aortic dissection
Introduction
Introduction to aortic dissection Aortic dissection, the formation of the aortic wall dissection, used to be called a dissection aortic aneurysm (dissectionaorticaneurysm), refers to the rupture of the intima of the aortic wall caused by various reasons, the blood enters through the breach of the intima The middle layer of the aortic wall forms a hematoma, causing stratification of the vessel wall, and the stripped inner membrane is separated to form a "double lumen aorta." However, Coady reported that there were no intimal tears in 8% to 15% of cases, which may be due to aortic wall hemorrhage, also known as intramural hematoma (intramuralhematoma). The expansion of the aortic wall in the aortic lumen is different from the aortic aneurysm. basic knowledge The proportion of the disease: the incidence of the disease in patients with hypertension is about 0.006% - 0.008% Susceptible people: 50-70 years old, male is higher than female Mode of infection: non-infectious Complications: aortic dissection, acute renal failure, vascular injury, cerebrovascular disease
Cause
Aortic dissection
(1) Causes of the disease
The cause is still unknown.
Cystic degeneration
Degenerative changes in the middle aorta, ie collagen and elastic tissue degeneration, often accompanied by cystic changes, are considered to be prerequisites for aortic dissection. Cystic middle degeneration is an intrinsic feature of connective tissue genetic defects, especially in Marfan. Syndrome and Ehler-Danlos syndrome, aortic dissection, especially proximal dissection is often a serious and common complication of Marfan syndrome. It has been reported that 6% to 9% of patients with aortic dissection are Marfan syndrome. Recently, aortic dissection has been reported in patients with Noonan and Turner syndrome. Cystic middle degeneration may be a common problem. There is an unexplained relationship between pregnancy and aortic dissection. Female aorta under 40 years old. About half of the dissection occurs during pregnancy, and occurs mostly within 3 months of pregnancy or early in the puerperium. Women with Marfan syndrome and aortic root dilatation have an increased risk of acute aortic dissection during pregnancy, blood volume, cardiac output. Increases in volume and blood pressure may also be risk factors during pregnancy but have not been confirmed.
hypertension
More than 80% of patients with aortic dissection have hypertension, and many patients have cystic necrosis. Hypertension is not the cause of cystic necrosis, but it can promote its development. Hypertension is an important factor leading to dissection, about half of which is near End and almost all of the distal aortic dissection have hypertension, elevated blood pressure in acute attacks, sometimes accompanied by aortic atherosclerotic ulcer surface, because long-term hypertension can cause smooth muscle cell hypertrophy, degeneration and middle necrosis .
trauma
Direct trauma can cause aortic dissection, blunt contusion can cause local aortic tear, hematoma formation of aortic dissection, intra-aortic intubation or intra-aortic balloon intubation can cause aortic dissection, cardiac surgery For example, aortic-coronary artery bypass grafting can also cause aortic dissection.
(two) pathogenesis
The basic lesion of this disease is cystic middle layer necrosis. The middle elastic fiber of the artery has local rupture or necrosis. The matrix has mucous-like and cyst formation. The aortic wall divides into two layers, with blood and blood clots accumulating, and the aorta is enlarged. It is fusiform or saclike. If the lesion is involved in the aortic annulus, the ring enlarges and causes aortic regurgitation. The lesion can be extended from the aortic root to the distal, up to the radial artery and femoral artery. Involving the branches of the aorta, such as the innominate artery, the common carotid artery, the subclavian artery, the renal artery, etc., the coronary artery is generally unaffected, but the clot of the aortic root may have an oppressive effect on the opening of the coronary artery, and the origin of most dissections The transverse rupture of the intima is often located above the aortic valve. There are also two ruptures. The dissection is in communication with the aortic cavity. The inner membrane of a few dissections is intact and there is no rupture. In some cases, the outer membrane ruptures and causes massive hemorrhage. In the ascending aorta, bleeding easily enters the pericardial cavity, and the lower rupture site can also enter the mediastinum. The chest cavity is easy to enter the pericardial cavity, and the lower rupture site can also enter. Septal, thoracic or retroperitoneal space, a chronically dissected dissection can form a double-chamber aorta, one tube nested in another, this condition is seen in the descending branch of the thoracic aorta or aortic arch, DeBakey divides the aortic dissection into Type 3: Type I sandwiches from the ascending aorta and descend to the descending aorta, type II is confined to the ascending aorta, type III dissection extends from the descending aorta and extends distally. In addition, Daily and Miller divide the aortic dissection For the two types: those with ascending aorta involvement are type A (including DeBakey type I and type II), and the distal opening of the left subclavian artery is type B (ie DeBakey type III), and type A accounts for about 2/3 of all cases. Type B accounts for about 1/3.
