Thoracoabdominal Aortic Aneurysm Repair

Thoracoabdominal aortic aneurysms (TAAAs) are generally asymptomatic and are discovered incidentally on thoracic or abdominal imaging. When they are identified, management is often expectant, depending on the size of the aneurysm and its rate of growth. Surgery is indicated for larger aneurysms and those that expand rapidly so as to avoid the catastrophic rupture of the aneurysm. Here, we present the case of a 70-year-old female with a TAAA, whom we had been following with serial computed tomographic angiography scans. The decision to operate was made when the aneurysm began revealing growth in diameter. Her anatomy was not conducive to endovascular treatment; therefore, we repaired her aneurysm using a traditional open approach.

Cardiovascular diseases; vascular diseases; aneurysm; aortic aneurysm; thoracoabdominal.

Aortic aneurysms are focal dilatations of the aorta that can occur at any point along its length from the root, just above the aortic valve, down to the bifurcation in the pelvis. Classification is by anatomic location and divided into thoracic, abdominal, or thoracoabdominal aneurysms. Thoracic aneurysms are further divided into those that involve the root and ascending aorta, those that involve the aortic arch, and those that involve the descending thoracic aorta. Thoracoabdominal aortic aneurysms (TAAAs) are categorized using the Crawford classification: Extent I encompasses the majority of the descending thoracic aorta, spanning from the left subclavian artery to the suprarenal abdominal aorta. Extent II is the most extensive, involving the aorta from the left subclavian artery down to the aortoiliac bifurcation. Extent III includes the distal thoracic aorta and extends to the aortoiliac bifurcation. Extent IV is confined to the abdominal aorta below the diaphragm. Safi’s group introduced Extent V, which involves the distal thoracic aorta, including the origins of the celiac and superior mesenteric arteries but excluding the renal arteries (Figure 1).⁵⁷

Figure 1. Crawford Classification of Thoracoabdominal Aortic Aneurysm, Modified by the Safi's Group. Legend: (R) SCA - Right Subclavian Artery, (R) CCA - Right Common Carotid Artery, (L) CCA - Left Common Carotid Artery, (L) SCA - Left Subclavian Artery, (L) GA - Left Gastric Artery, CHA - Common Hepatic Artery, SA - Splenic Artery, (R) RA - Right Renal Artery, (L) RA - Left Renal Artery, SMA - Superior Mesenteric Artery, IMA - Inferior Mesenteric Artery, (R) CIA - Right Common Iliac Artery, (L) CIA - Left Common Iliac Artery.

Etiology of dilation is typically multifactorial and the result of both hereditary and environmental factors whose final common pathway results in a degradation of collagen and elastin fibers and/or inhibition of their proper synthesis. These two extracellular matrix proteins of the aortic wall are principally responsible for its tensile strength and elasticity.¹ In addition to collagen and elastin, other components of the aortic wall extracellular matrix (such as glycosaminoglycans) are found to be decreased in patients with aortic aneurysms, which is proposed to be due to aberrantly active matrix metalloproteinase activity.² Other factors such as angiotensin II, mineralocorticoids, reactive oxygen species, and cells classically found in the systemic inflammatory response have also been implicated in the formation of aortic aneurysms.^3,4,5 Secondary causes of aneurysm formation are trauma and infection, the latter classified as mycotic aneurysms. Finally, inherited and spontaneous genetic mutations coding for the aortic well components mentioned above may result in aneurysm formation in association with specific syndromes such as Ehlers-Danlos type IV and Marfan syndrome.⁶

Risk factors traditionally associated with the pathogenesis of aortic aneurysmal degeneration include male sex, family history, and cigarette smoking. Sex differences in aortic aneurysm prevalence are significant, with a 5:1 male to female ratio of affected patients, though a single unifying mechanism for these sex differences has not yet been elucidated.^7,8 The exact pathogenesis of cigarette smoking on aneurysm formation is complex given the heterogeneous constituents of tobacco smoke, though the association with increased matrix metalloproteinase expression is well supported in the literature.^9,10

