Thoracic aortic aneurysm surgery

Thoracic aortic aneurysm Microchapters
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aarti Narayan, M.B.B.S [2]

Overview

Indications for surgical repair of a thoracic aortic aneurysm include rupture; symptoms such as pain consistent with impending rupture; aortic regurgitation; growth ≥ 0.5 - 1 cm/year; bicuspid aortic valve; asymptomatic patients with degenerative thoracic aneurysm, chronic aortic dissection, intramural hematoma, penetrating atherosclerotic ulcer, mycotic aneurysm, or pseudoaneurysm, who are otherwise suitable candidates once a TAA reaches a pre-specified size (>5 cm in the ascending aorta, >6 cm in the descending segment) referral for surgical or endovascular repair sholuld be initiated. Most patients undergo repair once they reach >5.5 cm diameter in the ascending aorta and > 6.5 cm in the descending thoracic aorta, respectively. Patients with Marfan syndrome or other genetically mediated disorders (vascular Ehlers-Danlos syndrome, Turner syndrome, bicuspid aortic valve, or familial thoracic aortic aneurysm and dissection) should undergo elective operation at smaller diameters (4.0 to 5.0 cm depending on the condition. To avoid acute dissection or rupture, adult patients with Loeys-Dietz syndrome should undergo surgery for an aortic diameter of >4.4 to 4.6 cm. If a Marfan syndrome patient is contemplating pregnancy, they should undergo aortic root replacement if the diameter is greater than 4 cm, and patients undergoing aortic valve repair or replacement and who have an ascending aorta or aortic root of greater than 4.5 cm should be considered for concomitant repair of the aortic root or replacement of the ascending aorta. A woven dacron tube graft is most commonly used in the repair of thoracic aortic aneurysms.

Evaluating The Patient's Risk Of Dissection And Rupture

The annual risk of rupture is closely related to aneurysm size (3% for TAAs <4 cm and 7% for >6 cm). Shown below is the annual risk of thoracic aortic rupture, dissection or death for different diameters of thoracic aortic aneurysms. The curvilinear nature of the risk of cardiovascular events forms the basis for performing surgery when the aorta is 5.0 to 6 cm in diameter depending upon whether the patient has Marfan syndrome or Loeys-Dietz syndrome or not.

Once a thoracic aortic aneurysm is identified, the patient should be followed with clinical and noninvasive testing every three months and then every six months for yearly thereafter.

Indications for Surgery

• Rupture
• Symptomatic states
  • Pain consistent with rupture
  • Compression of adjacent organs
  • Significant aortic regurgitation
• Growth ≥ 0.5 - 1 cm/year
• Bicuspid aortic valve
  • Immediate surgical repair is recommended, as this condition is associated with faster rate of aortic dilatation
• Absolute size

	Marfan's	Non-Marfan's
Ascending aorta	5.0 cm	5.5 cm
Descending aorta	6.0 cm	6.5 cm

• Patients with Marfan syndrome or other genetically mediated disorders (vascular Ehlers-Danlos syndrome, Turner syndrome, bicuspid aortic valve, or familial thoracic aortic aneurysm and dissection) should undergo elective operation at smaller diameters (4.0 to 5.0 cm depending on the condition; to avoid acute dissection or rupture
• Adult patients with Loeys-Dietz syndrome should undergo surgery for an aortic diameter of >4.4 to 4.6 cm
• If Marfan syndrome patient is contemplating pregnancy, they should undergo aortic root replacement if the diameter is greater than 4 cm.
• Asymptomatic patients with degenerative thoracic aneurysm, chronic aortic dissection, intramural hematoma, penetrating atherosclerotic ulcer, mycotic aneurysm, or pseudoaneurysm, who are otherwise suitable candidates and for whom the ascending aorta or aortic sinus diameter is 5.5 cm or greater should be evaluated for surgical repair
• Patients undergoing aortic valve repair or replacement and who have an ascending aorta or aortic root of greater than 4.5 cm should be considered for concomitant repair of the aortic root or replacement of the ascending aorta

