What are the angiographic differences between acute coronary syndrome (ACS) and stable angina?

Angiographic Differences Between Acute Coronary Syndrome and Stable Angina

Acute coronary syndrome (ACS) is characterized by culprit lesions with eccentric morphology, irregular borders, ulceration, haziness, and filling defects suggestive of intracoronary thrombus, while stable angina typically presents with smooth, concentric, and calcified lesions without evidence of thrombus or plaque rupture. 1

Key Angiographic Features

Acute Coronary Syndrome Lesions

• Plaque Morphology:

  • Eccentric lesions with irregular borders
  • Ulceration visible on angiography
  • Haziness of the lesion borders
  • Filling defects characteristic of intracoronary thrombus 1
  • Greater plaque area (approximately 17.5 ± 5.9 mm² vs. 13.5 ± 10.7 mm² in stable angina) 2

• Remodeling:

  • Positive remodeling with higher remodeling index (approximately 1.4 ± 0.3 vs. 1.2 ± 0.3 in stable angina) 2
  • Outward expansion of vessel wall at the lesion site

• Plaque Composition:

  • Higher prevalence of non-calcified (soft, lipid-rich) plaque (100% in culprit ACS lesions) 2
  • Less calcification compared to stable lesions
  • Often lipid-rich, vulnerable plaques with thin fibrous caps

Stable Angina Lesions

• Plaque Morphology:

  • More concentric, smooth-bordered lesions
  • Well-defined borders without haziness
  • Absence of filling defects or thrombus
  • Smaller plaque area (approximately 13.5 ± 10.7 mm²) 2

• Remodeling:

  • Less positive remodeling (remodeling index approximately 1.2 ± 0.3) 2
  • More likely to show constrictive remodeling

• Plaque Composition:

  • Higher degree of calcification (85% of stable lesions) 2
  • More fibrous tissue content
  • Thicker fibrous caps

Clinical Implications of Angiographic Differences

Diagnostic Approach

• Coronary angiography has good specificity but poor sensitivity for thrombus detection compared to angioscopy 1
• Intravascular ultrasound or optical coherence tomography may provide more precise information about stenosis severity and plaque morphology than angiography alone 1
• Fractional flow reserve (FFR) can assess the hemodynamic significance of angiographically intermediate lesions 1

Treatment Considerations

• In ACS with significant intracoronary thrombus, it may be appropriate to postpone intervention in stable patients and prepare with aggressive anticoagulation and intensive antiplatelet treatment 1
• Stent implantation in ACS helps mechanically stabilize the disrupted plaque at the site of the lesion 1
• GP IIb/IIIa inhibitors significantly reduce major complications during PCI in ACS patients 1

Pitfalls and Caveats

1. Angiographic Limitations:

   • Visual assessment often overestimates lesion severity when coronary stenosis is ≥50% 1
   • Diffusely diseased coronary arteries may lack a normal reference segment, leading to underestimation of lesion severity 1
   • Significant interobserver variability exists in grading coronary artery stenosis 1

2. Physiological vs. Anatomical Significance:

   • Many stenoses considered severe by visual assessment (≥70% luminal narrowing) may not restrict coronary blood flow 1
   • Conversely, lesions considered "insignificant" (<70% luminal narrowing) may be hemodynamically significant 1

3. Thrombus Detection:

   • Coronary angiography has limited sensitivity for thrombus detection compared to more advanced imaging techniques 1
   • Angiographic appearance may change rapidly in ACS due to dynamic thrombotic processes

4. Technical Considerations:

   • Extreme tortuosity, calcification, or location in a bend are important findings that may preclude percutaneous coronary intervention with stent implantation 1
   • Complications of diagnostic angiography (1.5% incidence) include death, stroke, MI, bleeding, and contrast-induced nephropathy 1

By recognizing these angiographic differences between ACS and stable angina, clinicians can better identify the culprit lesion responsible for instability, choose appropriate interventions, and improve patient outcomes.