Thoracic aortic aneurysm resident survival guide

Thoracic aortic aneurysm Resident Survival Guide Microchapters
Overview
Causes
Screening
Treatment
Do's
Don'ts

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Roghayeh Marandi

Synonyms and keywords: Thoracic aortic aneurysm workup, Screening approach to thoracic aortic aneurysm, Thoracic aortic aneurysm approach

Overview

Thoracic aortic aneurysm (TAA) is a permanent localized thoracic aortic dilatation that has at least a 50% diameter greater than normal size and three aortic walls which are called a true aneurysm.Its shape could be fusiform or saccular. It classified to aortic root aneurysm, ascending aorta aneurysm, aortic arch aneurysm which is above the ligamentum arteriosum. Their pathophysiology is not related to typical arterial risk factors. It has a noncalcified wall accompanied by no debris or clot and descending aorta and thoracoabdominal aneurysms, which are below the ligamentum arteriosum. The disease process primarily is atherosclerotic, with an irregular calcified wall accompanied by debris and clot. Patients with TAA are usually asymptomatic and diagnosed during imaging studies for other diagnostic reasons. Only about 5% of patients experience symptoms before an acute event occurs, and for 95% of patients, death is the first “symptom", but if it's symptomatic, symptoms could be due to aneurysmal dissection, rupture, or bony erosion, or due to mass effect from a large thoracic aortic aneurysm, presents with Hoarseness due to pressure on (recurrent laryngeal nerve), or dyspnea due to mass effect on (trachea, mainstem bronchus, pulmonary artery), or central venous hypertension (superior vena cava syndrome), dysphagia (esophagus), or due to rupture of thoracic aortic aneurysms (rupture of an ascending aortic aneurysm) which may cause cardiac tamponade or a rupture in the descending aorta may cause hemothorax, aortobronchial fistula, or aortoesophageal fistula. Screening for TAA is not recommended in the general population. certain population substrates, such as those with history of marfan's syndrome, turner's syndrome, ehlers-danlos type IV syndrome, familial thoracic aortic disease syndromes, bicuspid aortic valve, takayasu arteritis, giant cell arteritis, loeys-dietz syndrome or a confirmed genetic mutation known to predispose to familial aortic aneurysms ( TGFBR2,ACTA2, or MYH11) should have imaging study to screen for TAAs.Once aortic dilation is suspected, based on echocardiography and/or chest X-ray, it is reasonable to obtain definitive aortic imaging with CT or magnetic resonance angiography(MRA). If the aneurysm is too small to justify surgery, non-surgical medical therapy is recommended, then repeat imaging at six months to document stability. If the aortic dimensions remain stable, annual follow-up with CT or MRA is reasonable. If a significant size has reached or growth has been documented, they may elect to undergo surgical repair. However, it is beneficial to have early discussions with the potential surgical candidate about the area of concern and its types of operations, outcomes, and associated risks and benefits.

Causes

Life Threatening Causes

• Rupture of thoracic aortic aneurysm
• Aortic dissection
• Post-repair

Common Causes

The true etiology of thoracic aortic aneurysms is probably multifactorial, and it occurs in individuals with multiple risk factors.

Risk factors
Arteriolosclerosis
Hypertension
Hyperlipidemia
Aging
Smoking
Genetic syndromes associated with thoracic aortic aneurysm and dissection: Marfan’s syndrome due to (FBN1 mutations) Loeys-Dietz syndrome due to (TGFBR2 or TGFBR1 mutations) Ehlers Danlos syndrome (vascular form) due to (COL3A1 mutation) Turner syndrome because of 45 XO karyotype Autosomal dominant polycystic kidney disease implicated genes (less common): PKD1, PKD2.
Gene defects associated with familial thoracic aortic aneurysm and dissection: ACTA2 indicates actin, alpha 2, smooth muscle aorta MYH11, smooth muscle-specific beta‐myosin heavy chain TGFBR2, transforming growth factor‐beta receptor type II
Inflammatory causes: Syphilis Mycotic aneurysm from endocarditis Giant-cell arteritis Takayasu arteritis
Trauma
Known aortic valve disease (e.g.bicuspid AV)
Recent aortic manipulation (surgical or catheter-based)
Cocaine abuse
Extreme Weightlifting
Aortic coarctation

Screening

Screening for AA in certain population

Certain populations, such as those with history of marfan's syndrome, turner's syndrome, ehlers-danlos type IV syndrome, familial thoracic aortic disease syndromes, bicuspid aortic valve, takayasu arteritis, giant cell arteritis, loeys-dietz syndrome or a confirmed genetic mutation known to predispose to aortic aneurysms and aortic dissections (TGFBR1, TGFBR2, FBN1, ACTA2, or MYH11) should have imaging study to screen for TAAs. [Applying classification of recommendations and level of evidence classification( ACC AHA guidelines classification scheme)

Screening for AA in patients with Marfan's syndrome

Screening for TAA in Marfan's syndrome

An echocardiogram is recommended at inital visit Marfan syndrome to determine the aortic root and ascending aortic diameters and 6 months later to determine the rate of enlargement of the aorta (Class I, Level of Evidence: C)

Annual imaging is recommended if the stability of the aortic diameter is documented.