Aortic cystic degeneration leads to repeated flexion of the aorta, hemodynamics and trauma caused by hypertension in the aorta, causing aortic intimal tear to form a dissection hematoma, about 60% of tears occur in the ascending Arteries, 10% in the aortic arch, 30% in the first part of the descending thoracic aorta, the depth of the mesenteric invasion and the distance of the mesothelioma spread, are related to the extent of aortic degeneration, the blood in the aortic lumen enters the middle layer, the endometrium Separated from the middle layer, the separation of the wall generally develops toward the distal end of the artery, and can also extend upwards in a short distance. The aortic dissection spirals in the wall of the arterial tube, and when it is widely sandwiched, it can be involved. The branch affects the blood supply of the adjacent organs; or the middle layer first has hemorrhage, forming a hematoma, and the longitudinal development divides the aortic cavity into a true cavity and a false cavity, and the rupture of the false cavity causes the blood to return to the arterial cavity to form a "natural cure." ", but more is broken into the pericardium or broken into the pleural cavity, mediastinum, retroperitoneal, etc., leading to serious complications, experiments have shown that promoting the expansion of the meridian hematomas is the pulse steepness (dp /dt) and blood pressure, which is the theoretical basis for acute aortic dissection.
Prevention
Aortic dissection prevention
The disease is rare, the incidence rate is about 5 to 10 cases per million people per year, but more rapid onset, 65% to 75% of patients in the acute phase (within 2 weeks) die of cardiac tamponade, arrhythmia and other cardiac complications, The peak age is 50-70 years old. The male incidence rate is higher than that of females. The ratio of male to female is 2~3:1. According to the onset time, it is divided into acute phase and chronic phase: the onset is acute within 2 weeks, more than 2 weeks. In the chronic phase, according to the extent of the intimal tear site and the aortic dissection aneurysm, it can be divided into type A: the intimal tear can be located in the ascending aorta, the aortic arch or the proximal descending aorta, and the extension can involve the ascending aorta. The arch can also extend to the descending aorta or even the abdominal aorta. Type B: The intimal tear is often located in the aortic isthmus. The extension only affects the descending aorta or extends to the abdominal aorta, but does not involve the ascending aorta.
Most cases die within a few hours to several days after onset. The hourly mortality rate is 1% to 2% within the first 24 hours, depending on the location, extent and extent of the lesion. The more distal, the smaller the range, the amount of bleeding. Less prognosis is better.
Patients with high blood pressure should monitor blood pressure changes at least twice a day, adopt a healthy lifestyle, use drugs to control blood pressure in a normal range, appropriately limit physical activity, and avoid excessive exercise to induce disease, accompanied by Patients with aortic valve mitral valve malformation and Ma Fang syndrome should limit severe activities, regular physical examination, monitoring changes in the condition, and timely surgical treatment to prevent the occurrence of aortic dissection.
Complication
Aortic dissection Complications aortic dissection acute renal failure vascular injury cerebrovascular disease
After the formation of the aortic dissection, the celiac artery is compressed, the mesenteric artery causes nausea, vomiting, bloating, diarrhea, melena; compression of the cervical sympathetic ganglia causes Horners syndrome; compression of the recurrent laryngeal nerve causes hoarseness; compression of the superior vena cava causes Vena cava syndrome; involving the renal artery causing hematuria, urinary retention and elevated blood pressure after renal ischemia, and can affect the blood supply to vital organs, such as the heart, brain, internal organs, etc., is also an important cause of death, 65% ~ 75% of patients died of cardiac complication, arrhythmia and other cardiac complications in the acute phase (within 2 weeks).
Different surgical treatments for this disease have different complications. Here, the perioperative complications of aortic dissection stent graft endovascular repair will be described in detail.
