Nontraumatic Aortic Dissection
aka Acute Aortic Syndrome (AAS)
Dr. Tushar Alladi
Epidemiology of Acute Aortic Syndromes
Frequently missed, rapidly fatal, falsely low incidence
Often misdiagnosed
Mostly male
Bimodal age distribution
Underlying disease > younger onset
Age-related/chronic changes > older onset
Associated risks:
HTN (most common)
Connective tissue disorders
Vasculitis
Prior cardiac surgery
Iatrogenic
Deceleration Trauma
Type A AAS higher mortality than Type B AAS
Some numbers worth highlighting:
First, incidence may be falsely low
since if 40% are instantly fatal with morality increasing by 1% per hour thereafter
14-39% are misdiagnosed
Mean age
Men: 63 years old
Women: 67 years old
There are racial differences between black and white patients in terms of risks
Black patients tend to be younger with type B dissections
However, hospital mortality has been found to be the same
For HTN, think of associated causes (e.g. smoking, cocaine, hyperlipidemia)
Connective tissue disorders (e.g. Marfan Syndrome, Ehlers Danlos Type IV, bicuspid valve
Vasculitis (e.g. GCA, Takayasu, Bachet, syphilis aortitis)
Pathophysiology
Figure 1:
All dissections result from 2 primary insults: tunica intima wall stress and tunica media wall weakness
Classic dissection is the most common
Intimal violation lets blood flow into a weak media separating the layers and forming a false lumen
Usually proximal at sinotubular junction also seen distal to left subclavian artery at ascending/descending junction
Extension of lumen may be distally (more common) or proximally or both
Progression may see dissection through the adventitia which is rapidly fatal
May also progress by re-dissection through the intima at the opposite end of initial intimal insult resulting in false spontaneous resolution
Intramural hematoma
Infarction of the media, usually at vasa vasorum
May resolve spontaneously or dissect
Penetrating aortic ulcer
Insult at the intima
Develops into IMH or transmural penetration
Usually middle or lower portion of descending aorta, rare at ascending or abdominal aorta
Figure 2:
Debakey
1 = ascending and descending
2 = ascending only
3 = descending only
Stanford – better for us as it risk stratifies quickly saying to a surgeon “this needs surgical intervention” vs “this can be managed medically”
A = any involvement of ascending
B = descending only
There is a third classification type Svensson which aims to categorize by underlying etiology of the dissection
e.g. classic vs IMH vs subtle vs penetrating ulcer vs iatrogenic/traumatic
Type A = higher risk of mortality ~22%
Type B = lower ~14%
Presentation of AAS
Figure 1 & 2: Acute aortic syndromes: diagnosis and management, an update, European Heart Journal, Volume 39, Issue 9, 01 March 2018, Pages 739–749d
Classic = intimal flap separating false lumen and true lumen
•Classic acute aortic dissection 85-95% of AAS
•Most common associations not very specific
•Even classic findings can be absent on presentation
•Need a high index of suspicion to detect for AAD before any complications occur
•Symptomatic presentation is highly variable in part due to the different pathologies that could present with dissection e.g. IMH or penetrating ulcer usually not as symptomatic due to the focal symptoms
•Important to note the presentation differences between type A and type B
•Type A noted sicker looking with more of our “classic” presentation on initial CP workup
•Type B with fewer classic findings
Key:
Most common symptoms
Classic presentation
More common in Type A
More common in Type B
Data from IRAD dataset
If the presentation is so non-sensitive, what can we do to help us?
Luckily, the ACEP has some recommendations!
1. Are there clinical decision rules for identifying "low risk" patients?
In adult patients with suspected acute non-traumatic thoracic aortic dissection, are there clinical decision rules that identify a group of patients at very low risk for the diagnosis of thoracic aortic dissection?
Level C Recommendation
In an attempt to identify patients at very low risk for acute nontraumatic thoracic aortic dissection, do not use existing clinical decision rules alone. The decision to pursue further workup for acute non-traumatic aortic dissection should be at the discretion of the treating physician.
Workup
FAST: CBC, CMP, Troponin, BNP, TxS
EKG
CXR
D-Dimer*
Slow: POCUS
CTA
2. How do we use a D-Dimer in "low risk" groups?
In adult patients with suspected acute non-traumatic thoracic aortic dissection, is a negative serum D-dimer sufficient to identify a group of patients at very low risk for the diagnosis of thoracic aortic dissection?
Level C Recommendation
In adult patients with suspected nontraumatic thoracic aortic dissection, do not rely on D-dimer alone to exclude the diagnosis of aortic dissection.
HOW DO WE RULE OUT AORTIC DISSECTION WITHOUT D-DIMER?
Diagnostic Accuracy of the Aortic Dissection Detection Risk Score Plus D-Dimer for Acute Aortic Syndromes: ADvISED Prospective Multicenter Study
Background: Is the integration of pretest probability assessment with D-dimer a safe and efficient diagnostic strategy for AAD
Methods:
Multicenter, prospective, observational
Includes patients with 1+ chest/abdominal/back pain, syncope, perfusion deficit, and if AAS was in the differential diagnosis
Pretest tool = Aortic Dissection Detection – Risk Score (ADD-RS)
Final adjudication by diagnostic imaging, surgery, autopsy, or 14 day follow up
Results = 1850 total pt
24% score = 0
58% score = 1
18% score > 1
13% with AAS
Failure rate 0.3% - 3 cases of AAS in pt with score 0 or 1 and negative dDimer
Aortic Dissection Detection Risk Score
Results = 1850 total pt
24% score = 0
58% score = 1
18% score > 1
13% with AAS (high)
Failure rate 0.3% - 3 cases of AAS in pt with score 0 or 1 and negative dDimer
Use for patients you think may be lower risk to decide if you want a D-Dimer
Score range from 0-3
0 is low risk
1 is intermediate risk
2-3 is high risk
EXCLUDES PTS WHO HAVE MULTIPLE FINDINGS IN SAME CATEGORY
Score >1 will go straight to CTA
Score 1 or 0 can get a Dimer for rule out
Test characteristics
Proposed use
AAD in the differential at the top
Caution ruling out AAS if sx <2h or >1 week
Limitations
Not externally validated
"Needs to be on differential” makes this subjective
No blinding for pretest probability
No comparison to clinical gestalt
½ patients with presumptive negative diagnosis at 14 day follow up and had inconclusive imaging