If the maximal aortic diameter is 4.5 cm or greater, or if the aortic diameter shows significant growth from baseline, more frequent imaging should be considered.

Refer to surgeon,if Aortic root or ascending aorta diameter > 5.0 cm if there is a family history of TAA at <5.0 cm Descending aorta diameter>6.0cm Aortic cross-sectional area-to-height ratio>10cm2 Rapidly expanding aneurysm presence or significant aortic valve regurgitation

Screening for AA in Loeys-Dietz syndrome or confirmed genetic mutation known to predispose (TGFBR1, TGFBR2, ACTA2, or MYH11)

Screening for TAA in Asymptomatic person with Loeys-Dietz syndrome or a confirmed genetic mutation known to predispose ( TGFBR1, TGFBR2, ACTA2, or MYH11)

complete aortic imaging is recommended at inital visit to determine the aortic root and ascending aorta diameters and 6 months later to determine the rate of enlargement of the aorta ( Class I, Level of Evidence: B) Patients with Loeys-Dietz syndrome should have yearly magnetic resonance imaging from the cerebrovascular circulation to the pelvis. ( Class I, Level of Evidence: B)

Refer patients with Loeys-Dietz syndrome to surgeon,if Ascending aorta diameter >4.2 by transesophageal echocardiography or 4.4-4.6 cm by CT or MRI

Screening for AA in patients with Turner syndrome

Screening for TAA in Asymptomatic person with Tuner syndrome

Patients with Turner syndrome should undergo imaging of heart and aorta at the time of initial diagnosis.

If the initial imaging is normal and there are not any risk factors for aortic dissection, repeat imaging is performed every 5–10 years.(Class I, Level of Evidence: C)

If abnormalities exist, annual imaging is recommended.

If additional risk factors (bicuspid aortic valve, coarctation of the aorta, pregnant or desiring pregnancy, and/or hypertension) exist, it increase risk of TAA or aortic dissection.(Class I, Level of Evidence: C)

Screening of family members of patients with AA or genetic mutations associated with aortic aneurysm

Screening of relatives of person with Thoracic Aortic Aneurysms and Dissections

Aortic imaging is recommended for first‐degree relatives of patients without mutant genes or with a bicuspid aortic valve, to identify asymptomatic persons.

If the mutant gene (FBN1, TGFBR1, TGFBR2, COL3A1, ACTA2, MYH11) associated with aortic aneurysm and/or dissection is identified in a patient, first‐degree relatives should undergo counseling and testing.(Class I, Level of Evidence: C)

If one or more first‐degree relatives are found to have thoracic aortic dilatation, aneurysm, or dissection, referral to a geneticist may be considered. Imaging of second‐degree relatives is reasonable.

only the relatives with the genetic mutation should undergo aortic imaging.

Treatment

Once aortic dilation is suspected, based on echocardiography and/or chest X-ray, it is reasonable to obtain definitive aortic imaging with CT or magnetic resonance angiography. If the aneurysm is too small to justify surgery, non-surgical medical therapy is recommended, then repeat imaging at six months to document stability. If the aortic dimensions remain stable, annual follow-up with CT or MRA is reasonable. If a significant size has been reached or growth has been documented, they may elect to undergo surgical repair. however, it is beneficial to have early discussions with the potential surgical candidate about the area of concern and the types of operations available, their outcomes, and associated risks and benefits.

Treatment of TAA: Medical treatment Surgery( 2 Options): 1-Excision of Aneurysm and Replacement Grafting 2-Endovascular Repair

All aneurysms must be treated with risk-factor reduction measures ❑Recommendation for blood pressure control: ❑Antihypertensive therapy should be administered to hypertensive patients with thoracic aortic diseases to achieve a goal of less than 140/90 mm Hg (patients without diabetes) or less than 130/80 mm Hg(patients with diabetes or chronic kidney disease) to reduce aortic wall stress with beta-blocker(in the absence of contraindications for beta-blocker)in these patients. ❑Recommendation for Dyslipidemia: Dyslipidemia must be treated. Statins should be administered to achieve a target LDL cholesterol of less than 70 mg/dL and it is reasonable for patients with a coronary heart disease risk equivalent such as noncoronary atherosclerotic disease, atherosclerotic aortic aneurysm, and coexistent coronary heart disease at high risk for coronary ischemic events ❑Recommendation for Smoking Cessation:patients with thoracic aortic aneurysm must be counseled about smoking cessation