1, aortic dissection
Intraoperative and postoperative aortic dissection is more common. The most serious result is ruptured active dissection and cardiac tamponade leading to death. If found in time, the patient can survive. Ascending aortic dissection is undoubtedly the most serious complication. The reasons may be as follows:
(1) Intraoperative operation of various guide wires, catheters and conveyors may cause damage to the aortic intima.
(2) Top-end bare stents All the stent grafts have bare metal stents at the head end, and the head end is sharp. It is in close contact with the aortic wall. As the artery beats, there will be some degree of friction, which may cause A new breach.
(3) The larger the stent is, the larger the radial tension is, the greater the radial tension may cause aortic injury.
(4) When the patient's own blood vessel wall condition has a connective tissue disease, the blood vessel wall of the patient is weak and cannot bear the support of the stent graft.
2, the original breach is not completely closed
In some patients with internal leakage, the false lumen can be kept open for a long time, and thrombus can form part of it. The diameter of the descending aorta can be increased or not increased. Some endoscopic leaks can disappear. Complete thrombus formation, stent leakage is a common complication, the greater the intimal rupture, the closer to the left subclavian artery opening, the more likely to produce endoleak, even if the left subclavian artery is completely closed, it can not be completely Avoid internal leaks.
3. Acute renal failure
4, cerebrovascular accident
Some patients may have cerebral infarction during the operation and cause hemiplegia. Patients with severe complications may have cerebral hemorrhage and die. Most of them occur in patients with high postoperative blood pressure. The cause of intraoperative cerebral infarction is unknown, and may be related to intraoperative arteries. Sclerotherapy plaque detachment is associated with intraoperative controlled hypotension. Postoperative cerebral hemorrhage is associated with hypertension. Patients with aortic dissection often have hypertension and arteriosclerosis.
5, peripheral vascular injury
Symptom
Aortic dissection symptoms Common symptoms Weekly sweating nausea and vomiting limbs blood pressure pulse asymmetry chest pain shock syncope
Depending on the location of the lesion, the main performance is as follows:
Sudden severe pain
This is the most common symptom at the onset of the disease and can be found in more than 90% of patients with the following characteristics:
(1) The intensity of pain is more characteristic than its location: pain is extremely intense and unbearable from the beginning; the nature of pain is pulsating, tearing, knife cutting, and often accompanied by vasovagal excitation, such as sweating Dripping, nausea, vomiting and syncope.
(2) The pain site helps to indicate the initial site of separation: severe pain in the front chest, mostly in the proximal dissection, and the most severe pain in the interscapular region is more common in the initial distal dissection; although proximal and distal The mezzanine can feel pain in the chest and back at the same time, but if there is no pain in the posterior interscapular region, the distal dissection can be ruled out because more than 90% of patients with distal dissection have back pain; neck, pharynx, forehead or Tooth pain often suggests a dissection involving the ascending aorta or aortic arch.
(3) The pain site is migratory. The range of the aortic dissection is expanding: the pain can be moved from the beginning to other parts, often along the path and direction of separation, causing pain in the head and neck, abdomen, waist or lower limbs. 70% of patients have this feature and dysfunction of adjacent organs of the branches of the aorta due to the expansion of the extent of the dissection hematoma.
(4) Pain is often persistent: some patients continue to die after the onset of pain, analgesics such as morphine are difficult to relieve; some due to rupture of the distal endometrium of the dissection causes the blood in the dissected hematoma to return to the aortic canal In the cavity, the pain disappears; if the pain disappears after repeated disappearance, it should be alert that the aortic dissection continues to expand and there is a risk of outward rupture; a small number of patients without pain often cover up with pain due to syncope or coma in the early stage of the disease.
2. Symptoms of hypertensive patients
Due to severe pain, there is shock appearance, anxiety, sweating, pale, heart rate acceleration, but blood pressure is often not low or increased, about 80% to 90% of the distal dissection and part of the proximal dissection are high Blood pressure, many patients with high blood pressure after the onset of pain make blood pressure higher, low blood pressure, often the result of mezzanine separation caused by pericardial tamponade, pleural cavity or peritoneal cavity rupture, and when the dissection involves the brachiocephalic blood vessels to damage the limb arteries Or when occlusion, blood pressure cannot be accurately measured and pseudohypotension occurs.
