HISTORY

A 6-month-old male puppy (Lion d'occitanie) was referred to the Cardiology Unit because of severe depression associated with an abnormal cardiovascular examination. On physical examination, the dog was lethargic. A thoracic wall deformity was observed. Bilateral femoral arterial pulses were markedly decreased. Cardiac auscultation was normal. Thoracic radiographs confirmed the deformation of the thorax, and revealed a marked dilation of the proximal aorta without cardiomegaly. Arterial blood pressure measurement revealed a decreased arterial differential pressure. Transthoracic echocardiography showed a mild dilation of the pulmonary trunk and a markedly dilated proximal aorta (twice as normal). The aortic dilation extended from the aortic root to the level of the left subclavian artery, and was associated with a small aortic insufficiency detected with color-flow and continuous-wave Doppler. Several linear echoic structures were seen within aortic lumen between aortic root and the emergence of the brachiocephalic trunk. Aortic dissection and coarctation were excluded, but fusiform aortic aneurysm associated with a proximal twisting course was confirmed using transesophageal echocardiography (TEE) and magnetic resonance angiogram (MRA) after intravenous injection of gadolinium. Moreover, MRA showed abnormal constitution of major intrathoracic arterial trunks and abnormal curved course of the left subclavian artery. Owner decided the euthanasia. Histology of the ascending aorta revealed cystic medial degeneration (CMD).

DISCUSSION

In this case, the abnormal conformation of ascending aorta was detected with transthoracic echocardiography. However, TEE and MRA were also performed, because these techniques are both more sensitive for diagnosis of thoracic aortic malformations (especially aortic dissection, aortic coarctation and twisting aorta). A precise analysis of the proximal aorta may be obtained with TEE, while MRA allows a global exploration of principal thoracic arterial trunks.

CMD is well described in humans, but not in dogs. This abnormal degenerative change of the aorta is known to induce a weakening of the arterial wall, which may lead to a fusiform aneurysm, as in this case. The aortic dilation may place traction on valvular annulus, pulling it apart, and aortic regurgitation may occur secondary. In humans, CMD may be idiopathic or may result from connective tissue disorders (especially Marfan's syndrome), which may affect several arterial trunks (as in this case). At this time, Marfan's syndrome was never described in dog, but was in cow.

Twisting aorta is an uncommon finding associated with aortic aneurysm. The diagnosis of this abnormality is difficult, because of possible confusion with other disease including aortic dissection. Certitude could only be obtained here using combination of TEE and MRA. Origin of this twisting was attributed to both aortic dilatation and abnormal thoracic conformation with secondary displacement of the heart.