Aortic dissection is a disease of the vasa vasorum

Mortality risk and burden of aortic aneurysm and dissection attributable to low temperatures: A nationwide case-crossover analysis in Brazil, a predominantly tropical country

BACKGROUND

Low temperatures are adverse contributors to cardiovascular diseases, but the associations between short-term exposure to cold and the risk of death from aortic dissection and aneurysm remain unclear, particularly in tropical regions.

OBJECTIVE

This study was conducted based on 123,951 records of deaths caused by aortic dissection and aneurysms extracted from the national Mortality Information System in Brazil between 2000 and 2019.

METHODS

Relative risks and 95 % confidence intervals (CI) for the aortic-related deaths associated with low ambient temperatures were estimated using the conditional logistic model combined with the distributed lag nonlinear model. Subgroup analyses were performed by age group, sex, race, education level, and residential region. Furthermore, this study calculated the number and fraction of aortic-related deaths attributed to temperatures below the temperature threshold to quantify the cold-related mortality burden of aortic diseases.

RESULTS

During the study period, aortic-related deaths and mortality rates in Brazil exhibited a steady increase, rising from 4419 (2.66/100,000) in 2000 to 8152 (3.88/100,000) in 2019. Under the identified temperature threshold (26 °C), per 1 °C decrease in daily mean temperature was associated with a 4.77 % (95 % CI: 4.35, 5.19) increase in mortality risk of aortic-related diseases over lag 0-3 days. Females, individuals aged 50 years or older, Asian and Black race, and northern residents were more susceptible to low temperatures. Low temperatures were responsible for 19.10 % (95 % CI: 17.71, 20.45) of aortic-related deaths in Brazil.

CONCLUSION

This study highlights that low temperatures were associated with an increased risk of aortic-related deaths, with a remarkable burden even in this predominantly tropical country.

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.

Condition "Vasa Vasorum" in Patients with Thoracic Aortic Aneurysm

It is known that vasa vasorum contributes substantially to the blood supply and nutrition of one-third of the wall of the ascending thoracic aorta. Therefore, we focused on studying the relationship between inflammatory cells and vasa vasorum vessels in patients with aortic aneurysm. The material for the study was biopsies of thoracic aortic aneurysms taken from patients during an aneurysmectomy (34 men, 14 women, aged 33 to 79 years). The biopsies belonged to patients with non-hereditary thoracic aortic aneurysm. An immunohistochemical study was carried out using antibodies to antigens of T cells (CD3, CD4, CD8); macrophages (CD68); B cells (CD20); endothelium (CD31, CD34, von Willebrand factor (vWF)); and smooth muscle cells (alpha actin). Samples without inflammatory infiltrates contained less vasa vasorum in the tunica adventitia than samples with inflammatory infiltrates, and this difference was statistically significant p < 0.05. T cell infiltrates in the adventitia of aortic aneurysms were found in 28 of 48 patients. In the vessels of the vasa vasorum, surrounded by inflammatory infiltrates, T cells that adhered to the endothelium were found. The same cells were also localized in the subendothelial area. The number of adherent T cells in patients with inflammatory infiltrates in the aortic wall dominated the number of these cells in patients without inflammation of the aortic wall. This difference was statistically significant, p < 0.0006. Hypertrophy and sclerosis of the arteries of the vasa vasorum system, the narrowing of their lumen, and, as a result, impaired blood supply to the aortic wall, were found in 34 patients with hypertension. In 18 patients (both in patients with hypertension and in patients without hypertension), T cells that adhered to the vasa vasorum endothelium were found. In nine cases, massive infiltrates of T cells and macrophages were found, which surrounded and squeezed the vasa vasorum, preventing blood circulation. In six patients, parietal and obturating blood clots were found in the vasa vasorum vessels, which disrupted the normal blood supply to the aortic wall. We believe that this indicates the importance of the state of the vessels of the vasa vasorum in the development of an aortic aneurysm. In addition, pathological changes in these vessels may not always play a primary role, but always a very important role, in the pathogenesis of this disease.

