Thoracic aortic disease is an important public health problem. In recent years, with the improvement of medical personnel's understanding of aortic diseases, as well as the advancement of diagnostic imaging, surgical techniques, and anesthesia techniques, the diagnosis rate of descending thoracic aortic aneurysm (DTAA) has been increasing, and the incidence of surgical complications and mortality rate has been significantly reduced. However, due to the lack of large-scale prospective randomized controlled trial (RCT) studies on the treatment of DTAA, there are still many controversies in the industry about the diagnosis and treatment of this disease.

In order to standardize and guide the clinical diagnosis and treatment of aortic disease, the European Society for Vascular Surgery (ESVS) released guidelines for the treatment of descending thoracic aorta (DTA) disease in 2017 [1-2]; the American Society for Vascular Surgery ( Society for Vascular Surgery (SVS) published guidelines for endoluminal repair of DTAA in 2020, with more updates and modifications to previous versions of the guidelines [3]. The above guidelines have made corresponding recommendations for the diagnosis, treatment and follow-up of DTAA. At present, the diagnosis and treatment of DTAA in China basically follow the above guidelines, but there is no systematic diagnosis and treatment standar

d for DTAA in China.

In view of this, relying on the Vascular Surgery Group of the Surgery Branch of the Chinese Medical Association, the group organized some domestic experts to formulate a consensus on the diagnosis and treatment of DTAA based on the new clinical research results, especially based on the clinical research on Chinese patients, referring to the guidelines and consensus issued by the international related associations and organizations, and combining with China's national conditions and clinical practice, and recommending the principles of diagnosis and treatment, in order to provide guidance and references for medical decision-making.

I. Anatomy, definition and staging

1.Anatomy

The aorta can be divided into 11 zones, which are used to describe the segments of the aorta and the branches that may be covered or replaced during endoluminal repair. Six zones are located in the thoracic aorta, of which zones 3 to 5 are located in the DTA [4].Zone 3 is the proximal DTA from the distal end of the opening of the left subclavian artery to 2 cm distal to the opening of the left subclavian artery; zone 4 is the straight portion of the DTA from the opening of the left subclavian artery to the midpoint of the DTA (at about the level of T6); and zone 5 is the proximal part of the opening of the abdominal trunk from the midpoint of the DTA (at about the level of T6) to the opening of the abdominal trunk, and is the distal DTA. DTA. see Figure 1.

Picture

2.Definitions

An aortic aneurysm is defined as a segmental dilatation of the aorta due to various causes with a diameter greater than 1.5 times that of the adjacent normal aorta [5-7]. Aortic aneurysms occurring in the region of the DTA are known as DTAA.Given that the diameter of the aneurysm is closely related to the rate of growth of DTAA and the risk of rupture, the diameter of the aneurysm is of great significance in the diagnosis, treatment, and prognosis of DTAA [8-9].

3.Staging

Currently, there is no recognized method of staging DTAA. It can be typed according to the area of aneurysm involvement; DTAA can also be classified into spindle-shaped DTAA and saccular DTAA according to the morphology of the aneurysm, and saccular aneurysm may be a manifestation of plaque hemorrhage, aortic ulceration, or infection of the aortic wall [10-11].

II. Epidemiology

Currently, there is a lack of population-based epidemiologic data on DTAA in China. Some studies have shown that the annual incidence of DTAA and thoracic and abdominal aortic aneurysms in Europe and the United States is 6-10/100,000 per year. Of all thoracic aortic aneurysms, DTAA accounts for about 35%, ascending aortic aneurysms for about 40%, aortic arch aneurysms for about 15%, and thoracoabdominal aortic aneurysms for about 10% [12].

In recent years, the prevalence and incidence of thoracic aortic disease has been higher than previously reported and continues to increase.The increase in the prevalence of DTAA has been attributed to a number of factors, including advances in imaging technology, an aging population, and increased patient and physician awareness.