3. Dissection or compression symptoms
As the dissection of the hematoma compresses the surrounding soft tissue, affecting the large branches of the aorta, or breaking into adjacent organs causing damage to the corresponding organ system, the clinical manifestations of multiple system damage.
(1) Cardiovascular system:
1 aortic regurgitation: aortic regurgitation is one of the important features of the proximal aortic dissection, there may be a diastolic murmur in the aortic valve area, often a musical, clearer along the left sternal border, with high blood pressure However, according to the degree of reflux, other peripheral vascular signs of aortic regurgitation may also occur, such as pulse pressure widening or water pulse, etc. Acute severe aortic regurgitation may occur with heart failure. The mechanism of aortic valve regurgitation caused by proximal dissection has four aspects: A. The dissection expands the aortic root, the annulus enlarges, and the aortic valve leaflets cannot close during diastole; B. In the asymmetric sandwich, The dissected hematoma compresses a leaflet so that it is below the closing line of other leaflets, causing incomplete closure; C. tearing of the leaflet or annulus stent, causing a leaflet to be free or cleaved, resulting in insufficiency of the valve; The dissected endometrial tears are released from the aortic valve leaflets, affecting the closure of the aortic valve.
2 pulse abnormalities: half of the proximal dissection may involve the brachiocephalic vessels, and a few distal dissections may involve the left subclavian artery and the femoral artery, where the pulse is weakened or disappeared, or the strength of the two sides is different, or the blood pressure of both arms is obvious. Differences, or signs of vascular obstruction such as a decrease in blood pressure between the upper and lower extremities, may be due to a direct compression of the arterial lumen due to dissection, or a blockage of blood flow due to a torn inner membrane covering the vascular orifice.
3 other manifestations of cardiovascular damage: angina or myocardial infarction may occur when the dissection involves the coronary artery; the superior vena cava syndrome may occur when the hematoma is compressed into the superior vena cava; when the dissected hematoma ruptures into the pericardial cavity, it may rapidly cause pericardial hemorrhage. Causes acute pericardial tamponade and death.
(2) Nervous system: Dissection of hematoma along the innominate artery or common carotid artery, or involving the intercostal artery, vertebral artery, dizziness, confusion, limb numbness, hemiplegia, paraplegia and coma; oppression of the recurrent laryngeal nerve, There is hoarseness; compression of the cervical sympathetic ganglia can occur with Horner syndrome.
(3) Digestive system: The dissection involves the abdominal aorta and its branches. The patient may have severe abdominal pain, nausea, vomiting and the like. The meridian hematoma compresses the esophagus, and dysphagia occurs. Breaking into the esophagus may cause hematemesis; Hematoma compresses the superior mesenteric artery, which can cause ischemic necrosis of the small intestine and cause blood in the stool.
(4) urinary system: the dissection of the renal artery, can cause low back pain and hematuria, acute ischemia of the kidney, can cause acute renal failure or renal hypertension.
(5) Respiratory system: Dissection of the hematoma into the chest cavity, can cause pleural hemorrhage, chest pain, difficulty breathing or hemoptysis, sometimes accompanied by hemorrhagic shock.
The common classification method for aortic dissection is divided according to the location of the fracture, 1 ascending aorta within a few centimeters of the aortic valve; 2 thoracic descending aorta, often at the site of the lower arterial catheter at the opening of the subclavian artery There are three main classifications depending on the extent and extent of aortic involvement.
1. DeBakey classification type I, the dissection begins to ascend the aorta and crosses the ascending aortic arch to the descending aorta; type II, the dissection is initiated and confined to the ascending aorta; type III, the dissection begins with the descending aortic left clavicle The distal end of the inferior artery opens and can extend to the infraorbital abdominal aorta. A relatively rare condition is a retrograde distal extension involving the aortic arch and the ascending aorta.
2.Daily and Miller classification: type A, that is, all proximal aortic dissection and those with distal dissection but reverse extension involving the bow and ascending aorta (including DeBakey type I and type II); type B, ie, mezzanine Only in the proximal part of the left subclavian artery opening and not involving the proximal end, 3 anatomical type "proximal" aortic dissection (deBakey type I and type II or type A); "distal" aortic artery wall Interlayer formation (deBakey type III or type B).
