Spontaneous Coronary Artery Dissection (SCAD)
The most probable diagnosis is spontaneous coronary artery dissection (SCAD), given the combination of a young postpartum woman with fibromuscular dysplasia presenting with acute ST-elevation myocardial infarction and equal bilateral blood pressures. 1, 2
Clinical Reasoning
Why SCAD is the Leading Diagnosis
SCAD accounts for 22–35% of acute coronary syndromes in women under 60 years and is the most common cause of pregnancy-associated myocardial infarction. 1, 2 This patient has three critical risk factors that make SCAD overwhelmingly likely:
Fibromuscular dysplasia is present in up to 72% of SCAD patients and represents the strongest association with SCAD. 1, 2 This patient's documented FMD dramatically elevates her pre-test probability.
The peripartum period represents a high-risk window for SCAD, with pregnancy-associated SCAD comprising 5–17% of all SCAD cases and up to 43% of pregnancy-related acute coronary syndromes. 2 Her recent cesarean section places her in this critical risk window.
Over 90% of SCAD cases occur in women, typically aged 30–55 years without traditional cardiovascular risk factors. 1, 2 At 32 years old, she fits the classic demographic profile.
The clinical presentation with retrosternal chest pain, ST-segment elevation in leads I, aVL, and V3–V6 (indicating anterolateral STEMI), and elevated troponin is entirely consistent with SCAD presenting as an acute coronary syndrome. 2, 3
Why Other Diagnoses Are Less Likely
Aortic root dissection is effectively excluded by equal bilateral blood pressures (135/80 mm Hg in both arms). 4 Aortic dissection typically produces blood pressure differentials >20 mm Hg between arms and would not explain the specific anterolateral ST-elevation pattern seen here. 4
Acute pulmonary embolism does not produce ST-segment elevation in leads I, aVL, and V3–V6. 4 PE may cause right heart strain patterns (S1Q3T3, right-sided lead changes) but not the anterolateral STEMI pattern demonstrated in this case.
Postpartum cardiomyopathy presents with heart failure symptoms and dilated cardiomyopathy, not acute ST-elevation myocardial infarction with elevated troponin. 4 While it occurs in the peripartum period, it does not cause acute coronary occlusion patterns on ECG.
Prinzmetal (vasospastic) angina typically causes transient ST-elevation that resolves with nitrates and occurs at rest (often at night), without sustained troponin elevation. 4 The persistent ST-elevation and elevated troponin indicate true myocardial infarction, not reversible vasospasm.
Immediate Diagnostic and Management Algorithm
Step 1: Emergency Coronary Angiography
Activate the cardiac catheterization laboratory immediately for emergency coronary angiography—this is the gold-standard diagnostic test for SCAD and must be performed urgently in the setting of STEMI. 2, 5 Do not wait for additional testing or serial troponins. 5
Primary PCI should be performed within 120 minutes of first medical contact when STEMI is confirmed, with a target door-to-balloon time <90 minutes. 5 However, recognize that SCAD requires a fundamentally different approach than atherosclerotic MI.
Step 2: Angiographic Recognition
Look for one of three angiographic SCAD patterns during coronary angiography: 2
- Type 1: Multiple radiolucent lumens with contrast dye staining the arterial wall (pathognomonic but least common)
- Type 2 (most common): Long, diffuse, smooth narrowing from intramural hematoma
- Type 2A: >50% stenosis (obstructive)
- Type 2B: <50% stenosis (non-obstructive)
- Type 3: Focal stenosis mimicking atherosclerosis (requires high index of suspicion)
Administer intracoronary nitrates before final interpretation to exclude coronary vasospasm. 2
Step 3: Advanced Imaging if Needed
If angiographic findings are equivocal (especially for Type 3 SCAD), use optical coherence tomography (OCT) or intravascular ultrasound (IVUS) to definitively demonstrate intramural hematoma or double lumen. 2 These modalities provide definitive diagnosis when standard angiography is inconclusive.
Step 4: Treatment Strategy
Conservative medical management is strongly preferred for clinically stable SCAD patients; revascularization is reserved only for ongoing ischemia, hemodynamic instability, or left-main/proximal two-vessel dissection. 2 This is a critical distinction from atherosclerotic MI.
Percutaneous coronary intervention carries an approximate 50% failure rate in SCAD and may extend the dissection—use extreme caution. 2 The intramural hematoma makes guidewire passage and stent deployment hazardous.
Step 5: Acute Medical Therapy
While awaiting or during catheterization: 5
- Administer intravenous morphine 4–8 mg with additional 2 mg doses every 5 minutes for pain relief
- Give aspirin 160–325 mg immediately
- Provide supplemental oxygen only if saturation <90% (routine oxygen may be harmful)
- Start anticoagulation (unfractionated heparin or LMWH)
- Maintain continuous ECG monitoring with defibrillation capability
Long-Term Management and Screening
Secondary Prevention
Beta-blocker therapy significantly lowers the risk of recurrent SCAD and is the cornerstone of secondary prevention. 2, 6 Beta-blockers reduced recurrent SCAD with a hazard ratio of 0.36 (p=0.004) in prospective follow-up. 6
Aggressive blood pressure control is essential because hypertension independently predicts SCAD recurrence (hazard ratio 2.46, p=0.011). 2, 6
Systematic FMD Screening
Upon confirmation of SCAD, perform systematic CT or MR angiography screening of the renal, carotid, and iliac arterial territories to assess for multifocal fibromuscular dysplasia. 2 Look specifically for the classic "string-of-beads" appearance. 2
Screen for connective tissue disorders (Marfan syndrome, Ehlers-Danlos syndrome, systemic lupus erythematosus) as these predispose to SCAD. 2
Critical Pitfalls to Avoid
Do not misdiagnose SCAD as atherosclerotic acute coronary syndrome and proceed with aggressive PCI in a stable patient—this can worsen the dissection and lead to catastrophic outcomes. 2 The young age, female sex, peripartum status, and FMD history should immediately raise suspicion for SCAD rather than plaque rupture.
Do not assume a normal echocardiogram excludes acute coronary occlusion—early wall motion abnormalities may be absent before necrosis develops. 5 Echocardiography is useful for ruling out other causes (pericardial effusion, aortic dissection) but has limited sensitivity for early ischemia. 4
Do not delay coronary angiography to obtain serial troponins when diagnostic ST-elevation is present—this increases door-to-balloon time and worsens outcomes. 5 The diagnosis of STEMI is made by ECG, not biomarkers.
Recognize that Type 3 SCAD mimics atherosclerosis on angiography and is frequently missed—maintain high clinical suspicion in young women with FMD. 2 Use OCT/IVUS liberally when the angiographic appearance seems discordant with the clinical profile.
Prognosis
Over 10-year follow-up, the estimated rate of major adverse cardiac events in SCAD patients approaches 50%, with recurrent SCAD occurring in approximately 17–30% of cases. 2 This underscores the importance of aggressive secondary prevention with beta-blockers and blood pressure control. 2, 6