Why should computed tomography be used to exclude fibromuscular dysplasia (FMD) in young female patients with spontaneous coronary artery dissection (SCAD)?

Why CT Screening for FMD is Essential in SCAD Patients

All patients with confirmed SCAD should undergo systematic non-invasive vascular imaging with CT or MR angiography of the renal, carotid, and iliac arteries to screen for fibromuscular dysplasia, which is present in up to 72-86% of SCAD patients and represents a critical underlying arteriopathy that requires identification and monitoring. 1, 2

The Strong Association Between SCAD and FMD

The relationship between SCAD and FMD is remarkably prevalent and clinically significant:

• FMD is found in 45-86% of SCAD patients, making it the most common associated vascular abnormality 1, 3, 2
• The American Heart Association identifies FMD as a key research priority in understanding "the proportionate contribution of FMD and other systemic arteriopathies to the development and recurrence of SCAD" 4
• FMD likely represents an underlying predisposing arteriopathy—patients may have undetected coronary FMD that makes them vulnerable to spontaneous dissection 2

Clinical Implications of Detecting FMD

Identifying High-Risk Vascular Territories

Extracoronary vascular abnormalities occur in 66% of SCAD patients and follow a predictable anatomic distribution:

• Renal arteries: 36-58% of patients 3, 2
• Iliac arteries: 28-49% of patients 3, 2
• Cerebrovascular arteries: 27-47% of patients 3, 2
• Intracranial aneurysms: 14% of patients with head imaging 3

Understanding Recurrence Risk and Prognosis

While the presence of FMD itself has not been definitively proven as an independent predictor of recurrent SCAD, the detection of FMD provides critical context 4:

• Coronary tortuosity—a manifestation of FMD—is the only identified risk factor for SCAD recurrence 4
• The 10-year estimated rate of major adverse cardiac events approaches 50%, with recurrent SCAD occurring in 17-30% of patients 4, 5
• Identifying FMD helps clinicians understand the patient's underlying vascular phenotype and systemic arteriopathy burden 2

The Diagnostic Algorithm

When SCAD is confirmed on coronary angiography, the following systematic screening should be performed:

1. CT or MR angiography covering renal, carotid, and iliac arterial territories 4, 1
2. Head imaging (CT or MR angiography) to evaluate for intracranial aneurysms, particularly given the 14% prevalence 3
3. Look for the classic "string-of-beads" appearance of multifocal FMD on imaging 4

Why CT/MRA Rather Than Invasive Angiography

• Non-invasive imaging avoids the risks of catheter-based procedures in patients with fragile arterial walls 1
• CT angiography provides comprehensive evaluation of multiple vascular beds in a single study 3, 2
• The diagnostic yield is high given the 72-86% prevalence of FMD in this population 1, 2

Common Pitfalls to Avoid

Failing to screen for FMD represents a missed opportunity to:

• Identify patients with multifocal arteriopathy who may benefit from closer surveillance 3
• Detect potentially life-threatening intracranial aneurysms that require monitoring or intervention 3
• Understand the patient's complete vascular phenotype and counsel them appropriately about their systemic disease 2

The presence of FMD should not change acute SCAD management (conservative therapy remains preferred), but it provides essential prognostic information and identifies patients who need long-term vascular surveillance 1, 5

Additional Screening Considerations

Beyond FMD, SCAD patients should also be evaluated for:

• Connective tissue disorders (Marfan syndrome, Ehlers-Danlos syndrome, systemic lupus erythematosus) 1
• Hypertension, which independently predicts recurrent SCAD and requires aggressive control 1
• Pregnancy status in women of childbearing age, as pregnancy-associated SCAD carries higher complication rates 1