COVID-19 and Vasa vasorum: New Atherogenic Factor? A Case Report and Autopsy Findings

Patients with COVID-19 demonstrate higher rates of cardiovascular complications, including thromboses and thromboembolism. One may suppose that the action of SARS-CoV-2 transforms stable atherosclerotic plaques into unstable status. Cardiovascular complications in COVID-19 may be caused by progressive viral alteration of the blood vessels, including Vasa vasorum. A lethal case of ischemic brain disease caused by cerebral atherosclerosis and exacerbated by a stroke during COVID-19 infection is briefly described. The results of the autopsy showed perivascular lymphocytic infiltration and signs of Vasa vasorum vasculitis with thrombi of adventitial microvasculature. The data discussed in the article are interpreted in the context of the concept giving the important role in atherogenesis to Vasa vasorum.

Arterial dissections: Common features and new perspectives

Arterial dissections, which involve an abrupt tear in the wall of a major artery resulting in the intramural accumulation of blood, are a family of catastrophic disorders causing major, potentially fatal sequelae. Involving diverse vascular beds, including the aorta or coronary, cervical, pulmonary, and visceral arteries, each type of dissection is devastating in its own way. Traditionally they have been studied in isolation, rather than collectively, owing largely to the distinct clinical consequences of dissections in different anatomical locations - such as stroke, myocardial infarction, and renal failure. Here, we review the shared and unique features of these arteriopathies to provide a better understanding of this family of disorders. Arterial dissections occur commonly in the young to middle-aged, and often in conjunction with hypertension and/or migraine; the latter suggesting they are part of a generalized vasculopathy. Genetic studies as well as cellular and molecular investigations of arterial dissections reveal striking similarities between dissection types, particularly their pathophysiology, which includes the presence or absence of an intimal tear and vasa vasorum dysfunction as a cause of intramural hemorrhage. Pathway perturbations common to all types of dissections include disruption of TGF-β signaling, the extracellular matrix, the cytoskeleton or metabolism, as evidenced by the finding of mutations in critical genes regulating these processes, including LRP1, collagen genes, fibrillin and TGF-β receptors, or their coupled pathways. Perturbances in these connected signaling pathways contribute to phenotype switching in endothelial and vascular smooth muscle cells of the affected artery, in which their physiological quiescent state is lost and replaced by a proliferative activated phenotype. Of interest, dissections in various anatomical locations are associated with distinct sex and age predilections, suggesting involvement of gene and environment interactions in disease pathogenesis. Importantly, these cellular mechanisms are potentially therapeutically targetable. Consideration of arterial dissections as a collective pathology allows insight from the better characterized dissection types, such as that involving the thoracic aorta, to be leveraged to inform the less common forms of dissections, including the potential to apply known therapeutic interventions already clinically available for the former.

On vasa vasorum: A history of advances in understanding the vessels of vessels

The vasa vasorum are a vital microvascular network supporting the outer wall of larger blood vessels. Although these dynamic microvessels have been studied for centuries, the importance and impact of their functions in vascular health and disease are not yet fully realized. There is now rich knowledge regarding what local progenitor cell populations comprise and cohabitate with the vasa vasorum and how they might contribute to physiological and pathological changes in the network or its expansion via angiogenesis or vasculogenesis. Evidence of whether vasa vasorum remodeling incites or governs disease progression or is a consequence of cardiovascular pathologies remains limited. Recent advances in vasa vasorum imaging for understanding cardiovascular disease severity and pathophysiology open the door for theranostic opportunities. Approaches that strive to control angiogenesis and vasculogenesis potentiate mitigation of vasa vasorum-mediated contributions to cardiovascular diseases and emerging diseases involving the microcirculation.

Updates in aortic wall pathology

Several studies have investigated the pathogenesis of aortic wall abnormalities such as aortic dissection or aneurysm; however, the comprehensive pathological in situ event involved in the development of the disease is not understood well. The vasa vasorum form a network of capillaries or venules around the adventitia and outer media, which play an important role in the aortic wall structure and function. Impairment of their function may induce tissue hypoxia, impede the transfer of cellular nutrients, and cause aortic medial degeneration, which is considered the major predisposing factor to this aortic wall pathology. This review updates our understanding of the pathological changes in the aortic media and vasa vasorum of patients with aortic dissection and aortic aneurysm.

Low ambient temperature and temperature drop between neighbouring days and acute aortic dissection: a case-crossover study

AIMS

The incidence of acute aortic dissection (AAD) has been shown to have seasonal variation, but whether this variation can be explained by non-optimum ambient temperature and temperature change between neighbouring days (TCN) is not clear.

