Emergencies of the AortaHoward Blumstein, MDWake Forest UniversityMarch 2010

Outline

• Aortic Aneurysm• Aortic Dissection• Traumatic Aortic Disruption

Objectives

• Understand Relevant Anatomy• Recognize Typical Clinical Presentations• Order Appropriate Imaging• Stabilize Patients as Best Possible

Note

• Peter Cameron’s book (Chapter 5.10) combines– Aortic Dissection

– Intramural Hematoma

– Aortic Transection

• I will combine these with Aortic Aneurysm

Aorta Anatomy

• Illustration shows isolated aorta• Major branches• Not labeled:

– Coronary arteries– Celiac and mesenteric arteries

Abdominal Aortic Aneurysm

• Majority of aortic aneurysms are abdominal– Not thoracic

• True aneurysm involves all three layers of aorta– Intima– Media

– Adventitia

True and False Aneurysms

Normal Aorta

True Aneurysm

Pseudo- Aneurysm

Prevelence

• Rare under 50 years of age• More common in men than women• Risk factors are same as risks for

atherosclerosis

• Factors aside from atherosclerosis are probably also involved

Diabetes High Blood Pressure

Cholesterol Tobacco Abuse

Age Family History

Aneurysm Location

• 90% of AAA are infrarenal

• About 70% rupture into retroperitoneum

• 10-30% have free rupture– Die quickly

Aortic Aneurysm Growth

Other Aortic Aneurism Facts

• Inflammatory Aneurysms– 5% of aneurysms– Dense fibrous reaction in aneurysm wall– Can cause obstruction of branches of aorta

• Distal emboli– Clot and/or atherosclerotic material

• Other more rare causes of aneurysms

AAA Clinical Presentation

• Unruptured aneurysms typically without symptoms

• Ruptured– Pain in abdomen, flank, back, genitals,

chest– Syncope– Vomiting– Very similar to renal colic

• Classic Triad: Pain, hypotension, mass

AAA Physical Exam

• Varies with size of aneurysm and body– Easier to find large aneurysms– Easier in thin patients

• Palpable mass (50-85%)

• Distal pulses usually intact

• Abdominal bruit usually heard in only 10% of patients.

Abdominal X-Rays

• Usually not diagnostic• Sometimes calcification of wall visible

– “Eggshell calcification”– Rarely seen

• Even if AAA see, you cannot tell– Size of aneurysm– If it is leaking

Ultrasound

• Positive • Negative• Performed at bedside• Quick and easy

• 100% accurate if technically adequate

• Can see free fluid if ruptured into peritoneal cavity

• Can be difficult with obese patient or bowel gas

• Cannot detect retroperitoneal fluid

If ultrasonography reveals an AAA in an unstable patient, aneurysm rupture is presumed, and the patient requires immediate aneurysm repair.

CT Scan

• Positives • Negatives

• Nearly 100% accurate• Can detect leaking• Can help define

anatomy– Plan surgical

approach

• Can detect alternate diagnoses

• Takes longer– Can delay surgery in

unstable patients

• Use of IV contrast – Adds to treatment

delay

– Risk of contract complications

Unruptured Infrarenal AAA

Unruptured Infrarenal AAA

Ruptured AAA

Treatment of Leaking AAA

• Two large bore IVs• Type and cross for blood transfusion• Support BP with crystalloid and blood

– Controversial

• Definitive treatment is surgery– Call surgeon as soon as possible

How Big?

• Risk of rupture goes up as size of aneurysm increases

• Typically operate on AAA 5 cm or larger– Symptoms consistent with rupture– No other cause for symptoms

Mortality Rates

• Elective surgery for unruptured AAA: 5%• Emergency surgery, unruptured AAA: 20-

25%• Emergency surgery, ruptured AAA: 50%• All patients presenting with acute, ruptured

AAA: 80%• Hypotension is strongest predictor of

mortality

Aortic Fistula

• Can form fistula with variety of structures• Can present as

– GI bleeding– Infection of aorta

– Heart failure

• Erosion into adjacent structures– Graft– Inflammatory aneurysm

Pitfalls in AAA

• Mistaking ruptured aneurysm for kidney stone• Failure to contact vascular surgeon quickly• Failure to have blood ready for transfusion• Misinterpretation of ultrasound

Aortic Dissection

• Incidence reported 0.5-1 per 100,000 population annually

• Cameron says this is more common than AAA rupture. But he combines– Aortic dissection (no trauma)

– Aortic disruption (trauma)

• With dissection alone, it is less common that AAA

Aortic Dissection

• Blood gets into media of the aorta• “Rips” the intima from the blood vessel• Required elevated blood pressure

Aortic Dissection Mechanism

• Two Theories

• Tear in intima layer of aorta allows blood to rip into the media

• Elevated pressure in vaso vasorum causes rupture within the media– Then blood

dissection to to the lumen of the aorta

Aortic Dissection Mechanism

Dissection requires two things

• Elevated arterial blood pressure

• Weakness or degeneration of media (“Medial Degeneration”)

