Aortic regurgitation in aortic dissection will be seen as retrograde diastolic blood flow from the aortic arch, seen with Doppler (Diebold).
Aorta ultrasound, is a quick way to see if the aortic dissection involves the abdominal aorta.
This suprasternal notch view shows an aortic dissection involving the aortic arch and the brachiocephalic and left common carotid artery. This particular patient presented with unilateral right sided weakness.
This transthoracic parasternal long axis view shows a echogenic dissection flap just distal to the aortic valve.
- Type A involves the ascending aorta and may progress to involve the aortic arch and thoracoabdominal aorta.
- Type B originates distal to the left subclavian artery and can involve the descending thoracic or thoracoabdominal aorta.
- Type I involves the ascending aorta, arch, and descending thoracic aorta and may progress to involve the abdominal aorta.
- Type II involves only the ascending aorta.
- Type IIIa involves the descending thoracic aorta distal to the left subclavian artery and proximal to the celiac artery.
- Type IIIb originates distal to the left subclavian artery and involves the thoracic and abdominal aorta distal to the celiac artery.
Aortic dissection is the most common in the ascending thoracic aorta: (Larson)
- Ascending aorta: ∼ 65% of cases
- Descending aorta: 20% of cases
- Aortic arch: 10% of cases
- Abdominal aorta: 5% of cases
It is possible to diagnose aortic dissection with transthoracic echocardiography (TTE). It offers a quick diagnosis without having to transfer unstable patients out of the ED. However, transthoracic echocardiography must be used with caution. Although it is highly specific (99-100%), it is not as sensitive (67-80%). Therefore the absence of an intimal flap on TTE does not rule out aortic dissection (Fojtik). CT angiography and transesophageal echo remain the gold standard for diagnosis of aortic dissection.
Below are some examples of aortic dissection seen using transthoracic echocardiography, abdominal aorta ultrasound, and the suprasternal notch views.
An aortic dissection occurs when a tear in the arterial intima allows blood, under high systolic pressures, to dissect along the arterial media and create a “false lumen” in the aorta. The dissection can travel in an anterograde or retrograde direction.
Unfortunately, aortic dissections are one of the most difficult diagnoses to make since the symptoms can vary from chest pain, abdominal pain, to neurologic deficits depending on what parts of the aorta the dissection involves.
Using the techniques for visualizing the abdominal and thoracic aorta described above, you may detect a free flap in the aortic lumen. The presence of an intimal flap in the aortic lumen is used to diagnose aortic dissection using ultrasound (Siegal).
In the Stanford Classification, dissections are classified into two groups – those that involve the ascending aorta and/or aortic arch (Stanford Type A), and those that originate only distal to the brachiocephalic artery, including the abdominal aorta (Stanford Type B). There is also the DeBakey Classification, which subdivides aortic dissections as class I, II, IIIa, and IIIb as pictured below.