Diseases of the Descending Thoracic Aorta

These diseases include thoracic aortic aneurysm (TAA), aortic dissection (AD), penetrating aortic ulcer (PAU) traumatic aortic injury, and intramural hematoma.

Patient History 

Thoracic aortic aneurysms (TAA), are more common in elderly males with peak incidence in the sixth decade of life.^36-41 AD, and intramural hematoma (IMH) are also more common in males aged 40-70 years, with a peak in the range of 50-65 years. Patients commonly present with chest pain or interscapular back pain, in the setting of severe hypertension. Some patients with AD  could have symptoms of abdominal pain, flank pain, or acute lower limb ischemia suggestive of malperfusion.  

A comprehensive medical and family history, focusing on cardiac disease and, as well as a history of uncontrolled hypertension, trauma, or aneurysm disease can help establish the diagnosis. 

A history of drug use, particularly methamphetamine in young patients with thoracic aortic dissections, should be elicited.  

A history of prior open or endovascular abdominal aortic repair is particularly important to note as it increases the risk of spinal cord ischemia during TAA repair.  

Patients with fever, chills and night sweats should raise the suspicion for mycotic aneurysm or aortitis. Alternatively, some vasculitis such as Takayasu and giant cell arteritis have been reported to affect the aorta and its main branches causing stenosis, aneurysms, and dissections.  

Patients presenting with hemoptysis or hematemesis could have an aortobronchial or  aortoesophageal fistula, respectively. A Kommerell diverticulum is a rare aortic dilatation affecting the origin of an aberrant right subclavian artery that can cross posterior to the esophagus and cause dysphagia (dysphagia lusoria) or recurrent laryngeal nerve palsy. Hoarseness has been also reported with large descending thoracic aneurysms.  

Physical Examination 

A careful physical examination including pulse (upper and lower) symmetry, malperfusion  (abdomen), signs of stroke (ascending dissection) and blood pressure measurement in both arms,  is required in all patients suspected of thoracic aortic disease. Patients should be examined for clinical signs of cardiac compromise, such as aortic regurgitation, cardiac murmur, pericardial rub, signs of tamponade, as well as abdominal aortic expansion. Synchronous aneurysms tend to occur in other anatomic locations; thus, palpation of the abdomen and popliteal fossa for aneurysms should be a routine part of the physical examination. 

All patients should undergo a detailed physical examination designed to detect the presence of a genetic syndrome associated with AD or TAA (e.g., Marfan, Loeys-Dietz, Ehlers-Danlos, or  Turner syndrome). Physical examination should include special attention to the presence of palpable femoral pulses and other potential access sites to deliver the endovascular repair  (TEVAR). 

Imaging  

The diagnosis of thoracic aortic disease is based on imaging and the choice of imaging modality should be based on the patient’s condition and optimal institutional protocols.  

CTA offers a detailed visualization of the entire aorta and its surrounding structures. It can distinguish different aortic pathologies and is quick and widely available. CTA has replaced digital subtraction aortography (DSA) as the “gold standard” for aortic imaging.^{40, 41} The CTA  should include the chest abdomen and pelvis and to assess the access vessels (iliac and femoral arteries). Current guidelines recommend that all patients with clinical suspicion of thoracic aortic  disease and abnormal chest radiograph should undergo CTA for diagnosis confirmation.³⁶  

Important disadvantages of CTA include the use of nephrotoxic contrast agents and the exposure of patients to ionizing radiation. In patients at increased risk of contrast induced nephropathy,  circulating volume expansion with either isotonic sodium chloride or sodium bicarbonate solutions is recommended.  

Postero-anterior and lateral chest radiographs can be used to diagnose calcification within atheromatous lesions, left pleural effusions, aortic enlargement, and anomalous aortic contours in asymptomatic or symptomatic patients. A left pleural effusion can indicate a frank rupture, an exudate from inflammation of the adventitia or, less commonly, inflammatory aortic disease. 

Although chest X-rays might be used in very low-risk patients to exclude thoracic aortic diseases,  these potentially lethal diseases require a conclusive diagnosis with the use of multiplanar  imaging techniques such as computed tomographic angiography (CTA). 

