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Case Report | Discussion

Case report:

A 30 year-old-man presented with severe chest and abdominal pain with radiation to the back.. He was a known hypertensive but was incompliant and on irregular treatment. On examination, the blood pressure was 160/110mm of mercury. Other parameters were normal.

An radiograph of the chest was normal. The ECG was within normal limits.

A CT angiogram was performed following intravenous injection of 100 cc of 76% ionic contrast at the rate of 3cc/s with care bolus tracking on a multislice scanner (Siemens Somatom Volume Zoom).

Post contrast axial images show an intimal flap in the ascending aorta and the descending thoracic aorta. The flap is seen to divide the ascending aorta into true and false lumen, with a thrombus partially occluding the false lumen.(Fig. 1)

Fig. 1

The intimal flap extends upto the bifurcation of the aorta.(Fig. 4)

Fig. 4

The celiac axis and the left renal artery are seen to arise from the false lumen.(Fig.2 & 3)

Fig. 2

Fig. 3

However, the flap is not seen to extend into these major branches. No pleural or pericardial effusion is seen. A three dimensional reconstruction and volume rendering was done which shows a better visualization of the intimal flap and also the extent of the dissection throughout the thoracic and abdominal descending aorta.(Fig. 5 & 6).

Fig. 5

Fig. 6

Diagnosis-Type A or DeBakey’s Type 1 aortic dissection.

Differential Diagnosis - Six hours after this investigation the patient was taken up for surgery . However, the patient could not withstand the procedure and died.

Discussion

Aortic dissection is the most common catastrophy of the aorta .

It is more common in men with a male-to-female ratio of 3:1.Dissections occur more during the 4th through the 7th decades of life.

Dissections of aorta have been classified by two different methods. The more commonly used is the Stanford classification, based on the involvement of the ascending aorta. Type A involves the ascending aorta ; Type B does not.

Another classification is the DeBakey classification –Type l involves the ascending aorta ,aortic arch and the descending aorta. Type ll is confined to the ascending aorta. Type lll is divided into llla which originates distal to the left subclavian artery but extends both proximally and distally. Type lllb refers to dissections that originate distal to the left subclavian artery but extend only distally.

A few predisposing conditions have been described. Dissections are seen in hypertensive patients in about 90% cases. Other diseases such as Marfan syndrome, coarctation of the aorta, aortitis and connective tissue disorders increase the probability of dissections. The incidence among the women increases during pregnancy.

Chest pain is the most common presenting complaint in patients with aortic dissection. The pain is typically tearing in nature. The patient may be completely asymptomatic in 10% of the cases or may come with abdominal pain, stroke or congestive heart failure.

Imaging studies include plain chest radiographs , angiography ,CT , MRI and transesophageal echocardiography(TEE).

Chest radiographs show widening of the mediastinum , tortuous aorta , blunted aortic knob. The "Ring" sign i.e, displacement of the aorta more than 5mm past the calcified aortic intima is considered to be specific.

Other abnormalities include tracheal deviation, depression of the left main stem bronchus and loss of the paratracheal stripe.

Aortography, considered as the gold standard , is being replaced by newer imaging modalities. Benefits of angiography include visualization of the true and false lumens, intimal flap, aortic regurgitation and coronary arteries. The procedure is invasive and may cause difficulty in diagnosis in cases of thrombosis of the false lumen.

With the advent of helical CT with multiplanar and 3D reconstruction, CT has proved to be a very accurate method for evaluation of the dissection. Presence of an intimal flap or two lumens are pathognomonic of an aortic dissection. Indirect signs consist of compression of the true lumen , thickening of the aortic wall, ulcer like projection and dilatation of the aorta. CT is very useful in differentiating the ulcer like projection which reflects the connection between the true and the false lumens from a penetrating atherosclerotic ulcer. Pericardial and pleural fluid collections indicating rupture can also be detected. Disadvantages of CT are the inability to evaluate the aortic valve for insufficiency .

Advantages of MRI lie in the fact that it requires no contrast medium and no ionising radiation. Cardiac gated trans-axial and parasagittal T1 spin echo images are very useful. But patients with cardiac pacemakers may not be able to undergo MRI.

Trans esophageal echocardiography is useful in detecting involvement of the coronaries , aortic insufficiency and cardiac tamponade. It is a quick and a bedside non invasive study.

Differential diagnosis include penetrating atherosclerotic ulcer, ruptured aortic aneurysm, aortic regurgitation etc.

Management of aortic dissection involves hemodynamic stabilization of the patient and definitive surgical intervention. Emergency surgery is required in patients with Stanford type A dissection.

Resection and graft placement is done in such cases.

Type B dissections are medically treated to control blood pressure. Surgery is reserved for distal dissections that are leaking , ruptured or compromising blood flow to a vital organ.