DTAA is most commonly seen in the elderly. The mean age of patients with thoracic aortic aneurysms at diagnosis is 65 years, with a male to female ratio of 1.7:1 [13].DTAA is clearly associated with genetic factors, with more than 20% of patients affected by aneurysmal disease in first-degree relatives [14].

III. Etiology and risk factors

Most DTAA is degenerative in nature and is associated with atherosclerotic risk factors. Other etiologic factors include systemic autoimmune diseases, aortic infections, and connective tissue diseases (e.g., Marfan syndrome, Loeys-Dietz syndrome, and Ehlers-Danlos syndrome) [15-16].

1. Atherosclerosis: Most DTAA are degenerative and associated with risk factors for atherosclerosis, such as smoking, hypertension and hypercholesterolemia, but the role of atherosclerosis in aneurysm formation is not clear. Hypertension is an important risk factor and is seen in more than 60% of DTAA patients.

2. Inflammatory diseases: A variety of inflammatory diseases can lead to DTAA, including giant cell arteritis, aortitis, rheumatoid arthritis, ankylosing spondylitis, granulomatous polyangiitis and reactive arthritis. Giant cell arteritis is the inflammatory disease that most often leads to thoracic aortic aneurysms. As many as 11% of patients with giant cell arteritis develop DTAA or related thoracic aortic disease [12].

3. Hereditary connective tissue disorders: the most common are Marfan syndrome, Loeys-Dietz syndrome and Ehlers-Danlos syndrome. Aortic dilatation in hereditary connective tissue disorders is more rapid than in degenerative aneurysms and is more likely to require intervention. In addition, in patients with inherited connective tissue disease, if the first aortic surgery is for type A aortic coarctation, the postoperative risk of progression of the residual chronic coarctation in the distal aorta to an aortic aneurysm is extremely high, and postoperative follow-up is mandatory.

4. History of previous aortic coarctation: Acute aortic coarctation often involves the ascending and descending aorta. Surviving patients with acute aortic coarctation who do not require immediate surgery may develop aneurysmal changes leading to progressive aortic dilatation and delayed aortic dissection.

5. Trauma: Chest trauma may result in pseudo-DTAA of the aortic isthmus due to deceleration forces.6. Infection: Aortic infections leading to DTAA can originate from direct bacterial invasion, bacteremia seeding, and neighboring site infections. Infection can weaken the arterial wall components, leading to rapid aneurysm formation. These aneurysms are usually associated with penetrating aortic ulcers and are often saccular.

7. Anatomic variations: Several anatomic variations carry a high risk of DTAA, such as bilobed aortic valves, aortic constriction (aortic constriction surgery in infancy), and Kommerell's diverticulum.

IV. Diagnosis

1 Medical History

The degree of risk in patients with DTAA can be assessed by a clinical history, such as a history of hypertension and blood pressure control, history of use of important medications, history of connective tissue disease, history of vasculitis, history of aortic surgery, and history of thoracic trauma. In addition, a detailed family history and history of familial aneurysm and entrapment should be taken.

2 Clinical manifestations

DTAA is usually asymptomatic unless there is pain associated with entrapment or aneurysm rupture, and it is usually detected during physical examination or other disease diagnosis and treatment [17].DTAA associated with entrapment may manifest as poor organ perfusion or neurological complications, etc. Rupture of DTAA may present with the manifestations of hemorrhagic shock, including indifference or coma, pallor of the skin, tachycardia, tachypnea, dyspnea, dysuria, and drop in blood pressure, etc. DTAA rupture may enter the adjacent esophagus, which may cause a decrease in the blood pressure. Rupture may enter the adjacent esophagus or bronchus, resulting in an aorto-esophageal fistula or aorto-bronchial fistula, which may be manifested by vomiting blood or hemoptysis. A large DTAA can compress the esophagus causing dysphagia, the left recurrent laryngeal nerve or left vagus nerve causing hoarseness, and the phrenic nerve causing unilateral diaphragmatic paralysis [18]. If the trachea or bronchus is compressed, rales, cough, hemoptysis, dyspnea, or pneumonia may occur. Compression of the central vein or superior vena cava can lead to thromboembolism or superior vena cava syndrome (swelling of the neck, face, or upper extremities) due to superior vena cava occlusion.DTAA may erode the adjoining spine leading to back pain.