Diagnostic metric of 14 day follow up, not clear if this is sufficient capture
3. CTA v.s. TEE v.s. MRA?
In adult patients with suspected acute non-traumatic thoracic aortic dissection, is the diagnostic accuracy of computed tomography angiogram (CTA) at least equivalent to transesophageal echocardiogram (TEE) or magnetic resonance angiogram (MRA) to exclude the diagnosis of thoracic aortic dissection?
Level B Recommendation
In adult patients with suspected nontraumatic thoracic aortic dissection, emergency physicians may use CTA to exclude thoracic aortic dissection because it has accuracy similar to that of TEE and MRA.
Ultrasound (TTE and TEE)
Pros: Functional and structural data
Early detection of functional complications of AAS
AR
Effusion/tamponade
WMA
Bedside
Cons: Low sensitivity
TTE = 78-100% for Type A
TTE = 31-55% for Type B
TEE = 99% for Type A
TEE = 80% for Type B
Limited imaging window
Poor data for serial exams or long-term tracking
TEE needs sedation
4. Can you diagnose AAS with POCUS?
In adult patients with suspected acute non-traumatic thoracic aortic dissection, does an abnormal bedside transthoracic echocardiogram (TTE) establish the diagnosis of thoracic aortic dissection?
Level B Recommendations
In adult patients with suspected nontraumatic thoracic aortic dissection, do not rely on an abnormal bedside TTE result to definitively establish the diagnosis of thoracic aortic dissection.
Level C Recommendations
In adult patients with suspected nontraumatic thoracic aortic dissection, immediate surgical consultation or transfer to a higher level of care should be considered if a TTE is suggestive of aortic dissection. (Consensus recommendation)
POCUS can help with surgical consult but is not definitive.
MRA
Pros: Detailed Anatomy
Functional data
Surveillance or at-risk individuals
Cons: Long exam (20-30 min)
MRI contraindications
CT w/o contrast followed by angiography
Pros: High resolution anatomy
Large imaging window
High pooled sensitivity (100%) and pooled specificity (98%)
Quick (minutes)
Accessible
Cons: Contrast contraindications
Intimal fenestration not visualized
Non-ECG gated artifact
62 year old male who presented with chest pain and a known thoracic aortic aneurysm
Image 1: Is that an early dissection?
Image 2: less motion artifact, do we still see dissection?
CTA TRO (triple rule out) in the ED?
Pulmonary angiogram + coronary angiogram + aortic angiogram
Mixed studies on efficacy
Low comparative incidence of PE or AAS compared to ACS
Technically difficult study
5. What heart rate and blood pressure targets lower mortality?
In adult patients with acute non-traumatic thoracic aortic dissection, does targeted heart rate and blood pressure lowering reduce morbidity and mortality?
Level C Recommendations
In adult patients with acute nontraumatic thoracic aortic dissection, decrease blood pressure and pulse if elevated. However, there are no specific targets that have demonstrated a reduction in morbidity and mortality.
Treatments
Class I recommendations (Level of evidence C for all)
Short-acting ß-antagonist (~60 BMP <120 SBP after)
Esmolol 0.1-0.5 mg/kg IV over 1 min; 0.025-0.2 mg/kg/min IV
Labetalol 10-20 mg IV; spot dose 20-40 mg q10 min (MAX 300 mg)
Non-dihydropyridine CCB acceptable alternate rate control
If pressure remains uncontrolled (>120 systolic) but adequate heart rate control obtained may add ACEi/vasodilators for further blood pressure management
Class III Recommendations
Vasodilator therapy should only be initiated after adequate rate control obtained to avoid reflex tachycardia
Definitive Management
Class I Recommendations
Urgent surgical consultation for all patients with thoracic aortic dissection regardless of anatomic classification (Level of evidence C)
Dissection involving the ascending aorta should have urgent evaluation for emergent surgical repair (Level of evidence B)
Dissections involving descending aorta should be management medically unless life threatening complications develop (Level of evidence B)
Disposition: ICU
References
Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 9e. McGraw Hill; 2020.
2005. Acute Aortic Syndromes. Circulation, 112(24), pp.3802-3813.
Acute aortic syndromes: diagnosis and management, an update, European Heart Journal, Volume 39, Issue 9, 01 March 2018, Pages 739–749d, https://doi.org/10.1093/eurheartj/ehx319
Diagnostic Accuracy of the Aortic Dissection Detection Risk Score Plus D-Dimer for Acute Aortic Syndromes. Circulation, 137(3), pp.250-258.
Diagnosis and treatment of uncomplicated type B aortic dissection. Vascular Medicine. 2016;21(6):547-552. doi:10.1177/1358863X16643601
Clinical Policy: Critical Issues in the Evaluation and Management of Adult Patients With Suspected Acute Nontraumatic Thoracic Aortic Dissection. Annals of Emergency Medicine, 65(1), pp.32-42.e12.
2010 ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM Guidelines for the Diagnosis and Management of Patients With Thoracic Aortic Disease. Journal of the American College of Cardiology, 55(14), pp.e27-e129.