The use of Transthoracic echocardiography to assess the descending thoracic aorta (DTA) is limited by structures in the thorax that weaken or distort the ultrasound signal and compromise image quality. Transesophageal echocardiography can visualize the DTA from the left subclavian artery to the celiac artery. This diagnostic test is generally used as a second line imaging modality and is useful to differentiate between AD, IMH, and penetrating aortic ulcer (PAU).  

The semi-invasive nature of transesophageal echocardiogram (TEE) has rare procedure related risks, but it can cause patient discomfort, requires sedation, and is contraindicated in the presence of esophageal pathologies. In the majority of cases, CTA scanning is performed as the first imaging modality, providing all required information. TEE may be used in specific circumstances as a second-line option. 

Alternative imaging modalities such as Magnetic Resonance Imaging/Magnetic Resonance  Angiography (MRI/MRA) and rarely intravascular ultrasound (IVUS) can be considered based on the patient’s comorbidities, anatomy, and urgency. 

Medical Management and Lifestyle Changes  

Medical management of patients with thoracic aortic disease includes control of hypertension and heart rate to control cardiac impulse statin therapy/lipid optimization, and smoking cessation, and investigation of the underlying cause of disease (aortitis, penetrating aortic ulcer/intramural hematoma, connective tissue disorder, genetic etiology, etc.).  

Medical therapy with antihypertensive agents is widely used as a first-line treatment in patients with aortic disease. Blood pressure control is based on anti-impulse therapy to limit the ventricular ejection force and the aortic wall stress and is eespecially important in cases of symptomatic aneurysms or acute aortic syndromes. Beta blockers such esmolol or labetalol are considered first line therapy. The goal of therapy is to reduce the systolic blood pressure to <120  mm Hg and the heart rate to <60 beats/min, when possible, prior to surgery. This is usually achieved with intravenous beta blockers (or alpha/beta blockers) as first-line therapy. For patients who do not respond to, or are intolerant of beta blockers, calcium channel blockers or angiotensin-converting enzyme inhibitors or blockers can be used as alternatives or adjuncts. 

For patients with dyslipidemia, treatment with a statin to achieve a target low-density lipoprotein cholesterol level of <70 mg/dL is reasonable and may be helpful in controlling the progression of aneurysms. Counseling for smoking cessation, reduction of environmental tobacco exposure,  referral to special programs for cognitive-behavioral therapy, initiation of pharmacotherapy, or,  preferably, multimodal management to achieve complete tobacco abstinence is strongly recommended for patients who have active tobacco use or exposure.^{7, 40, 41} Tobacco exposure cessation and abstinence is imperative to reduce progression of aortic aneurysmal disease. 

Risk Stratification for Surgery (cardiac and pulmonary) 

Preoperative workup in patients undergoing open surgical (OSR) and endovascular repair  (TEVAR). The preoperative cardiac assessments should follow the general recommendation of  the American College of Cardiology/American Heart Association (ACC/AHA) guidelines.³¹ 

Cardiovascular and pulmonary disease remain the leading causes of early and late death after  OSR or TEVAR. Given the risk associated with either OSR or EVAR, it is essential to evaluate the overall operative risk associated with either method of repair.³¹ The first step should be to determine whether an active cardiovascular condition exists, which would mandate further assessment and management before planned aneurysm repair. In the absence of an active cardiovascular condition, further testing, as dictated by functional capacity and cardiovascular risk factors, is indicated only if the results will change the planned treatment approach. 

Current guidelines state that in patients with active cardiac conditions, including unstable angina,  decompensated heart failure, severe valvular disease, and significant arrhythmia, a cardiology consultation is recommended before TEVAR or OSR.⁴¹ In patients with significant clinical risk factors, such as coronary artery disease, congestive heart failure, cerebrovascular disease, diabetes mellitus, chronic renal insufficiency, and unknown or poor functional capacity (MET < 4), who are to undergo OSR or TEVAR, the guidelines suggest noninvasive stress testing. In addition, the guidelines recommend a preoperative resting 12-lead ECG in all patients undergoing TEVAR or  OSR within 30 days of planned treatment.