METHODS AND RESULTS

We performed a time-stratified case-crossover study in the Registry of Aortic Dissection in China covering 14 tertiary hospitals in 11 cities from 2009 to 2019. A total of 8182 cases of AAD were included. Weather data at residential address were matched from nearby monitoring stations. Conditional logistic regression model and distributed lag nonlinear model were used to estimate the associations of daily temperature and TCN with AAD, adjusting for possible confounders. We observed an increase of AAD risk with lower temperature cumulated over lag 0-1 day and this association became statistically significant when daily mean temperature was below 24°C. Relative to the referent temperature (28°C), the odds ratios (ORs) of AAD onset at extremely low (-10°C) and low (1°C) temperature cumulated over lag 0-1 day were 2.84 [95% confidence interval (CI): 1.69, 4.75] and 2.36 (95% CI: 1.61, 3.47), respectively. A negative TCN was associated with increased risk of AAD. The OR of AAD cumulated over lag 0-6 days was 2.66 (95% CI: 1.76, 4.02) comparing the extremely negative TCN (-7°C) to no temperature change. In contrast, a positive TCN was associated with reduced AAD risk.

CONCLUSION

This study provides novel and robust evidence that low ambient temperature and temperature drop between neighbouring days were associated with increased risk of AAD onset.

KEY QUESTION

Incidence of acute aortic dissection (AAD) was reported to have seasonal trends, but it remains unclear whether non-optimum ambient temperature and temperature change between neighbouring days (TCN) is associated with AAD onset.

KEY FINDING

Daily mean temperature lower than 24°C was significantly associated with increased risk of AAD at lag 0-1 day. A negative TCN (temperature drop) was associated with increased risk of AAD, whereas a positive TCN was associated with decreased risk.

TAKE HOME MESSAGE

This multi-centre, case-crossover study provides novel and robust evidence that low ambient temperature and temperature drop between neighbouring days were associated with increased AAD risk.

Mathematical Modeling and Numerical Simulation of Atherosclerosis Based on a Novel Surgeon's View

This paper deals with the mathematical modeling of atherosclerosis based on a novel hypothesis proposed by a surgeon, Prof. Dr. Axel Haverich (Circulation 135(3):205-207, 2017). Atherosclerosis is referred as the thickening of the artery walls. Currently, there are two schools of thoughts for explaining the root of such phenomenon: thickening due to substance deposition and thickening as a result of inflammatory overgrowth. The hypothesis favored here is the second paradigm stating that the atherosclerosis is nothing else than the inflammatory response of of the wall tissues as a result of disruption in wall nourishment. It is known that a network of capillaries called vasa vasorum (VV) accounts for the nourishment of the wall in addition to the natural diffusion of nutrient from the blood passing through the lumen. Disruption of nutrient flow to the wall tissues may take place due to the occlusion of vasa vasorums with viruses, bacteria and very fine dust particles such as air pollutants referred to as PM 2.5. They can enter the body through the respiratory system at the first place and then reach the circulatory system. Hence in the new hypothesis, the root of atherosclerotic vessel is perceived as the malfunction of microvessels that nourish the vessel. A large number of clinical observation support this hypothesis. Recently and highly related to this work, and after the COVID-19 pandemic, one of the most prevalent disease in the lungs are attributed to the atherosclerotic pulmonary arteries, see Boyle and Haverich (Eur J Cardio Thorac Surg 58(6):1109-1110, 2020). In this work, a general framework is developed based on a multiphysics mathematical model to capture the wall deformation, nutrient availability and the inflammatory response. For the mechanical response an anisotropic constitutive relation is invoked in order to account for the presence of collagen fibers in the artery wall. A diffusion-reaction equation governs the transport of the nutrient within the wall. The inflammation (overgrowth) is described using a phase-field type equation with a double well potential which captures a sharp interface between two regions of the tissues, namely the healthy and the overgrowing part. The kinematics of the growth is treated by classical multiplicative decomposition of the gradient deformation. The inflammation is represented by means of a phase-field variable. A novel driving mechanism for the phase field is proposed for modeling the progression of the pathology. The model is 3D and fully based on the continuum description of the problem. The numerical implementation is carried out using FEM. Predictions of the model are compared with the clinical observations. The versatility and applicability of the model and the numerical tool allow.