Aortic aneurysm repair is undertaken to avoid rupture, which in most cases is fatal if not treated urgently or emergently.¹¹

As noted above, aortic aneurysms are commonly insidious in nature and present asymptomatically, with the diagnosis often made incidentally on computed tomography (CT) for another indication. Aneurysms that have grown to become large may cause back or chest pain, or symptoms secondary to compression of surrounding structures. Some patients may also endorse the sensation of a “pulsating mass”, at the level of the aneurysm. Embolic stigmata from mural thrombus separating from the aneurysm wall can manifest as infarctions within abdominal organs or purpuric lesions in the lower extremities, the so-called “trash-toe” or “blue-toe” syndrome. As discussed, aneurysm patients may have elements of their history that elevate their risk for aneurysm development, such as smoking history, history of uncontrolled hypertension, or history of atherosclerotic cardiovascular disease. If there are secondary complications of the aneurysm, such as infection, the patient may present with subjective fever and other systemic symptoms.

Two distinct physical exam scenarios are relevant: incidental detection of a non-ruptured aneurysm and exam at the time of impending or active rupture. The former may present as a particularly prominent and pulsatile mass in the abdominal region above and slightly to the left of the umbilicus. Patient body habitus and aneurysm size will greatly affect the ability to appreciate this finding. Embolic stigmata in the lower extremities can occasionally be seen, particularly if lower extremity pulses are palpable through the pedal level. In cases of mycotic or inflammatory aneurysms, associated constitutional symptoms such as fevers and rigors may be present. 

Unlike their asymptomatic counterparts, rupture or impending rupture most commonly presents with pain at any location along the distribution of the aneurysm. Contained rupture may result in compression of adjacent organs or structures such as the ureter resulting in hydronephrosis. Fistulization into luminal structures such as the bowel will result in GI bleeding, whereas rupture into surrounding structures such as the vena cava can result in acute onset of heart failure and a classic loud machinery bruit in the abdomen. Contained rupture into the retroperitoneum can manifest externally as Grey Turner (flank ecchymosis) or Cullen (peri-umbilical ecchymosis) signs.

Most aneurysms are discovered incidentally during other studies; however, in those who have never had such imaging, the United States Preventive Services Task Force (USPSTF) recommends a one-time abdominal ultrasound in men aged 65 to 75 who have any smoking history for abdominal aortic aneurysm (AAA) screening (B recommendation). These recommendations are not the same for women within the same age category and substance use history (I statement).¹²

Patients identified to have aortic aneurysms are followed up according to the size of the dilation. According to recommendations by the American Academy of Family Physicians, patients with AAA 3.0 to 3.9 cm in diameter should be monitored via ultrasonography of the abdomen every two to three years (C recommendation). Patients with AAAs 4.0 to 5.4 cm in diameter should be followed via ultrasonography or CT every six to twelve months (C recommendation).13, 14 Patients with aortic diameters exceeding 5.5 cm are referred for elective surgical repair. In thoracic aortic aneurysms (TAA), surveillance is typically repeat axial imaging six months after the initial detection and diagnosis to assess for growth or stability. Management and specific imaging modalities for continued surveillance of TAAs are dependent on extent, size, and rate of growth. Echocardiography and magnetic resonance imaging may also be options.¹⁵ Screening for TAA is appropriate in patients with a strong family history.^16,17

Due to screening recommendations from the USPSTF, Society for Vascular Surgery, and American College of Radiology, abdominal aortic aneurysms are able to be detected and appropriately followed up with where they otherwise may have continued to grow. This allows for planned mitigation depending on the extent of the aneurysm’s size or rate of growth via risk factor management or surgical consultation.

