A Type A aortic dissection is a tear in the inner wall of the aorta that involves the ascending portion of the vessel, the large section that rises directly out of the heart. It is the more dangerous of the two main dissection types and is treated as a surgical emergency. Without an operation, the death rate climbs at roughly 0.5% per hour, reaching nearly 24% within the first 48 hours.
How the Tear Forms
The aorta has three layers. In a dissection, blood forces its way through a tear in the innermost layer (the intima) and pushes between that layer and the muscular middle layer. This creates a second channel, called a false lumen, that runs alongside the normal blood flow path. The tear most commonly starts on the right side of the ascending aorta, within about 5 centimeters of the aortic valve, where the force of each heartbeat hits the vessel wall hardest.
In some cases, the process works in reverse: bleeding starts spontaneously inside the vessel wall itself, and the inner layer tears afterward. Either way, once the false channel forms, it can extend forward or backward along the aorta, blocking branch arteries and cutting off blood supply to organs downstream.
Type A vs. Type B
The Stanford classification system divides aortic dissections into two categories based on location. Type A means the ascending aorta is involved, regardless of whether the tear also extends into the descending aorta. Type B means the tear starts after the branch point of the left subclavian artery and only involves the descending aorta. An older system, the DeBakey classification, breaks this down further: DeBakey Type I involves both the ascending and descending aorta, while Type II is confined to the ascending aorta alone. Both DeBakey I and II fall under Stanford Type A.
The distinction matters because it determines treatment. Type A dissections almost always require emergency open surgery. Type B dissections can often be managed initially with blood pressure control and monitoring, though some need intervention if complications develop.
What It Feels Like
The hallmark symptom is sudden, severe chest or upper back pain that patients often describe as tearing or ripping. It typically starts abruptly and at maximum intensity, which distinguishes it from the pain of a heart attack, which tends to build gradually. The pain can radiate to the neck, jaw, or between the shoulder blades.
Beyond pain, a Type A dissection can produce a wide range of symptoms depending on which branch arteries get compromised:
- Stroke-like symptoms: sudden vision changes, difficulty speaking, or weakness on one side of the body, caused by reduced blood flow to the brain
- Loss of consciousness
- Shortness of breath
- Leg pain or difficulty walking, from impaired blood flow to the lower body
- Severe abdominal pain, if the dissection extends far enough to affect arteries supplying the gut or kidneys
Pulse differences between the right and left arm are a classic physical finding. Because the tear can obstruct blood flow through certain branches of the aorta, one arm may have a noticeably weaker pulse than the other.
Why It Is So Dangerous
The ascending aorta sits right next to the heart, and a tear in this location can rapidly cause life-threatening complications. The most common cause of death before patients even reach a hospital is cardiac tamponade, which occurs in 8% to 31% of cases. This happens when blood leaks through the outer aortic wall and fills the sac surrounding the heart (the pericardium). Even a small amount of rapidly accumulating fluid creates enormous pressure, preventing the heart from filling properly and causing cardiovascular collapse.
The dissection can also extend backward into the aortic valve, causing it to leak severely. It can block the coronary arteries, triggering a heart attack. And if the false channel compresses branch arteries feeding the brain, spinal cord, kidneys, or intestines, those organs begin to fail from lack of blood flow. This is called malperfusion, and it can affect multiple organ systems simultaneously.
How It Is Diagnosed
CT angiography, a contrast-enhanced CT scan of the chest, is the primary diagnostic tool. A meta-analysis of studies using modern multi-detector CT scanners reported 100% sensitivity and 98% specificity for detecting dissections. The scan clearly shows the intimal flap separating the true and false lumens and reveals how far the dissection extends.
Two other imaging methods perform similarly well. MRI of the chest achieves sensitivity and specificity near 100%, but it takes longer and is less practical in emergencies. Transesophageal echocardiography, an ultrasound probe passed into the esophagus to image the aorta from behind the heart, also reaches up to 100% sensitivity and is useful when a patient is too unstable to leave the emergency department. Standard transthoracic echocardiography (the external ultrasound) is far less reliable, detecting only 59% to 85% of cases, so a normal result does not rule out a dissection.
Emergency Surgical Repair
Open surgery to replace the damaged section of the ascending aorta remains the standard of care and is performed as soon as possible. The goal is to remove the segment containing the tear, replace it with a synthetic graft, and restore normal blood flow. If the aortic valve is damaged, it may be repaired or replaced at the same time.
The operation requires temporarily stopping the heart and using a heart-lung machine. Surgeons typically connect the machine through the axillary artery in the armpit or directly through the ascending aorta itself. The complexity of the procedure depends on how far the dissection extends. Some patients need only the ascending aorta replaced, while others require work on the aortic arch or additional procedures to restore blood flow to compromised organs.
With surgery, the death rate at 48 hours drops to about 4.4%, compared to nearly 24% without it. In-hospital survival has improved over the past two decades as surgical techniques and postoperative care have advanced.
Long-Term Outlook After Surgery
Patients who survive the initial operation generally do well. In a study comparing outcomes across two eras, one-year survival after surgery was around 92%, and five-year survival ranged from 75% to 81%. Ten-year survival improved significantly in the more recent era, reaching nearly 70% compared to about 53% for patients treated in earlier years. These gains reflect improvements in surgical technique, imaging, and follow-up care.
Long-term monitoring is essential because the remaining aorta may still contain a false lumen or weakened segments that can enlarge over time. Most survivors undergo regular imaging, typically CT scans, to track the size and condition of the aorta. Some will eventually need additional procedures on other sections of the vessel.
Who Is at Risk
High blood pressure is the single most common risk factor, present in the majority of patients. The chronic force of elevated blood pressure weakens the aortic wall over years, making it vulnerable to tearing.
Certain genetic connective tissue disorders dramatically increase risk, often at younger ages. Marfan syndrome and Loeys-Dietz syndrome both cause structural weakness in the aortic wall. People with a bicuspid aortic valve (a valve with two flaps instead of the usual three) also have higher rates of aortic enlargement and dissection. A family history of aortic dissection or aneurysm raises risk even without a known genetic syndrome.
Other contributing factors include cocaine use (which causes sudden blood pressure spikes), pregnancy (particularly in the third trimester), and pre-existing aortic aneurysms. Age is also a factor: most dissections occur in people between 60 and 80, though genetic conditions can cause them decades earlier.
Preventive Surgery for Enlarged Aortas
Because dissection risk rises as the aorta widens, people with known aortic enlargement are monitored with regular imaging. When the aorta reaches a certain diameter, elective surgery to replace the weakened section before it tears becomes the safer option. Recent guidelines from the American College of Cardiology and American Heart Association lowered the threshold for considering preventive surgery, reflecting evidence that dissections can occur at smaller diameters than previously thought.
Rather than using a single diameter cutoff for everyone, the current approach accounts for patient size by indexing the aorta’s cross-sectional area to the patient’s height. This means a shorter person with a 5-centimeter aorta may be a stronger surgical candidate than a taller person with the same measurement. For someone with a bicuspid valve and an aorta measuring 5.2 centimeters, for example, elective repair is now considered reasonable even without additional risk factors, whereas older guidelines would have recommended waiting until 5.5 centimeters.