Risk Assessment  

A multidisciplinary approach to care can improve outcomes. Medical specialists and team members can assist patients with risk factor modification, such as smoking cessation, maintaining glycemic control, normalizing blood pressure and lipid levels, maintaining antiplatelet therapy  and fostering participation in exercise programs, thereby promoting a positive patient experience.  Discharge planning should be considered at time of surgical planning. (Fleisher LA, Fleischmann KE) 

a. Cardiac 

Current guidelines suggest continuation of beta blocker therapy during the perioperative period if it is part of an established medical regimen.⁴¹ If a decision is made to start beta blocker therapy  (because of the presence of multiple risk factors, such as coronary artery disease, renal insufficiency, and diabetes), initiation should be well in advance of surgery to allow sufficient time to assess safety and tolerability. 

The SVS guidelines suggest coronary revascularization before aneurysm repair in patients with acute ST-segment or non-ST-segment elevation MI, unstable angina, or stable angina with left main coronary artery or three-vessel disease.⁴¹ The same applies in patients with stable angina and two-vessel disease that includes the proximal left descending artery and either ischemia on noninvasive stress testing or reduced left ventricular function (ejection fraction < 50%).  

In patients who may need aneurysm repair in the subsequent 12 months and in whom percutaneous coronary intervention is indicated, the guidelines suggest a strategy of balloon angioplasty or bare-metal stent placement, followed by 4 to 6 weeks of dual antiplatelet therapy. 

b. Pulmonary 

TEVAR is better tolerated than OSR, particularly if TEVAR is performed under local anesthesia.  However, patients with severe COPD exhibit increased in-hospital mortality, pulmonary complications, major adverse events, and decreased five-year survival whether they are treated with open repair or TEVAR. 

Smoking cessation is recommended for at least two weeks prior to aneurysm repair. In addition,  preoperative pulmonary function studies, including room air arterial blood gas determinations, are suggested in patients with a history of symptomatic COPD, long-standing tobacco use, or inability to climb one flight of stairs. Administration of pulmonary bronchodilators for at least 2 weeks before aneurysm repair is suggested in patients with a history of COPD or abnormal results of pulmonary function testing. 

Although there are few supporting data, in trying to determine whether a patient with severe  COPD is a candidate for open TAA repair or TEVAR, the SVS guidelines recommend considering pulmonary function testing preoperatively in an attempt to determine baseline pulmonary function, if general endotracheal anesthesia is being considered, to determine risk of ventilator dependency postoperatively and ultimately to guide the choice of anesthesia.⁴¹

c. Renal 

Preoperative renal insufficiency is an established risk factor for poor outcome after aneurysm  repair.^{13, 14} 

Current guidelines recommend pre-procedure and post-procedure hydration with normal saline or  5% dextrose for patients at increased risk of contrast induced nephropathy undergoing TEVAR,  and preoperative hydration in all non-dialysis-dependent patients with renal insufficiency before aneurysm repair.⁴¹ 

d. Diabetes Mellitus 

Diabetic patients have increased operative mortality after TAA repair, with reduced survival two to five years after surgery, consistent with an increased burden of cardiovascular disease. Whether  diabetes is a distinct risk factor for major adverse events or death after OSR or TEVAR is not well-defined, however. 

Preoperative Labs 

Standard CBC, chemistry profile and coagulation profile are recommended preoperatively.  Serial troponins in patients presenting with chest pain to rule out myocardial infarction.  

The SVS guidelines also recommend perioperative transfusion of packed red blood cells if the hemoglobin level is <7 g/dL.⁴¹ 

Preoperative Medication Adjustment  

• Current guidelines recommend intravenous administration of a first-generation cephalosporin or, in the event of penicillin allergy, vancomycin within 30 minutes before  OSR or TEVAR.⁴¹ Prophylactic antibiotics should be continued for no more than 24  hours. 
• In addition, thromboprophylaxis with unfractionated or low-molecular-weight heparin is  suggested for patients undergoing aneurysm repair who are moderate- to high-risk for venous thromboembolism and low-risk for bleeding.  
• ACE Inhibitors: If significant volume depletion is anticipated, it is suggested to hold ACE  inhibitors and angiotensin receptor antagonists on the morning of surgery and restarting these agents after the procedure, once euvolemia has been achieved. 
• Diabetes Mellitus: It is suggested to hold metformin at the time of administration of contrast material among patients with an eGFR of <60 mL/min or up to 48 hours before  administration of contrast material if the eGFR is <45 mL/min and restarting no sooner  than 48 hours after administration of contrast material as long as renal function has  remained stable. This is recommended to prevent metformin-associated lactic acidosis  (MALA). Diabetic patients who receive intermediate or long-acting insulin should receive half the scheduled dose when nil per os (NPO) in preparation for surgery. Glycemic  control should be considered per the current guidelines of the American Diabetes  Association.¹⁸ 

