Diagnosis: Aortic Dissection

Review of the CTA chest revealed a type A dissection of the ascending aorta and aortic arch. The patient was taken immediately to the operating room by cardiothoracic surgery where he underwent resection and primary repair of a chronic ascending aortic dissection with partial resection of an ascending aorta and aortic arch aneurysm, and resuspension and repair of the aortic valve under cardiopulmonary bypass with deep hypothermic circulatory arrest. 

Epidemiology

• most common risk factor --> hypertension

• other risk factors: 
• male gender
• stimulant use
• age >40
• previous cardiac surgery
• bicuspid aortic valve
• aortic balloon-pump insertion
• Marfan syndrome
• Ehlers-Danlos syndrome 

• inflammatory vasculitides associated with aortic dissection: 
• Takayasu's arteritis
• Giant cell arteritis 
• Behcet's disease

• 44% of patients with Marfan syndrome develop aortic dissection and account for 5% of cases

Classification

• The Stanford classification is based on whether there is involvement of the ascending aorta
• Type A dissections involve the ascending aorta
• 62%
• more lethal
• Type B dissections do not 
• 38%
• can be managed conservatively

• Acute dissection: < 2 weeks
• Chronic dissection: > 2 weeks

                           Stanford type B aortic dissection 

Presentation

• abrupt 
• "sharp," "tearing," "ripping" chest or back pain
• diaphoresis, nausea, vomiting, light-headedness
• syncope in 9% of patients often due to extension of dissection into pericardium producing pericardial tamponade; can aldo be due to brief cessation of cerebral blood flow

Workup

• contrast CT aortography = test of choice (100% sensitive, 98% specific) 
• faster and more readily available than TEE or MRI 
• CXR is abnormal in 80-90% of patients, however is nonspecific and rarely diagnostic 
• mediastinal widening occurs in majority of cases
• routine labs rarely helpful
• ECG useful for excluding MI 
• bedside cardiac ultrasound useful for identifying pericardial effusion, tamponade, or aortic regurgitation

Management

There are 2 goals of medical management: 

     1) reduce blood pressure (target SBP 100-120 and HR <60)

     2) decrease the rate of rise of arterial pulse (dP/dt) to reduce shearing forces

First-line agent: beta-blockers (esmolol, labetalol)

• both are short-acting and titratable 
• both can be used as monotherapy 
• esmolol: 500 ug/kg IV bolus followed by 50-200 ug/kg/min maintenance drip 
• labetalol: 20mg IV q5-10 min, can increase up to 80mg IV doses until HR <60
• do not exceed 300mg 
• 1-2 mg/min maintenance drip 

Non-beta-Blocker agents such as nitroprusside or nifedipine can be considered but only after a beta-blocker is on board to prevent reflexive tachycardia which will increase shearing forces.

Opioids are a good choice for analgesia (fentanyl, morphine) as they will also decrease sympathetic tone and help reduce blood pressure and shearing force. 

Patients on anti-platelet drugs (aspirin, plavix, etc), many require platelet transfusion in anticipation of surgery. The patient in this case received 1 unit of platelets given he reported taking aspirin just prior to presentation.

Disposition

• All type A dissections require prompt surgical management
• Type B dissections can usually be managed with conservative medical therapy alone, disposition is dependent on the clinical situation (history and exam) 

Outcome

  

References: 

Rosen's Emergency Medicine Concepts and Clinic Practice, 8th Ed, 2014, Chapter 85: Aortic Dissection by Felix K. Ankel 

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