Emergency Management in Aortic Dissection

Introduction

The aorta is a large and major blood vessel that begins from the heart and runs throughout the torso. It runs upwards through the middle of the chest, arches back under the base of the neck, and travels downwards in front of the spine through the chest and abdomen (thoracic and abdominal aorta). It branches below the naval into two blood vessels (right and left common iliac arteries). The aorta wall is made up of three layers of tissue. Aortic dissection is a condition that tears the aorta's inner layer.

The blood flows through the tear and separates the inner and middle layers of the aorta, causing the aorta to split or dissect. This appears as a bulge in the aorta at the site of the tear. This is known as aortic dissection. As the blood flow gets diverted and the blood rushes in between the tissue layers of the aorta, the normal blood supply to other body parts and organs gets disrupted. The aortic dissection can lead to the rupture of the aorta, which can be fatal. Aortic dissection requires immediate medical attention, and it can cause death if not recognized or treated.

What Are the Two Main Types of Aortic Dissection?

Splits or dissection in the wall of the aorta occur in areas where the stress on the aortic wall is high or in areas that are weak (due to high blood pressure or inherited causes). The weakening of the aorta may go unnoticed for several years until a tear occurs. Aortic dissection is classified into the following:

1. Stanford Type A Aortic Dissection: When the aorta splits or dissects closer to the heart (ascending aorta), it is considered stanford type A aortic dissection.

2. Stanford Type B Aortic Dissection: This type of aortic dissection occurs farther from the heart and involves the descending aorta beyond the arch of the aorta. This can be managed medically or through endovascular stenting (a minimally invasive procedure to insert a stent graft device into the aorta). Surgery may be needed depending on the location of the tear and its severity.

What Are the Complications of Aortic Dissection?

When the blood rushes in between the layers of the aorta wall, it affects the blood supply to the body parts. As a result, vital organs such as the brain and other body tissues do not get sufficient oxygen and undergo damage and loss of function. Aortic dissection can lead to the following complications:

1. Stroke: A medical emergency that occurs due to interrupted blood supply to the brain. In a stroke, the patient has trouble speaking, walking, and understanding and has paralysis and numbness of the arms, legs, and face.

2. Aortic Valve Damage: The valve between the aorta and the heart’s lower chamber or ventricle that pumps blood can get damaged due to aortic dissection. As a result, there is a backflow of blood into the heart.

3. Organ Damage: Damage to the vital organs, such as the brain and kidney, can occur in aortic dissection leading to loss of function.

4. Cardiac Tamponade: Aortic dissection can cause fluid to accumulate between the heart and the sac covering the heart, exerting excessive pressure on the heart. This prevents the heart from beating properly.

5. Aortic Rupture and Death: The weakened aorta with dissection can rupture easily, causing massive internal bleeding and death.

What Are the Warning Signs of Aortic Dissection?

Tear in the aorta wall can occur abruptly at any time, during work, exercise, rest, or sleep. Aortic dissection can be life-threatening and cause aortic rupture (40 percent of the patients die). Every minute delay in treatment worsens the condition and affects survival. Therefore, one must seek emergency care (call emergency services or rush to the emergency department) if suspected aortic dissection or has the following warning signs:

• Sudden severe, sharp stabbing pain in the chest or upper back.

• Fainting.

• Breathlessness or shortness of breath.

• Dizziness.

• Low blood pressure.

• The pressure difference of 20 mmHg between arms.

• Heart sounds appear muffled.

• Abnormal heart sounds or murmur.

• Weak pulse.

• Rapid pulse and heartbeat.

• Profuse sweating.

• Vision loss.

• Confusion.

How Is Acute Aortic Dissection Diagnosed?

Acute aortic dissection that occurs suddenly with severe chest pain and with symptoms of other life-threatening conditions requires immediate medical attention. Quick and prompt assessment and diagnosis are essential to save lives. The various diagnostic tests that help diagnose aortic dissection include the following:

1. Chest X-Ray: The images of all the structures in the chest (heart, lungs, aorta, bones) can be seen in a chest X-ray that aids in diagnosis. A chest X-ray may be nonspecific but is quick and useful if the person requires immediate surgery.

2. Computed Tomography and Angiography: A clear image of the aorta and aortic dissection can be seen in a computed tomography scan. Dyes or contrasts can be used during imaging to identify the site of the tear.