Patients who fall outside the risk categories for screening may still develop aortic aneurysms and may never have them visualized, where they may be asymptomatic to the point of rupture. Some studies have suggested that an estimated 70–80% of patients brought to the ER for ruptured aortic aneurysms had no known history or knowledge of a diagnosed aortic aneurysm.^18,19

Asymptomatic aortic aneurysms that do not meet the appropriate diameter/expansion criteria for repair are managed via the reduction of cardiovascular risk factors. This is achieved through antihypertensive and statin therapy, in addition to smoking cessation. Other pharmacologic therapies such as doxycycline are being investigated for their anti-MMP properties, but as it stands there is no data that suggests any substantial benefits for aneurysm risk mitigation outside of those previously mentioned.^20,21,22

Aortic aneurysms in which the risk for rupture exceeds the risk of surgery are referred for a surgical consultation to repair the aneurysm. Though considered prophylaxis, repair of a high-risk aortic aneurysm has a significantly better 5-year survival rate than repair of a ruptured aortic aneurysm.²³ Surgical options for aneurysm repair include open, endovascular, or a hybrid of the two. The choice between the procedural modalities is dependent on the specifics of the patient’s case, such as the location along the aorta or other anatomical considerations, in addition to the extent of the aneurysm. Other more nuanced considerations, such as the exact etiology of the aneurysm (degenerative vs. part of a genetic syndrome) also factor into the decision, as patients who otherwise would be good candidates for endovascular therapy are instead treated surgically if the etiology of the aneurysm is thought to be genetic in nature.

Of course, the patient’s medical comorbidities that would impact their surgical candidacy are taken into consideration as well.

Endovascular repair involves placing a collapsed fabric tube woven to a stent, a stent graft, into the aorta from one or both femoral arteries. The stent graft is brought into position across the aneurysm under fluoroscopy and then deployed so that it can expand and bridge from the normal aorta proximally to the normal aorta or iliac arteries distally. The aneurysm is effectively “sealed” off from the systemic blood pressure and flow is maintained through the aorta. Aneurysms involving the thoracoabdominal aorta, however, are much more challenging because major blood vessels supplying the abdominal organs arise from the aneurysm itself. Traditionally stent graft deployment through the area would result in disrupting blood flow to these organs. While advanced and very elegant endovascular techniques exist to address and maintain blood flow to these vessels while simultaneously sealing the aneurysm, details are beyond the scope of this chapter. Rather, the focus here is on the open surgical repair of TAAA. The operation entails exposing the aorta by accessing both the chest and abdominal cavities, mobilizing the adjacent organs and tissues off the aorta, controlling the aorta above and below the aneurysm, controlling all branch vessels arising from the aneurysm, arresting blood flow through the aneurysmal segment and then replacing all of the aneurysmal aorta with a fabric graft and restoring flow to the branch arteries. Adjuncts such as atrial-femoral bypass are used to help minimize and mitigate the effects of organ ischemia during repair.

Endovascular therapy has been shown in observational and prospective studies to confer a perioperative mortality benefit, though the superiority of endovascular therapy versus surgical therapy remains contested when considering short-term mortality, especially regarding repair of the thoracic aorta.^24-31 Conclusions from the DREAM, EVAR-1, OVER, and ACE trials, evaluating infrarenal AAA management, appear to corroborate with prior studies identifying a short-term mortality benefit versus open surgery, though these trials show no significant difference in long-term outcomes up to 10 years.^32-42 These data have helped providers identify the most appropriate procedural course for patients that fit into these categories. Older patients who are at perioperative risk are more appropriate candidates for endovascular therapy, though the risk for younger, otherwise healthy patients with lower perioperative risk is less clear and warrants further investigation.^43-47

The patient in this case was diagnosed with a type I TAAA, meaning aortic involvement extended from the descending aorta to the suprarenal abdominal aorta. In this patient’s specific case, their aneurysm begins just beyond the origin of the left subclavian artery and extends through the thoracic aorta ending at their visceral segment. The plan for this patient’s surgery involves exposure of the thoracic, abdominal, and proximal infrarenal aorta, control of visceral vessels, placement of the patient in left atrial femoral bypass, graft placement, and abdominal closure.

