What is Acute Aortic Syndrome?
The term ‘acute aortic syndrome’ (AAS) was first used in 1998 and refers to a group of severe and potentially life-threatening heart conditions. These include acute aortic dissection (AAD), a tear in the inner layer of the aorta, intramural hematoma (IMH), a bruise on the wall of the aorta, and penetrating aortic ulcers (PAU), which are sores that occur in the wall of the aorta. These conditions have similar symptoms but are distinct ailments that could potentially develop into one another or exist simultaneously at the time of diagnosis. In fact, around 12% of patients with AAD also have IMH or PAU.
It’s crucial to promptly recognize and diagnose AAS because the conditions can worsen rapidly. For example, type A aortic dissection can increase the risk of death by up to 2% per hour within the first 48 hours. Thus, early detection is absolutely vital.
What Causes Acute Aortic Syndrome?
Acute Aortic Syndrome involves three separate conditions that have similar symptoms, causes, and triggering factors.
The first, Acute Aortic Dissection, constitutes 70 to 80% of all Acute Aortic Syndrome (AAS) cases. It is triggered by a tear in the inner layer of the aorta, often existing in patients with conditions like cystic medial necrosis or medial degeneration. Continuous exposure to high blood pressure can contribute to the tear development, creating an opening or ‘flap.’ Blood may flow into this newly-formed path and separate the inner layer from the outer wall of the aorta. This separation or dissection might extend upward or downward from the spot of the tear, and openings could form, creating a passage between the true and false paths.
The second condition, Intramural Haematoma, still has an ongoing debate about its exact cause. The most popular theory is the spontaneous rupture (breakage) of the vasa vasorum—a blood vessel—supplying oxygen to the outer layers of veins and arteries. Another explanation is the formation of thrombosis (a clot) due to stagnant blood resulting from a tear without any re-entrance. Intramural Haematoma and Acute Aortic Dissection can both occur after trauma from inserting a vascular catheter—a tube used inside the blood vessels.
The third condition, Penetrating Aortic Ulcer, involves plaque formation that ultimately destroys the aorta’s inner layers and extends outward. The condition can stay the same, progress to Acute Aortic Dissection or Intramural Haematoma, or even lead to aortic rupture or visceral ischemia—a condition that reduces blood flow to organs.
Common triggers for Acute Aortic Syndrome include high blood pressure, smoking, high cholesterol level, cocaine use, genetic disorders like Marfan syndrome, Ehlers-Danlos syndrome, Turner syndrome, inherited valvular disease like bicuspid aortic valve or coarctation of the aorta, vascular inflammation due to autoimmune disorders or infection, trauma, or medical procedures involving the heart or aortic valves.
Risk Factors and Frequency for Acute Aortic Syndrome
Reports show that a disease called AAD affects 2.6 to 7.2 out of every 100,000 people each year, based mostly on data from western countries. About 65% of the patients are male, most frequently presenting symptoms in their seventies. Risk factors for AAD vary. Patients over 70 usually have high blood pressure, hardening of the arteries, or medical damage from heart-related procedures. Younger patients are more likely to have hereditary conditions like Marfan Syndrome, abnormal aortic valves, or use cocaine.
Those with a condition called IMH have the same risk factors as AAD, but usually start showing signs in their eighties. IMH accounts for 5 to 25% of AAS cases, with an average of 1.2 cases per 100,000 people a year.
- PAU represents 2 to 7% of AAS cases, averaging around 2.1 cases per 100,000 people annually.
- It’s usually connected to severe hardening and narrowing of the arteries.
- Most patients with PAU also have high blood pressure, and heart disease.
- Some studies show that up to 68% of patients also have lung disease (COPD).
- Between 42 to 61% of patients also have a ballooning blood vessel also known as an aortic aneurysm.
Signs and Symptoms of Acute Aortic Syndrome
AAS, or acute aortic syndrome, often presents with severe aortic pain. This comes across as chest and/or back pain and is frequently described as a tearing, ripping, moving, or pulsating sensation. According to the International Registry of Acute Aortic Dissection, the largest collection of data on the subject, sharp, severe pain is the most common initial complaint. However, about 4.5% of patients reportedly do not experience any pain and are diagnosed through regular health screening procedures or by chance.