In addition, aortic dissection can also be staged according to the length of the disease: patients with a disease duration shorter than 2 weeks, an "acute" aortic dissection; patients with a course longer than 2 weeks, a "chronic" aortic dissection, in the untreated acute In patients with aortic dissection, the mortality rate can reach 75% to 80%. Among the diagnosed patients, 2/3 are acute aortic dissection and 1/3 are chronic aortic dissection.
Examine
Aortic dissection
Routine laboratory tests have no special significance for the diagnosis of aortic dissection. They can only be used to rule out the possibility of other diagnoses. Occasionally, acute onset of aortic dissection may be associated with stress-related leukocytosis, or severe bleeding and massive blood inflow. Anemia caused by false cavities, diffuse intravascular coagulation has been reported separately; serum transaminase is generally not elevated unless dissection of the hematoma involves myocardial infarction in the coronary arteries; erythrocyte sedimentation rate does not increase significantly, but it has been reported that when serous hemorrhage occurs ESR can increase; when the superior mesenteric artery is involved and affects the pancreas, serum amylase can be increased; when the kidney is involved, hematuria can occur; when the stroke is present, bloody cerebrospinal fluid can occur.
Electrocardiogram
There is no specific electrocardiographic changes in the aortic dissection. In the past, there may be hypertensive patients with left ventricular hypertrophy and strain. When coronary artery involvement, myocardial ischemia or myocardial infarction may occur. When pericardial hemorrhage, acute pericarditis may occur. The ECG changes.
2. Chest X-ray film
In recent years, various imaging diagnostic methods have been paid more and more attention, and are widely used to diagnose aortic dissection, but according to clinical diagnosis and treatment requirements, X-ray film should be used as a diagnostic routine for aortic diseases, thoracic aortic aneurysm and chronic main Arterial dissection can be observed by plain film, posterior anterior and lateral radiographs, widening of the superior mediastinum, prolongation of aorta, irregular aortic shape, local elevation, calcification in the aorta Shadow, at this time can accurately measure the thickness of the aortic wall, if it increases to 10mm, it suggests that there may be a sandwich, if more than 10cm can be considered as a mezzanine, especially before the onset of chest radiographs with similar conditions and post-morbid conditions In comparison, or after a series of chest radiographs to observe the width of the aorta, it is more meaningful, but often the chest radiograph does not have a diagnostic value, there are certain limits for "qualitative" and "quantitative", and its diagnosis depends on other images. Learn diagnostic techniques.
3. Echocardiography and Doppler
Two-dimensional echocardiography has important clinical value in the diagnosis of ascending aortic dissection. It is very reliable to observe the aortic sway in the aorta and the aortic true and false double-chamber sign of the aortic dissection, and the aortic root dilatation can be seen. Aortic wall thickening and aortic valve insufficiency, and easy to identify complications, such as pericardial hemorrhage, pleural hemorrhage, etc., Doppler ultrasound can not only detect abnormal blood flow between the double echo of the aortic dissection wall, To determine whether there is a thrombus in the pseudocavity, and to have an important diagnostic value for aortic dissection, rupture location, quantitative analysis of aortic regurgitation and left ventricular function, although transthoracic echocardiography has aortic dissection. Different degrees of diagnosis or screening diagnosis, and easy to check, but the complete display of the entire thoracic aorta, especially the diagnosis of localized aortic dissection or descending aortic dissection is limited, the false positive rate is relatively high In recent years, transesophageal echocardiography (TEE) examination can almost clearly show the entire thoracic aorta, including the proximal aorta, aortic arch And the morphological structure of the thoracic descending aorta, especially the application of biplane and multiplanar probes, reduces the blind area of the thoracic aorta to a minimum, greatly improving the echocardiography in the thoracic aortic dissection, especially the descending aortic dissection. The diagnostic value, as well as the observation of blood flow in the true and false lumen of the dissection, the location of the fracture and the thrombus of the wall, the diagnostic compliance rate can reach 100%, and some authors believe that it is superior to CT scan and angiography.