Surgery for Thoracic aortic aneurysm

The choice of operation depends on-

• Underlying pathology
• Extent of the disease (both proximally and distally)
• Patient's life expectancy
• Desired anti-coagulation status

Ascending aortic aneurysms

Ascending aorta with normal aortic valves, annulus and sinus of Valsalva	Simple dacron tube graft
Diseased aortic valve and normal sinus and annulus	Replace aortic valve separately from repair of aneurysm (with supracoronary synthetic graft)
Normal valves with aneurysmal sinus and aortic insufficiency	1) Remodelling method: resecting the sinus tissue and repair with dacron graft to form new sinus 2) Re-imaplantation method: reimplanting the scalloped valve with dacron graft
Diseased aortic valve and diseased aortic root	Aortic root replacement. Younger individuals: composite valve graft consisting of mechanical valve inserted into a Dacron graft coronary artery reimplantation. Older individuals, women of child bearing age, those with contraindications to use of warfarin: aortic homografts, pulmonary autografts
Marfan syndrome	Valve sparing aortic root replacement or complete aortic root replacement

Aortic arch

Proximal arch involvement with ascending aorta	Hemiarch replacement with Dacron graft
As a part of delayed repair of descending aortic aneurysm	Dacron graft is telescoped into the descending aorta, facilitating later replacement of the descending aorta

Hybrid procedures for aortic arch

• They are a combination of both open and endovascular procedures.
• Advantages:
  • Less invasive
  • No aortic cross-clamping required
  • Decreased overall morbidity and mortality

Descending aorta and thoracoabdominal aneurysm

• Endovascular stent grafts
  • GORE TAG - FDA approved nitinol based stent graft
  • Zenith TX2 endovascular graft
  • Talent thoracic stent graft
• Open surgery

Factors deciding the type of surgery:

• Age
• Co-morbidities
• Symptoms
• Life expectancy
• Aortic diameter
• Extent of the lesion

Complications Of Thoracic Aorta Aneurysm Surgery

Bleeding

• Bleeding is a potential complication of all aneurysm repairs, particularly a large one such as aortic aneurysm repair

Neurologic injuries

• Stroke- major cause of mortality
• Due to an obstructed blood vessel by embolized atherosclerotic debris
• Patients undergoing aortic arch repairs are at the highest risk of neurologic complications
• Paraparesis and paraplegia

Cardiac

• Myocardial infarction due to technical problems with coronary ostia implantation during root replacement for ascending aortic aneurysms; may require reoperation
• Congestive heart failure

Pulmonary

Acute respiratory distress syndrome)

Endovascular Stenting Complications

• Endoleaks
• Stent fractures
• Stent graft migration or thromobosis
• Iliac artery rupture
• Retrograde dissection
• Microembolization
• Aortoesophageal fistula

2010 ACC/ AHA Guidelines - Surgical and Endovascular Treatment by Location of Disease (DO NOT EDIT)

Asymptomatic patients with Ascending Aortic Aneurysm (DO NOT EDIT)

Class I

"1. Asymptomatic patients with degenerative thoracic aneurysm, chronic aortic dissection, intramural hematoma, penetrating atherosclerotic ulcer, mycotic aneurysm, or pseudoaneurysm, who are otherwise suitable candidates and for whom the ascending aorta or aortic sinus diameter is 5.5 cm or greater should be evaluated for surgical repair. (Level of Evidence: A)"

"2. Patients with Marfan syndrome or other genetically mediated disorders (vascular Ehlers-Danlos syndrome, Turner syndrome, bicuspid aortic valve, or familial thoracic aortic aneurysm and dissection) should undergo elective operation at smaller diameters (4.0 to 5.0 cm depending on the condition; to avoid acute dissection or rupture. (Level of Evidence: C)"