Genetic Counseling and Screening 

Genetic predisposition in descending thoracic aortic aneurysm disease likely represents small contributions from a large number of risks alleles but is important to consider in certain populations (i.e., age <60, signs suggestive of connective tissue disorder, family history of aneurysm or sudden death, etc.).  

It is important to note that classical physical exam findings of connective tissue disorder are only seen in a minority of patients with genetic thoracic aortic aneurysm and dissection (TAAD).⁴²Referral to a genetic counselor or medical geneticist should be routinely incorporated into the care plans for patients with clinical or historic features of genetic TAAD. 

Specific screening and surveillance recommendations should be followed for patients with a  personal or family history of genetic syndromes, such as Marfan syndrome, Ehlers-Danlos syndrome, Loeys-Dietz syndrome, Familial Thoracic Aortic disease, or Turner syndrome. 

Nutrition Evaluation and Optimization 

Current guidelines recommend optimization of preoperative nutritional status before elective open aneurysm repair if repair will not be unduly delayed.⁴¹ 

In addition, parenteral nutrition is recommended if a patient is unable to tolerate enteral support seven days after aneurysm repair. 

Recommended Consultations (pain management, GMT, tobacco) 

Current guidelines recommend multimodality treatment for pain management, including epidural  analgesia, for postoperative pain control after OSR of an TAA.⁴¹

General:

• Shaving performed with clippers
• Skin preparation: CHG wipe timeout for three minutes to dry
• Perioperative antibiotics are weight based and initial dose should be administered prior to incision.
• Foley is placed by trained staff
• The placement of large bore IV access and arterial line for hemodynamic monitoring is recommended.
• A number of prevention strategies have been employed to mitigate risk of spinal cord injury (SCI), including preservation of the left subclavian artery and hypogastric patency, staging strategies for long-segment aortic coverage, prophylactic Cerebrospinal Fluid (CSF) drainage, anemia prevention, permissive hypertension, steroid and naloxone therapy, burst suppression, permissive hypothermia, and hyperoxygenation therapy.
• The SVS guidelines recommend increasing perfusion pressure through controlled hypertension (mean arterial pressure >90 mm Hg) as a component of a spinal cord protection protocol in patients at high risk of SCI because of extensive coverage length (>15 cm), poor hypogastric perfusion (occluded or significantly stenosed hypogastric arteries), or coverage of important collaterals (subclavian/hypogastric arteries).41
• Somatosensory and motor-evoked potentials permit continuous monitoring of the spinal cord’s function, assist in the early detection of SCI, and are popular techniques used in high-risk cases but are rarely used in the setting of simple TEVAR.
• Full dose anticoagulation is administered prior to introducing large sheath and when advancing catheters and wires into the arch; ACT is maintained above 200s.
• Normothermia should be maintained intra-operatively.

Anesthesia Management 

a. Optimization and Risk Assessment  

Patients presenting with thoracic aortic aneurysm disease often have multiple significant comorbidities such as poorly controlled hypertension, coronary artery disease (CAD), and/or chronic obstructive lung disease (COPD) due to long-standing smoking. These comorbidities may significantly impact the anesthesia plan.  

Patients with significant CAD and congestive heart failure may benefit from intraoperative TEE  to evaluate for regional wall motion abnormalities and left heart strain during cross clamping.  

Acute blood loss may precipitate intraoperative myocardial ischemia in patients.

b. Anesthesia Management for Open Procedures 

i) Anesthesia Techniques for Open Procedures  

Open thoracic aortic aneurysm repair is performed under general endotracheal anesthesia.

