Traumatic aortic dissection-CT Angiography

28 year old male patient came to emergency with road traffic accident, emergency thoracic CT angiography showed dissection of aortic arch distal to the left subclavian artery. Note the intimal flap (arrow) with true and false lumen (Type B dissection).

Discussion:

Up to 15% of all deaths following motor vehicle collisions are due to injury to the thoracic aorta. Many of these patients are dead at scene from complete aortic transection. Patients who survive to the emergency department usually have dissection, small tears or partial-thickness tears of the aortic wall with pseudoaneurysm formation.

Chest radiograph has a low sensitivity and has got high negetive predictive value (98%). Most sensitive indicator is abnormal appearing mediastinum, mediastinal widening of more than 8 cm at the level of aortic arch. Sensitivity of CT scan with the advent of MDCT is increased and is 97 to 100%. Intimal flap with true and false lumen are seen clearly.

Treatment is edovascular stent graft in type B dissection and surgical management if it is type A.

Aberrant right subclavian artery

Coronal curved CT reformatted image of the 62 year old male patient presented with cough showing incidentally detected aberrant right subclavian artery arising from the left sided aortic arch (arrow).

Axial curved CT reformatted image of the 62 year old male patient presented with cough showing incidentally detected aberrant right subclavian artery arising from the left sided aortic arch (arrow) causing compression on the esophagus.

Sagittal oblique curved reformatted image better depicts the aberrant artery.

Discussion:

The aberrant artery usually arises just distal to the left subclavian artery and crosses in the posterior part of the mediastinum usually behind the esophagus on its way to the right upper extremity. Such course of this aberrant vessel may cause a vascular ring around the trachea and esophaugus. Dysphagia due to an aberrant right subclavian artery is termed dysphagia lusoria. Palsy of the recurrent laryngeal nerve is termed Ortner's syndrome.

The aberrant right subclavian artery frequently arises from a dilated segment of the proximal descending aorta, the so-called Diverticulum of Kommerell.

Cardiac hydatid cyst

CT scan of 58 year old male patient showing large well defined well capsulated hypodense lesion seen in the myocardium of the left ventricle with multiple daughter cysts within suggestive of hydatid cyst.

• Hydatid disease is a parasitic infection caused by larvae of Echinococcus granulosus, which is still endemic in many sheepraising countries.
• Hydatid cysts can be located in various tissues, although they are most common in the liver (50–70% of cases) and the lung (20–30% of cases) in humans.
• Cardiac involvement in hydatid disease is uncommon, constituting only 0.5–2% of all cases of hydatidosis.
• Heart involvement - LV – 60%, RV – 10%, pericardium – 7%, pulm Artery – 6%, left atrial appendage – 6%, and interventricular septum is rare – 4%.
• Cardiac involvement occurs by invasion of the myocardium - Through coronary circulation or pulmonary vein from rupture of pulm cysts in to vein.

• Signs and Symptoms •No symptoms due to its latency and slow growing nature unless it is situated in critical site. •Signs and symptoms are extremely variable and directly related to location and size of the cysts. •Precordial pain is the most common symptom and is most often vague and does not resemble angina pectoris. •Sudden rupture of intracardiac cysts is a frightful complication and can cause acute pericarditis or tamponade, acute pulmonary hypertension by embolization of several scolices, systemic arterial embolization, and severe anaphylactic shock can be life thretening.

• Imaging - Echocardiography, CT, and MRI can show the cystic nature of the mass and its relation to the cardiac chambers •CT best shows wall calcification. •MRI depicts the exact anatomic location and nature of the internal and external structures and is the technique used for posttreatment follow-up.
• The appearance of a hydatid cyst on MRI is usually a characteristic oval lesion that is hypointense on T1-weighted images and hyperintense on T2-weighted images. •A typical finding on T2-weighted images is a hypointense peripheral ring, which represents the pericyst (a dense fibrous capsule from the reactive host tissue). •A variety of tumors in the heart and a congenital pericardial cyst must be considered in the differential diagnosis; however, the multivesicular nature of the cystic mass and membrane detachment indicate the true diagnosis.
• The cysts may be single or multiple, uni or multiloculated, and thin or thick walled. •More specific signs are •Cyst wall calcification. •Presence of daughter cysts and Membrane detachment.
• •Surgery remains the treatment of choice in the management of hydatid disease. •Although antihelminthic drugs have been used in the preoperative and postoperative periods since 1977, extirpation of the lesion under cardiopulmonary bypass is recommended.
• To conclude CT and MRI are helpful for localizing and defining the morphologic features of hydatid cysts. •Specific signs include calcification of the cyst wall, presence of daughter cysts, and membrane detachment. •CT best shows wall calcification, whereas MRI depicts the exact anatomic location and nature of the internal and external structures.

Pericardial cyst

A 40-year-old man came for routine health checkup. Chest radiograph was found to be abnormal. He said he had no symptoms, and the results of a physical examination were normal. The chest radiograph (Fig 01) showed a smoothly marginated density in the region of the left cardiophrenic angle that partially obscured the left border of the heart and left dome of diaphragm. A computed tomographic scan (Fig 02) showed a homogeneous and smooth fluid attenuation lesion abutting the left ventricle. No septations or calcifications. The heart and great vessels were otherwise normal, and there was no adenopathy. Coronal and sagittal reformated images (fig03) depict the lesion better. The findings are consistent with pericardial cyst.

Pericardial cysts are an uncommon benign congenital anomaly in the middle mediastinum. They represent 6% of mediastinal masses, and 33% of mediastinal cysts. Other cysts in the mediastinum are bronchogenic – 34%, enteric – 12%, thymic and others – 21%. In the middle mediastinum 61% of presenting masses are cysts. Pericardial and bronchogenic cysts share the second most common etiology after lymphomas.

On CT scan pericardial cysts are thin-walled, sharply defined, oval homogeneous masses . Their attenuation is slightly higher than water density 30 to 40 HU. They fail to enhance with intravenous contrast. USG shows hypoechoic lesion with no calcification or septations. MRI is diagnostic, they appear hypointense on T1 and Hyperintense on T2 W images. They will not enhance on contrast study.