Clinically, the presentation of AAD is subject to the extent of the dissection, with complaints corresponding to those affected cardiovascular structures. Three fundamental questions that must be addressed when taking a history of a patient with suspected AAD are the quality, radiation, and intensity of pain at the onset. Various studies identified the intensity of onset of pain as the most reliable historical factor.  While increasing the probability of AAD when present, classically cited physical findings, such as a discrepancy of blood pressures in the upper extremities, a pulse deficit, or presence of a diastolic murmur, are present in less than 50% of confirmed cases of AAD.  Additionally, the presence of chest pain with any neurological finding, the combination of chest and abdominal pain, or chest pain accompanied by limb weakness or paresthesia should alert the clinician to the possibility of AAD.

The pain of AAD is often sudden in onset, reaches maximal severity quickly, and can be tearing in nature. In about 10% of patients, the AAD is painless, which is more common in Marfan syndrome. The pain can be located in the anterior chest in case of ascending aorta and in the back if the dissection is descending. It may have a migrating character as dissection propagates caudally.

At the time of presentation, neurological deficits are present in 1/5th of patients. Syncope is also common and may be due to hypovolemia, arrhythmias, MI, or an increased vagal tone. If the dissection is antegrade, it may involve the extremity vessels leading to loss of pulses, paresthesias, and pain.

Hoarseness and Horner syndrome have also been described in patients with AAD.

If the AAD is leaking or ruptured in the mediastinum, then the patient may have dyspnea and hemoptysis.

Physical findings

Hypertension is very common in AAD; if the patient presents with hypotension then this is a grave sign most likely indicating a rupture. A difference of more than 20mmHg in blood pressure between the arms should raise suspicion of AAD. Other features include:

• Wide pulse pressure
• Aortic insufficiency
• Diastolic murmur
• Muffled heart sounds (suggesting cardiac tamponade)
• Syncope
• Altered mental status
• Loss of peripheral pulses
• Horner syndrome

Routine studies like an ECG and chest x-ray can help differentiate other possible causes for chest pain but can be misleading. The presence of ECG findings consistent with an acute myocardial infarction occurs in eight percent of cases of AAD.  Furthermore, while the widening of the aortic silhouette increases the likelihood of AAD, its absence does not reliably exclude the diagnosis. Confirmation of AAD requires cardiovascular imaging to identify the presence of an intimal tear, establish the Stanford classification, and detect valvular or branch involvement. Most society guidelines recommend either CT aortography or transesophageal echocardiogram (TEE) for the diagnosis of AAD. Deciding which modality to employ as a first-line screen should be based on institutional availability and expertise. For most emergency departments (EDs), CT angiography will likely be the first advanced imaging technique on account of its widespread availability.[7]

Blood work should include CBC, electrolytes, troponin, D-dimer, and renal function. Smooth muscle myosin heavy chain assay is elevated is specific for AAD.

The chest x-ray may show a widened mediastinum (>8cm) or fluid collection in the hemithorax due to rupture. X-ray features that suggest AAD include:

• Left apical cap
• Pleural effusion
• Deviation of the esophagus
• Deviation of the trachea to the right
• Depression of the left mainstem bronchus
• Loss of the paratracheal stripe

If the patient is stable, a CT scan with contrast is recommended. The spiral CT can quickly detect the location of the intimal tear and help the surgeon plan the procedure. Suggestive of AAD findings include:

• Intimal dissection flap
• Double lumen
• Aortic dilation and hematoma
• Regions of malperfusion
• Contrast leak indicates aortic rupture

Echocardiography is also a useful modality to detect AAD. TEE is the preferred technique that can be done at the bedside and used for intraoperative visualization. The key drawback is the operator experience. However, if the patient is unstable, TEE is the recommended procedure. Other indications for TEE include renal insufficiency and contrast allergy. Findings may include:

• Dissection flap with differential Doppler flow
• True and false lumen in the ascending aorta
• Thrombosis in the false lumen
• Central displacement of intimal calcification
• Pericardial effusion

Aortography is not much used today unless there are plans to repair the dissection using stents.

A 12 lead ECG is mandatory to rule out an MI.

Once the diagnosis of AAD is confirmed or highly suspected, urgent cardiothoracic or vascular surgery consultation should be obtained, regardless of the dissection location. Acute dissections involving the ascending aorta are considered surgical emergencies. The patient should have an arterial line and central venous catheter for monitoring. A foley should be inserted to assess urine output.

Concurrently commence medical therapy including providing adequate analgesia (morphine is the preferred analgesic, as it decreases sympathetic output as well) and administering a short-acting IV beta-blockers aiming for a heart rate of ~60 bpm (reductions in heart rate and blood pressure reduces aortic wall tension and limit the extent of dissection). In patients with contraindications to b-blockade non-dihydropyridine calcium channel blockers can be used for rate control.  If the systolic blood pressure remains elevated, nitroprusside can be added to achieve a systolic blood pressure goal of 100 to 120 mmHg (maintain blood pressure in this range as long as there is no compromise of mentation or urine output). Other agents that can be used to lower blood pressure include esmolol, labetalol, or diltiazem. B-blockers should be used with caution in the settings of acute aortic regurgitation because they block compensatory tachycardia.