Lung isolation and single lung ventilation may be necessary during the procedure. This can be achieved by the placement of a double-lumen endotracheal tube (ETT) or the placement of a  bronchial blocker. Correct placement of either device and successful lung isolation need to be confirmed by bronchoscopy prior to incision. 

Preoperative placement of an epidural catheter allows for intraoperative sparing of opioids as well as postoperative pain control.  

Maintenance of anesthesia can be accomplished using volatile anesthetics such as sevoflurane and desflurane or with a propofol drip. Opioids like fentanyl or sufentanil can be used for intraoperative pain control. Non-steroidal drugs such as ketorolac or ibuprofen may need to be avoided depending on the risk of kidney injury. 

Most patients are transferred to the Intensive Care Unit intubated after open thoracic aortic repair for further management and weaning of ventilation.  

If an epidural catheter could not have been placed preoperatively, intercostal nerve block in the surgical field may be an option to optimize postoperative pain control. 

ii) Monitoring and Access 

• Invasive Arterial Blood Pressure Monitoring Pressure: Placement of an arterial catheter pre-induction allows for tight blood pressure and impulse control particularly  during induction. Of anesthesia and endotracheal intubation. Arterial access also  allows for intraoperative blood draws for ACT measurements. 
• Central venous catheter: The use of vasoactive drugs for tight blood pressure control may require the placement of a CVL after induction of anesthesia.
• Large bore IV access: The possibility of acute intraoperative blood loss requires large bore intravenous access for volume resuscitation. 

iii) Intraoperative Concerns 

During aortic cross-clamping, the blood pressure should be kept high, above the patient’s baseline, in order to promote collateral blood flow to the kidneys. This may not be needed in patients who undergo an atrio-femoral bypass to maintain visceral perfusion.  

Renal protection during suprarenal aortic cross-clamping remains a controversial topic and thus  no recommendations have been included in recent guidelines.^{3, 21} ischemia can be reduced by  using bypass modalities such as axillo-femoral bypass or partial cardiopulmonary bypass, 

Prior to release of the cross clamp the administration of an intravenous fluid bolus (500ml  crystalloid or colloid infusion) can mitigate the effects of central hypovolemia caused by aortic cross-clamping and the subsequent release of the clamp if no bypass technique was used.

Acute hypoxemia during single-lung ventilation may require for intermittent inflation of the operative lung, and the need for holding respiration during intraprocedural imaging may make neuromuscular blockade necessary. 

c. Anesthesia Management for Endovascular Procedures (TEVAR) 

i. Anesthesia Techniques for Endovascular Procedures 

TEVAR can be performed under a variety of anesthesia techniques. General endotracheal anesthesia may be best suited if prolonged episodes of apnea to improve imaging quality are warranted. Maintenance of anesthesia can be accomplished using volatile anesthetics such as sevoflurane and desflurane or with a propofol drip. Opioids like fentanyl or sufentanil can be used for intraoperative pian control. Non-steroidal drugs such as ketorolac or ibuprofen may need to be avoided depending on the risk of kidney injury. 

Depending on the percutaneous or cut-down approach, TEVAR can be performed under local anesthesia, regional anesthesia with a nerve plexus block such as ilioinguinal plexus block, or neuraxial anesthesia in the form of epidural or spinal anesthesia.  

The ilioinguinal nerve plexus block can be performed by the surgeon in the sterile field. 

Both the iliohypogastric and the ilioinguinal nerves originate from the nerve root of L1 and perforate the transverse abdominis muscle near the anterior part of the iliac crest. In the anterior abdominal wall, the nerves travel between the transverse abdominis and the internal oblique muscles. The nerve bundle can be visualized using ultrasounds and the injection of 10-20 ml of local anesthetic (e.g., mepivacaine, ropivacaine or bupivacaine) will anesthetize the groin area, as well as the lower portion of the abdominal wall and the upper thigh. 

Local anesthesia or regional anesthesia technique can be supplemented with mild to moderate sedation with a propofol or dexmedetomidine drip for patient comfort. 

ii) Monitoring and Access 

Placement of an arterial catheter pre-induction allows for tight blood pressure and impulse control in particular during induction of anesthesia and endotracheal intubation. 