"3. Patients with a growth rate of more than 0.5 cm/y in an aorta that is less than 5.5 cm in diameter should be considered for operation. (Level of Evidence: C)"

"4. Patients undergoing aortic valve repair or replacement and who have an ascending aorta or aortic root of greater than 4.5 cm should be considered for concomitant repair of the aortic root or replacement of the ascending aorta. (Level of Evidence:C)"

Class IIa

"1. Elective aortic replacement is reasonable for patients with Marfan syndrome, other genetic diseases, or bicuspid aortic valves, when the ratio of maximal ascending or aortic root area (πr2) in cm2 divided by the patient's height in meters exceeds 10. (Level of Evidence:C)"

"2. It is reasonable for patients with Loeys-Dietz syndrome or a confirmed TGFBR1 or TGFBR2 mutation to undergo aortic repair when the aortic diameter reaches 4.2 cm or greater by transesophageal echocardiogram (internal diameter) or 4.4 to 4.6 cm or greater by computed tomographic imaging and/or magnetic resonance imaging (external diameter. (Level of Evidence:C)"

Symptomatic patients with Thoracic Aortic Aneurysms (DO NOT EDIT)

Class I

"1. Patients with symptoms suggestive of expansion of a thoracic aneurysm should be evaluated for prompt surgical intervention unless life expectancy from comorbid conditions is limited or quality of life is substantially impaired. (Level of Evidence: A)"

Open Surgery for Ascending Aortic Aneurysm (DO NOT EDIT)

Class I

"1. Separate valve and ascending aortic replacement are recommended in patients without significant aortic root dilatation, in elderly patients, or in young patients with minimal dilatation who have aortic valve disease. (Level of Evidence: C)"

"2. Patients with Marfan, Loeys-Dietz, and Ehlers-Danlos syndromes and other patients with dilatation of the aortic root and sinuses of Valsalva should undergo excision of the sinuses in combination with a modified David reimplantation operation if technically feasible or, if not, root replacement with valved graft conduit. (Level of Evidence: B)"

Surgery for Aortic Arch Aneurysm (DO NOT EDIT)

Class IIa

"1. For thoracic aortic aneurysms also involving the proximal aortic arch, partial arch replacement together with ascending aorta repair using right subclavian/axillary artery inflow and hypothermic circulatory arrest is reasonable. (Level of Evidence:B)"

"2. Replacement of the entire aortic arch is reasonable for acute dissection when the arch is aneurysmal or there is extensive aortic arch destruction and leakage. (Level of Evidence:B)"

"3. Replacement of the entire aortic arch is reasonable for aneurysms of the entire arch, for chronic dissection when the arch is enlarged, and for distal arch aneurysms that also involve the proximal descending thoracic aorta, usually with the elephant trunk procedure. (Level of Evidence:B)"

"4. For patients with low operative risk in whom an isolated degenerative or atherosclerotic aneurysm of the aortic arch is present, operative treatment is reasonable for asymptomatic patients when the diameter of the arch exceeds 5.5 cm. (Level of Evidence:B)"

"5. For patients with isolated aortic arch aneurysms less than 4.0 cm in diameter, it is reasonable to reimage using computed tomographic imaging or magnetic resonance imaging, at 12-month intervals, to detect enlargement of the aneurysm. (Level of Evidence:C)"

"6. For patients with isolated aortic arch aneurysms 4.0 cm or greater in diameter, it is reasonable to reimage using computed tomographic imaging or magnetic resonance imaging, at 6-month intervals, to detect enlargement of the aneurysm. (Level of Evidence:C)"

Descending Thoracic Aneurysm Surgery (DO NOT EDIT)

Class I

"1. For patients with chronic dissection, particularly if associated with a connective tissue disorder, but without significant comorbid disease, and a descending thoracic aortic diameter exceeding 5.5 cm, open repair is recommended. (Level of Evidence: B)"