Sometimes, neurological signs like fainting can show up along with the pain. This suggests that there’s limited blood flow to the central or peripheral nervous system, which happens due to changes in the spinal and aortic outflow as a result of the aortic wall’s pathology affecting the blood flow.
If the dissection occurs in the ascending aorta, it may be linked with heart muscle ischemia, aortic regurgitation because of the aortic valve’s involvement, or pericardial effusion (fluid around the heart).
Testing for Acute Aortic Syndrome
When you go to the doctor because of severe chest pain, it could be due to various reasons, one of them being a condition called Acute Aortic Syndromes (AAS). In this case, doctors need to conduct further tests, which can be of two types: imaging-based and non-imaging based.
Non-Imaging Based Tests
These involve an ECG (a test that measures the electrical activity of your heart) and several blood tests. This can help doctors determine if your chest pain is caused by other heart issues such as a heart attack. Sometimes, you could have both a heart attack and AAS, which can be a complex situation requiring careful management. For example, in a group of 464 patients, about 31% who had a specific type of AAS had normal ECG results, while the rest showed a variety of different ECG changes.
The laboratory tests can include a full blood count, a test to check the function of your liver, checks for the levels of various chemicals in your body like CRP, D-dimer, troponin, lactate, and creatinine kinase, as well as an arterial blood gas test. These investigations can help to confirm or deny the possibility of AAS, and also rule out other possible causes of your symptoms.
Imaging Tests
The next step is usually imaging tests including chest radiation tests, CT scan, ultrasound, and MRI.
Typical chest X-rays can detect AAS symptoms in about 64% of cases, and are specific to them about 86% of times. Doctors may see signs like a widening of the middle part of your chest, widening of your aorta, the shift of your windpipe, or double shadow of your aorta.
CT scans are the best imaging test for diagnosing AAS as of now. They can be easily carried out in most emergency departments, are non-invasive, need relatively less skills to operate, and take less time. They can successfully identify AAS in about 95% of cases and are specific to AAS between 87% to 100% of the cases.
There are also different types of ultrasounds that could be used. Normal ultrasounds (TTE) can suddenly help identify AAS in the parts of the aorta close to your chest. But TEE, another form of ultrasound, which involves inserting the probe down your throat to get closer to the aorta, can successfully spot AAS 99% of the time with a specificity rate of 89%. But TEE requires more skills to operate, is less available in emergency settings, and is a bit more invasive.
Finally, MRI is rarely used as the first test to diagnose AAS because they are less available during emergencies and AAS can be a life-threatening condition. But MRIs are the best test to identify all types of AAS and could be used when the initial tests do not clearly show what’s causing your symptoms.
Treatment Options for Acute Aortic Syndrome
Acute aortic syndromes (AAS) can be divided into two types: those affecting the ascending aorta and those impacting the descending aorta. Those that affect the ascending aorta need immediate surgical treatment. However, AAS that affect the descending aorta are typically managed non-surgically, unless there’s active progress, risk of rupture, extreme pain, or harm to an organ or limb.
In an emergency, the initial treatment of AAS involves lowering the blood pressure below 120mmHg and reducing the rate at which the blood pressure changes to prevent the condition from worsening or the aorta from rupturing. The primary medication used for this is an intravenous beta-blocker such as Labetalol. If a patient cannot tolerate beta-blockers, calcium channel blockers may be an alternative. Vasodilators can also be used alongside.
Acute aortic dissection (AAD) of the ascending aorta requires immediate surgery, typically performed as an open procedure. The main goal is to remove the false lumen – a tear inside the aorta – and use synthetic grafts to strengthen the aortic wall. If the aortic valve is affected, it may require repair or even full replacement. The downside of endovascular repair, or using a catheter to place a stent graft in the aorta, is that it’s hard to treat a dissection that involves the aortic valve and root.
