eMedicine Specialties > Thoracic Surgery > Vascular

Aortic Dissection: Treatment

Author: Mary C Mancini, MD, PhD, Professor, Department of Surgery, Louisiana State University Health Sciences Center
Contributor Information and Disclosures

Updated: Apr 16, 2009

Treatment

Medical Therapy

Initiate medical therapy as soon as the diagnosis is considered. The goal is to decrease the blood pressure and the shearing forces of myocardial contractility in order to decrease the intimal tear and propagation of the dissection.

Admit the patient to the intensive care unit or coronary care unit for hemodynamic studies, as follows:

• Arterial blood pressure monitoring with an arterial line
• Central venous pressure monitoring with a central catheter
• Cardiac performance and filling pressures with Swan-Ganz catheterization
• Urine output monitoring with a Foley catheter and bag

Initiate therapy to reduce cardiac contractility. Administer drugs with negative inotropic effects, such as beta-blockers (the agents of choice); administer calcium channel blockers if beta-blockers are contraindicated. The following beta-blockers are commonly used:

• Intravenous or oral labetalol
• Intravenous or oral propranolol
• Intravenous or oral esmolol

Initiate therapy to reduce systemic arterial pressure and shear stress if the patient's blood pressure allows for this type of intervention. The following agents are commonly used:

• Intravenous nitroprusside drip
• Intravenous labetalol - Has a dual effect by decreasing blood pressure and cardiac contractility
• Calcium channel blockers (eg, diltiazem) - Lower blood pressure and cardiac contractility

The following conditions contraindicate beta-blocker therapy:

• Hypersensitivity to drug/class
• Severe asthma
• Heart block
• Uncompensated heart failure
• Bradycardia (heart rate <60 beats/min)
• Severe chronic obstructive pulmonary disease
• Hypotension

The following conditions contraindicate calcium channel blocker therapy:

• Hypersensitivity to drug/class
• Second- or third-degree atrioventricular block
• Sick sinus syndrome
• Hypotension
• Left ventricular dysfunction
• Pulmonary congestion

The following conditions contraindicate nitroprusside infusion:

• Hypersensitivity to drug/class
• Poor cerebral perfusion
• Poor coronary perfusion

Pain management is always difficult in persons with aortic dissection. Narcotics and opiates are the preferred agents. Medical therapy is also administered to surgical patients preoperatively, intraoperatively, and postoperatively to prevent progression or recurrence of aortic dissection.

Surgical Therapy

The major objectives of surgery for aortic dissection are to alleviate the symptoms, decrease the frequency of complications, and prevent aortic rupture and death.

Improved cardiopulmonary bypass circuits have decreased the prevalence of injury to blood elements. A decrease in complications such as brain injury has resulted from a more detailed understanding of the physiology and limitations of hypothermic circulatory arrest.

Aortic arch repair and reconstruction can be partial or complete. A number of advances have resulted in a decreased frequency of complications associated with surgery on the aorta. Dacron grafts with impregnated collagen or gelatin have been developed that are impervious to blood.

Adjunct procedures, including distal aortic perfusion, profound hypothermia, cerebrospinal fluid drainage, and monitoring of somatosensory and motor evoked potentials in the brain and spinal cord, have decreased the frequency of procedure-related spinal cord injury during descending aorta and thoracoabdominal surgeries.

Percutaneous fenestrations and stent placements are performed. The area of the aorta with the intimal tear is usually resected and replaced with a Dacron graft.

The operative mortality rate is usually less than 10%; serious complications are rare with ascending aortic dissections.

The development of more impermeable grafts, such as woven Dacron, collagen-impregnated Hemashield (Meadox Medicals; Oakland, NJ), aortic grafts, and gel-coated Carbo-Seal Ascending Aortic Prothesis (Sulzer CarboMedics; Austin, Tex), has greatly enhanced the surgical repair of thoracic aortic dissections.

