Type A Aortic Dissection
I. General Background Information
Aortic dissection occurs when the inner layer (intima) of the aorta tears and blood passes through this separation in the aortic wall. This produces a false channel (lumen), which spirals throughout a segment or commonly, the entire length of the aorta. Therefore, blood can pass through the true lumen as well as the false lumen. Commonly, the false lumen will compress the true lumen and appear larger on imaging studies than the true lumen. In the United States the prevalence of aortic dissection ranges from 0.2 to 0.8 per 100,000 per year resulting in roughly 2000 new cases per year.
II. Presentation/Symptoms
Aortic dissection usually causes a severe sharp, tearing pain in the chest and upper back. The involvement of the ascending aorta is referred to as Type A aortic dissection. This acute weakening of the aortic wall can lead to aortic rupture within hours of the acute event. The presence of the false channel can result in regurgitation of the aortic valve, myocardial infarction (heart attack), stroke, and lack of blood supply to the intestines and ultimately death. The patient’s mortality increases 1% per hour. Most patients that develop a Type A aortic dissection have a history of elevated blood pressure, an ascending aortic aneurysm, connective tissue disorder, bicuspid aortic valve, or have endured a stressful/emotional life event. The diagnosis is most commonly made based on history and symptoms however echocardiogram and/or CT scan are commonly used. A chronic Type A aortic dissection is rare because most patients are treated emergently with surgery. However, chronic ascending aortic dissection is treated urgently depending on the patient’s overall condition.
III. Diagnosis
The diagnosis of a Type A aortic dissection is primarily based on clinical symptoms and radiographic imaging studies. The chest x-ray may provide the first suggestion of thoracic aortic pathology. The chest x-ray may show a widen heart shadow or silhouette indicating possible aortic aneurysm or aortic rupture. Obviously, the chest x-ray may tell the physician that another medical condition is causing the symptoms. An excellent study to diagnose an aortic dissection and is accessible in most emergency departments is a CT scan (or CT angiogram). MRI/A is also an excellent radiographic study however; it’s less accessible, more time consuming, and less patient friendly. A transesophageal echocardiogram (TEE) is a very good study to perform to diagnosis an aortic dissection however; it requires local and IV anesthesia, less accessible and patient friendly.
A blood test that may increase the suspicion of an acute aortic dissection is D-dimer. However, D-dimer is elevated in other medical conditions. However, some studies have suggested that if the D-dimer is above a certain level the likelihood of an aortic dissection is greater than 90% especially if the test is performed within 6 hours of onset of symptoms [1]. As the time interval increases to 24 hours the sensitivity and specificity diminishes significantly. At this time, D-dimer can be used to stratify patients with symptoms suggestive of acute dissection to further imaging studies or continued observation.
IV. Treatment
Emergency surgery to replace the ascending aorta with a prefabricated tubular prosthesis. The aortic valve may be repaired or replaced during the operation. The video shows replacement of the ascending aorta and repair of the aortic valve by reinforcing the aorta and re-suspending the aortic valve.
1. Suzuki T, Distante A, Zizza A, Trimarchi S, Villani M, Salerno Uriarte JA, De Luca Tupputi Schinosa L,Renzulli A, Sabino F, Nowak R, Birkhahn R, Hollander JE, Counselman F, Vijayendran R, Bossone E,Eagle K; IRAD-Bio Investigators.Diagnosis of acute aortic dissection by D-dimer: the International Registry of Acute Aortic Dissection Substudy on Biomarkers (IRAD-Bio) experience. Circulation. 2009 May 26;119(20):2702-7.