analysis, and analyzed for intersection with genetic aortic trait data.

RESULTS

We sequenced 71 689 nuclei from human thoracic aortas and identified 14 clusters, aligning with 11 cell types, predominantly vascular smooth muscle cells (VSMCs) consistent with aortic histology. With unbiased methodology, we found 7 vascular smooth muscle cell and 6 fibroblast subclusters. Differentially expressed genes analysis revealed a vascular smooth muscle cell group accounting for the majority of differential gene expression. Fibroblast populations in aneurysm exhibit distinct behavior with almost complete disappearance of quiescent fibroblasts. Differentially expressed genes were used to prioritize genes at aortic diameter and distensibility genome-wide association study loci highlighting the genes JUN, LTBP4 (latent transforming growth factor beta-binding protein 1), and IL34 (interleukin 34) in fibroblasts, ENTPD1, PDLIM5 (PDZ and LIM domain 5), ACTN4 (alpha-actinin-4), and GLRX in vascular smooth muscle cells, as well as LRP1 in macrophage populations.

CONCLUSIONS

Using nuclear RNA sequencing, we describe the cellular diversity of healthy and aneurysmal human ascending aorta. Sporadic aortic aneurysm is characterized by differential gene expression within known cellular classes rather than by the appearance of novel cellular forms. Single-nuclear RNA sequencing of aortic tissue can be used to prioritize genes at aortic trait loci.

Medial degeneration and atherosclerosis show discrete variance around the circumference of ascending aorta aneurysms

Medial degeneration is the most common histological finding in ascending aortic aneurysms with lesser but significant involvement by atherosclerosis. The overall extent and severity can be potentially underrated because of their uneven distribution and macroscopic inconspicuousness of medial degeneration. This study aims to compare the distribution of degenerative and atherosclerotic lesions around ascending aorta circumference, also considering aortic valve cuspidity. We evaluated 88 cases of resected ascending aortae, 25 with a tricuspid aortic valve and 63 with a malformed aortic valve, oriented by a cardiac surgeon and sent for pathological examination. We applied the consensus documents from 2015 and 2016 for microscopic evaluation of aortic specimens. The medial degeneration and atherosclerosis were graded semi-quantitatively for each aortic quadrant: convexity, anterior wall, concavity, and posterior wall. Nearly all quadrants showed at least mild medial degeneration; more severe findings of medial degeneration and atherosclerosis were in the aneurysms associated with the tricuspid valve. In the aneurysms with the tricuspid aortic valve, there was more frequent and more severe atherosclerosis at the concavity than at the anterior wall (p = .046); the frequency and severity of medial degeneration did not differ significantly. The aneurysms with a malformed aortic valve showed more severe medial degeneration at the concavity compared to the convexity (p = .011); atherosclerosis was less common and did not show any significant differences. More than half of the samples also revealed at least a one-grade (mostly one-grade) difference among the quadrants in individual cases for both atherosclerosis and medial degeneration. Extreme differences were rare except for atherosclerosis in the tricuspid group. The results revealed only slight overall differences around the aortic circumference, with concavity being the most susceptible. Still, thanks to occurring inter- and intraindividual variability, the examination of all quadrants seems meaningful not to miss the most severe changes and to underscore the findings.

Acute Aortic Syndrome Revisited: JACC State-of-the-Art Review

The purpose of this paper is to describe all available evidence on the distinctive features of a group of 4 life-threatening acute aortic pathologies gathered under the name of acute aortic syndrome (AAS). The epidemiology, diagnostic strategy, and management of these patients has been updated. The authors propose a new and simple diagnostic algorithm to support clinical decision making in cases of suspected AAS, thereby minimizing diagnostic delays, misdiagnoses, and unnecessary advanced imaging. AAS-related entities are reviewed, and a guideline to avoid imaging misinterpretation is provided. Centralization of patients with AAS in high-volume centers with high-volume surgeons is key to improving clinical outcomes. Thus, the role of multidisciplinary teams, an "aorta code" (streamlined emergent care pathway), and aortic centers in the management of these patients is boosted. A tailored patient treatment approach for each of these acute aortic entities is needed, and as such has been summarized. Finally, a set of prevention measures against AAS is discussed.

