What is Aortic Dissection?
Although it’s not common, acute aortic dissection (AAD) is a very serious and often fatal condition. It occurs when the different layers of the aorta, the main blood vessel in the body, start to separate. This usually happens because of a tear in the inner layer of the vessel, and blood gets forced between the layers either forwards or backwards, extending the dissection. AAD has a high mortality rate; many people die even before they reach the hospital. On the other hand, people with chronic aortic dissection, a condition that’s been going on for more than two weeks, stand a slightly better chance.
While people usually describe experiencing a sudden, severe pain in their chests like something tearing, the symptoms can often be milder, making this condition difficult to diagnose. In fact, doctors are able to spot it correctly in only 15% to 43% cases of confirmed AAD. If not treated promptly, chances of dying from this condition are about 50% within the first two days. However, despite loads of information available, many cases of aortic dissection are not caught in time in the emergency room.
Doctors use two main systems to classify aortic dissection, primarily based on which part of the aorta is involved. The most commonly used is the Stanford system, which distinguishes between two types:
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Type A, which involves the part of the aorta that ascends or goes upwards, irrespective of where the initial tear is. Specifically, type A dissection is when the dissection is located before the artery leading to the right arm.
– Type B dissection starts after the artery to the left arm and only involves the part of the aorta that descends or goes downwards.
The DeBakey classification is another system that’s based on where the dissection starts:
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Type 1 starts in the ascending aorta and extends to at least the curve of the aorta.
– Type 2 is confined to just the ascending aorta.
– Type 3 begins in the descending aorta and extends downwards either above the diaphragm (type 3a) or below it (type 3b).
Notably, dissections in the ascending aorta are almost twice as common as those in the descending aorta.
What Causes Aortic Dissection?
There are several risk factors that can potentially lead to a non-traumatic aortic dissection, which is a serious condition where the inner layer of the aorta tears. These include:
– High blood pressure: This is a common factor, occurring in 70% of patients who have a certain type of aortic dissection known as Standford type B AAD.
– A sudden, severe spike in blood pressure: This can happen during heavy weight lifting or after using certain stimulants like cocaine, ecstasy, or energy drinks.
– Genetic conditions: These include Marfan syndrome, Ehlers-Danlos syndrome, Turner syndrome, and having a two-part aortic valve, or a narrowed aorta. In fact, Marfan syndrome was found in half of the under-40 patients in one review, compared to just 2% of older patients. Those with Marfan syndrome also often see a specific type of tissue damage called cystic medial necrosis.
– Already having an aortic aneurysm: This is a bulge in the aorta that could potentially rupture.
– Plaque build-up in the arteries, known as atherosclerosis.
– Pregnancy and childbirth: This risk increases for pregnant women who also have a connective tissue disorder, such as Marfan syndrome.
– Family history
– Going through aortic procedures or surgeries: This includes things like heart bypass surgery, replacing aortic or mitral valves, or inserting a stent or catheter.
– Diseases that cause inflammation or infection of the blood vessels, such as syphilis, or can be induced by cocaine use.
Risk Factors and Frequency for Aortic Dissection
Aortic dissection is a condition that occurs in 5 to 30 cases out of a million people each year. To put this into a perspective, it’s considerably less prevalent than acute myocardial infarction, a heart problem affecting around 4,400 people out of a million per year. Among those who visit emergency departments with symptoms like acute back, chest, or abdominal pain, aortic dissection is diagnosed in three out of every thousand patients.
Age is a significant risk factor – about 75% of aortic dissection cases are found in individuals between 40 and 70 years old, with most cases occurring between 50 and 65 years. However, there are important differences noted between older and younger patients when the ascending aorta is affected.
- Older patients are more likely to have related conditions such as atherosclerosis, prior aortic aneurysm, iatrogenic (caused by medical treatment) dissection, or an internal blood clot.
- Younger patients, on the other hand, are less likely to have a history of high blood pressure, but are more susceptible if they have a certain type of connective tissue disorder like Marfan syndrome.
Furthermore, aortic dissection is three times more frequent in men than in women, though women tend to detect it later and are likely to face more severe outcomes.
