Teaching Case

53-year-old female patient presenting with acute pleuritic chest pain.She had a past medical history of chronic obstructive pulmonary disease and alpha 1 antitrypsin deficiency and had been admitted 2 years ago with a similar presentation when she had a computed tomographic pulmonary angiography (CTPA); pulmonary embolism had been ruled out, while the pulmonary arteries were dilated (Fig.1).

Echocardiography ruled out pulmonary hypertension and showed dilation of the ascending and the abdominal aorta.

CT aortography showed aortic dissection confined to the lower thoracic aorta (Fig. 2a), further dissection commencing at the level of the coeliac axis and extending throughout the abdominal aorta (Fig. 2b) into the left common iliac artery (CIA), ending at the CIA bifurcation (Fig. 2c). The ascending aorta and the aortic arch were dilated but there was no type A dissection (Fig. 2e).

Flow was identified both in the true and false lumen in the thoracic and abdominal components of the dissection. The aorta was aneurysmal at the level of the aortic hiatus of the diaphragm (Fig. 2d, f).

Only after this new study, an even earlier CTPA examination performed 3 years ago became available (Fig. 3a, b). Although performed during the pulmonary arterial phase, its review showed aortic dissection, a diagnosis missed prospectively. This review also clarified that this was chronic dissection.

Background:
Alpha 1 antitrypsin (A1AT) is a protease inhibitor, which protects the tissue from proteolytic enzymes (e.g. neutrophil elastase [1]). The locus for the A1AT protein is on chromosome 14q32.1. The M allele is associated with normal levels of A1AT in the serum, whereas S and Z alleles are associated with reduced levels of plasma A1AT respectively [2]. A genetic deficiency in A1AT manifests systemically, causing pulmonary emphysema, hepatic cirrhosis and vascular diseases [2]. Vascular pathologies associated with A1AT deficiency manifest in the aorta, the visceral and intracranial arteries [3]. Unopposed proteolytic activity in severe deficiency of A1AT leads to vascular damage, causing the vascular manifestations of A1AT deficiency, above all dissection [4].

Clinical Perspective:
The main clinical presentation of aortic dissection is chest and/or back pain, mainly depending on the involved site of the aorta [5]. Syncope, hypotension, shock and hypertension are other common presenting features [6].
A1AT deficiency is found to be associated with extracranial arterial dissection and aortic dissection [7]. In these cases, the overall prognosis is poor [8, 9]; early recognition and diagnosis in the suspected patients with A1AT deficiency are imperative.

Radiologist Perspective:
Aortic dissection can be demonstrated using multiple imaging modalities, including magnetic resonance angiography (MRA), computed tomographic aortography (CTA), and transoesophageal echocardiography (TEE) [10].
CTA is the most commonly used initial modality, due to its widespread availability, particularly in the emergency setting [5]. More than one study is often required to get the information necessary to fully guide the treatment. Patients found to have both aortic dissection and massive, predominantly basal bullous lung disease/emphysema need to be investigated for a possible common aetiology, and A1AT deficiency is one amongst those.

Outcome:
The patient was referred to the vascular team and treated conservatively, because of the comorbidities, mainly the poor lung function.

Take Home Message:
1) Aortic dissection must be ruled out in patients with chest pain and other suspicious clinical signs.
2) Consider aortic involvement in patients presenting with chest pain who are known to have A1AT deficiency.
3) Always evaluate all vascular territories imaged in angiographic studies performed for one specific vascular area, even when the chosen phase is suboptimal.

Written informed patient consent for publication has been obtained.