The need for vasoactive drugs as well as significant blood loss is rare during TEVAR procedure,  hence the placement of central venous catheters is rarely needed. Intravenous access should be adequate to the anticipated blood loss. 

d. General & Procedure-Specific Concerns 

General intraoperative concerns: Skin preparation (CHG wipe timeout for three minutes to dry),  Foley placed by trained staff, shaving performed with clippers, maintenance of normothermia. 

Techniques to minimize contrast nephropathy for endovascular procedures in patients with CKD  include perioperative hydration, the use of CO2 imaging as needed, minimizing the use of contrast agent, and the possible use of intravascular ultrasound for imaging. One has to be cognizant of the risk of neurotoxicity related to inadvertent C02 injection into the cerebral circulation. Avoidance of CO2 injection above the diaphragm can minimize the potential complications.  

Techniques to minimize paralysis following endovascular repair include lumbar drain insertion for TAA/AAA, as well as EEG/SSEP monitoring in patients who are at-risk for spinal cord ischemia. 

Placement of prophylactic CSF drainage catheter placement during TEVAR is controversial, and  CSF drains should be used as only one part of a multimodal protocol to reduce the risk of SCI.  Some authors recommend selective CSF drain placement for only high-risk patients, whereas others perform CSF drain placement preoperatively routinely. The drain is placed below the level of the termination of the cord (L2-L3 or below) and connected to a manometer which should be set at 10cm/H2O, measured from the lumbar drain insertion site.  

High-risk features that warrant prophylactic CSF drainage for SCI protection in TEVAR cases  include:^{38, 39} 

• Covering extensive length of descending aorta (more than 15cm);  
• Previous aortic coverage, including EVAR and open AAA repair;  
• Compromised pelvic perfusion with diseased or occluded common or internal iliac  arteries; 
• Diseased or occluded vertebral arteries 
• Planned left subclavian artery (LSA) coverage; or  
• The patient is deemed to be high-risk by the operating surgeon. 

Steps Prior to Discharge 

• Patients might require a stay in the intensive care unit (ICU) in order to be monitored for cardiopulmonary complications and in order to achieve optimal blood pressure control. 
• Prophylactic lumbar drains can be monitored for up to 72 hours and are removed by  the anesthesia team after any coagulopathy is corrected.  

General steps include: 

• Foley removal ASAP 
• Pulmonary toilet 
• Perioperative glycemic control as indicated 
• Ambulation instruction, physical therapy as needed 

Wound Care: If applicable (e.g., incisional negative pressure dressing, dry dressing, steps  to prevent wound breakdown) 

Medication: Resumption of home medications and antithrombotic medications as indicated.

Steps After Discharge 

• Follow-up: Follow up call within the first week after surgery.  
• Office / Telehealth Visit: Follow-up within one month postoperative, unless indicated sooner. 
  • SVS guidelines recommend contrast enhanced CT scanning at 1 and 12 months after TEVAR and then yearly for life, with consideration of more frequent imaging if an endoleak or other abnormality of concern is detected at 1 month.⁴¹ 
  • All patients with thoracic aortic disease require aggressive management of hypertension, secondary prevention of cardiovascular diseases, and close follow up to monitor the evolution of the diseased aorta. In particular, conservatively treated patients are prone to develop progression of disease and patients treated with open repair can develop anastomotic pseudoaneurysm, new para-anastomotic aneurysms, graft infection or graft occlusion. TEVAR may result in stent graft  related complications such as endoleak, stent graft migration, or stent graft collapse. The primary importance of the surveillance protocols is to prevent these complications. 
  • CTA is the modality most often used for follow-up in DTA disease. However,  cumulative lifetime radiation exposure caused by multiple CTA examinations must be taken into account during planning of follow up. In addition, iodinated intravenous contrast agents are associated with nephrotoxic effects. MRI can be used to avoid radiation and iodinated contrast media. MRI compatible stent grafts are a prerequisite, as the presence of stainless-steel implants causes artifacts. 
• Medication: The use of long-term medications can be coordinated with the patient’s primary care provider and can include the use of statins or a PCSK9 inhibitor in order to achieve optimal LDL control. In addition, anti-platelet agents, anti-hypertensive agents,  and agents for glycemic control should be prescribed, as indicated. 

References