1. Open surgery for aneurysm-like lesions of the thoracic and abdominal aorta

Conventional treatment of thoracic and abdominal aortic aneurysm-like lesions relies primarily on open surgery, which requires a high degree of skill number of surgeons and a high level of perioperative anesthesia and monitoring management, and is often only performed in large medical centers with sophisticated surgical capabilities and associated ancillary measures. Despite the accompanying high risk of mortality and paraplegia, surgical treatment is still recommended for relatively young and low-risk patients. At the same time, with continued advances in surgical techniques and improved postoperative care, the outlook for long-term survival and health of patients is more favorable.

2. Open surgery for thoracoabdominal aortic aneurysm bulk report

The study by Coselli et al. covered 3,309 patients with thoracoabdominal aortic aneurysms treated with conventional open surgery, of which 914, 1,066, 660, and 669 were of different types (Crawford type I, II, III, and IV), respectively. Of these patients, 723 (21.8%) were operated on as emergencies with an intraoperative mortality rate of 7.5%. Postoperative complications included temporary hemiplegia (2.9%) and permanent paraplegia (2.4%), and temporary renal failure (5.7%). Postoperative survival decreased over time, with 1-, 5-, 10-, and 15-year survival rates of 83.5%, 63.6%, 36.8%, and 18.3%, respectively. The study also compared 445 (13.3%) of the 3,346 patients operated on between 1986 and 2015 who were <50 years of age with 2,901 (86.7%) who were >50 years of age, and found that the group of patients <50 years of age had a lower rate of operative mortality and complications.

3. 2017 ESVS guideline opinion on TAAA recommendations for open surgery

According to the 2017 guidelines on open surgery for thoracoabdominal aortic aneurysms (TAAA) published by the European Society for Vascular Surgery (ESVS), the majority of reports on this procedure originate from large, experienced medical centers around the world. These data show that the mortality rate for open surgery ranges from 5% to 15%, with major complications including respiratory failure (60% of cases), neurologic complications (including spinal cord ischemia, 3% to 18% of cases), and renal failure (3% to 15% of cases). In contrast, surgical mortality and complication rates at non-large, less-experienced medical centers were almost twice as high as those at large centers.

4. An updated clinical meta-analysis of open surgery for TAAA

Cornell Medical Center conducted a meta-analysis for open surgery for TAAA, covering 12,245 cases over a ten-year period from 2008 to 2018. The analysis showed that the overall mortality rate for open surgery was 10.4%, with 6.6% for descending aortic aneurysm surgery and 10.5% for TAAA surgery. Distant mortality was 0.6%. The overall incidence of postoperative complications included stroke in 4.9%, temporary spinal cord ischemia in 5.7%, permanent spinal cord ischemia in 3.0%, renal failure in 13.2%, respiratory failure in 23.3%, and myocardial infarction in 2.7%.

1. Hybridization therapy for thoracoabdominal aortic aneurysms

TAAA affects both the thoracic aortic segment and the abdominal aorta, or involves both the suprarenal abdominal aorta. Despite its low morbidity, TAAA has a high perioperative mortality and paraplegia rate, especially in conventional open surgery, with mortality rates averaging up to 11.6% and paraplegia rates ranging from 6% to 9%.

With the rapid development of endoluminal techniques, thoracic aortic aneurysm endoluminal repair (TEVAR) has become a more minimally invasive and safer treatment option.Quinones-Baldrich pioneered the introduction of the hybridization technique for the treatment of thoracic and abdominal aortic aneurysms in 1999. This hybrid technique combines visceral arterial debranching with TEVAR, and maintains hemodynamic stability during the procedure by avoiding the need for aortic blockade, extracorporeal circulation, hypothermic anesthesia, and adjunctive measures such as organ preservation, as compared to traditional open surgery. Hybridization is an integrated surgical strategy combining surgical and endoluminal therapy, where open surgery aims at debranching reconstruction of visceral arteries; endoluminal therapy carries out overlying stent implantation. This surgical approach avoids the direct blockage of the aorta in conventional open surgery and reduces hemodynamic disruption to the patient. In addition, hybridization permits staged procedures, and reconstruction of the visceral arteries can be accomplished in a relatively short period of time, which not only reduces the risk of postoperative functional failure of visceral organs due to ischemia, but also significantly reduces the probability of postoperative paraplegia.