3 Laboratory Tests

Initial laboratory tests in patients with DTAA include routine blood tests, liver and kidney function, electrolytes, coagulation, D-dimer, and cardiac markers. These laboratory tests may be helpful in guiding the treatment of patients with DTAA. In patients with systemic manifestations (e.g., fever, weight loss), an elevated white blood cell count may suggest aortic infection or inflammation, and an elevated D-dimer may suggest a large tumor [19-20]. Anemia may suggest that shock is due to acute blood loss, and elevated lactate levels are helpful in assessing the severity of ischemia.

4 Imaging

1. Chest radiograph: DTAA can change the transverse diameter of the mediastinum, so that the chest radiograph of the patient shows widening of the mediastinum. In addition, chest radiographs of patients with DTAA may also show the disappearance of the aortic silhouette, tracheal deviation, bronchial depression, and pleural effusion caused by ruptured aneurysm, etc. [21]. However, chest radiography is often prone to misdiagnosis in the diagnosis of DTAA.

2. computed tomography angiography (CTA): at present, CTA is the preferred imaging method for patients with suspected DTAA, with the advantages of wide popularity, rapid acquisition, high sensitivity and specificity, high spatial resolution and multiple post-processing modalities. If thoracic endovascular aortic repair (TEVAR) is planned, it is recommended that the whole aorta be imaged using CTA with a layer thickness of ≤0.25 mm, with an acquisition range from the thoracic inlet to the level of the pubic symphysis, up to the three branches of the supra-arterial arch, and down to the bilateral femoral arteries [22]. Cardiac gated CT scanning with 64 rows or more is recommended to minimize artifacts due to cardiac and aortic pulsations. Attention is paid to the dosage and injection rate of intravenous contrast agent to minimize aortic interference from enhanced images of the left cephalic arm vein and superior vena cava. Multi-angle and multi-plane 3D reconstruction is useful for assessing the morphology of the aorta, and centerline-based diameter measurement is more accurate [23-25].

3. MRI: Considering the advantages of wide popularity, fast acquisition and high spatial resolution of CTA, MRI is not used as a routine examination for DTAA. For patients with iodine allergy, hyperthyroidism, renal insufficiency, pregnant women (early 3rd trimester) or other relative or absolute contraindications to CTA, MRI is the preferred alternative test.The diagnostic efficiency of MRI for DTAA is similar to that of CTA. Compared with CTA, MRI has greater soft-tissue resolution and can characterize or quantify functional parameters. In patients with comorbid vasculitis, MRI provides better imaging of the tube wall. However, MRI scanning time is long and is not indicated for acutely ill patients with unstable circulation. It is also not suitable for claustrophobic patients with life support devices or magnetic metal implants in the body.Another advantage of MRI is that it can provide aortic morphology and flow parameters without iodine contrast or radiation.

4. Echocardiography: Transthoracic echocardiography (TTE) is portable and widely available, and allows simultaneous assessment of cardiac function, aortic valve, and aortic sinus. TTE is less accurate than CT or MRI in the diagnosis of DTAA. width, obesity, emphysema and mechanical ventilation, etc. Transesophageal echocardiography (TEE) can overcome these problems and significantly improve the diagnostic accuracy. However, as an invasive examination, TEE carries certain risks for patients with DTAA and is not recommended to be performed under non-general anesthesia.

