I. What is a thoracic aortic coarctation aneurysm all about?
Aortic blood flow enters the aortic wall through the endothelial rupture and forms a hematoma within the aortic wall. This disease was described by Sennertus in 1542 and Morgagni in 1761, and by Laennec in 1826. The incidence of aortic coarctation aneurysm is about 5 to 10 cases per million population per year. The ratio of men to women is about 3:1, and the age of onset is mostly above 40 years.
Second, the formation of aortic aneurysm causes.
There are many reasons for the formation of aortic coarctation: atherosclerosis, hypertension, cystic necrosis of the middle layer of the artery, Marfan’s syndrome, aortic constriction, aortitis, trauma and syphilis. Except for trauma, the pathological basis is the alteration of the middle layer of the aorta and smooth muscle.
III. Clinical manifestations of thoracic aortic aneurysm.
The vast majority of patients with entrapped aortic aneurysms appear with a sudden feeling of severe pain like cutting or tearing in the abdomen, chest or back. Chest pain may radiate to the neck and arm, similar to acute myocardial infarction. The pain is not relieved by the administration of morphine-like drugs. The pain is persistent and does not resolve on its own until the entrapment aneurysm has ruptured. Patients often show signs of shock such as pale skin, sweating, and peripheral cyanosis, but blood pressure remains above normal. Abdominal pain is easily confused with acute abdomen, but cases of entrapment aneurysm rarely present with nausea, vomiting, abdominal pressure and abdominal muscle tension. Aortic wall dissection lesions involving the ascending aorta may present with a diastolic heart murmur of aortic valve insufficiency. Those involving the subclavian, common carotid, and iliofemoral arteries may have a localized vascular murmur, with decreased or absent ipsilateral pulses and blood pressure. Lesions involving the cerebral vessels may be confused with cerebral hemorrhage or cerebral thrombosis due to hypertension. Intercostal artery involvement may result in sudden paraplegia.
Pathological changes
Degenerative lesions of the middle layer of the aortic wall, where the adhesion of the layers of tissue is reduced and the aortic wall is affected by the impact of blood flow or the rupture of the vascular trophoblast, leading to the rupture of the intima, then the middle layer of the aortic wall is peeled off, forming an intermural hematoma with a thin outer layer and a thick inner layer. Stress from the heartbeat has the greatest effect on the ascending and proximal descending aorta, so that in 60-70% of cases, the clogged aneurysm originates in the ascending aorta and in 25% in the proximal descending aorta. Hypertension is also present in approximately 90% of cases. After the formation of a clogged aneurysm, it may extend to the distal aorta, involving the entire length of the thoracic aorta and the abdominal aorta and its branches, and to the proximal aorta, involving the coronary artery and aortic valve, resulting in coronary circulation flow blockage or aortic valve closure insufficiency. The involvement of the common carotid artery may lead to cerebral ischemia; the intercostal artery may lead to paraplegia due to spinal cord ischemia; the renal artery may lead to renal failure; and the iliac and femoral arteries may lead to limb necrosis. If the outer layer of the clogged aneurysm penetrates into the pericardial or pleural cavity, it may cause pericardial compression or massive hemothorax, leading to death. In some patients, if the inner layer of the aneurysm penetrates into the aortic cavity, two blood flow channels are formed in the aorta, and the process of aortic wall dissection is no longer developed and the disease is relieved.
V. Clinical staging of thoracic aortic aneurysm.
(1) In 1965, DeBakey classified three types according to the site and extent of the occurrence of the coarctation aneurysm, which are widely used in clinical practice.
Type I: The endothelial rupture is located in the ascending aorta, and the extent of aortic wall dissection originates in the ascending aorta, involving the aortic arch and descending aorta, and may extend to the abdominal aorta.
Type II: The endothelial rupture is located in the ascending aorta, and the aortic wall detachment is limited to the ascending aorta.
Type III: The endothelial rupture is located in the proximal descending aorta distal to the opening of the left subclavian artery. The aortic wall is dissected in the direction of the descending aorta and may extend to the abdominal aorta, but does not involve the ascending aortic wall.
(2) Stanford’s staging is divided into two types, A and B, according to whether the ascending aorta is involved or not.
Type A: The intimal rupture may be located in the ascending aorta, aortic arch or proximal descending aorta. The Stanforda type is equivalent to DeBakey’s type I and type II. type A accounts for approximately 66% of cases.
Type B: The intimal rupture is often located in the proximal descending aorta, and the extent of the entrapment aneurysm is limited to the descending aorta or extends into the abdominal aorta, but does not involve the ascending aorta. Type B accounts for about 33% of cases.
VI. Related tests.
1.Electrocardiogram examination
The electrocardiogram generally shows no abnormal signs, and the diagnosis of myocardial infarction can be excluded. Cases with hypertension may show left ventricular hypertrophy.