Morbidity and mortality rates associated with this highly invasive surgery have decreased with the introduction of profound hypothermic circulatory arrest and retrograde cerebral perfusion.¹⁴

Dissections involving the arch are more complicated than those involving only the ascending aorta because the innominate, carotid, and subclavian vessels branch from the arch. Deep hypothermic arrest is usually required. If the arrest time is less than 45 minutes, the rate of CNS complications is less than 10%. Retrograde cerebral perfusion may improve the protection of the CNS during the arrest period.

The mortality rate associated with aortic arch dissections is approximately 10-15%, with significant neurologic complications occurring in an additional 10% of patients.

Medical management remains the treatment of choice for descending aortic dissections unless they are leaking or ruptured. With the progress in stenting technology, descending dissections can be approached with this modality in selected cases.^{15,16,17,18,3,5}

Preoperative Details

Numerous factors may increase mortality and morbidity rates for surgical intervention on the aorta, including a history of myocardial infarction, respiratory failure, renal failure, or stroke.

Preoperative evaluation is, therefore, essential in patients with these histories. Because aortic dissection is more common in elderly patients (ie, aged 70-80 y), this group of patients has different comorbidities.

Patients older than 50 years have a high prevalence of atherosclerotic heart disease and may require a thorough cardiac workup. Symptoms of aortic dissection are always difficult to differentiate from those of myocardial infarction.

Patients with ECG changes suggestive of myocardial infarction or ischemia undergo workups with emergency cardiac catheterization and angiography, followed by percutaneous transluminal coronary angioplasty or coronary artery bypass grafting concomitant with aortic repair or construction.

Patients with valvular heart disease undergo workups with echocardiography or coronary angiography. If any valvular abnormalities are found, then appropriate surgical correction (valve replacement or commissurotomy) is performed prior to or simultaneous with aortic repair.

Surgeries involving the descending or thoracoabdominal aorta require a lateral thoracotomy. A history of smoking or chronic obstructive pulmonary disease is of significant concern; perform pulmonary function testing on such patients. Additionally, arterial blood gas testing may be required. In elective cases, treat reversible restrictive diseases and excessive sputum production with antibiotics and bronchodilators.

Preoperative renal dysfunction is considered the most important predictor of postoperative acute renal failure (ARF). Preoperative management involves adequate hydration and avoidance of hypotension, a low cardiac output state, and hypovolemia in order to decrease the frequency of ARF.

Perform appropriate workups for patients presenting with any neurological signs suggestive of CNS pathology (eg, stroke). This usually consists of Doppler imaging of the carotid arteries and, if needed, angiography of brachiocephalic and intracranial arteries. If the study findings are positive, perform a carotid endarterectomy before the aortic surgery.

Intraoperative Details

The objectives of surgical therapy for aortic dissection are to resect the damaged segment, excise the intimal tear, and obliterate the entry into in the false lumen. Suturing the edges of the dissected aorta both proximally and distally obliterates the entry into the false lumen. The desirability of obliterating the entrance to the false lumen is controversial because of multiple portals. Aortic continuity after dissection of a diseased segment is reestablished by means of a prosthetic sleeve graft between the 2 ends of the aorta.

Patients with type A dissections are treated with immediate surgical correction. This involves transfer to the operating room, where median sternotomy is performed. Profound hypothermia is initiated after the patient is placed on cardiopulmonary bypass. Cardiopulmonary bypass is performed by femoral-femoral cannulation and through the superior vena cava for retrograde cerebral perfusion. Myocardial temperature is kept below 15°C (59°F) by cardioplegic perfusion via the coronary sinus. This provides myocardial protection throughout the procedure. Ventricular distension is avoided by decompressing the left ventricle by venting through the left superior pulmonary vein or artery. The pump is stopped when the electroencephalogram is isoelectric and the nasopharyngeal temperature reaches 12°C (53.6°F). Retrograde cerebral perfusion is then started via the superior vena cava.

The ascending aorta is inspected for the site and extent of the tear and the involvement of the transverse arch and for an assessment of intimal disruption that requires repair. Through a longitudinal approach, the ascending aorta is opened and transected just proximal to the innominate artery. If the transverse arch is free of reentry, the intima and adventitia are sutured together with fine 4-0 and 5-0 polypropylene suture. A gelatin- or collagen-woven Dacron graft is sutured to the reinforced proximal aortic arch in end-to-end fashion and reinforced from both inside and outside with 4-0 pledgeted sutures.