Indications for surgical treatment of TAAs are based on 1-Size 2-Growth rate 3-Symptoms

Size

Growth ≥ 0.5 - 1 cm/year

Symptomatic patients should undergo aneurysm resection, regardless of aneurysm size(Class I,Level of Evidence: C) ❑Pain consistent with rupture, or symptoms due to compression of adjacent organs ❑Significant aortic regurgitation, or Acute Aortic dissection For the treatment of aortic dissection click here.

Elective repair of Ascending aorta aneurysm diameter> 5.5 cm Descending aorta aneurysm> 6.5 cm for patients without any familial disorders such as Marfan syndrome.(Class I,Level of Evidence: C) Aortic arch diameter >5.5cm in patients with low operative risk in whom an isolated degenerative or atherosclerotic aneurysm of the aortic arch is present(Class I,Level of Evidence: B)

Patients with Marfan's 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 ❑Ascending aortic diameter>5 cm, descending aortic diameter >6 cm, aortic cross-sectional area-to-height ratio > 10 cm2 /m(Class IIa,Level of Evidence: C), or >4 cm if patient is contemplating pregnancy in a patient with Marfan's syndrome ❑ Aortic diameter > 5.5 cm in a patient with bicuspid aortic valve, or >5-5.5 cm if additional risk factors are present (rapid growth or family history of aortic dissection), or if the patient is at low surgical risk and the surgery is performed by an experienced surgical team with a diameter > 4.5 cm if there is an indication for aortic valve replacement ❑Adult patients with loeys-Dietz syndrome should undergo surgery for an aortic diameter of >4.4 to 4.6 cm measured by Ct/MRI.(Class IIa,Level of Evidence: C) ❑For patients with chronic dissection, particularly if associated with a connective tissue disorder, but without significant co morbid disease, and descending thoracic aortic diameter exceeding 5.5 cm, open repair is recommended.(Class I, Level evidence:B)

Do's

• 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 years after that.
• For patients with a current thoracic aortic aneurysm or dissection, or previously repaired aortic dissection, employment and lifestyle restrictions are reasonable, including the avoidance of strenuous lifting, pushing, or straining that would require a Valsalva maneuver. (Class I,Level of Evidence: C)
• 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. (Class I,Level of Evidence: C)
• 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. (Class I, Level of Evidence: B)
• In preparation for surgery, imaging studies adequate to establish the extent of disease and the planned procedure's potential limits are recommended. (Class I,Level of Evidence: C)
• Patients with a 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. (Class I,Level of Evidence: C)
• Patients with unstable coronary syndromes and significant coronary artery disease should undergo revascularization before or at the time of thoracic aortic surgery or endovascular intervention with percutaneous coronary intervention or concomitant coronary artery bypass graft surgery. (Class I,Level of Evidence: C)
• 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. (Class I, Level of Evidence: C)
• Preoperative hydration and intraoperative mannitol administration may be reasonable strategies for the preservation of renal function in open repairs of the descending aorta. (Class IIa,Level of Evidence: C)
• During thoracoabdominal or descending aortic repairs with exposure of the renal arteries, renal protection by either cold crystalloid or blood perfusion may be considered.
• Cerebrospinal fluid drainage is recommended as a spinal cord protective strategy in the open and endovascular thoracic aortic repair for patients at high risk of spinal cord ischemic injury. (Class I, Level of Evidence: B)
• Spinal cord perfusion pressure optimization using techniques, such as proximal aortic pressure maintenance and distal aortic perfusion, is reasonable as an integral part of the surgical, anesthetic, and perfusion strategy in open and endovascular thoracic aortic repair patients at high risk of spinal cord ischemic injury. Institutional experience is an essential factor in selecting these techniques. (Class IIa, Level of Evidence: B)
• Moderate systemic hypothermia is reasonable for the protection of the spinal cord during open repairs of the descending thoracic aorta. (Class IIa, Level of Evidence: B)

Don'ts

• 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.(Class III,Level of Evidence: C)
• 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. (Class III,Level of Evidence: C)
• Furosemide, mannitol, or dopamine should not be given solely for the purpose of renal protection in descending aortic repairs. (Class III, Level of Evidence: B)
• Perioperative brain hyperthermia is not recommended in repairs of the ascending aortic and transverse aortic arch as it is probably injurious to the brain. (Class III, Level of Evidence: B)