5. Intravascular ultrasound: it can real-time and dynamically display the three-dimensional structure of the aortic cavity, and can be used as an important auxiliary means of endoluminal treatment of thoracic aortic lesions. The use of intravascular ultrasound can reduce the amount of intraoperative contrast medium and the use of radiation, providing important value for the treatment of DTAA. The use of intravascular luminal ultrasound is recommended for TEVAR to assess the distal landing zone of DTAA and to evaluate in detail the distal landing zone or important branch vessel origins.

V. Treatment

1 Perioperative management

Perioperative management of patients with DTAA includes control of blood pressure, regulation of blood lipids and smoking cessation.

1. Blood pressure control: the use of antihypertensive drugs is the first-line treatment option for patients with aortic lesions. Blood pressure control is achieved primarily by decreasing left ventricular contractility and rate of contraction, thereby reducing aortic wall stress, which is particularly important in patients with symptomatic aneurysms and acute aortic syndromes. The goals of treatment are to reduce systolic blood pressure to less than 120 mmHg (1 mmHg = 0.133 kPa) and to reduce heart rate to 60 to 80 beats/min as much as possible during the perioperative period of TEVAR.Intravenous beta-blockers (or alpha/beta blockers) are the first-line therapeutic agents for blood pressure control. In patients intolerant to β-blockers, calcium channel blockers and/or angiotensin-converting enzyme inhibitors/blockers can be used as alternative therapy or supplements [26]. Since hypertension is a relevant risk factor for the development of aortic aneurysms and is associated with accelerated enlargement and rupture of the aorta, it is recommended that blood pressure be managed in accordance with the American Heart Association/American College of Cardiology guidelines [27].

2. Lipid regulation: For DTAA patients with dyslipidemia, statins should be used to control LDL cholesterol levels to less than 70 mg/dl, which may help to control aneurysm progression [28].

3. Smoking cessation: DTAA patients are advised to quit smoking and avoid secondhand smoke to reduce the risk of aortic dissection [29-30].

2 Open surgery

There are no prospective RCT studies comparing the clinical outcomes of open surgery and TEVAR for the treatment of DTAA. In reports of thoracic aortic aneurysms, the risk of perioperative morbidity and mortality remains high with open surgery. The mortality rate after open surgery for ruptured thoracic aortic aneurysms approaches 26% in some highly specialized clinical centers [31]. In comparison, the overall mortality rate for elective open surgery for thoracic aortic aneurysms in the United States is approximately 22% [32]. In addition, some clinical centers have reported very low rates of mortality and spinal cord ischemia after open surgery, 4.8% and 4.6%, respectively [33]. However, a large number of studies have consistently demonstrated that TEVAR is a safe alternative to open surgery for isolated thoracic aortic aneurysms, significantly reducing patient complication rates and mortality, and shortening hospitalization time [34-35]. A review comparing open surgery and TEVAR in thoracic aortic aneurysms showed that TEVAR was technically feasible and showed a reduction in early adverse outcomes (e.g., paraplegia, mortality, and length of hospitalization) through nonrandomized studies, but further validation is needed in high-quality RCT studies [36-37]. Therefore, in patients with DTAA for whom both methods, open surgery and TEVAR, are indicated, TEVAR is recommended as the preferred method for the elective treatment of DTAA due to its reduced complication rate and near-term mortality, as well as shorter duration of treatment and hospitalization.