At the time of completion of the distal anastomosis, retrograde cerebral perfusion is stopped and cardiopulmonary bypass is restarted via the femoral artery. This evacuates all air and debris from the brachiocephalic vessels. The graft is clamped proximal to the origin of the innominate artery. Flow to the cerebral and systemic circulation is restored after clamping the graft proximal to the origin of the innominate artery.

Hypothermic circulatory arrest is a valuable tool in aortic dissection repair. Emptying the major vessels allows ingress of air, which causes complications related to air embolism, a major hazard associated with this procedure. Ensure that the patient's head is not elevated; rather, depress it and allow blood to gravitate into the head vessels, thus displacing the air (upward) to the periphery. This is essential.

The patient is rewarmed with restoration of anterograde flow through a side arm line inserted in the ascending aorta. The aortic valve is suspended with 4-0 polypropylene pledgeted sutures if it is normal and no evidence of aortic root dilatation is present. The intima and adventitia of the aorta superior to the coronaries are sutured together and reinforced from inside the graft. If the aortic valve or the root is dilatated, a composite valve graft is placed.

A button or modified Cabrol technique is used to reattach the coronaries. When aortic regurgitation is present, simple decompression of the false lumen may be all that is required to allow resuspension of the aortic leaflets and restoration of valvular competence. More often, however, the 2 layers of the dissected aortic wall are approximated, and resuspension of the commissures is accomplished with pledgeted sutures. Prosthetic aortic valve replacement also may be necessary in certain situations. After the procedure is completed and the patient is brought to sinus rhythm by defibrillation, the patient is weaned from cardiopulmonary bypass.

In patients with involvement of the transverse aortic arch, either the proximal arch or the total arch is replaced. If the intima is fragmented or shows evidence of rupture, then the whole arch is replaced.

Surgical management of acute type B aortic dissections is undertaken only in the presence of indications such as persistent pain, aneurysmal dilatation greater than 5 cm, end organ or limb ischemia, or evidence of retrograde dissection to the ascending aorta. The remaining patients are treated with intense medical therapy.⁵

The operation involves transection of the proximal descending aorta distal to the left subclavian artery. Similar to operation on the ascending aorta, the proximal and distal intima and adventitia of the transected aorta are reinforced in the same manner as that for the ascending aorta, with a 4-0 polypropylene suture. A gelatin- or collagen-woven Dacron graft is sewn directly to the reinforced acutely dissected proximal thoracic aorta, with the posterior row reinforced using interrupted polypropylene sutures. Blood is rechanneled into the true lumen of the distal aorta by cutting the descending thoracic graft and suturing it to the reinforced distal aorta.

Adjunct procedures are used to minimize complications. The entire thoracoabdominal aorta is opened if extensive involvement of the descending and abdominal aorta is present that requires replacement. The septum between the false and true lumen is excised, and the visceral vessels and renal arteries are reattached to the graft directly or via a Dacron graft.

In chronic dissections, the intercostal arteries (T9-T12) are reimplanted by side graft or a side hole. This is in contrast to acute dissections, in which the intercostals and lumbar arteries are ligated. Newer surgical techniques have been developed that use fibrin sealant or gelatin-resorcin-formaldehyde glue.

Glue replaces the use of pledgeted sutures to seal the false lumen of the aortic stumps after resection of the diseased aortic segment and before the implantation of the Dacron prosthesis. The glue hardens and reinforces the dissected aortic tissue. Other advantages include simplification of the operation, facilitation of the resuspension of the aortic valve, and, possibly, reduction in the frequency of late aortic root aneurysm formation.

Because of high operative mortality rates in people with renal or visceral artery compromise from dissection, endovascular techniques are under investigation. Several endovascular techniques are available.^15,18,19 One involves the formation of a site of reentry to allow blood to pass from the false lumen to the true lumen. This requires passing a wire past the intact intimal flap, passing a balloon-tipped catheter over the wire, and tearing a hole in the intimal flap by inflating the balloon.

