Acute aortic dissection is a catastrophic complication of hypertension. The diagnosis is suggested by chest pain that may be tearing in quality with radiation to the back and neck. Symptoms may also arise from compromised blood supply to the brain, heart or abdominal viscera. On physical examination, the acute onset of aortic regurgitation and asymmetric pulses support the diagnosis.
Transesophageal echocardiography (TEE)
Transesophageal echocardiography, or TEE, provides high resolution images of aortic anatomy and blood flow. In aortic dissection, TEE allows visualization of the intimal flap, entry site, true and false lumens and the presence of aortic regurgitation.
TEE
This is a still-frame of a transesophageal echocardiogram in the transverse axis of the descending aorta, from a patient with aortic dissection. It shows a dilated aorta and a tortuous appearing intimal flap separating the true lumen from the false lumen. In the real-time study that follows, note the unusual, serpentine-like motion of the intimal flap as it whips about within the aorta during systole and diastole.
Aortography
Aortography may also define the diagnosis of aortic dissection. To help understand the following aortogram from a paient with a proximal aortic dissection, a diagram of the aorta is shown in the lateral view. The dissecting hematoma, or false lumen, and the intimal flap are labeled as is the aortic valve.
Aortogram
This is a still-frame of an aortogram in the lateral view that clearly shows a dissection of the ascending aorta. Note the markedly dilated proximal aorta and intimal flap. In the real-time study that follows, the movement of the intimal flap is well seen.
Most aortic dissections
Most aortic dissections are proximal, arising in the ascending aorta near the aortic valve. Even minimal progression poses the risk of aortic rupture, cardiac tamponade, increasing aortic regurgitation and myocardial infarction. The treatment is urgent surgical intervention. Endovascular stent-grafting is occasionally performed instead as an alternative. Dissections arising distal to the aortic arch typically have a better prognosis and, if stable, may be treated medically.
Surgical repair
The following surgical repair of an acute dissection of the ascending aorta is presented through the courtesy of Drs. Robert Hall and Denton Cooley, and was carried out at the Texas Heart Institute.
The patient is already on cardiopulmonary bypass and cardioplegic solution injected into the ascending aorta.
As the needle is removed, a column of this clear cardioplegic solution is seen escaping from the ascending aorta. Next, the aorta is opened with a scalpel. The false lumen of the aorta is filled with blood. Blood can also be seen coming retrograde from the aorta distal to the clamp. The intimal flap delineates the true and false lumens.
A portion of the media and adventitia were then excised, along with the damaged aortic valve. A dacron conduit with an attached aortic valve is used to replace the damaged structures.
The conduit has been lowered into place and sutures are carefully placed in the aortic valve prosthesis sewing ring under direct vision.
After completing the proximal repair, the conduit has been trimmed to size and the distal repair is carried out by sewing the dacron conduit to the distal aortic segment.
The last step in the repair, which will not be shown, will involve anastomosing the coronary arteries to the proximal dacron conduit.