SSCTS

Ascending Aortic Aneurysms

The big dilemma is timing of intervention to prevent complications (especially rupture or dissection). As risk of complications increases proportionally with increasing size, due to increasing wall tension (Laplace’s Law), size criteria is widely adopted for intervention.

Pathophysiology

All involved pathologic dilatation and thinning of the aortic wall

Ascending aortic aneurysms are grouped into 3 main categories of association

Other associations include:

• Atherosclerosis
• Aortic Dissection
• Infection - Mycotic and Syphilitic
• Vasculitis/Arteritis
• Trauma
• Pseudoaneurysms

Other Risk Factors, in addition to the above, include Hypertension and Smoking

Connective Tissue Diseases –

• The most common diseases are are Marfan, Ehlers-Danlos and Loeys-Dietz syndromes
• These happen at younger age and show more rapid growth compared to sporadic

• There is Cystic Medial Degeneration leading to weakened aortic wall

Sporadic –

• These have a more predictable course

• They usually enlarge at a rate of 0.1 cm/year. As such the prescribed management for these is serial follow-up and elective treatment when size criteria are met.

Bicuspid Aortic Valve –

• These are less predictable than the above
• The tend to be less aggressive than the aneurysms associated with connective tissue diseases and more aggressive than the sporadic ones in terms of aggressiveness

• Intervention is recommended at smaller diameters than for sporadic aneurysms.

Clinical Presentation

Ascending aortic aneurysms tend to present in either of 3 ways:

1. Asymptomatic with incidental finding on imaging - most patients

2. Symptomatic Aneurysm - chest pain, voice changes (due to stretching of the recurrent laryngeal nerve, or stridor (rarely)
3. Sudden Death from acute rupture

Diagnosis

Diagnosis is based on imaging based – most commonly CTA/MRA + Echocardiography

• Echocardiography is indespensible for assessing the aortic valve and root but can have limitations, most notably:
• Skill of sonographer can vary

• Inability to visualize the distal extent of the aneurysm

• Computed Tomography Angiography (CTA) or Magnetic Resonance Angiography (MRA):

• Can give precise measurements and sizing

• There is less variability in technique
• Comparison of aneurysm growth over time for serial follow-up

• They can have the disadvantages of – Ionizing radiation and intravenous contrast (in the case of CTA), are expensive, time consuming and not suitable for patients on haemodynamic monitoring equipment (in the case of MRA).

Treatment

Surgical Intervention is influenced by 3 main factors:

1. Symptoms
2. Size and Growth criteria
3. Aetiology

• Symptomatic Aneurysms (Acute aortic syndrome) – requires urgent surgical repair to prevent an aortic catastrophe.

• If asymptomatic then treatment depends on the size and aetiology

• Commonly accepted size criteria for surgical intervention of isolated ascending aortic aneurysms are:

• Connective tissue disease associated aneurysms: 4.5 – 5.0cm

• Bicuspid Aortic Valve associated aneurysms: 5.0 – 5.5cm

• Sporadic Aneurysms: 5.5 – 6.0cm

• Risk of rupture dramatically increases at 6cm and over and patients with ≥ 5.5cm are offered repair.

• Surgical intervention may be performed during concomitant cardiac surgery such as aortic valve replacement, even though size threshold may not be met.

• Growth rate of > 1cm/year is an acceptable indication for intervention.

• The type of surgical repair is based on anatomic location and presence of concomitant aortic valve pathology:

• Aneurysm replacement with tube graft – if isolated aneurysm and normal aortic root

• Aortic valve and ascending aorta replacement with a separate valve and graft (the aortic root is preserved) – if the valve is abnormal but the aortic root is normal.

• Combined (Composite) valve root and ascending aorta (Modified Bentall) with re-implantation of the coronary arteries (the valve can be either biological or mechanical). This is done if the valve cannot be spared.

• Valve-Sparing root procedure with tube graft – if abnormal ascending aorta and aortic root with a normal or near normal aortic valve.

• Aortic homograft – useful in endocarditis or prior prosthetic infection

• Ross Procedure – in young patients who would benefit from growth of the autograft. Controversial in adults.

• Generally in Marfan patients the root is replaced (with or without valve replacement), regardless of the appearance of the root.

• Standard cardiopulmonary bypass is used in surgery if the distal extent of the ascending aortra allows sufficient room for aortic cross-clamping. If not then Arch or Hemiarch replacement is indicated using Deep Hypothermic Circulatory Arrest.

Non-Surgical Management Adjuncts:

• Control of Hypertension is essential in these patients. Beta-blockers are a commonly used agent.
• Lifestyle modification - especially STOP SMOKING !
• It must however be noted that surgery remains the definitive management for ascending aortic aneurysms.