Signs and Symptoms of Aortic Dissection
Acute Aortic Dissection (AAD) is a medical condition where the inner layer of the aorta, the main blood vessel branching off the heart, tears. The presentation of AAD depends on how far the tear has progressed, with affected areas causing corresponding symptoms. Clinicians pay special attention to three crucial details when suspecting AAD: the quality of the pain, its intensity, and whether the pain radiates to other parts of the body. It’s been found that the suddenness and intensity of this pain are the most consistent indicators. Classic signs of AAD, which include differing blood pressures in the upper limbs, a pulse deficit, or a murmur that happens during the relaxation phase of a heartbeat, may not always be present. However, the combination of chest pain with neurological symptoms, chest and abdominal pain, or chest pain paired with limb weakness or tingling could suggest AAD.
The pain associated with AAD can start suddenly, peak swiftly, and feel like tearing. Around 10% of patients with AAD, especially those with Marfan syndrome, may not experience any pain. Depending on whether the tear is in the part of the aorta that’s going upwards or coming down, patients can feel this pain in their chest or back, respectively. The pain may even shift lower down the body as the tear extends in that direction. Neurological defects, such as loss of consciousness, are found in 20% of the patients on arrival, mainly due to blood volume deficits, irregular heart rhythms, heart attacks, or excessive activation of the vagus nerve, the body’s main nerve related to calming responses. The tear can cause complications like loss of pulse, tingling, and pain if it involves vessels supplying the arms and legs.
Some patients with AAD may exhibit hoarseness and Horner syndrome – a condition involving eye and facial abnormalities. If there is a leak or rupture in the space between the lungs, the patient might face difficulty in breathing and cough up blood.
High blood pressure is common in AAD. If the patient shows low blood pressure, it could be a severe sign indicating a potential rupture. A noticeable difference in blood pressure readings between the two arms should alert health professionals to possible AAD. Some other symptoms include:
- Wide gap between the systolic and diastolic readings
- Leaky aortic valve
- Murmur during the relaxation phase of the heartbeat
- Diminished heart sounds indicating potential fluid accumulation around the heart
- Fainting
- Change in mental status
- Loss of limb pulses
- Horner syndrome
Testing for Aortic Dissection
Common checks such as an ECG (electrocardiogram) and chest x-ray can help rule out other reasons you might be feeling chest pain, but these can be misleading at times. For instance, an ECG indicating a heart attack is noted in approximately 8% of AAD (Aortic Aneurysm Dissection) cases.
Contrarily, while a broadened aortic silhouette or shadow on an x-ray may indicate AAD, not seeing this doesn’t necessarily mean AAD is not present. The surest way to confirm AAD is through cardiovascular imaging, where professionals look for a tear in the innermost layer of the aorta and decide its classification. Also, this method can identify any complications with valves or branches of the aorta. So, you might get recommended for a CT scan or TEE (transesophageal echocardiogram) per most society guidelines. The selection mainly depends on what facilities your healthcare institution has.
Typically, an emergency department would likely turn to the CT scan as it’s quite universally available. Alongside imaging, blood tests for elements like CBC (Complete Blood Count), electrolytes, troponin (a protein that can indicate heart damage), D-dimer, and renal function are crucial. A higher level of smooth muscle myosin heavy chain protein in these test results could point to AAD.
Further signs of AAD visible in a chest x-ray could be a broadened mediastinum (the space between your lungs), fluid collection due to rupture, and other features such as a left apical cap, pleural effusion, and the esophagus and trachea deviating from their normal positions. A CT scan with contrast is advisable if the person is stable. The scan can spot the location of the tear quickly and help in surgical planning.
Echocardiography is another useful way of detecting AAD. TEE is preferred as it can be done at the bedside and during surgery. Its major drawback, however, is that it requires a highly skilled operator. In an unstable patient, TEE is the recommended procedure. Other indications for TEE include renal insufficiency and contrast allergy. Some findings may include different segments of Doppler flow in the dissection flap, clotting in the false lumen (blood-filled space within the aorta’s wall), displacement of intimal calcification, and pericardial effusion (fluid around the heart).
Aortography (imaging of the aorta) is not commonly performed today unless planning for surgical repair using stents. Lastly, a 12-lead ECG is essential to rule out a heart attack.
Treatment Options for Aortic Dissection
If someone is suspected to have acute aortic dissection, a serious heart condition, they’ll require immediate consultation with heart or blood vessel surgeons. Acute episodes that affect the rising section of the aorta, the main blood vessel branching from the heart, are considered emergencies that need surgery.