Acute type B dissection can be complex or straightforward. The complex form represents 25% of acute Type B cases and is characterized by instability or malperfusion, where either an organ system or limb isn’t getting enough blood. The best treatment for this is to place a stent graft in the aorta and implementing rigorous medical therapy.
Traditionally, uncomplicated type B aortic dissections are managed only with medication, but there may be a case for preventive endovascular treatment to prevent the disease from getting worse. However, data on this topic is inconclusive due to a lack of long-term studies.
Intramural hematomas (IMH), although having lower mortality than AAD, have similar treatment due to the risk of dissection, aneurysm, or aortic rupture. Depending on their location, they can be managed either by an endovascular approach, medical treatment, or surgery. As these hematomas change in size over time, placing a stent graft can be hard because of the likelihood of leakage.
Asymptomatic penetrative atherosclerotic ulcers (PAU) can be safely managed with medication. However, symptomatic PAUs, which are more likely to lead to aneurysm, pseudoaneurysm, or rupture, require surgical intervention. Here, endovascular repair in combination with stent grafts has shown the greatest reduction in mortality, particularly given older patients’ common co-morbidities.
What else can Acute Aortic Syndrome be?
Doctors might consider several other conditions when dealing with symptoms that typically indicate problems with the aorta. These conditions include:
- Aortic Dissection, which is a tear in the large blood vessel branching off the heart
- Intramural Hematoma, a condition that causes bleeding into the wall of the aorta
- Penetrating Aortic Ulcer, a complication where the wall of the aorta gets ulcerated
- Thoracic Aortic Aneurysm, an abnormal widening of the upper part of aorta
- Abdominal Aortic Aneurysm, similar to thoracic Aortic Aneurysm but in the abdomen
- Traumatic Aortic Injury, which is damage to the aorta caused by physical trauma
- Myocardial Infarction, commonly known as a heart attack
- Pulmonary Embolism, a condition when a blood clot ends up in the lungs
A proper diagnosis is crucial, as each condition may require a different approach to treatment.
What to expect with Acute Aortic Syndrome
Aortic Aneurysm Dissection (AAD) carries a significant risk of death which varies based on where the dissection occurs. If dissection impacts the ascending aorta and is treated medically, there’s an overall mortality rate of 24% in the first 24 hours, 44% within a week, and up to 49% after two weeks. When surgical intervention is used to manage type A dissection, the mortality rates are much lower: 10% in the first day, 16% in a week, and up to 20% after two weeks. Type B dissection tends to have a less fatal outcome, with a risk of death up to 10% within a month. If complications arise the mortality rate can increase dramatically, with some studies showing up to 25% by the 30th day.
Distinguishing Intramural Hematoma (IMH) from co-existing Acute Aortic Syndrome (AAS) can be difficult as research shows up to 30% of patients have both AAD and IMH when diagnosed. IMH can take two paths: either it can be reabsorbed, which happens in about 10% of cases, or it can lead to Aortic Dissection, reported in up to 47% of patients. Patients with type A IMH who receive surgical treatment showed better results than those treated medically, with a lower mortality rate of 14% compared to 36%. Type B IMH has closer mortality rates with a 14% mortality rate for medically managed cases and a surgical mortality rate of 20%.
Possible Complications When Diagnosed with Acute Aortic Syndrome
Here are some potential complications that can occur:
- Formation of an aortic aneurysm
- Rupture of the aorta
- Reduced blood flow to an organ
- Reduced blood flow to a limb
- Issues with the aortic valve
- Blood accumulation in the pericardium
- Fluid in the chest (pleural effusion)
- Dissection of the coronary artery
- Death
- Stroke
- Heart attack (Myocardial infarction)
Preventing Acute Aortic Syndrome
People should be educated and urged to make the following positive changes:
– They should stop smoking
– They need to manage high blood pressure properly
– The use of recreational drugs, especially cocaine, should be eliminated
– It is encouraged to lead a healthy lifestyle and maintain a balanced diet