2.Chest X-ray examination
Chest X-ray is a simple and reliable diagnostic method. In cases where the aortic aneurysm involves the ascending aorta, the chest X-ray shows a widening of the mediastinal shadow to the right, and to the left in cases where the descending aorta is involved. The aortic arch is confined and elevated, and the ascending and descending aorta have different external diameters, and the ascending aorta and aortic arch are enlarged and deformed. The aortic wall is thickened, resulting in a widening of the distance between the intimal calcified spots and the outer edge of the aorta. Repeat films taken at half-hour intervals show altered morphology of the thoracic aorta and mediastinum. Sometimes the aorta shows a double-lumen shadow. Some cases may show pleural cavity effusion.
3.Aortography
Aortography should be performed immediately if the chest X-ray shows the above abnormalities, which is required to fully show the full length of the aorta (from the aortic valve to the abdominal aortic bifurcation). Aortogram can show the abnormal blood flow channel formed by aortic wall dissection compressing the aortic cavity, and understand the length of the dissected section of the aortic wall, the site of endothelial rupture, the anatomy and function of the aortic valve, and the involvement of the main branches of the aorta such as the common carotid artery and the renal artery. Positive signs of aortic angiography in the case of a coarctation aneurysm include: the contrast is divided into two channels in the aorta and the morphology is not neat, the contrast fails to enter the main branches of the aorta and the aortic valve is not closed.
4.Double-dimensional echocardiography
It can show the aortic endothelial rupture flap at the entrance of the entrapped aneurysm.
VII. This disease should be differentially diagnosed with the following diseases.
(1) The torn endothelial sheet is distinguished from the artifact. The former is a thin and slightly curved linear structure, whereas the strip artifacts show a thicker linear structure.
(2) When the false lumen is filled with thrombus, it must be distinguished from the thrombosis of an aneurysm. A true aortic aneurysm presents as a single manifestation and dilated lumen surrounded by a thin layer of aortic wall, together with peripheral calcification along the aortic wall. Aortic coarctation, on the other hand, presents as two developing lumens separated by a thin endothelial sheet or two lumens with different times and rates of development.
(3) Note the adjacent normal or abnormal anatomic structures to differentiate them.
Differential diagnosis.
When DeBekay type I and II dissection involves the aortic valve, diastolic or systolic murmurs in the aortic valve area appear. Acute left heart failure is highly likely to occur with rapid heart rate and dyspnea when the aortic valve is incompetently closed. In case of clammy dissection involving coronary artery, it can cause acute myocardial ischemia or myocardial infarction, and in case of clammy dissection breaking into pericardium, pericardial tamponade can occur rapidly, leading to sudden death. When the peripheral arteries are blocked several hours after the onset of the disease, carotid artery or limb artery pulsation may occur with varying intensity, and in severe cases, limb ischemic necrosis may occur. In severe cases, ischemic necrosis of the limbs may occur. If the interposition involves the cephalobrachial artery of the aortic arch, it may cause insufficient blood supply to the brain and even coma and hemiparesis. Intercostal artery involvement in the descending aorta may affect spinal cord blood supply and cause paraplegia. Involvement of the abdominal organ branches may cause inadequate blood supply to the liver, impaired liver function, abdominal manifestations or gastrointestinal bleeding, renal impairment and renal hypertension.
VIII. Treatment.
Aortic coarctation aneurysms are extremely dangerous, with a survival rate of only 40% for 24 hours, 25% for 1 week, and 10% for 3 months after the occurrence of a coarctation aneurysm. The prognosis is even worse for lesions involving the ascending aorta, with a 1-month survival rate of only 8%, while the 1-month survival rate for lesions involving only the thoracic descending aorta can be as high as 75%. Hypertension accelerates the process of aortic wall dissection, exacerbates pain and contributes to early death due to hemopericardium, hemothorax or mediastinal hemopericardium caused by clamping rupture, which has a negative effect on the condition. Therefore, cases of aortic coarctation aneurysm should be treated before the diagnosis is confirmed by aortogram. Drugs are given to lower blood pressure, reduce peripheral vascular resistance and decrease left ventricular contractility so that the aortic wall dissection does not expand. The most commonly used drugs are Arfonad or sodium nitroprusside. Monitor ECG, blood pressure, central venous pressure, pulmonary microembolic pressure, pulmonary artery pressure and urine output closely. After stabilization, aortography is performed immediately to identify the site and extent of the aortic wall dissection lesion. The aortic wall tissue is fragile and easily broken in cases of clogged aneurysm, making surgical operation difficult and the mortality rate high. In cases of aortic wall dissection involving the ascending aorta, i.e. Stanford classification type a or DeBakey classification type I and II, surgical treatment should be performed; in cases of Stanford classification type B or DeBakey classification type III, most of the cases are stabilized by medical treatment and can continue medical treatment, but surgical treatment should be performed in the following cases: 1.
1, the aortic wall dissection lesion continues to expand its main manifestations are: aortic wall hematoma is significantly enlarged, the aortic head and arm branches or aortic valve present murmur and pulsation is weakened, suggesting that the dissection lesion involves the ascending aorta. The presentation of coma, stroke, painful chills in the limbs, decreased urine output or absence of urine suggests compression or obstruction of the main branches of the aorta.