The patient will likely need an arterial line and central venous catheter for monitoring, as well as a urinary catheter to keep track of urine production.
At the same time, pain relief medication should be given, typically morphine, which also helps decrease sympathetic responses. Doctors will also use beta-blockers, a type of medication that slows heart rate, to target a beat rate of about 60 beats per minute. This helps lower blood pressure, which also reduces tension in the aorta and limits the extent of the dissection. If beta-blockers aren’t suitable, calcium channel blockers may be used instead.
If blood pressure remains too high, additional medications, such as nitroprusside, might be used to lower it to a goal of 100 to 120 mmHg. However, if the person becomes confused or their urine output decreases, blood pressure may be raised again.
If the person’s blood pressure is too low, intravenous fluids may be administered. If it’s still too low, medicines to raise it can be used, but cautiously because they can exacerbate the condition. Medicines that increase the force and rate of heart contraction should be avoided as they can worsen the stress on the aortic wall.
Surgery for type A aortic dissection usually involves removing the tear in the aorta, closing off the false channel, and reconstructing the aorta with a synthetic graft. Surgery for type B dissection is usually reserved for more complex cases. A less invasive alternative to surgery, endovascular stent grafting, can also be used, especially for complex type B dissections.
In cases where the rising aorta is affected, it must be replaced, and the heart valve evaluated. Often, the heart valve also needs to be replaced. Dissections involving the descending aorta are complex and carry a risk of paralysis. The toughest cases are those that involve the aortic arch, with surgical mortality rates ranging from 5-20%.
Endovascular procedures are being increasingly used for acute aortic dissection due to the high risk associated with surgery. This approach involves placing a stent and has lower complications compared to surgery, but choosing the right patient is critical.
What else can Aortic Dissection be?
When a doctor suspects a patient might have an aortic dissection, they also need to consider other serious conditions that can cause similar symptoms. These include:
- Heart attack (myocardial infarction)
- Swelling of the large blood vessel in the abdomen or chest (aortic aneurysm)
- Build-up of fluid around the heart, leading to decreased heart function (cardiac tamponade)
- Tearing of the esophagus (Boerhaave syndrome)
- Collapse of the lung (spontaneous pneumothorax)
- Blockage in one of the lung’s blood vessels (pulmonary embolism)
- Stroke or transient ischemic attack (a short-term blockage of blood flow to the brain)
If the patient is experiencing abdominal pain, doctors should consider conditions like kidney stones, gallstones, blocked or perforated intestine, or an insufficient blood supply to the intestines not related to aortic dissection.
Changes in the patient’s pulse can indicate a situation where blood clots have been carried in the bloodstream and have blocked a distant artery, or a blockage in an artery which is not due to aortic dissection.
What to expect with Aortic Dissection
Aortic dissection, a serious heart condition, has a high fatality rate. Around 30% of patients unfortunately pass away after reaching the hospital’s emergency room. Even with surgery, the death rates are between 20-30%. Those who do survive often struggle with other health issues, resulting in a lesser quality of life.
The most critical time is within the first 10 days of an acute aortic dissection, where the risk of passing away is highest. People with a chronic form of aortic dissection tend to fare better, but their life expectancy is still lower compared to the average person.
Possible Complications When Diagnosed with Aortic Dissection
- Failure of multiple organs
- Stroke
- Heart attack (MI – myocardial infarction)
- Paralysis in the lower part of the body (Paraplegia)
- Kidney failure
- Amputation of limbs
- Dying of bowel tissue due to reduced blood flow (Bowel ischemia)
- Pressure on the heart due to fluid buildup (Tamponade)
- Sudden leaking of the aortic valve in the heart (Acute aortic regurgitation)
- Compression or blockage of the large vein carrying blood from the upper body to the heart (Superior vena cava compression)
- Death
Recovery from Aortic Dissection
After a patient has received surgical or medical treatment, it’s crucial to regularly manage their blood pressure. The patient’s condition must be carefully monitored to track any advancement of the aortic dissection. To do this accurately, periodic chest CT scans or MRIs are recommended, typically at 3-6 month intervals, which will help doctors determine if the disease is progressing.
Preventing Aortic Dissection
It’s essential to regulate your blood pressure, refrain from using illegal drugs, keep a healthy weight, and quit smoking. These steps help maintain good health and lower the risk of various diseases.