3TEVAR

1. Indication for surgery: the 5-year survival rate for untreated thoracic aortic aneurysms with a diameter of 6.0 cm is 54%, with a risk of rupture of 3.7%/year and a risk of death of 12.0%/year [38-39]. A prospective database that included more than 1,600 patients with thoracic aortic aneurysms and aortic coarctation found that the average annual growth diameter of DTAA was 0.10 cm [40]. In saccular aneurysms with a high risk of rupture, TEVAR can be performed when the aneurysm diameter is less than 6.0 cm. In “low-risk” asymptomatic DTAA patients with good aortic anatomy, TEVAR is recommended when the maximum aneurysm diameter exceeds 5.5 cm. A higher aortic diameter threshold for TEVAR is recommended for DTAA patients at high risk of death, renal failure, and paraplegia, because the benefits of treatment in these patients are lower than the risks associated with the natural course of the aneurysm. There is a lack of compelling long-term data on the use of TEVAR to treat infected aortic disease. Although TEVAR may be effective when used for the temporary management of ruptured infected thoracic aortic aneurysms or combined aorto-esophageal fistulas/aorto-bronchial fistulas, this subset of patients is characterized by high complication rates and mortality. Therefore, TEVAR is recommended as a temporary therapeutic measure for symptomatic infectious DTAA, but data on long-term benefit are lacking.

2. Intraoperative renal protection strategies: acute kidney injury (AKI) occurring during hospitalization or after TEVAR is one of the most important risk factors predicting mortality, especially when AKI progresses to the need for dialysis. When AKI occurs after TEVAR (incidence 10%-15%), mortality increases 10-fold even if dialysis is not required [41-42]. Risk factors for postoperative AKI include advanced age, chronic renal failure, diabetes mellitus, congestive heart failure, blood loss, major surgery, and arterial embolization associated with endoluminal manipulation. Importantly, contrast nephropathy is the third leading cause of AKI in hospitalized patients, with an incidence of 5% to 25%. Risk factors for contrast nephropathy include age, diabetes mellitus, prior renal disease, and excessive contrast dose [43-44]. Therefore, preoperative TEVAR surgical planning, including stent and stent anchorage zone sizing, is recommended to minimize the use of iodine-containing contrast agents. If feasible, CTA navigation techniques and intracavitary ultrasound should be used intraoperatively to minimize the use of contrast media. The use of nonionic hypotonic contrast agents is recommended, especially in patients at high risk for contrast nephropathy. Dilution of iodine-containing contrast agents in high-pressure syringes is recommended when possible (usually to 50% or 70%). Intraoperative mapping software for digital subtraction angiography equipment, such as roadmap, CT fusion, or navigation techniques, is recommended to help localize the anchoring zone and reduce repeat imaging.

3. Intraoperative strategies: During TEVAR in patients with high-risk DTAA, guidewires, catheters, or sheaths can be pre-positioned in the aortic branches to mark the location of the target branch, thereby minimizing repeat imaging. To minimize embolization due to arterial plaque dislodgement, it is recommended to avoid unnecessary manipulation of the aortic arch and visceral arterial regions during TEVAR. To avoid spinal cord ischemia and lower extremity ischemia, it is recommended to reduce the duration of retention of the large transfemoral arterial sheath. When prolonged retention is required, it is recommended that the head end of the large sheath be retreated to the external iliac artery so that the ipsilateral internal iliac artery can provide blood supply to the side branches [3].

4. Access for TEVAR: Although access complications for TEVAR are decreasing as stent delivery systems become more lubricated and outer diameters are reduced, access-related problems remain a common source of post-operative TEVAR complications. A number of ancillary measures can be applied to access patients with small iliac artery ductus venosus, including the use of more proximal arteries and open surgery [35, 45].

(1) Femoral artery access: percutaneous common femoral artery puncture is a common approach for TEVAR. Various techniques are available to identify the femoral artery, such as transverse small incision to establish access and ultrasound guidance, with a success rate of 92% to 96% [46-47]. In most centers, ultrasound guidance has become a routine method of percutaneous creation of vascular access, as it helps the operator to identify and avoid anatomical factors that may lead to failure of vascular closure, such as crossing the inguinal ligament or calcification on the anterior wall of the artery. The results of a Meta-analysis showed that of 469 TEVAR percutaneous creation of femoral arterial access, the overall success rate was 94%, the inguinal complication rate was 3.6%, and only 1.6% of patients required open inguinal open repair. The most common complication was groin 

hematoma (1.8%), followed by pseudoaneurysm (0.7%). Factors that improve the success rate of percutaneous puncture include ultrasound guidance and sheath size less than 20 F. Other anatomical factors that improve the success rate of percutaneous access include femoral artery diameter at the puncture site of greater than 1 cm and absence of anterior wall calcification, absence of severe scarring in the groin, and autogenous arterial access and access vessel diameter of greater than 5 mm [48].