4. Computed tomography (CT)
CT can show the aortic dilatation of the lesion, and it is found that the aortic intimal calcification is superior to the X-ray plain film. If the calcified endometrium is displaced to the center, the aortic dissection is prompted. If the displacement to the periphery suggests a simple aortic aneurysm, due to its scanning. Perpendicular to the longitudinal axis of the aorta, it is easier to detect the torn intima vertical slices than angiography. The latter presents a very thin low-density line, which divides the aortic dissection into true, false two-chamber, fresh thrombus in the false lumen. In the plain scan, the density is increased. This is one of the most specific signs of diagnosis of aortic dissection. CT has high accuracy for descending aortic dissection, but it can produce dissection of the aortic ascending segment due to arterial distortion. False positive or false negative; in addition, it can not diagnose aortic insufficiency, nor can it understand the location of the aortic dissection and the branching of the aorta.
5. Magnetic resonance imaging (MRI)
MRI is similar to CT, but compared with CT, it can be multi-directional, multi-parameter imaging, such as horizontal axis, sagittal, coronal and left anterior oblique position, and can fully observe the type and extent of lesion without using contrast agent. And anatomical changes, its diagnostic value is better than Doppler ultrasound and CT, the specificity and sensitivity of the diagnosis of aortic dissection are more than 90%, especially when the aortic dissection is spirally torn to the abdominal aorta, still It can directly display the true and false aortic dissection, more clearly showing the location of the intimal tear and the relationship between the lesion and the aortic branch. The disadvantage is that it is expensive and cannot be used for pacemakers and knots. Patients with metal objects are not satisfied with the coronary and aortic valve conditions.
6. Digital subtraction angiography (DSA)
Less invasive intravenous DSA, the diagnosis of type B aortic dissection can basically replace common angiography, can correctly find the location and extent of aortic dissection, aortic hemodynamics and perfusion of major branches, some patients In the DSA, the torn inner membrane is clearly visible, and it is easy to find calcification that can not be detected by aortic angiography. However, for type A or Marfan syndrome, the aortic dissection, venous DSA has its limitations, poor resolution, and conventional arteries. Fine structures such as intimal tears that can be found by angiography may be missed.
7. Aortic angiography
At present, the method of transcatheter retrograde intubation angiography is used. The biggest advantage is that the entrance and exit of the intimal tear can be confirmed, the involvement of the aortic branch is confirmed, and the severity of aortic regurgitation is estimated. Most surgeons still It is considered that aortic angiography is essential when establishing a diagnosis and planning a surgical procedure. The disadvantage is that it is invasive, especially for acutely critical acute patients, and the DSA of arterial injection can produce satisfactory results. It is a promising method of examination. 8. Blood and urine examinations often increase white blood cell counts, hemolytic anemia and jaundice, red blood cells in the urine, and even gross hematuria.
Diagnosis
Diagnosis of aortic dissection
The clinical manifestations of aortic dissection are more complex, involving almost all systemic systems, often manifested as acute chest pain, high blood pressure, sudden aortic regurgitation, bilateral pulse unequal or pulsatile mass should be considered, chest pain often Considered as acute myocardial infarction, but the chest pain begins to be less severe when the myocardial infarction begins, gradually worsens, or worsens after the reduction, does not radiate to the chest below, can be effective with painkillers, with characteristic changes of ECG, if there is shock appearance, blood pressure Often low, does not cause the pulse on both sides, the above points are adequately identified, so it should be noted in the early differential diagnosis of aortic dissection.
(1) persistent severe chest pain, abdominal pain, rapid onset, morphine, etc. can not be alleviated.
(2) Although there is chest pain, abdominal pain, and signs of shock, but the blood pressure is slightly reduced or not decreased, or even increased.
(3) Sudden onset of aortic regurgitation, or progressive deterioration of heart failure.
(4) Upper sternal fossa, the abdomen touches the pulsatile mass.
(5) Both sides of the radial artery, the femoral artery pulsation is different, and even there is no pulse.
(6) Similar to acute myocardial infarction, and there is no characteristic change in ECG.
(7) chest pain with nervous system symptoms, such as syncope, hemiplegia and sudden emergence of consciousness disorders in the elderly.
In case of the above performance, it is necessary to highly suspect the possibility of aortic dissection. Imaging examination should be performed in time. In recent years, various examination methods have greatly helped to establish aortic dissection. Echocardiography, CT scan, and magnetic resonance can be used for diagnosis. It is still necessary to consider the aortic angiography of the operator.