Risk Factors

• Bicuspid aortic valve (14%)

• Cardiac Surgery (18%)

• Marfan’s Disease (5%)

• Other connective tissue disorders

Two Directions

• Antegrade Dissection • Retrograde Dissection

Classification

Clinical Presentation

• Pain– Chest, arms, neck, between scapulae, back– Tearing or ripping quality

• Occlusion of blood vessels– Stroke or altered mental status

– Myocardial ischemia/infarction

• Pericardial tamponade• Acute aortic valve insufficiency

Risk Factors

• Bicuspid aortic valve• Cardiac surgery• Connective tissue

disorders– Marfan’s– Ehlers-Danlos

Syndrome

– other

• Turner’s Syndrome

• Pregnancy• Syphilis• Familial

hyperlipidemia

Physical Exam

• Hypertension• Aortic valve insufficiency (about 1/3)

– New murmur– CHF

• Pericardial effusion– Hypotension– Muffled heart sounds– Jugular venous distension

Physical Exam

• Neurologic abnormalities (obstruction of carotid artery)

• Interruption of blood flow to limb– Pulse deficits– Differential blood pressure

• 15 mmHg between arms

• not very helpful– Ischemic limb

EKG

• Many patients can have ischemia or infarction on EKG

• Can cause confusion with acute myocardial infarction

• Pericardial effusion– Electrical alternans

– Low voltages

• No EKG findings are specific for dissection

Chest X-Ray

• Most have abnormal chest x-rays– 10-20 percent have normal CXR

• Wide mediastinum• Abnormalities of aortic arch or knob• Not terribly useful, usually

CT Angiography

• Preferred study most hospitals in U.S.

• Highly sensitive• High sensitivity for

inclusion of arch vessels

CT Aortogram

• Newer Scanners Preferred

• 32 or 64 slices• Much faster• Little motion artifact• Better detail• 3 Dimension

reconstruction

CT Aortogram

• Potential Problems

• Time delay– Minimized if CT

scanner is in ED

• IV Contrast– Risk of side effects

• Cannot define severity of aortic insufficiency

Echocardiography

• Transthoracic echo (TTE)– Quick, non invasive– Can show Aortic valve function– Inadequate sensitivity

• Transesophageal echo (TEE)– Much more sensitive

– Invasive, may require sedation– Requires specialized operator

Angiography

• Rarely used in U.S.– Supplanted by CT scans

• Invasive• Time consuming• Not performed in ED• May be best option if TEE and high definition

CT not available

Physiology

• Each pulse transmits pressure to the blind pouch of the dissecting segment

• Will either– Reenter the lumen– Rupture through the

wall of aorta

Treatment• Goals • Drugs

• Reduce heart rate• Reduce blood

pressure• Reduce pulse

pressure

• Beta Blockers– Esmolol– Labetolol

• Other BP lowering drugs– Nitroprusside– Nitroglycerine

• Avoid arterial dilating drugs– Hydralazine

– Nifedipine

Surgery and Mortality

• Type A– Surgery is best option– Mortality 5-21%

• Type B– Usually treated medically

– Mortality approximately 20%

Pitfalls of Aortic Dissection

• Missed diagnosis – mistaken for– Myocardial infarction– Stroke

• Delay in care– Call Cardiothoracic surgeon promptly

– Establish diagnostic protocols in advance

• Failure to adequately control blood pressure

Aortic Disruption

• Caused by blunt thoracic trauma• Several proposed mechanisms

– Compression– Whiplash effect (deceleration)

– Rotational injury

• Grade 1: Intimal flap• Grade 2: Subadventitial rupture• Grade 3: Aortic transection with active

bleeding

Mortality

• 60-90% of patients die at scene of accident or within a few hours of hospital arrival

• If patient goes to OR, mortality rates reported 20-50%

Diagnostic Strategies

• Chest X-Ray• CT Scan• Angiography

Chest X-Ray

• Wide mediastinum– Classically thought to be useful in ruling out

aortic injury– Now reported to miss up to 45% of aortic

disruptions

• Variety of other findings• Ultimately, sensitivity and specificity of CXR

is not adequate to rule out aortic injury

CT Scan

• Has become the standard test for aortic injury

• Highly accurate• Most patients will be getting CT scans of

abdomen anyway• Probably overused in U.S.

Treatment

• Complicated by presence and/or risk of other injuries

• If possible, treat like aortic dissection– Pulse and BP control– Have blood available for transfusion

– Prompt involvement of Cardiothoracic and Trauma Surgery

Surgery

• Treatment varies according to grade of injury• Grade 3 usually gets surgery• Grade 1 usually doesn’t• No randomize trials or good scientific

investigation of appropriate intervention