Femoral arteriotomy is another common approach for TEVAR by incising at the level of the inguinal ligament, exposing the common femoral artery and controlling the proximal and distal femoral arteries. Transverse or oblique groin incisions are preferred over vertical incisions due to fewer incision-related complications, which are associated with up to 18% of postoperative complications [49].

Therefore, if the TEVAR access is established by means of femoral artery puncture, ultrasound-guided puncture is recommended to minimize complications. If the femoral artery is of suitable diameter and the anterior wall is not significantly calcified, it is recommended to use puncture instead of incision to establish a femoral TEVAR access. If the TEVAR femoral access is established by incision, a transverse or oblique incision is recommended.

(2) Other accesses: in addition to the conventional femoral artery access, TEVAR can also be performed through iliac artery, aorta, carotid-axillary and other accesses [50]. If the external iliac artery or femoral artery is severely stenotic, occluded, or calcified, it is suggested that an extraperitoneal approach can be used to implant an aortic stent via iliac artery bypass or puncture of the iliac artery. In cases where the transfemoral or iliac artery approach is not available, the cephalic brachial artery approach is an alternative for TEVAR device delivery.

4 Treatment of symptomatic and ruptured DTAA

The results of a Swedish study showed a high early mortality rate for open surgery for ruptured DTAA, with an in-hospital mortality rate close to 100%, and a more optimistic outcome for TEVAR [51]. Based on the results of the Medicare database, the percentage of patients with ruptured DTAA treated with TEVAR increased from 17% in 2004 to 49% in 2007, and the mortality rate decreased from 45% with open surgery to 24% with TEVAR [52]. There are other advantages of TEVAR for the treatment of ruptured DTAA compared to open surgery. A related study showed that the incidence of perioperative myocardial infarction was significantly lower with TEVAR compared with open surgery [53]. In addition, the incidence of stroke, paraplegia, and death within 15 years after TEVAR was lower than that of open surgery [54]. Therefore, TEVAR is recommended as an alternative to open surgery for the treatment of ruptured DTAA in patients with appropriate anatomical conditions.

Follow-up management

Regardless of the treatment modality, patients with DTAA need to be regularly followed up for a long time or even for life, in order to observe whether complications such as endoleak, stent migration and aneurysm expansion occur or progress. If there is no contraindication, imaging follow-up should be CTA.Currently, there is no uniform standard for the frequency of imaging follow-up, and the most commonly used follow-up protocols are 1, 6, and 12 months after TEVAR, and 1 imaging follow-up per year thereafter [55-56]. For patients with a continuous stabilization time of more than 5 years, the frequency can be appropriately relaxed to 1 follow-up in 2 to 3 years. For patients with DTAA who underwent TEVAR on an emergency basis, CTA is required during hospitalization or within 1 week after surgery [57]. If endoleak or other abnormalities are detected during follow-up, more frequent imaging should be considered. For patients with contraindications to CTA, MRI follow-up may be considered.

Correspondence should be addressed to FU Weiguo, Prof. CHEN Zhong

Cite this article as: Mao Le, Dong Zhi, Fu Weiguo, et al. Chinese expert consensus on the diagnosis and treatment of thoracic descending aortic aneurysms (2024 edition)[J]. Chinese Journal of Vascular Surgery (in Chinese and English), 2024, 9(1): 8-15. DOI: 10.3760/cma.j.cn101411-20231220-00055.

Reprinted from: Chinese Journal of Vascular Surgery