What is the classification of stent thrombosis based on timing after stent placement?

Classification of Stent Thrombosis Based on Timing

Stent thrombosis is classified according to the timing after implantation as early (0-30 days), late (31-360 days), and very late (>360 days), with early stent thrombosis further subdivided into acute (0-24 hours) and subacute (>24 hours to 30 days). 1

Detailed Classification System

The Academic Research Consortium (ARC) has established standardized definitions for stent thrombosis based on timing after stent placement:

1. Early Stent Thrombosis (0-30 days)

   • Acute: Within 24 hours of stent implantation
   • Subacute: >24 hours to 30 days after stent implantation

2. Late Stent Thrombosis (31-360 days)

   • Occurs between 1 month and 12 months after stent implantation

3. Very Late Stent Thrombosis (>360 days)

   • Occurs more than 1 year after stent implantation

Clinical Significance of Timing

The timing of stent thrombosis has important clinical implications:

• Early stent thrombosis (0-30 days) is the most common timeframe, with subacute stent thrombosis occurring in approximately 1% of patients in the current era of dual antiplatelet therapy 1

• Late stent thrombosis (1-12 months) was not readily apparent with bare-metal stents but occurs in approximately 0.19% of patients with drug-eluting stents 1

• Very late stent thrombosis (>1 year) is more common with drug-eluting stents than with bare-metal stents, with cases reported occurring months or even years after implantation 2

Risk Factors for Stent Thrombosis

Several factors increase the risk of stent thrombosis across all time periods:

• Premature discontinuation of antiplatelet therapy (strongest predictor)
• Stenting of complex lesions (bifurcation, small vessels, long lesions)
• Multiple or overlapping stents
• Suboptimal stent deployment (underexpansion, malapposition)
• Patient factors: diabetes mellitus, renal failure, low ejection fraction, advanced age
• Acute coronary syndrome presentation 1, 2

Clinical Presentation and Outcomes

Stent thrombosis typically presents as a catastrophic event with:

• ST-segment elevation myocardial infarction
• High mortality rates (20-45%)
• Overall incidence of death or MI associated with stent thrombosis of approximately 64.4% 1

Preventive Strategies

Dual antiplatelet therapy (DAPT) duration recommendations based on stent type:

• Bare-metal stents: Minimum 1 month
• Sirolimus drug-eluting stents: Minimum 3 months
• Paclitaxel drug-eluting stents: Minimum 6 months
• All drug-eluting stents: Ideally up to 12 months if not at high risk for bleeding 1

Important Considerations

• The timing of thrombosis appears to be delayed in drug-eluting stents compared to bare-metal stents
• Premature discontinuation of antiplatelet therapy is the leading independent predictor for stent thrombosis
• The risk of very late stent thrombosis (>1 year) is higher with drug-eluting stents than with bare-metal stents
• Understanding the timing classification is critical for appropriate risk stratification and management decisions, especially regarding the duration of dual antiplatelet therapy