What is SCAD (Spontaneous Coronary Artery Dissection) in relation to a heart attack?

Spontaneous Coronary Artery Dissection (SCAD) and Heart Attack

Spontaneous Coronary Artery Dissection (SCAD) is a non-atherosclerotic cause of heart attack characterized by the spontaneous formation of an intramural hematoma in the coronary arterial wall, which compresses the true lumen and leads to myocardial infarction. 1

Definition and Pathophysiology

SCAD occurs when blood accumulates within the arterial wall, creating:

• Intramural hematoma: Blood collects between the layers of the coronary artery wall
• Compression of true lumen: The accumulated blood narrows or blocks blood flow
• Myocardial ischemia/infarction: Reduced blood flow causes heart attack

SCAD can occur through two primary mechanisms:

1. Formation of intramural hematoma without visible intimal tear
2. Blood entering the arterial wall through an intimal tear 1

Epidemiology and Risk Profile

• Accounts for 0.1-0.7% of all acute coronary syndrome (ACS) cases
• Responsible for 8.7-24.2% of ACS cases in women ≤50 years 2
• Strong female predominance (87-95% of cases are women)
• Typical presentation age: 44-53 years
• Often affects individuals without traditional cardiovascular risk factors 2

Associated Conditions

SCAD is frequently associated with:

• Fibromuscular dysplasia (FMD): Present in up to 62.7% of SCAD patients 3
• Pregnancy: Pregnancy-associated SCAD accounts for 5-17% of all cases 2
• Connective tissue disorders: Present in approximately 4.9% of cases 3
• Systemic inflammatory diseases: Present in about 11.9% of cases 3

Clinical Presentation

• Chest discomfort: Present in 96% of patients
• Other symptoms: Arm pain (49.5%), neck pain (22.1%), nausea/vomiting (23.4%), diaphoresis (20.9%), dyspnea (19.3%), back pain (12.2%) 4
• Presentation as MI: All patients present with myocardial infarction
  • STEMI (ST-elevation MI): 24-25.7%
  • NSTEMI (Non-ST-elevation MI): 74.3% 4, 3
• Arrhythmias: Ventricular tachycardia/fibrillation occurs in 8.1-8.9% of patients 4, 3

Diagnosis

SCAD is often underdiagnosed or misdiagnosed due to:

• Atypical presentation in young, otherwise healthy individuals
• Lack of angiographic recognition by clinicians 5

Diagnostic approach:

1. Coronary angiography: Primary diagnostic tool showing three angiographic types:

   • Type 1: Multiple radiolucent lumens or arterial wall contrast staining
   • Type 2: Diffuse stenosis of varying severity and length
   • Type 3: Focal or tubular stenosis mimicking atherosclerosis 1

2. Intracoronary imaging when diagnosis is uncertain:

   • Optical coherence tomography (OCT)
   • Intravascular ultrasonography (IVUS)
   • These can confirm intramural hematoma or multiple lumens 1

Management

Acute management depends on clinical stability and coronary anatomy:

• Clinically stable patients: Conservative medical therapy is preferred

  • Monitor as inpatient for 3-5 days 1

• Unstable patients with ongoing ischemia: Consider revascularization

  • Percutaneous coronary intervention (PCI) if feasible
  • Coronary artery bypass grafting (CABG) based on technical considerations 1

Medical therapy typically includes:

• Aspirin
• Beta-blockers (may reduce recurrence risk) 3

Prognosis and Recurrence

• In-hospital major adverse event rate: 7.3%
• Long-term major adverse cardiac event rate: 19.9%
• Recurrence rate: 10.4-19% of patients
• Risk factors for recurrence:
  • Hypertension increases risk
  • Beta-blocker therapy appears protective 3

Important Considerations

• SCAD should be suspected in young patients, especially women, presenting with ACS symptoms without traditional cardiovascular risk factors
• Pregnancy-associated SCAD tends to have more severe features, including left main/multivessel dissections 2
• Recurrence typically affects new coronary artery segments 2
• Conservative management is generally preferred over invasive approaches when patients are stable 1, 3

Pitfalls to Avoid

• Misdiagnosing SCAD as atherosclerotic coronary artery disease
• Unnecessary or potentially harmful invasive interventions in stable patients
• Failing to screen for associated conditions like FMD
• Overlooking SCAD in young patients with atypical symptoms, leading to delayed diagnosis and management 6
• Underestimating the risk of recurrence and need for long-term follow-up