Another technique involves percutaneous stenting to decrease the ischemic complications of aortic dissection. This is performed on arteries that have compromised flow from the dissection. Sutureless intraluminal prostheses placed during cardiopulmonary bypass are also being used. Another technique involves percutaneously placed intraluminal stent-grafts using a transfemoral catheter technique. This procedure results in the closure of the site of entry into the false lumen and decompresses and promotes thrombosis of the false lumen. It also alleviates obstruction of the branch vessels complicating a dissection.

Intramural hematomas and penetrating atherosclerotic ulcers of the aorta are conditions that result in aortic dissection or rupture. Both are more common in the descending aorta; medical therapy is the first-line treatment. When either affects the ascending aorta or the arch, the need for surgery is more likely. Intramural hematomas are hemorrhage into the medial layer of the aortic wall without an intimal tear. Because these hematomas have a natural history similar to aortic dissection and aneurysm, they are treated similarly.

Surgical therapy is initiated for patients with proximal hematomas; medical therapy is reserved for patients with distal hematomas. Medical therapy consists of optimizing blood pressure control, decreasing aortic pulse pressure, controlling risk factors for atherosclerosis, and maintaining close long-term follow-up care. Penetrating atherosclerotic ulcers penetrate the internal elastic lamina, causing hematoma formation within the media of the aortic wall. Almost all are in the descending aorta. Because the natural history of these ulcers is undefined, a definitive treatment strategy has not been formulated.

Consider surgery in patients with penetrating atherosclerotic ulcers who are hemodynamically unstable or who have evidence of pseudoaneurysm formation or transmural rupture. Other indications for surgery include recurrent pain, distal embolization, and progressive aneurysmal dilatation from the ulcer. If patients present without these complications, they are treated with antihypertensive medications and close monitoring.²⁰

Postoperative Details

Postoperative complications for extensive disease involving the thoracoabdominal aorta include myocardial infarction, respiratory failure, renal failure, stroke, and paraparesis or paraplegia.

Follow-up

Provide the following long-term care for patients with aortic dissection, whether treated medically or surgically:

• One-month follow-up check for any new symptoms, such as chest or back pain, and signs suggestive of progression of the aortic dissection
• Adequate blood pressure control, with the systolic blood pressure maintained at 90-120 mm Hg
• Routine chest radiographs, CT scans with contrast, and MRIs, at 3-, 6-, and 12-month intervals, respectively, in an outpatient setting to evaluate any progression of the condition

Complications

Complications are diverse and numerous; anatomic-related complications are deducible and include the following:

• Hypotension and shock as a result of aortic rupture and eventual death from exsanguination
• Pericardial tamponade secondary to hemopericardium - Complicates type A aortic dissection
• Acute aortic regurgitation as a complication of proximal aortic dissection propagating into a sinus of Valsalva with resultant aortic valve insufficiency
• Pulmonary edema secondary to acute aortic valve regurgitation
• Rare occurrence of right or left coronary ostium involvement leading to myocardial ischemia
• Neurologic findings due to carotid artery obstruction - Ischemic cerebrovascular accident (CVA), hemiplegia, hemianesthesia (Aortic branch involvement can lead to spinal cord ischemia, ischemic paraparesis, and paraplegia.)
• Mesenteric and renal ischemia - Can lead to bowel or visceral ischemia, renal infarction, hematuria, or acute renal failure (ARF)
• Compressive symptoms, such as superior vena cava syndrome, Horner syndrome (when it affects the superior cervical ganglia), dysphagia (when it involves the esophagus), airway compromise, and hemoptysis (when it compresses the bronchus)
• Other compressive symptoms - Can be associated with vocal cord paralysis and hoarseness
• Claudication - Can develop from extension of the dissection into the iliac arteries
• Redissection and progressive aortic diameter enlargement
• Aneurysmal dilatation and saccular aneurysm - Also can complicate aortic dissection

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