"2. For patients with degenerative or traumatic aneurysms of the descending thoracic aorta exceeding 5.5 cm, saccular aneurysms, or postoperative pseudoaneurysms, endovascular stent grafting should be strongly considered when feasible. (Level of Evidence: B)"

"3. For patients with thoracoabdominal aneurysms, in whom endovascular stent graft options are limited and surgical morbidity is elevated, elective surgery is recommended if the aortic diameter exceeds 6.0 cm, or less if a connective tissue disorder such as Marfan or Loeys-Dietz syndrome is present. (Level of Evidence: C)"

"4. For patients with thoracoabdominal aneurysms and with end-organ ischemia or significant stenosis from atherosclerotic visceral artery disease, an additional revascularization procedure is recommended. (Level of Evidence:B)"

2010 ACCF/AHA Guideline Recommendations: Perioperative Care for Open Surgical and Endovascular Thoracic Aortic Repairs (DO NOT EDIT)

Preoperative Evaluation (DO NOT EDIT)

Class I

"1. In preparation for surgery, imaging studies adequate to establish the extent of disease and the potential limits of the planned procedure are recommended. (Level of Evidence: C) "

"2. Patients with thoracic aortic disease requiring a surgical or catheter-based intervention who have symptoms or other findings of myocardial ischemia should undergo additional studies to determine the presence of significant coronary artery disease. (Level of Evidence: C)"

"3. Patients with unstable coronary syndromes and significant coronary artery disease should undergo revascularization prior to or at the time of thoracic aortic surgery or endovascular intervention with percutaneous coronary intervention or concomitant coronary artery bypass graft surgery. (Level of Evidence: C)"

Class IIa

"1. Additional testing is reasonable to quantitate the patient’s comorbid states and develop a risk profile. These may include pulmonary function tests, cardiac catheterization, aortography, 24-hour Holter monitoring, noninvasive carotid artery screening, brain imaging, echocardiography, and neurocognitive testing. (Level of Evidence: C)"

"2. For patients who are to undergo surgery for ascending or arch aortic disease, and who have clinically stable, but significant (flow limiting), coronary artery disease, it is reasonable to perform concomitant coronary artery bypass graft surgery. (Level of Evidence: C)"

Class IIb

"1. For patients who are to undergo surgery or endovascular intervention for descending thoracic aortic disease, and who have clinically stable, but significant (flow limiting), coronary artery disease, the benefits of coronary revascularization are not well established. (Level of Evidence: B)"

Choice of Anesthetic and Monitoring Techniques (DO NOT EDIT)

Class I

"1. The choice of anesthetic techniques and agents and patient monitoring techniques should be tailored to individual patient needs to facilitate surgical and perfusion techniques and the monitoring of hemodynamics and organ function. (Level of Evidence: C) "

Class III (Harm)

"1. Regional anesthetic techniques are not recommended in patients at risk of neuraxial hematoma formation due to thienopyridine antiplatelet therapy, low-molecular-weight heparins, or clinically significant anticoagulation. (Level of Evidence: C)"

"2. Routinely changing double-lumen endotracheal (endobronchial) tubes to single-lumen tubes at the end of surgical procedures complicated by significant upper airway edema or hemorrhage is not recommended. (Level of Evidence: C) "

Class IIa

"1. Transesophageal echocardiography is reasonable in all open surgical repairs of the thoracic aorta, unless there are specific contraindications to its use. Transesophageal echocardiography is reasonable in endovascular thoracic aortic procedures for monitoring, procedural guidance, and/or endovascular graft leak detection. (Level of Evidence: B)"

"2. Motor or somatosensory evoked potential monitoring can be useful when the data will help to guide therapy. It is reasonable to base the decision to use neurophysiologic monitoring on individual patient needs, institutional resources, the urgency of the procedure, and the surgical and perfusion techniques to be employed in the open or endovascular thoracic aortic repair. (Level of Evidence: B)"