The main signs of aortic wall hematoma with imminent risk of rupture are aortogram showing a pocket clot aneurysm or clotted aneurysm with significant enlargement within a few hours, pleural cavity or pericardial cavity showing blood accumulation; internal treatment fails to control pain.
3. After 4 hours of active medical medication, the blood pressure failed to decrease and the pain was not reduced.
IX. Surgical operation.
1. In cases where the aortic wall dissection lesion involves the ascending aorta, i.e. Stanforda type or DeBakey type I and II cases, a median sternotomy is made, the pericardium is incised, and after systemic heparinization, a single lead catheter is inserted into the right atrium, and the arterial feeding vessel is inserted into the common femoral artery that is not involved by the aortic wall dissection lesion. Extracorporeal circulation was started and the body temperature was lowered to about 25°C. Ice saline was injected into the pericardial cavity for deep local cooling of the heart. A decompression catheter was placed in the left atrium. The ascending aorta is blocked near the origin of the innominate artery. A longitudinal incision is made in the wall of the ascending aorta, the aortic lumen is incised, and cold cardioplegic fluid is cannulated through the left and right coronary artery openings. The site of endothelial rupture and the involvement of the aortic sinus in the aortic wall dissection lesion are visualized. If the dissecting lesion involves the aortic sinus and the aortic valve is still functioning normally, the ascending aorta is cut above the sinus and then a small polyester spacer is placed inside and outside the aortic wall at the aortic junction, and the junction is fixed with mattress sutures through the aortic wall. Then a circular narrow strip of woven fabric is placed inside and outside the aortic wall at each of the proximal and distal cut ends of the ascending aorta, and the aortic wall is reinforced with sutures, and then the proximal and distal cut ends of the ascending aorta are closed with successive sutures. If the endothelial rupture site involves the aortic arch, the aortic arch can be partially removed and replaced with an artificial vessel, and then the aortic wall can be wrapped around the artificial vessel to provide reinforcement and hemostasis.
In the case of lesions requiring removal of the aortic valve, after removal of the aortic valve and the diseased ascending aorta, aortic valve replacement and artificial vessel implantation can be performed, or the artificial valve end can be sutured to the aortic valve annulus with a valve, and a small window can be cut in the artificial vessel to anastomose with the aortic wall near the coronary artery opening, or a saphenous vein shunt can be performed between the artificial vessel and the coronary artery to ensure coronary artery The other end of the artificial vessel is connected to the ascending artery. The other end of the artificial vessel is anastomosed with the distal section of the ascending aorta.
Most of the cases are stable after medical treatment and do not require surgical treatment. The length of the resected aortic segment is reduced as much as possible according to the lesion. In order to avoid ischemic and hypoxic damage to the spinal cord and internal organs caused by blocking the descending aorta, surface hypothermia anesthesia and drug control of upper body blood pressure can be used; a temporary external shunt catheter can be applied; left heart diversion or femoral vein-femoral artery diversion can be performed, and after blocking the proximal and distal aorta of the diseased segment, cold lactate Ringer’s solution can be injected under pressure to lower the spinal cord temperature and protect the spinal cord.
A left posterior dissection incision is made and the chest is entered through the 5th or 6th rib bed. An aortic blocking clamp is placed between the proximal descending aorta or common carotid artery and the left subclavian artery, and another descending aortic blocking clamp is placed distal to the lesion. The descending aorta is dissected longitudinally and the posterior wall of the aorta is observed for the intercostal artery opening, preserving as much of the posterior wall of the aorta at the intercostal artery opening as possible. After removal of the diseased descending aorta, the inner and outer cut ends of the proximal and distal aortic wall are reinforced with a circular narrow strip of woven fabric, and the aortic wall and woven fabric are fixed with continuous sutures, and then a section of artificial vessel of appropriate length, caliber and shape is used to make a butt-end anastomosis with the proximal and distal aortic cut ends. If the posterior wall of the aorta and the intercostal artery are preserved, the end of the artificial vessel should be trimmed obliquely. After completion of the anastomosis, the distal vascular clamp of the descending aorta is relaxed, and if there is any blood leakage from the anastomosis, several additional stitches are required before the proximal aortic blocking clamp is slowly relaxed and removed. The implanted artificial vessel is wrapped and sutured with the wall of the intercalated aneurysm, which acts as a reinforcement and hemostasis.
The postoperative management is the same as that of general major cardiac vascular surgery, but the blood pressure should be closely monitored to prevent any elevation. Postoperative follow-up review should pay attention to whether the residual aneurysm pseudo-tracts are enlarged, and those enlarged should be treated in time to avoid rupture.
Results of surgical treatment: The surgical mortality rate for entrapped aneurysms remains high. In cases where the lesion involves the ascending aorta, the operative mortality rate is 20-40%, and in cases where the lesion is limited to the descending aorta, the operative mortality rate is 25-60%. The main causes of death are bleeding from aortic or anastomotic rupture, acute heart failure, cerebrovascular lesions, mesenteric or renal vascular infarction, and pulmonary complications. Postoperative paraplegia is a complication in about 10-20% of cases. The 5-year postoperative survival rate is about 50%, and the survival rate decreases to 30% and 5% at 10 and 20 years after surgery.