Why is the plaque in Non-ST-Elevation Myocardial Infarction (NSTEMI) white?

The Pathophysiology of White Plaque in NSTEMI

In NSTEMI, the plaque appears white due to the formation of a non-occlusive, platelet-rich "white thrombus" that develops on a disrupted atherosclerotic plaque, as opposed to the completely occlusive red thrombus seen in STEMI. 1

Plaque Disruption and Thrombus Formation in NSTEMI

The pathophysiology of NSTEMI involves several key processes:

1. Plaque Vulnerability and Disruption

   • NSTEMI begins with the disruption of an atherosclerotic plaque, typically through rupture or erosion of the fibrous cap 2
   • This disruption exposes thrombogenic material to circulating blood 1
   • Plaque rupture usually occurs at the shoulder of areas with a thin fibrous cap (≤90 μm in 96% of cases) 3

2. White Thrombus Formation

   • When the plaque ruptures, platelets adhere to the exposed subendothelial matrix
   • This leads to the formation of a platelet-rich "white thrombus" 1
   • Unlike STEMI, where a red fibrin-rich thrombus completely occludes the vessel, in NSTEMI the thrombus is typically non-occlusive or subtotally occlusive 2

3. Plaque Composition Differences

   • NSTEMI plaques typically have:
     • Greater minimal luminal area compared to STEMI plaques 3
     • Lower lipid content than STEMI plaques 3
     • Shorter rupture length and smaller area of missing fibrous cap 3
     • Lower mean signal intensity on imaging 4
     • Higher proportion of non-calcified plaque material 5

Clinical Implications of White Plaque in NSTEMI

Understanding the white plaque composition in NSTEMI has important clinical implications:

• Diagnosis and Risk Stratification

  • The presence of non-calcified plaque in non-obstructive lesions is associated with increased risk of recurrent events 5
  • Imaging characteristics like positive remodeling and low-density plaque can help identify vulnerable plaques 4

• Treatment Approach

  • The platelet-rich nature of the white thrombus explains why antiplatelet therapy is particularly important in NSTEMI management 1
  • Understanding that NSTEMI typically results from severe coronary artery narrowing, transient occlusion, or microembolization rather than complete occlusion guides treatment strategies 6

Distinguishing Features Between NSTEMI and STEMI Plaques

Feature	NSTEMI (White Plaque)	STEMI
Occlusion	Subtotally occlusive	Completely occlusive [2]
Thrombus composition	Platelet-rich (white)	Fibrin-rich (red) [1]
Minimal luminal area	Larger	Smaller [3]
Lipid content	Less	More [3]
Rupture length	Shorter	Longer [3]
Calcium content	Variable	Often less [4]

Common Pitfalls in Understanding NSTEMI Plaque

• Misconception: Assuming NSTEMI is always less severe than STEMI

  • Reality: NSTEMI can lead to significant myocardial damage and has important prognostic implications 2

• Misconception: Focusing only on the culprit lesion

  • Reality: Non-culprit vulnerable plaques also contribute to future risk 7

• Misconception: Relying solely on calcium scoring for risk assessment

  • Reality: The amount of non-calcified plaque is a better predictor of events after NSTEMI than calcium score 5

Understanding the white, platelet-rich nature of NSTEMI plaque helps guide appropriate antiplatelet and anticoagulant therapy to prevent further platelet aggregation and thrombus formation, ultimately improving patient outcomes.