3. Transthoracic Echocardiogram and Angiography: An ultrasound of the heart, its chambers, and the aorta (first portion or aortic root) can help arrive at a definitive diagnosis.

4. Magnetic Resonance Imaging (MRI): Detailed images of the aorta can be obtained using magnetic resonance imaging. The test is more time-consuming and is not usually used in emergencies. It provides moving images of the blood flow through the aorta, heart, and its valves.

5. Blood Tests: The blood tests performed to check for the presence of aortic dissection include:

• D-dimer.

• Complete blood count.

• Blood electrolyte levels (sodium, potassium).

• Cardiac markers.

• Lactate dehydrogenase test.

• Blood clotting factors and clot parameters.

• Blood crossmatch.

How Is Acute Aortic Dissection Managed?

Once the definitive diagnosis of aortic dissection is made, the patient is transferred promptly to a facility with expertise in managing aortic dissection and its complications. The aortic dissection is treated depending on the location and severity of the aortic dissection. Suppose the aortic dissection is close to the heart in the first part of the aorta (type A). In that case, emergency open surgery is performed to repair the tear or to replace the segment of the aorta that is dissected. Type B aortic dissection in the part of the aorta farther away from the heart may also require emergency surgery if the blood flow to the internal organs is affected.

Blood flow and damage to the vital organs such as kidneys, intestines, legs, and spinal cord are assessed, and if the blood supply appears cut off, immediate surgery is performed to minimize damage and loss of function. In addition, emergency surgery is performed if high-risk, life-threatening features are seen in the imaging (such as a computed tomography scan). Other less severe aortic dissections are managed with medications initially, and surgery is performed if complications arise. Medications such as beta-blockers that lower the patient’s heart rate and blood pressure are administered in such cases. The following are done in an aortic dissection emergency:

• Large-bore intravenous access is obtained to deliver medications into the veins if needed.

• Measures are taken to control blood pressure and heart rate.

• Medications such as Esmolol (beta-blockers) are administered intravenously to control heart rate and any rhythm irregularities. If beta blockers are not tolerated by the patient other alternatives such as Verapamil or Diltiazem are administered.

• Once the heart rate is brought to normal, vasodilators (medications that widen the blood vessels) are administered to lower the blood pressure. The vasodilator therapy includes Nitroprusside or Nicardipine infusions. These are not given before beta-blockers.

• Analgesics (medications to relieve pain), such as opioids, are administered intravenously.

• A catheter or tube (foley catheter) is inserted into the bladder to monitor kidney function and urine output.

• Surgical consultation is obtained immediately for cardiothoracic or vascular surgeries once the diagnosis is confirmed.

• When the aortic dissection is in the ascending aorta (close to the heart), emergency open surgery is the main treatment option to save the patient. Transesophageal echocardiography is used in the operating room to continuously check for fluid accumulation around the heart and to assess the aorta, aortic valve, and heart function (especially the lower chambers and the root of the aorta). Conventional open surgery with graft replacement involves removing the section of the aorta that is weak and replacing it with a synthetic fabric graft (tube) to allow smooth blood flow.

• Urgent aortic stenting and endovascular surgery are performed if the abdominal aorta (aorta in the abdomen region, farther away from the heart) is affected and the blood and oxygen supply to the vital organs is reduced (to ensure sufficient blood supply to all body parts and the internal organs). Endovascular surgery is minimally invasive, in which a stent graft is placed inside the aorta to reline and provide reinforcement of the weak part of the aorta.

• If no evidence of decreased blood supply to the vital organs due to abdominal aortic dissection is present, the patient is admitted to the intensive care unit for further management (medical management and imaging).

Conclusion

Aortic dissection is a condition that causes tears in the inner layer of the aorta. The blood flows through the tear and separates the layers of the aorta, causing the aorta to split or dissect. This leads to various complications such as stroke, organ damage, aortic valve damage, and fluid accumulation around the heart. These can be fatal without emergency care. When an aortic dissection is definitively diagnosed, the patient is immediately sent to a center that specializes in treating aortic dissection and associated complications. The aortic dissection is treated with conventional open surgery, minimally invasive surgery, and medications depending on the location and severity of the aortic dissection.