Ascending aorta dissection in a new classification system: Clinicopathological features of 62 cases

Herein we present a single institution 5-year experience with ascending aorta dissection biopsies depicting the clinicopathological features of 62 cases. To detect microscopic abnormalities in the aortic wall beside the dissection itself, we applied a new histopathological classification scheme from the consensus documents issued by The Society for Cardiovascular Pathology and The Association for the European Cardiovascular Pathology in 2015 and 2016. The most common finding was medial degeneration (MD) - 61 cases (98.4%); atherosclerosis (AS) was found in 19 aortae (30.6%), and chronic aortitis- giant cell pattern described in one aorta (1.6%). The medial degeneration constituents included mucoid matrix accumulation, smooth muscle cells and elastic fibers abnormalities, and medial fibrosis. The consensus document application led to increased MD reporting compared to older studies and to our previous experience, probably due to assessing more subtle and focal changes such as intralamellar fibrosis, intralamellar mucoid matrix accumulation, and loss of smooth muscle cell nuclei- these changes being also the most common MD abnormalities we are reporting. We have compared the results in patients with bicuspid (n = 7; 11.3%) versus tricuspid (n = 55; 88.7%) aortic valve, suggesting no significant differences except for translamellar fibrosis, which appeared to be more severe in the bicuspid valve group (p = 0.0397). The results might imply similar histopathological findings regardless of the aortic valve cuspidity in aortic dissection. These findings are in contrast to ascending aorta dilation (aneurysm), where more severe medial degeneration changes have been described in patients with the tricuspid aortic valve.

Aortic morphology post type A acute aortic syndrome: Prognosis significance and association with 24-hour blood pressure-monitoring parameters

BACKGROUND

After an emergent surgery for type A acute aortic syndrome, medical management is based on optimal blood pressure (BP) control. We assessed the prognostic significance of BP monitoring and its relationship with aortic morphology following type A acute aortic syndrome.

METHODS

The data of 120 patients who underwent BP monitoring after a type A acute aortic syndrome from January 2005 to June 2016 were retrospectively collected. The first CT angiogram performed after surgery was used for the morphological analysis.

RESULTS

The population included 79 males, with an overall mean age of 60 ± 12 years. Seven patients (5.8%) died during a median follow-up of 5.5 years. The median delay between BP monitoring and discharge was 3 (1-5) months. The mean 24-hour BP of the cohort was 127/73 mm Hg ± 10/17. During follow-up, different parameters of BP monitoring were not associated with the risk of aortic events. However, the diameter of the false lumen of the descending thoracic aorta was the best predictor associated with the risk of new aortic events during follow-up, particularly for the threshold of 28 mm or more (P < .001; Hazard ratio 4.7[2.7-8.2]). The diameter of the false lumen was associated with night-time systolic BP (P = .025; r = .2), 24-hour pulse pressure (P = .002; r = .28), and night-time pulse pressure (P = .008; r = .24).

CONCLUSION

The risk of new aortic events following type A acute aortic syndrome is associated with the size of the residual false lumen, but not directly with BP parameters. Night-time BP parameters are associated with the size of the residual false lumen.

The complex interplay among atherosclerosis, inflammation, and degeneration in ascending thoracic aortic aneurysms

OBJECTIVE

To assess the histopathological findings of a large series of ascending thoracic aortic aneurysm (TAA) surgical specimens applying the updated classification on noninflammatory degenerative and inflammatory aortic diseases proposed by the Association for European Cardiovascular Pathology and the Society for Cardiovascular Pathology clinicopathological correlations.

METHODS

A total of 255 patients surgically treated for ascending TAA were enrolled. Surgical ascending aorta specimens were examined.

RESULTS

The histopathological substrate of ascending TAAs was mainly degenerative (67.5%), but with a remarkable prevalence of atherosclerotic lesions (18.8%) and aortitis (13.7%). Degenerative patients more frequently had bicuspid aortic valve (37.2%; P = .002). Patients in the atherosclerotic group were older (median age, 69 years; P < .001), more often with a history of hypertension (87.5%; P = .059), hypercholesterolemia (75%; P = .019), diabetes (16.6%; P = .054), current smoking (22.9%; P = .066), and a history of coronary artery disease (18.7%; P = .063). Patients with aortitis represented the older group (median age, 75 years, P < .001), were mostly females (68.6%; P < .001), and had a larger ascending aorta diameter (median, 56 mm; P < .001). Both patients with atherosclerosis and aortitis presented a higher incidence of concomitant abdominal aortic aneurysm (20.8% and 22.8%, respectively; P < .001).

CONCLUSIONS

Although degenerative histopathology is the most frequent substrate in ascending TAA, atherosclerosis and inflammation significantly contribute to the development of chronic aortic thoracic disease.