The patient is placed in a right lateral decubitus position (as is customary in type I–III TAAA repair) to allow for ease of access to both the chest and abdomen. Spinal drains and motor evoked potential leads are also placed for assessment of the spinal cord throughout the procedure. The primary incision is made along the base of the neck between the spinal column and scapula at an oblique angle, passing under the tip of the scapula and following parallel to the ribs, terminating at a space between the patient’s umbilicus and symphysis pubis. 

Careful attention is taken during the primary incision to not penetrate the fascia before it is fully exposed along the entire incision. Small bleeding vessels are identified and electrocauterized to prevent bleeding when heparin is given later in the procedure. After exposure of the fascia, division of the overlaying musculature, including the latissimus dorsi, trapezius, serratus anterior, and rhomboids occurs separately, with the creation of flaps occurring to allow for easier reconstruction at the end of the procedure. Marking sutures are also placed to assist with identifying anatomical borders for the reconstruction of muscle. The sixth rib is identified and marked, as this will be the entry point into the thoracic cavity. Entry begins with the division of the intercostal muscles, freeing of the posterior rib from the diaphragm, and osteotomy of the sixth rib. Marking stitches are placed throughout for anatomical reference.

Once the diaphragm is exposed, a GIA stapler is used to divide the diaphragm. Lung adhesions to the thoracic aneurysm are then lysed. The left kidney was then identified and mobilized. The diaphragm is further divided, and the pericardium is exposed. The left renal artery and vein and superior mesenteric artery are identified in preparation for dissection from the aorta. Branches from the celiac trunk are then ligated and divided. The aorta is followed upwards, continuing to expose it and its branches for dissection and ligation prior to cannulation at the proximal anastomosis for atrio-femoral bypass. 

Clamp sites for the proximal anastomosis are identified at the descending thoracic aorta, and the left inferior pulmonary vein and ligament are mobilized before a purse-string suture is placed for the left inferior pulmonary vein prior to proximal cannulation. An incision is made in the lower extremity to dissect and place a purse string for the femoral artery, the distal anastomotic bypass site. Placement of a cannula from the left inferior pulmonary vein to the femoral artery allows for perfusion of the lower extremities while the aorta is repaired. Once proper exposure is achieved, the left femoral artery is dilated, and both the left inferior pulmonary vein and left femoral artery are cannulated.

Aortic repair after cannulation begins with clamping the proximal aorta before the anastomosis of the graft. During this phase, we manage pump flow at 500 mL/hr to ensure adequate perfusion. The graft is then sutured to the clamped proximal end of the aorta, and after the proximal anastomosis is completed, it is assessed for leaks at the suture site. Once the proximal anastomosis is secure, a second clamp is placed at the mid descending thoracic aorta, and the aorta is divided longitudinally, with ligation of any bleeding luminal vessels. Throughout the procedure, we maintain mean distal pressure at 70 mmHg to ensure proper organ perfusion, adjusting as necessary based on intraoperative monitoring. This technique is continued as the clamp is moved sequentially downward toward the distal segment of the aortic aneurysm, with continued longitudinal incision and ligation of bleeding intraluminal vessels. The graft is then measured to the appropriate length in preparation for the distal anastomosis.

The next part of the surgery involves visceral ischemia time, a time-sensitive portion of the procedure in which the visceral segment is ischemic due to ligation of the celiac artery. Similar to prior steps, the aorta is divided longitudinally and transected below the right renal artery, and intraluminal bleeding vessels are ligated. The aorta is then transected at the site of implantation, and the graft is anastomosed to the distal segment, with pledgets sutured at the site of the anastomosis to minimize the risk of leakage after the graft is fully sutured and assessed. Once assessed, the distal clamps are sequentially removed, allowing for perfusion of the lower extremities and viscera. The total clamp time for this surgery was 21 minutes. 

