Proximal Aortic Aneurysm surveillance clinic – St James’s Hospital “Aortic Clinic”

Written by Saleem Jahangeer, Consultant Cardiothoracic and Aortic Surgeon, St James’s Hospital, Dublin

Introduction

Proximal aortic aneurysms occur when the proximal aorta dilates to more than 1.5x the size of the normal aorta. Approximately 60% occurs in the Root/Ascending aorta, 10% in the arch, 40% in the descending aorta, and 10% in the thoracoabdominal aorta; however, an aneurysm may involve multiple aortic segments.

Proximal or thoracic aortic aneurysms tend to be clinically silent and more than 95% of cases are asymptomatic at the time of diagnosis. Most of those aneurysms are diagnosed incidentally, when patients undergo investigations looking for another pathology. Symptomatic aneurysms present as emergencies usually as an impending rupture or an acute dissection, both being usually lethal.

The incidence of proximal aortic aneurysms has been increasing throughout the world. In the UK between 1999 and 2010 hospital admissions for thoracic aortic aneurysm from 4.4 to 9.0 per 100,000 population. 1 These diseases have a high mortality; in the UK, mortality rates for thoracic aortic aneurysm is 7.5 per 100 000 inhabitants. While the increase in the incidence of proximal aneurysms has been largely attributed to a combination of an ageing population and more frequent imaging, there is evidence of a bona fide increase in the disease itself. 2 The volume of aortic procedures performed has more than doubled in the last decade, reflecting the increasing burden of aortic disease.

Risk Factors for aortic aneurysms

• Age, Atherosclerosis
• Hypertension
• Congenital/Connective tissue disorders – e.g. Marfan’s Syndrome, Bicuspid Aortic Valve
• Hx of previous dissection
• Drug use: Cocaine
• Infection/inflammatory: Aortitis, Vasculitis, Syphilis
• Family history

Natural history of aortic aneurysms

The normal aorta expands by 0.9mm/10 years in male and 0.7mm/10 years in female. In the presence of an aneurysmal wall, expansion tends to occur faster in larger aneurysms (Law of Laplace). In dimensions > 5cm, the rate of expansion can be around 0.8cm per year. Patients with familial aortopathy have faster growth rates of 0.21 cm/year compared with patients with sporadic aneurysms (0.16 cm/year) and thus present earlier.

The main complications of an enlarging aortic aneurysm are: Aortic dissection and Aortic rupture, both of which can be fatal. The annual risk of rupture or dissection is ∼2% for aneurysms between 4.0 and 4.9 cm, and reaches nearly 7% for sizes >6.0 cm. There is a drastic increase in the risk of rupture or dissection beyond a diameter of 6.0 cm (Figure 1).

Size is not all what matters

While the size of an aneurysms remains one of the most important predictors of rupture or dissection, there are other important factors that have to be considered:

1. Connective tissue disorders (CTD)

CTD’s such as Marfan’s syndrome or Loeys-Dietz syndrome are very frequently associated with aortopathy – Syndromic Aortopathy. In such conditions, aneurysmal-associated complications can occur at a smaller diameter. Prophylactic surgery is usually indicated at smaller diameter as compared to non-syndromic Aortopathies.

2. Bicuspid aortopathy

Presence of a bicuspid aortic valve is often associated with an aortic aneurysm; the configuration of the bicuspid leaflets usually dictating which part of the proximal aorta will dilate. Aortic intervention is usually recommended at a slightly lower threshold in patients undergoing bicuspid aortic valve replacement.

3. Family history

Patients with a significant family history of acute aortic syndromes are at a higher risk themselves. There is a large body of evidence implicating several genetic mutations such as ACTA2 or SMAD mutations. Patients with a family history (Non-Syndromic Familial Aortopathy) should be kept on a surveillance program.

4. Rate of expansion

Rate of expansion of the aneurysmal segment is a very important predictor of complications. An aneurysm expanding at > 0.5cm per is an indication for surgery even if the aneurysm is less than 5.5cm.

5. Aortic size index

A drawback of using aortic diameter solely for risk estimation is the inability to factor in a significant determinant of aortic dimensions: the patient’s body size. To this effect, an indexed aortic size, defined as aortic diameter divided by body surface area (BSA), has been introduced as a more patient-specific predictor of dissection, rupture, and death than absolute aortic diameter. The Yale Aortic Index (Figure 2) allows an estimated risk of annual rupture/complication based on the patient BSA. This allows for a more individualised approach in decision making rather than relying on size alone.

Aortic Surveillance Clinic

The aortic surveillance clinic set up at St James’s Hospital is the first of its kind in Ireland.

The clinic will enrol eligible patients in a surveillance programme to provide an integrated-care approach for management of patients with proximal aortic aneurysms.

The main aim of this surveillance clinic is to monitor aneurysmal growth over time and select patients for prophylactic surgical repair once they meet guidelines criteria for intervention. Offering prophylactic surgery at defined criteria prevents patients presenting acutely with life-threatening aneurysmal complications such as rupture or dissection.

All patients in Ireland will be suitable to be enrolled in the clinic. Specialist level care and decision making will be provided to patients, with active participation of referring team and primary care to ensure the patient remains at the centre of the process. The frequency and imaging modality for surveillance patients will guideline-based and coordinated between the aortic team in SJH and the local centre for the patient.

The aortic clinic will also provide support and counselling to patients. Patients with a suspected familial aortopathy will be referred to a geneticist for family investigations and molecular testing.

Surveillance will be life-long for the vast majority of patients. Even after surgical intervention, patients will still need to be monitored as the remaining segments of the native aorta can still expand over time.

The benefits of this surveillance programme can be summarised below:

• Tertiary and centralised level of expertise and care.
• Individualised management – taking into considerations other important factors such as rate of progression, aortic index, family history and connective tissue disorders.
• Guidelines-directed management – defined frequency of investigations, defined criteria for intervention, evidence based management of modifiable risk factors.
• Integrated model of care – Involvement of aortic surgeon, referring physician and primary care teams, with the patient being at the centre of the process.
• Coordination of care between SJH and local centre regarding imaging, risk factors modification etc.
• Patient-focused decision making process.
• Reduce loss of follow-ups.
• Aortic Database – Will allow provide a true picture of proximal aortic disease in Ireland.
• Ultimately reduce the incidence of acute aneurysmal-related complications (rupture and dissections).

There is currently a lack of ‘ownership’ of complex aortic patients in Ireland. With increasing incidence, complexity and awareness of proximal aortic aneurysms, there is a pressing need to offer these patients a dedicated and integrated-care approach for management and surveillance of their aneurysms. This is the aim of the Aortic Surveillance Clinic at St James’s Hospital.

Referral Process

Referrals to the clinic can be made directly by GP’s or clinicians, by sending an email to aorta@ stjames.ie

There will soon be an electronic referral form available on the St James’s Hospital website and Healthlink.

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