Basic Overview Aortic coarctation, also known as aortic coarctation aneurysm, is one of the more common and most complex and dangerous cardiovascular diseases, with an incidence of 50-100 people/100,000 people per year, and its incidence is on the rise as people’s life and dietary habits change. Aortic coarctation refers to the process of dissociation of the middle layer of the aorta, not the expansion of the aortic wall, through a break in the intima into the cystic degeneration of the middle layer of the aortic wall and the formation of a coarctation hematoma, which gradually expands within the middle layer of the aorta driven by blood flow pressure, as distinct from aortic aneurysm. This condition used to be called aortic coarctation aneurysm, but is now more commonly referred to as aortic coarctation hematoma, or aortic coarctation separation, or aortic coarctation. The disease has an acute onset, with sudden onset of severe pain, shock, and ischemic symptoms in the organs when the hematoma compresses the corresponding aortic branch vessels. 65-75% of patients die in the acute phase (within 2 weeks) from cardiac complications such as cardiac compression and arrhythmias. The peak age is 50-70 years, and the incidence is higher in men than in women, with a male to female ratio of 2 to 3:1. Pathogenesis of aortic coarctation The cause of aortic coarctation is still unknown. 80% of patients with aortic coarctation have hypertension, and many have cystic mesangial necrosis. Hypertension is not the cause of cystic middle lamina necrosis, but can contribute to its development. Clinical and animal experiments have found that it is not the height of blood pressure but the magnitude of blood pressure fluctuations that is associated with aortic coarctation splitting. In animal experiments, feeding pigs with sallow beans can cause aortic coarctation, and the beta-aminopropionitrile in sallow beans acts on the stroma of the artery, the muscle and elastic tissue of the middle layer, making the artery vulnerable. Feeding rats with aminoacetonitrile and deoxycorticosterone can also cause aortic coarctation; the lack of copper in the feed makes the animal synthesize elastic scleroprotein barriers, which can also produce similar results. Other genetic disorders such as Turner syndrome and Ehlers-Danlos syndrome also have a tendency to develop aortic coarctation. Aortic coarctation is also prone to occur during pregnancy for unknown reasons, but it is assumed that endocrine changes during pregnancy alter the structure of the aorta and make it prone to dehiscence. The aortic wall in normal adults is quite resistant to pressure, and it takes more than 66.7 kPa (500 mmHg) for the wall to rupture. Therefore, the prerequisite for a clamping rupture is a defect in the arterial wall, especially in the middle layer. In general, degenerative changes of the middle layer muscles predominate in older individuals, while in younger individuals, the lack of elastic fibers predominates. In the rare cases of aortic coarctation without intimal fissures, it may be due to intramural hemorrhage caused by rupture of the trophoblastic vessels within the lesion of mesodegeneration. The coexistence of atherosclerosis contributes to the development of aortic coarctation. Pathological changes Aortic coarctation The basic lesion is cystic mesangial necrosis. There is localized fracture or necrosis of the elastic fibers of the middle layer of the artery, and the stroma has mucinous and cystic formation. Splits often occur in the ascending aorta, which experiences the greatest blood flow impact, while the distal part of the aortic arch has fewer and less severe lesions. The aortic wall splits into two layers with accumulation of blood and clots between them, where the aorta is significantly enlarged and pyknotic or cystic in shape. If the lesion involves the aortic annulus, the annulus enlarges and causes aortic valve insufficiency. The lesion may extend distally from the aortic root as far as the iliac and femoral arteries, and may also involve branches of the aorta, such as the innominate artery, common carotid artery, subclavian artery, and renal artery. The coronary arteries are generally unaffected, but the clot in the aortic root can have a compressive effect on the coronary artery opening. Most clots have transverse fissures in the origin of the intima, often located above the aortic valve, and the fissures can also be in two places, with the clot communicating with the aortic lumen. In a few cases, the endothelium is intact without fissures. In some cases, the outer membrane ruptures and causes hemorrhage. The rupture is all in the ascending aorta, and the bleeding can easily enter the pericardial cavity, or the mediastinum or the thoracic cavity if the rupture site is lower, or the mediastinum, thoracic cavity or retroperitoneal space if the rupture site is lower. Chronic dehiscence can result in a double-lumen aorta, with one duct being placed in the other. This is seen in the thoracic aorta or the descending branch of the aortic arch.