Hemodynamically asymptomatic spontaneous rupture of the descending thoracic aorta masquerading as a lung mass.

Sir,

The rupture of the aorta is considered to be spontaneous if it occurs in the absence of thoracic trauma or a pre-existing aortic pathology. In such cases, the predisposition is weakening of the vessel walls, usually due to atherosclerosis. It normally presents as severe chest pain with hemodynamic instability and carries a high mortality if left untreated. We hereby present an atypical presentation of this rare disorder.

A 50-year-old smoker, postmenopausal female patient, presented with a complaint of pain in the left upper abdomen, of a 20-day duration. The pain was a dull ache, which was continuous, nonprogressive, and nonradiating, with no aggravating or relieving factors, and was not relieved by painkillers. On examination, the patient had a pulse rate of 78/minute and blood pressure of 120/84 in the left upper limb, 118/78 in the right upper limb, and 128/86 in both lower limbs. The cardiovascular system examination was within normal limits. The respiratory system examination revealed decreased air entry in the left infrascapular region, with reduced vocal fremitus and reduced vocal resonance. A chest roentgenogram was suggestive of a homogenous opacity in the left lung, abutting the cardiac shadow, suggestive of a mass lesion in the left lower lobe region [Figure 1]. Assuming the lesion to be a lung mass, contrast-enhanced computed tomography (CECT) imaging of the thorax was done, which revealed a ruptured thoracic aorta through its posterolateral wall, with an active contrast leak, and an organized hematoma [Figure 2]. CT angiography of the aorta was then obtained, which showed a 10 mm vent in the left posterolateral wall [Figure 3] of the descending thoracic aorta, with diffuse atherosclerotic plaques in the ascending, transverse arch, and descending aorta.

Figure 1

Chest roentgenogram showing a homogenous opacity abutting the left cardiac border

Figure 2

Contrast CT Thorax showing an organized hematoma (thick white arrow) displacing the aorta anteriorly (thin white arrow). There is presence of an active contrast leak (black arrows)

Figure 3

CT aortography with 3D reconstruction showing a 10 mm vent (arrow) in the left posterolateral wall of the thoracic descending aorta

Spontaneous aortic rupture is an extremely rare disorder with less than 40 cases reported worldwide.[1] The first such case was reported by Rodriguez and Rivera, in 1961.[2] Furthermore, for such a rare disorder, the presentation we encountered was unusual on three counts. First was the absence of a pre-existing comorbidity in our patient. In an analysis of 18 patients, Yokoyama et al.,[3] found that 72% of the patients had a history of hypertension, two patients had rheumatoid arthritis[4] and were on long-term steroids, and only three patients had no associated comorbidity. Second, the presenting symptom of pain in the left upper abdomen, of a 20-day duration, with no associated hemodynamic compromise, also contrasted with the previously reported cases, wherein, 78% of the patients had severe acute chest pain associated with shock. To our knowledge, this was the first such case with such a long duration of symptoms. Third, the common radiographic picture of a ruptured descending aorta was that of the left hemothorax, whereas, our patient had an organized hematoma, which resembled a mass lesion in the lung.

The cause behind a spontaneous aortic rupture is possibly a penetrating atherosclerotic aortic ulcer.[5] Atherosclerotic weakening of the intima can lead to a tear. This tear may extend between the intima and media and lead to the more common disorder of aortic dissection, or, rarely, the tear may extend through the media and adventitia and lead to an aortic rupture. In our patient, the angiography had revealed diffuse atherosclerotic plaques in the entire aorta, which may have been the culprits for the rupture.

Aortic rupture with hemodynamic instability warrants a high index of suspicion for a prompt diagnosis, as it can be mistaken for myocardial infarction or aortic dissection. The chest roentgenogram can be particularly helpful, as it may show mediastinal widening, enlarged cardiac shadow or a left hemothorax.[3] Definitive diagnosis can be established by aortography, either conventional or by CT. The treatment involves achieving hemodynamic stability first, and then going for definitive treatment, which is achieved by closure of the defect. This can be achieved by either the surgical or endovascular approach. Experience from previous cases suggests that mortality is very high in the absence of surgical repair.[3] Our patient was discharged in a stable condition and referred to a higher center for surgical intervention. Unfortunately she was lost to follow-up.

To conclude, we would like to state that spontaneous aortic rupture is an extremely rare entity, which presents a diagnostic challenge, particularly if the presentation is atypical. Prompt diagnosis and early surgical intervention can greatly reduce the associated mortality.