Translational Relevance and Recent Advances of Animal Models of Abdominal Aortic Aneurysm.

Human abdominal aortic aneurysm (AAA) pathophysiology is not yet completely understood. In conductance arteries, the insoluble extracellular matrix, synthesized by vascular smooth muscle cells, assumes the function of withstanding the intraluminal arterial blood pressure. Progressive loss of this function through extracellular matrix proteolysis is a main feature of AAAs. As most patients are now treated via endovascular approaches, surgical AAA specimens have become rare. Animal models provide valuable complementary insights into AAA pathophysiology. Current experimental AAA models involve induction of intraluminal dilation (nondissecting AAAs) or a contained intramural rupture (dissecting models). Although the ideal model should reproduce the histological characteristics and natural history of the human disease, none of the currently available animal models perfectly do so. Experimental models try to represent the main pathophysiological determinants of AAAs: genetic or acquired defects in extracellular matrix, loss of vascular smooth muscle cells, and innate or adaptive immune response. Nevertheless, most models are characterized by aneurysmal stabilization and healing after a few weeks because of cessation of the initial stimulus. Recent studies have focused on ways to optimize existing models to allow continuous aneurysmal growth. This review aims to discuss the relevance and recent advances of current animal AAA models. VISUAL OVERVIEW: An online visual overview is available for this article.

[Paradigm shifts in aortic pathology: clinical and therapeutic implications. Clinical imaging in chronic and acute aortic syndromes. The aorta as a cause of cardiac disease]. / Cambi di paradigma in tema di aorta: implicazioni cliniche e terapeutiche Imaging clinico nelle sindromi croniche ed acute. L'aorta come causa di malattia cardiaca.

Multimodal imaging plays a pivotal role in the assessment of the thoracic aorta, both in chronic and acute settings. Moving from improved knowledge on the structure and function of the aortic wall, as well as on its pathophysiology and histopathology, appropriate utilization of each imaging modality results into a better definition of the patient's need and proper treatment strategy. This review is aimed at highlighting the most critical aspects in this field, providing cardiologists with some novel clues for the imaging approach to patients with thoracic aortic disease.

Cervical artery dissection. A comparison of highly dynamic mechanisms: manipulation versus motor vehicle collision.

OBJECTIVE: To examine the similarities and dissimilarities between cervical chiropractic manipulative therapy and whiplash, and their respective relation to cervical artery dissection. DATA SOURCES: A literature synthesis used MEDLINE-PubMed and MANTIS literature searches. A total list of 99 relevant articles was generated. Additional references were collected from citations incorporated within the included articles. RESULTS: Both neck manipulation and motor vehicle collision events apply loads to the spinal column rapidly. While neck manipulation loads are slower to develop and displacements smaller, they may reach peak amplitudes on maximum effort comparable to those seen in low-velocity collision experiments. In contrast to reports that the vertebral artery experiences elongations exceeding its physiological range by up to 9.0 mm during simulated whiplash, strains incurred during cervical manipulative therapy have been reported to be approximately one ninth of those required for mechanical failure, comparable to forces encountered in the course of diagnostic range of motion examination. Additionally, long-lasting abnormalities of blood flow velocity within the vertebral artery have been reported in patients following common whiplash injuries, whereas no significant changes in vertebral artery peak flow velocity were observed following cervical chiropractic manipulative therapy. CONCLUSIONS: Perceived causation of reported cases of cervical artery dissection is more frequently attributed to chiropractic manipulative therapy procedures than to motor vehicle collision related injuries, even though the comparative biomechanical evidence makes such causation unlikely. The direct evidence suggests that the healthy vertebral artery is not at risk from properly performed chiropractic manipulative procedures.

The role of transcranial Doppler sonography in the identification of patients at risk of cerebral and brainstem ischemia.

OBJECTIVE: To review the literature pertaining to transcranial Doppler (TCD) examination of the anterior and posterior cerebral circulation. This paper focuses on the application of TCD as a screening modality for vertebral artery-induced brainstem ischemic events. DATA SOURCES: A Medline literature search was performed. Key terms included; transcranial Doppler, vertebral artery dissection, neck trauma, stroke and vertebrobasilar system. DATA EXTRACTION: The studies examined TCD techniques that monitor the hemodynamics of the circle of Willis. Papers pertaining to vertebral artery trauma and resulting brainstem injury were included. The validity and reproducibility of these procedures were also reviewed. CONCLUSION: TCD procedures provide hemodynamic data pertaining to intra-arterial vertebrobasilar stenosis and extra-arterial mechanical compression of the vertebral arteries. During cervical spine positional testing, brainstem symptoms may be correlated with TCD documented perfusion deficits. TCD increases the sensitivity of the standard positional test.