Aortic Dissection

Aortic dissection occurs when the inner layer (intima) of the aorta tears and blood passes through this separation in the aortic wall.  The tear of the inner wall 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. 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 3000 new cases per year. The most common associated medical condition to acute aortic dissection is hypertension (high blood pressure). There are two main types of  acute aortic dissections which depends on the location of the intimal tear and false channel.

Symptoms of acute aortic dissection usually include severe sharp, tearing pain in the chest and upper back.  Most patients will experience pain in their chest.  They will usually describe the pain as the worse pain they have ever experienced. The pain feels like a knife is stabbing you in the 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 or instantaneously.  The presence of the false channel can result in distortion of the aortic valve geometry leading to regurgitation (leaking), 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, a chronic ascending aortic dissection is treated urgently depending on the patient’s overall condition.

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 (about 65% of the time) a widen heart shadow or silhouette indicating possible aortic aneurysm, aortic rupture or other chest pathology. 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, however, the clinical scenario may ultimately  dictate the need for additional tests.

Please refer to the specific areas in the website dedicated to either Type A or B aortic dissections as well as chronic aortic dissections.

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.