In hypotensive patients, intravenous fluids administration is a reasonable first approach. Vasopressors can be added, if needed, to maintain adequate perfusion but may cause further false lumen propagation. Inotropic agents should be avoided as they are likely to increase the force and rate of ventricular contraction and therefore worsen aortic wall stress.

Surgical therapy for type A AAD involves excision of the intimal tear, obliteration of entry into the false lumen proximally, and reconstitution of the aorta with interposition of a synthetic vascular graft. Surgical intervention for type B AAD tends to be reserved for patients who have a complicated course. Endovascular stent-grafting (TEVAR) has been employed as a less invasive alternative to surgery, primarily for patients with complicated type B dissections.[2][8][9]

For AAD involving the ascending aorta, the aorta has to be replaced and the valve has to be assessed. In most cases, the aortic valve may also have to be excised and replaced with a prosthetic valve. Dissections involving the descending aorta are complex and there is a risk of paraplegia. The most difficult dissections are those that involve the aortic arch. Surgical mortality varies from 5-20%. Even those who survive have a long recovery.

Because of the high surgical mortality, today endovascular procedures are being performed for AAD. Endovascular stent placement is associated with significantly lower morbidity compared to surgery but the key is patient selection.

Alternative diagnoses on the differential of aortic dissection include the following life-threatening conditions: myocardial infarction, aortic aneurysm, cardiac tamponade (from another cause), esophageal rupture (Boerhaave syndrome),  spontaneous pneumothorax, pulmonary embolism, and stroke / transient ischemic attack. If a patient presents with abdominal pain, renal or biliary colic, bowel obstruction/perforation, non-dissection-related mesenteric ischemia should be considered. Pulse deficit can be a sign of non-dissection-related embolic phenomena or arterial occlusion. [10]

Aortic dissection still carries a very high mortality. At least 30% of patients die after reaching the emergency room and even after surgery, the mortality rates vary from 20-30%. For those who survive the surgery, the comorbidity also takes a toll and the quality of life is poor. the highest mortality of an acute aortic dissection is within the first 10 days. Patients with a chronic dissection tend to have a better prognosis, but even their life expectancy is shortened compared to the general population.

• Multiorgan failure
• Stroke
• MI
• Paraplegia
• Renal failure
• Amputation of extremities
• Bowel ischemia
• Tamponade
• Acute aortic regurgitation
• Compression of superior vena cava
• Death

• Once the patient is treated surgically or medically, the blood pressure must be controlled
• The patient must be closely monitored for the progression of the aortic dissection
• A regular CT scan of the chest or MRI is recommended at 3-6 month intervals to check for the progression of the disease

• Controlling blood pressure
• Avoid the use of illicit drugs
• Maintain a healthy weight
• Discontinue smoking

Despite the best of circumstances, it is next to impossible to diagnose every case of AAD presenting to the ED. Factors contributing to a high miss rate include perceived mildness of symptoms in some patients with AAD. A second factor leading to misdiagnosis is clinical symptoms and laboratory findings suggesting an alternative diagnosis such as acute coronary syndrome (ACS). A third factor was the lack of expected results such as a pulse deficit or absence of a widened mediastinum on chest x-ray. Approach every chest pain patient as if they could harbor an ADD, establish a risk factor profile, and remain cognizant of more subtle presentations.

Aortic dissection is a medical emergency with very high mortality if it is undiagnosed. The majority of patients present to the emergency department and hence an interprofessional team is the key.

Once the patent with an aortic dissection presents to the emergency room, a standardized system must be in operation to ensure that the diagnosis and management are done without any delay. The triage nurse should be fully aware of the importance of immediate admission of the patient and consult with the emergency physician and cardiac surgeon. The decision on how to make the diagnosis depends on patient stability and the availability of imaging tests. The two options include an ECHO or a CT scan. An unstable patient should never be sent to the radiology suite. Instead, a cardiologist should be consulted for a bedside echo. The intensivist should be notified as there is an urgent need to lower blood pressure. The operating room should be notified that a patient with a dissection has been admitted. Nurses should be fully aware of the potential complications of aortic dissection and know what medications to use to lower the blood pressure. In addition, nurses should monitor fluid input and output and keep the patient NPO. After surgery, the nurses need to closely monitor the patient for complications. Open communication between the team members is vital to improving outcomes. [9][11][12](Level V)

Outcomes

Several studies show that patient outcomes are improved when managed by an interprofessional team of healthcare professionals that include a cardiologist, intensivist, pulmonologist, nephrologist, cardiac surgeon, interventional radiologist, and anesthesiologist. In addition, the pharmacist must educate the patient about the importance of blood pressure control and compliance with medications. The outcomes of aortic dissection tend to be better in high volume centers compared to small centers which do less than 5 cases a year. [13][14][15](Level V)