The diagnosis of an acute aortic dissection is an emergency medical procedure. When a patient appears in an emergency room with symptoms of a classic acute aortic dissection, the medical team will first seek to stabilize the patient and then make a definite diagnosis.

By using a stethoscope, physicians may identify sounds that are caused by aortic dissection.  A “blowing” diastolic murmur may indicate an aortic dissection. There may also be signs of cardiac tamponade (a medical emergency in which fluid rapidly fills the membrane surrounding the heart) or hypovolemia (an abnormally low volume of blood circulating in the body). A variety of noninvasive tests may be performed to confirm or rule out a diagnosis of an aortic dissection:

• Electrocardiogram (EKG). A recording of the heart's electrical activity as a graph on a moving strip of paper or video monitor. The highly sensitive electrocardiograph machine helps detect heart irregularities, disease and damage by measuring the heart's rhythms and electrical impulses. This test is chiefly used to rule out heart attack. In many cases, people with aortic dissection have a normal EKG. 
  
  
• Echocardiogram. This test uses sound waves to visualize the structures and functions of the heart. A moving image of the patient’s beating heart is played on a video screen, where a physician can study the heart’s thickness, size and function. The image also shows the motion pattern and structure of the four heart valves, revealing any potential leakage (regurgitation) or narrowing (stenosis). During this test, a Doppler ultrasound may be done to evaluate cardiac blood flow. The echocardiogram can help to visualize an aneurysm or a dissection flap in the aorta. It can also detect fluid (blood) in the pericardium due to leakage of blood from the aorta into the pericardial space. 
  
  
• Transesophageal echocardiography. During this test, a small sensor is placed into the esophagus, which is located close to the aorta.
  
  
• MRI (magnetic resonance imaging). An imaging procedure that uses magnetic fields and a computer to produce high-resolution cross-sectional or three-dimensional images of the target area (in this case, the heart). Because this test takes a long time, during which physicians have limited access to the patient, it is not considered the preferred approach for patients with acute aortic dissection.
  
  
• CAT scan (computed axial tomography scan). A radiographic imaging technique that takes x-ray pictures of tissues from various angles through the body. A computer is used to consolidate the pictures to create a detailed three-dimensional cross-sectional image.
  
  
• Chest x-ray. A radiation-based imaging test that offers the physician a picture of the general size, shape and structure of the heart and lungs. The distance of the shadow of the waist of the heart is wider than normal due to the dissection.
  
  
• Aortography. During this test, a contrast material is injected into the aorta that is visible under x-ray. This test has mostly been replaced by other, noninvasive imaging techniques but may still be used if the patient cannot undergo the other tests.