Aortic Dissection Treatment & Management

Acute aortic dissection can be treated surgically or medically. In surgical treatment, the area of the aorta with the intimal tear is usually resected and replaced with a Dacron graft.

Emergent surgical correction is the preferred treatment for Stanford type A (DeBakey type I and II) ascending aortic dissection. It is also preferred for complicated Stanford type B (DeBakey type III) aortic dissections with clinical or radiologic evidence of the following conditions:

• Propagation (increasing aortic diameter)
• Increasing size of hematoma
• Compromise of major branches of the aorta
• Impending rupture
• Persistent pain despite adequate pain management
• Bleeding into the pleural cavity
• Development of saccular aneurysm

Cautions and relative contraindications to surgery include the following:

• Cerebrovascular accident
• Severe left ventricular dysfunction
• Coagulopathy
• Pregnancy
• Postmyocardial infarction (< 6 mo)
• Significant arrhythmias
• Advanced age
• Severe valvular disease

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.^{[2, 10, 25, 26, 27, 28]} Medical therapy is also administered to surgical patients preoperatively, intraoperatively, and postoperatively to prevent progression or recurrence of aortic dissection.

Medical management consists of decreasing the blood pressure and the shearing forces of myocardial contractility in order to decrease the intimal tear and propagation of the dissection. Medical management with antihypertensive therapy, including beta-blockers, is the treatment of choice for all stable chronic aortic dissections.^[29]

Pain management is an important but difficult aspect of medical therapy. Narcotics and opiates are the preferred agents.

For more information, see the Medscape Reference article Emergent Management of Acute Aortic Dissection.

Initiate medical therapy as soon as the diagnosis is considered. To guide medical therapy, 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, intravenously or orally:

• Labetalol
• Propranolol
• 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: it has a dual effect of decreasing blood pressure and cardiac contractility
• Calcium channel blockers (eg, diltiazem): they 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

The major objectives of surgery for aortic dissection are to alleviate the symptoms, decrease the frequency of complications, and prevent aortic rupture and death. The affected layers of the aorta are sutured together, and the aorta is reinforced with a Dacron graft.

Improved cardiopulmonary bypass circuits have decreased the prevalence of injury to blood elements. Morbidity and mortality rates associated with this highly invasive surgery have decreased with the introduction of profound hypothermic circulatory arrest and retrograde cerebral perfusion.^[30]

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. The development of more impermeable grafts has greatly enhanced the surgical repair of thoracic aortic dissections. Such grafts include the following:

• Woven Dacron
• Collagen-impregnated Hemashield (Meadox Medicals) aortic grafts
• Gel-coated Carbo-Seal Ascending Aortic Prosthesis (Sulzer CarboMedics)

The operative mortality rate with ascending aortic dissection is usually less than 10%. Serious complications are rare.

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%. Significant neurologic complications occur in an additional 10% of patients.

Postoperative complications for extensive disease involving the thoracoabdominal aorta include myocardial infarction, respiratory failure, renal failure, stroke, and paraparesis or paraplegia. The use of adjunct procedures has decreased the frequency of procedure-related spinal cord injury during descending aorta and thoracoabdominal surgeries. These include the following:

• Distal aortic perfusion
• Induction of profound hypothermia
• Cerebrospinal fluid drainage
• Monitoring of somatosensory and motor evoked potentials in the brain and spinal cord

Endovascular therapy is rapidly emerging as the preferred treatment for descending aortic dissection, provided vascular access is available. This methodology still remains controversial for ascending dissection.^{[31, 32, 33, 34, 35]} A 2011 study that included 28 complicated acute aortic dissection patients treated with endovascular repair supports that this technique has improved mortality versus traditional surgical interventions.^[36]

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 years), 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 electrocardiographic (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, 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 to decrease the frequency of ARF involves adequate hydration; hypotension, a low cardiac output state, and hypovolemia must be avoided.

Perform appropriate workups for patients presenting with any neurologic signs suggestive of central nervous system 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 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 distention 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.

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, the whole arch is replaced. 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 coronary arteritis. 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, the patient is brought to sinus rhythm by defibrillation. The patient is then weaned from cardiopulmonary bypass.

Surgical management of acute type B aortic dissections is undertaken only in the presence of indications such as the following:

• Persistent pain
• Aneurysmal dilatation greater than 5 cm
• End-organ or limb ischemia
• Evidence of retrograde dissection to the ascending aorta

Patients without such indications are treated with intensive medical therapy.^[10]

The operation involves transection of the proximal descending aorta distal to the left subclavian artery. 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 patients with renal or visceral artery compromise from dissection, endovascular techniques are under investigation. Several endovascular techniques are available.^{[25, 28, 37]} 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.

Thoracic endovascular aortic repair (TEVAR) is a minimally invasive approach used to treat patients who cannot tolerate open surgical repair. A study of outcomes following TEVAR in patients with retrograde type A aortic dissection (RAAD) and an entry tear in the descending aorta found it to be safe and effective for this group of highly selected patients. All surgeries were technically successful, with all patients surviving through the follow-up period. TEVAR resulted in a significant decrease in the diameter and the false lumen of both the ascending and descending aortas.^[38]

For endovascular therapy, the patient is prepared for general anesthesia and open procedure. The patient is then taken to the vascular suite, and after the induction of general anesthesia, bilateral groin cutdowns are performed to gain access to the common femoral artery. Due to the large size of the sheath needed to introduce the stent, a synthetic graft may be sewn to the artery to gain access. Once groin access is obtained, the patient is heparinized and the stent is positioned and deployed using radiographic guidance.^[35]

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 first-line treatment. When the ascending aorta or the arch is affected, the need for surgery is more likely.

Intramural hematomas are hemorrhages into the medial layer of the aortic wall without an intimal tear. Because these hematomas have a natural history similar to that of 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.^[39]

Once a thoracic dissection is suspected, consult a thoracic surgeon. Because many patients with this disorder have concomitant medical illness, the emergency department physician should consult the patient's primary care provider to expedite preoperative preparation. Early consultation is encouraged when ordering further imaging studies if the patient requires rapid operative intervention. Consult a radiologist prior to obtaining aortography.

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