Diagnosis of Spontaneous Coronary Artery Dissection (SCAD)
Invasive coronary angiography (ICA) is the primary diagnostic method for SCAD, with intracoronary imaging (OCT or IVUS) recommended when angiographic findings are ambiguous to confirm the presence of intramural hematoma or double lumen. 1
Clinical Presentation and Initial Recognition
SCAD should be suspected in specific patient populations presenting with acute coronary syndrome:
- Young women (<60 years) represent the highest-risk group, with SCAD accounting for 22-35% of ACS cases in this demographic 1
- Pregnancy-associated MI has particularly high SCAD prevalence 1
- Patients with fibromuscular dysplasia (present in 62.7% of SCAD cases), anxiety, depression, or neuropsychiatric disorders 1, 2
- Precipitating stressors are common: emotional stress in 48.3% and physical stress in 28.1% of cases 2
The typical presentation is elevation of cardiac biomarkers with chest discomfort, though clinical presentations vary considerably 1
Angiographic Diagnosis
Three Angiographic Types
ICA reveals distinct patterns that define SCAD types 1:
- Type 1: Contrast dye staining of arterial wall with multiple radiolucent lumens (classic appearance with visible intimal flap)
- Type 2: Long, diffuse, smooth narrowing (most common presentation)
- Type 2 with <50% stenosis = non-obstructive
- Type 2 with >50% stenosis = obstructive
- Type 3: Focal or tubular stenosis mimicking atherosclerosis (most challenging to diagnose)
Critical Diagnostic Pitfalls
False positive diagnoses occur frequently when other conditions mimic SCAD angiographically 3:
- Atherothrombosis
- Takotsubo cardiomyopathy
- Coronary embolism
- Coronary vasospasm
- Contrast streaming artifacts
- MINOCA from other causes
Role of Intracoronary Imaging
When angiographic findings are unclear, OCT or IVUS should be performed to definitively diagnose SCAD by demonstrating 1:
- Intramural hematoma
- Double lumen
- Intimal flap
OCT-guided assessment is particularly valuable as it provides the most accurate visualization of the coronary arterial wall layers and can distinguish SCAD from atherosclerotic plaque rupture or erosion 1
Non-Invasive Imaging Limitations
Coronary CTA has significant limitations for SCAD diagnosis 1:
- SCAD may be missed or undetectable on CCTA
- A negative CCTA should NOT exclude SCAD diagnosis when clinical suspicion remains high
- CCTA may be considered for follow-up in medically-managed patients with persistent or recurrent symptoms without evidence of recurrent MI 1
Diagnostic Algorithm
Step 1: Clinical Suspicion
Identify high-risk features: young woman, recent pregnancy, emotional/physical stress, fibromuscular dysplasia history, presenting with ACS 1, 2
Step 2: Initial Cardiac Workup
- Troponin monitoring (preferably high-sensitivity assays) to confirm myocardial injury 1
- 12-lead ECG for ST-segment changes 4
- Echocardiography to assess wall motion abnormalities and ventricular function 4
Step 3: Invasive Coronary Angiography
Perform ICA as the definitive diagnostic test when SCAD is suspected 1
Step 4: Intracoronary Imaging (When Needed)
Deploy OCT or IVUS if 1:
- Angiographic appearance is ambiguous
- Type 3 SCAD suspected (mimics atherosclerosis)
- Differentiation from atherothrombotic disease is uncertain
- Confirmation needed before revascularization decisions
Key Diagnostic Caveats
Avoid misdiagnosis by recognizing 3:
- SCAD is frequently missed due to lack of angiographic recognition
- Intracoronary imaging has revolutionized diagnosis but should be used judiciously (risk of extending dissection)
- When imaging is performed, use low-pressure contrast injections and gentle catheter manipulation
- Consider alternative diagnoses systematically when angiographic features are atypical
Do not rely solely on risk factor profiles - while atherosclerotic risk factors help distinguish SCAD from atherosclerotic disease, SCAD patients may have hypertension (which increases recurrence risk) 2