The 2017 JVS Descending Aortic Disease Guidelines clarify the effectiveness of hybridization procedures for the treatment of TAAA. The latest study states that hybridization procedures are not only suitable for urgent emergency procedures without waiting for custom stents, but they are also effective for patients with complex anatomical conditions. In addition, hybridization is economically advantageous, costing less than total endoluminal therapy. In terms of short-term postoperative safety, hybridization is superior to open surgery and has a lower rate of long-term reintervention than total endoluminal therapy.

2. TAAA emergency hybridization surgery

In emergency situations, hybridized surgical treatment of TAAA demonstrates some significant advantages. First, hybridization allows surgery to be readily scheduled in emergency situations, which is critical for the salvage of ruptured or near-ruptured TAAA. Second, this procedure follows conventional open surgical anesthesia without the need for hypothermia, extracorporeal circulation, or routine cerebrospinal fluid drainage, which simplifies the anesthesia process and reduces surgical complexity. In addition, bypass surgery of the visceral and renal arteries has less impact on the systemic circulation, and the visceral arteries are reconstructed in a controlled manner with a short ischemic time and relatively little bleeding. The endoluminal portion of the aortic repair is short and easy to perform.

However, there are some difficulties with hybridization surgery. In obese patients, surgical visualization may be difficult. If the tumor is too large, visualization of both renal arteries may also become complicated. In addition, variants of the renal arteries, such as the presence of double renal arteries, may make anastomosis more difficult. Nonetheless, having a hybridization operating room makes for a smoother surgical procedure, and if a hybridization operating room is not available, it can be transferred to a catheterization laboratory after bypass surgery to complete endoluminal repairs, which usually do not require specially tailored overlay stents.

3. Emergency hybridization techniques to deal with complications of complex TAAA lesions

The treatment of ruptured or ruptured TAAA with aura has always been a challenge and is usually managed with open surgery in conventional treatment. However, a study from Frankfurt Medical Center reported for the first time the use of emergency hybridization techniques in the treatment of TAAA and demonstrated its preliminary results. The study included 30 patients treated with emergency hybridization for TAAA between 2007 and 2013, with a mean maximum diameter of 72 mm. 23 of these patients had atherosclerosis, which was the most common etiology (76.7% of cases), and there were 7 cases of aortic coarctation (23.3%). Indications for emergency surgery included 19 ruptures (63.3%) and 11 cases with significant symptoms (36.7%). The mean follow-up was 16 months. On a technical level, the surgical success rate was 100%, with 101 vessels reconstructed, including 25 celiac trunks, 30 superior mesenteric arteries, 25 right renal arteries, and 21 left renal arteries. Nonetheless, the 30-day mortality rate was 26.7% (n = 8), and the causes of death included one patient with a prior rupture and seven patients with ruptures. In terms of vessel patency, the 30-day and 1-year bypass prosthetic vessel patency rates were 97.3% and 95.3%, respectively. In terms of complications, spinal cord ischemia with permanent paraplegia occurred in 3 patients (10%), and 2 patients (6.7%) required long-term dialysis. For patients with ruptured TAAA with aura, the incidence of spinal cord ischemia, hemorrhage, and gastrointestinal resection after hybridization was 0. The cumulative survival rate at 12 months after surgery was 57.8%.

4. Hybridization of chronic thoracoabdominal aortic coarctation aneurysms

Although hybrid surgical treatment of chronic TAAA has been poorly reported, major national and international medical centers usually use open surgery as the treatment of choice, which is considered the current standard of care. However, mortality and paraplegia rates remain high with this treatment approach, especially when dealing with larger entrapment aneurysms or those patients who have undergone overlying stenting. In these cases, the anastomosis with the overlying stent is complicated by the difficulty of blocking the true or false lumen of the proximal aorta and the possibility of stent displacement during the blocking process, all of which increase the risks of the procedure, such as the occurrence of complications such as anastomotic hemorrhage.

5. Experience of single-center hybridization for TAAA treatment in the vascular surgery department of West China Hospital

The Department of Vascular Surgery at West China Hospital first reported the four-branch total visceral arterial reconstruction TAAA hybridization in 2008, and by 2020 had completed 32 hybridizations for aneurysmal lesions of the thoracic and abdominal aorta, including 7 patients with Marfan syndrome. The mean age of the operated patients was 46.4 years, and the maximum diameter of the aneurysm reached 101 mm.

In our center, simultaneous and staged hybrid surgeries were performed as follows: 25 simultaneous hybrid surgeries and 7 staged hybrid surgeries were performed. The postoperative 30-day mortality rate for simultaneous procedures was 8% (2/25), a rate lower than the simultaneous (18%) and staged (9%) mortality rates in international systematic evaluations.

