An aortic dissection is a life-threatening condition in which there is a tear in the inner layer of the aortic wall, allowing blood to flow between the layers of the aorta, causing them to separate. This can lead to rupture, organ damage, or death. The treatment of aortic dissection depends on its type, location, and extent, with surgery often being required for severe or complicated cases.

Aortic dissection is classified into two types based on the Stanford classification:

• Type A: Involves the ascending aorta and may extend into the aortic arch or even the descending aorta.
• Type B: Involves only the descending aorta (below the left subclavian artery) and typically does not affect the ascending aorta.

Indications for Surgery

Surgery is typically required for Type A aortic dissections due to the risk of rupture and compromise to vital organs (e.g., the heart, brain). In Type B aortic dissections, surgery is generally reserved for cases involving complications such as:

• Uncontrolled pain.
• Progressive dissection or expansion of the false lumen.
• Rupture or impending rupture.
• End-organ ischemia (e.g., kidney failure, spinal cord ischemia).
• Aortic rupture or dilation causing aneurysmal changes.

For Type A dissections, the urgency of surgical intervention is paramount as delays can lead to fatal outcomes. Type B dissections can sometimes be managed medically unless complications arise.

Surgical Goals

• Restore normal aortic flow.
• Repair or replace damaged sections of the aorta.
• Prevent further extension of the dissection.
• Protect vital organs (brain, heart, kidneys, spinal cord).

Types of Surgical Procedures for Aortic Dissection

The surgical treatment for an aortic dissection depends on the location and extent of the dissection, as well as the patient’s overall condition. There are two primary approaches to surgery: open surgical repair and endovascular repair.

1. Open Surgical Repair of Aortic Dissection

This is the traditional approach, and it is often used in Type A aortic dissections and some complex Type B dissections. The procedure involves direct access to the aorta and the repair of the damaged sections.

Procedure Steps for Open Surgical Repair:

1. Preoperative Preparation:
• The patient is intubated and placed under general anesthesia.
• The patient is positioned supine, and the surgical area is prepared with antiseptic.
• Invasive monitoring is used to assess cardiovascular and respiratory status.
2. Accessing the Aorta:
• A midline sternotomy (cutting through the breastbone) or left thoracotomy (side chest incision) is performed, depending on the location of the dissection.
• For Type A dissection, the incision is usually made through the sternum to access the ascending aorta.
3. Cardiopulmonary Bypass (CPB):
• Cardiopulmonary bypass is initiated to temporarily take over the functions of the heart and lungs during the surgery. The patient’s blood is diverted through a heart-lung machine while the heart is stopped.
4. Repairing the Aorta:
• The surgeon locates the tear in the aorta and repairs the dissection.
• For Type A dissection, the ascending aorta may need to be replaced with a synthetic graft (usually Dacron or PTFE), and the aortic valve may need to be repaired or replaced if it is damaged.
• In cases where there is involvement of the aortic arch, a more complex arch replacement may be necessary.
• For Type B dissection, if the dissection involves the descending aorta and is complicated by rupture, end-organ ischemia, or persistent symptoms, surgery may involve replacing the diseased segment of the descending aorta.
5. Closing the Aorta:
• Once the dissection is repaired and blood flow is restored, the aorta is closed using sutures or staplers.
6. Weaning from Cardiopulmonary Bypass:
• Once the repair is confirmed to be successful and the patient is stable, the heart is restarted, and the patient is gradually weaned off the bypass machine.
7. Postoperative Care:
• The patient is closely monitored in the intensive care unit (ICU) for signs of complications like bleeding, infection, stroke, or organ failure.
• Chest tubes are often placed to drain any excess fluid or air after the surgery.
• Postoperative imaging (e.g., CT scan or echocardiography) is used to check the success of the repair.

2. Endovascular Repair (TEVAR - Thoracic Endovascular Aortic Repair)

Endovascular repair is a less invasive option, typically used for Type B aortic dissections or in patients who are high-risk for open surgery. This procedure involves inserting a stent-graft through the femoral artery to repair the dissection without opening the chest. This method may also be used for certain Type A dissections in patients with specific anatomical features or who are not candidates for open surgery.

Procedure Steps for Endovascular Repair:

1. Preoperative Preparation:
• Similar to open surgery, the patient is placed under general anesthesia.
• The groin area is cleaned, and the femoral arteries are accessed.
2. Inserting the Stent-Graft:
• A catheter is inserted through the femoral artery and guided under fluoroscopy (real-time X-ray) to the site of the dissection.
• A stent-graft (a tube-like device made of fabric and supported by a metal mesh) is deployed at the site of the dissection.
• The stent-graft is expanded to seal off the false lumen and create a new channel for blood flow, restoring normal circulation and preventing the dissection from spreading.
3. Final Assessment:
• The position and deployment of the stent-graft are carefully evaluated through imaging, ensuring that the dissection is sealed and blood flow is restored.
4. Postoperative Care:
• The patient is monitored for complications like stent migration, endoleaks (leakage of blood around the stent-graft), and renal function.
• Patients typically recover more quickly from endovascular surgery than from open surgery and may be discharged sooner.

Postoperative Care and Monitoring

After surgery, patients are closely monitored in the ICU for signs of complications such as:

• Bleeding: Ongoing bleeding from the aorta or surgical site is a significant risk and may require additional intervention.
• Organ Dysfunction: The kidneys, heart, and brain are most at risk during an aortic dissection and its surgery. Renal failure, stroke, or myocardial infarction can occur.
• Spinal Cord Ischemia: This is a potential complication, especially in patients with Type A dissection or those undergoing aortic arch replacement. Neurological monitoring is crucial.
• Hypertension: Postoperative blood pressure control is critical to avoid further stress on the repaired aorta and to prevent re-dissection.

Patients will typically undergo follow-up imaging (such as CT scans, echocardiography, or MRI) to monitor the aorta and ensure the repair is stable.

Complications and Risks

While surgical repair of aortic dissection has improved significantly, it still carries potential risks and complications:

1. Stroke: Caused by embolization of clot material or decreased blood flow to the brain.
2. Spinal Cord Ischemia: Caused by decreased blood supply to the spinal cord, leading to neurological deficits or paralysis.
3. Endoleaks: In endovascular repair, these occur when blood leaks outside the stent-graft, requiring further treatment.
4. Infection: As with any major surgery, there is a risk of infection.
5. Re-dissection: A recurrence of dissection or failure of the initial repair can occur, especially if the repair is not stable.
6. Renal Failure: Particularly in Type A dissection, where there may be compromised renal perfusion.

Prognosis and Outcomes

• Type A Aortic Dissection: Surgery for Type A dissections has a relatively high mortality rate if not treated immediately, but with successful surgery, long-term survival rates can improve significantly. Immediate intervention can save the life of most patients with Type A dissection, especially if the surgery is done within hours of diagnosis.
• Type B Aortic Dissection: For Type B dissections, outcomes are generally better because these do not involve the ascending aorta. With early detection and appropriate management (including possible surgery), the prognosis is often good. However, if complications arise, surgery is required, and the patient’s recovery depends on the severity of the dissection and the success of the procedure.

Conclusion

Aortic dissection surgery is a critical procedure to save lives and prevent catastrophic outcomes from aortic rupture or organ ischemia. Open surgical repair remains the treatment of choice for Type A dissections, while endovascular repair offers a less invasive option for Type B dissections or patients who are high-risk for open surgery. Both surgical approaches aim to restore blood flow, repair damaged portions of the aorta, and protect vital organs. Successful outcomes are closely linked to early diagnosis, prompt surgical intervention, and careful postoperative management.