Immediate Post-Stent Complication: Stent Thrombosis
Stent thrombosis is the immediate acute complication after coronary stent placement, not restenosis. Stent thrombosis most commonly occurs in the first month after stent implantation (termed "subacute stent thrombosis"), whereas restenosis is a delayed process that develops over months through neointimal hyperplasia 1.
Critical Timing Distinctions
Early stent thrombosis (0-30 days) represents the acute threat, occurring in approximately 1% of patients in the current era of dual antiplatelet therapy 1. This is the period of highest absolute risk, particularly within the first 5 days after implantation 2.
In contrast, restenosis develops gradually:
- After balloon angioplasty: 32-42% angiographic restenosis rate 1
- After bare-metal stents: 16-32% angiographic restenosis rate 1
- After drug-eluting stents: approximately 10% restenosis rate 1
Catastrophic Nature of Stent Thrombosis
The mortality and morbidity profile of stent thrombosis far exceeds that of restenosis, making it the more critical immediate concern:
- Death or myocardial infarction occurs in 64.4% of patients with angiographically documented stent thrombosis 1, 2
- Mortality rates range from 20% to 45% for stent thrombosis 1, 2, 3
- Left main stent thrombosis is fatal in the majority of cases 2
- Stent thrombosis typically presents as ST-elevation myocardial infarction or sudden death 1, 4, 5
By comparison, restenosis presents as recurrent angina requiring repeat revascularization but is not immediately life-threatening 1.
Pathophysiologic Mechanisms
Stent Thrombosis (Acute Process)
Thrombosis results from acute prothrombotic conditions that develop immediately after stent placement 1:
- Incomplete endothelialization of stent struts 1
- Endothelial cell injury 1
- Stent underexpansion, malapposition, or residual dissection 1, 2
- Circumferential granulomatous inflammation (particularly with drug-eluting stents) 1
- Fibrin deposition within neointima 1
Restenosis (Delayed Process)
Restenosis develops through different mechanisms over months 1:
- Smooth muscle cell migration and proliferation
- Neointimal hyperplasia (primary mechanism after stent implantation)
- Negative arterial remodeling (prevented by stents)
Critical Risk Factors for Early Stent Thrombosis
Premature discontinuation of dual antiplatelet therapy is the strongest independent predictor, with hazard ratios ranging from 27 to 161 for subacute stent thrombosis 1, 2, 3. Other high-risk features include 1, 2:
- Bifurcation lesions (present in ~63% of left main cases)
- Multiple or overlapping stents
- Long stent length
- Small vessel stenting
- Insulin-requiring diabetes (odds ratio ≈3.1)
- Malignancy (odds ratio ≈17.5)
- Renal failure
- Acute coronary syndrome presentation
Prevention Strategy
The American College of Cardiology/American Heart Association mandates dual antiplatelet therapy to prevent the immediate threat of stent thrombosis 1:
- Minimum 1 month after bare-metal stent implantation
- Minimum 3-6 months after drug-eluting stent implantation
- Ideally 12 months for drug-eluting stents if not at high bleeding risk
- Mandatory 12 months for acute coronary syndrome patients regardless of stent type 3
Common Pitfall
The most critical error is implanting stents in patients unlikely to comply with dual antiplatelet therapy (Class III: HARM recommendation) 3. This directly increases the risk of the immediate catastrophic complication—stent thrombosis—rather than the delayed, less lethal complication of restenosis.