After the graft is anastomosed both proximally and distally, the patient is decannulated at the site of the left inferior pulmonary vein with the closure of the purse-string suture on the left inferior pulmonary vein, followed by decannulation of the left femoral artery and closure of the incision at the femoral artery. As the incision for femoral artery access is closed, the aortic graft is clamped longitudinally and incised to facilitate anastomosis of a side-arm exit point. The side-arm anastomosis is assessed for leaks once it is fully sutured. The celiac artery is then anastomosed end-to-end to the distal segment of the side-arm graft, and assessed for leaks.

At this point, all transiently devascularized structures are revascularized, and the aneurysm sac is sewn back together with the patent graft carrying aortic blood inside. From there, the left hemidiaphragm and thoracotomy are repaired and thoracic drains are placed. The skin is closed, thus concluding the procedure.

To briefly touch on postoperative care of these patients, patients are kept intubated for 24 hours until they reach euthermia and are adequately resuscitated. After this period, extremely careful attention is paid to the patient’s neurologic assessment (hip flexion/leg extension), vitals (blood pressure), and complete blood counts (Hgb), as the risk of intraoperative spinal cord injury is assessed with meticulous detail. Additionally, the CSF drain in place must be managed with care to ensure an adequate arterial perfusion pressure to the spinal cord, which normally corresponds with a low CSF pressure. The CSF drain is normally kept in place for the first two postoperative days, followed by a clamping trial on the second or third postoperative day, and (assuming a successful clamping trial) the drain is removed on the third or fourth postoperative day.

Other than death, paraplegia secondary to poor spinal cord perfusion is a significant adverse event that may occur following this type of aortic aneurysmal repair. Crawford and colleagues demonstrated that cross-clamp time and aneurysmal extent are directly associated with this risk, and full, permanent spinal cord injury confers near 100% mortality at five years postoperation⁴⁸ Due to this potential morbidity, significant investigation and research has been done to optimize strategy and protect perfusion. Though much attention had been given to the anterior spinal artery (of Adamkiewicz) as the principal determinant of spinal cord perfusion, the paradigm has shifted to a “collateral network concept” as described by Backes, Jacobs, Griepp, Wynn and Acher.^49-52 These collateral networks include anastomoses from the subclavians, segmental (intercostal and lumbar), and internal iliac arteries. In this model, as long as adequate perfusion is maintained from two of these arteries, the disruption of one will minimally affect risk for permanent ischemic damage.⁵³ Paraplegia rates differ between open and endovascular TAAA repair, with reported incidences of approximately 8.5% for open repair and 1.7% for endovascular techniques in some studies. Further research is encouraged to confirm outcomes across populations, as approach depends on anatomy, circumstances, and expertise.^55,56

The rise of endovascular techniques for TAAA repair has reduced training opportunities for open surgical repair. With fewer open cases performed, trainees have limited exposure to the complex skills required for aortic dissection and graft placement. This trend risks a shortage of surgeons proficient in open repair, particularly for patients unsuitable for endovascular approaches. Addressing this issue requires alternative training strategies, such as high-fidelity simulation and centralized programs in high-volume centers.

Historically, repair of aortic aneurysms evolved from Rudolph Matas performing an endoaneurysmorraphy for arterial lesions in 1888, to 1951 with DeBakey and colleagues attempting excision and aortorrhaphy on patients with aneurysms, to the establishment of active aortic surgery programs at medical centers across the country. Medical innovation in the aortic aneurysm realm has recently exploded, with individual advancements in imaging modalities, grafts, anticoagulant medications, and cardiopulmonary bypass all contributing to better approaches to solving a medical problem with a near-fatal consequence if ruptured. Additionally, endovascular approaches have entered the foreground for principal considerations when planning aortic aneurysm repairs with no contraindications.⁵⁴ As our imaging, medications, surgical instruments, and other players in aortic surgery continue to evolve, so too will our ability to perform these procedures safely and effectively for our patients.

GIA stapler; prosthetic graft.

Nothing to disclose.

The patient referred to in this video article has given their informed consent to be filmed and is aware that information and images will be published online.