The overall mortality rate at 30 days postoperatively was 6.25% (2/32), including 1 case due to abdominal hemorrhage and 1 case due to pulmonary infection with multiple organ failure and paraplegia. The 12-month postoperative mortality rate was 3.13% (1/32), and the incidence of paraplegia was 9.375% (3/32), including 2 cases with gradual and complete recovery after 2 weeks and 1 death. The reintervention rate at 30 days postoperatively was 3.13% (1/32), involving 1 case of dissection for hemostasis, and at 12 months postoperatively was 3.13% (1/32), involving 1 case of renal aortic stenosis. There was one death during follow-up, 3.13% (1/32), due to rupture of an anastomotic pseudoaneurysm.

6. An analytical study of simultaneous and staged surgical options in vascular surgery at West China Hospital

A study from the Department of Vascular Surgery at West China Hospital examined the option of simultaneous versus staged hybridization procedures in the treatment of TAAA. The study showed that staged hybridization has advantages in the short-term postoperative period, mainly in terms of a lower risk of adverse cardiac events and intestinal complications, as well as a relatively low 30-day mortality rate. In terms of mid-term outcomes, 12-month postoperative survival, reintervention rates, incidence of endoleak, and bypass vessel patency did not differ significantly between staged and concurrent hybridization procedures. Based on these findings, the study recommends that when choosing a hybrid procedure, staged hybrid surgery should be prioritized if the aneurysm status is stable; conversely, if the aneurysm status is unstable, contemporaneous hybrid surgery is a more appropriate choice.

7. 2017 ESVS guideline opinion on TAAA recommendations for hybridization procedures

According to the guideline opinion on TAAA published by ESVS in 2017, in patients with low to intermediate surgical risk, open surgical or endoluminal (including hybridization) treatment should be considered when the TAAA has a diameter of >6 cm or a growth rate of >10 mm per year or when the patient presents with symptoms related to the TAAA (level IIa, C evidence).

There is still a lack of clinical reports with large sample sizes for hybridization procedures. Early outcomes, mortality, and the incidence of spinal cord ischemia currently reported vary widely from center to center. As a result, hybridization is still used as an alternative to open and total endoluminal surgery and is usually reserved for high-risk patients, patients with poor endoluminal anatomy, and patients in emergency situations.

8. Challenges to hybridization surgery

Hybridized surgical treatment of TAAA has been challenged by its high complication rate and high mortality, especially for debranching techniques used to address vessels involving viscera. A recent multicenter registry study published in Circulation analyzed the 5-year outcomes of 208 patients and provided a clearer picture of the effectiveness and limitations of debranching techniques in the treatment of complex aortic disease. Hybridization has shown advantages in the treatment of pararenal abdominal aortic aneurysms and thoracoabdominal aortic aneurysms, such as limiting the surgical incision to the abdomen, reducing the need for a combined thoraco-abdominal incision, and shortening the postoperative recovery time; and avoiding some of the disadvantages of traditional open surgery, such as the risk of open chest, single-lung ventilation, aortic clamping, and generalized visceral, spinal, and limb ischemia. However, most published studies of hybridization surgery are based on single-center experiences with limited numbers of patients and relatively short follow-up times. After hybridization surgery, the 5-year patency rate of visceral arteries can be as high as 90%, while the incidence of permanent spinal cord injury is approximately 6%. In experienced hybridization centers, the results of hybridization surgery may be similar or even superior compared with conventional or total endoluminal surgery in patients with TAAA in good general condition.

However, there is significant variability in the clinical outcomes of hybridization surgery across centers, which is closely related to the surgical sample size, technical preferences, and types of procedures each clinical center specializes in. In addition, it is often difficult to agree on the preoperative baseline characteristics of patients choosing different surgical approaches, leading to significant bias in the study results. Therefore, these factors need to be taken into account when evaluating the advantages and disadvantages of various surgical approaches to ensure the most appropriate treatment choice for patients.

In summary, although hybridization surgery has shown advantages in the treatment of TAAA with its theoretically less invasive and less physical and psychological burden on patients, especially for those high-risk patients who cannot tolerate the anatomical conditions of open surgery or total endoluminal treatment, however, the surgeon's surgical proficiency in debranching techniques and TEVAR has a direct impact on the complications and patient prognosis of hybridization surgery, and the Long-term prognosis and complication management are also more dependent on the surgeon's experience and individualized patient selection, and more large-scale case studies are expected. At the same time, the field of total endoluminal therapy is constantly evolving, and the research and refinement of new instruments and stents are indicative of the future direction of the field.