Stent Thrombosis: Timing, Causes, Diagnosis, and Prevention

Definition and pathophysiology

Stent thrombosis is thrombotic occlusion arising within a coronary stent or at its margins after percutaneous coronary intervention (PCI). It is a PCI-related myocardial infarction when angiography or autopsy documents thrombosis and the diagnostic criteria used for type 1 myocardial infarction are fulfilled. The temporal relationship to stent implantation should always be specified.

Coronary arterial thrombi are predominantly platelet-rich because they form under high-shear conditions. Disruption of an atherosclerotic plaque or injury associated with PCI exposes thrombogenic material, promoting platelet activation, aggregation, and fibrin formation. Within a stented segment, thrombus may also develop because of disturbed flow, residual dissection, inadequate stent expansion, incomplete apposition, or persistent disease at the inflow or outflow edges.

The contemporary incidence of stent thrombosis is approximately 1% during the first year after stenting, although the risk is higher after treatment of ST-segment elevation myocardial infarction (STEMI) and following complex PCI. Stent thrombosis remains multifactorial, reflecting interactions between patient-related, lesion-related, device-related, and procedural factors.

Temporal classification

Traditional definitions focused on cases presenting with acute coronary syndrome (ACS) and confirmed by angiography or pathology. The Academic Research Consortium framework additionally distinguishes definite, probable, and possible stent thrombosis for clinical research and outcome assessment.

Predisposing factors

Large thrombotic burdens increase procedural risk because thrombus can fragment, embolize to other coronary branches or vascular beds, propagate through gaps between stent struts, and compromise the treated lumen. Conventional angiography has limited sensitivity for detecting coronary thrombus.

Drug-eluting stents (DES) may prolong the period of susceptibility because their antiproliferative agents can inhibit endothelialization. Very-late thrombosis after contemporary DES has been reported at approximately 0.2%–0.5% per year beyond the first year, although the available material does not establish a significant increase in late morbidity or mortality attributable to these events.

Clinical presentation and symptoms

Most patients with stent thrombosis present with ACS. Clinical manifestations therefore commonly include recurrent myocardial ischaemia, recurrent infarction, or acute coronary occlusion. Stent thrombosis may occur within hours or days of implantation or many months to years later.

Recurrent chest pain after STEMI or PCI requires consideration of several possibilities:

• Extension of the original infarction or reinfarction

• Acute native-vessel thrombosis

• Stent thrombosis

• Mechanical complications of myocardial infarction

• Pericarditis

Dynamic recurrence of ST-segment elevation is particularly concerning for a new infarction. A pericardial rub and poor response to nitroglycerin may suggest pericardial pain, but clinical discrimination is often unreliable.

Hemodynamic compromise accompanying recurrent chest pain raises concern for a mechanical complication of infarction. In such circumstances, urgent echocardiographic assessment is important, while diagnostic coronary angiography may be necessary to exclude acute native-vessel or stent thrombosis.

Evaluation and physical examination

Evaluation begins with immediate assessment of symptoms, hemodynamic status, and evidence of recurrent myocardial ischaemia. Particular attention should be given to:

• Recurrent or persistent chest discomfort

• Hypotension or other evidence of hemodynamic compromise

• Dynamic electrocardiographic changes

• Evidence of heart failure

• A pericardial rub

• The temporal relationship between symptoms and PCI or stent implantation

• Whether DAPT has been interrupted, discontinued, or taken inconsistently

Physical findings alone are frequently insufficient to distinguish pericarditis from recurrent infarction or stent thrombosis. A pericardial rub and lack of response to nitroglycerin can support pericarditis, but urgent coronary assessment may still be required.

The possibility of stent thrombosis should be heightened when recurrent symptoms occur in the setting of risk factors such as recent acute myocardial infarction, diabetes, renal failure, heart failure, complex or multivessel PCI, long lesions, small vessels, overlapping stents, or interruption of antiplatelet treatment.

Diagnostics

Electrocardiography

The ECG should be assessed for new or dynamic ischaemic changes, particularly recurrent ST-segment elevation. Interpretation may be difficult soon after the index STEMI because normal infarct evolution can resemble recurrent infarction, and electrocardiographic changes may not clearly distinguish extension of the original necrosis from a new infarct in a separate myocardial territory.

Dynamic recurrence of ST-segment elevation should nevertheless prompt strong consideration of new infarction and urgent evaluation for acute coronary or stent thrombosis.

Cardiac biomarkers

Cardiac markers may remain elevated after the initial infarction, especially during the first 24 hours. Consequently, biomarker interpretation alone may not reliably distinguish reinfarction from persistent elevation related to the index event. Biomarkers must be interpreted in conjunction with symptoms, serial ECG findings, and imaging or angiographic evidence.

Transthoracic echocardiography

Transthoracic echocardiography (TTE) is useful in patients with recurrent chest pain and hemodynamic compromise. It can help identify or exclude mechanical complications of myocardial infarction and assess regional wall-motion abnormalities. It may also assist in evaluating alternative diagnoses such as pericardial complications, although it does not by itself establish stent thrombosis.

Coronary angiography

Urgent invasive coronary angiography (ICA) is indicated when stent thrombosis is suspected, particularly because most affected patients present with ACS. Angiography can confirm the diagnosis and permit restoration of coronary flow.

The angiographic predictors of reinfarction after primary PCI include:

• Final coronary stenosis greater than 30%

• PCI-related coronary dissection

• Intracoronary thrombus

• Multivessel coronary disease

• Greater total stent length

Following restoration of coronary flow, intracoronary imaging should be performed to identify an underlying mechanical cause. Angiography alone may not adequately characterize stent underexpansion, malapposition, edge pathology, or other structural problems.

Intracoronary imaging

Intracoronary imaging is encouraged after treatment of stent thrombosis to define the mechanism. Mechanical abnormalities may include:

• Stent fracture or collapse

• Residual edge dissection

• Underexpansion

• Incomplete wall apposition

Identifying the mechanism is essential because definitive treatment depends on the specific structural abnormality.

Electrophysiology

The source material does not describe an electrophysiological evaluation or electrophysiology-based treatment strategy for stent thrombosis.

Biomarkers and laboratory findings

The source material provides no specific biomarker thresholds or laboratory diagnostic algorithm for stent thrombosis. It emphasizes that cardiac markers may remain elevated after the index infarction, making isolated biomarker interpretation unreliable for diagnosing reinfarction during the early post-infarction period.

Laboratory assessment should therefore be integrated with the clinical course, serial ECG findings, echocardiography when indicated, and urgent coronary angiography. The source material also identifies reduced responsiveness to aspirin or clopidogrel and hypercoagulability as possible contributors, but it does not specify testing methods or laboratory criteria for these states.

Treatment and management

Acute management

The majority of patients with stent thrombosis present with ACS and should be managed according to contemporary ACS guidance. Urgent ICA is indicated both to confirm the diagnosis and to restore coronary flow.

After flow restoration:

• Intracoronary imaging should be performed to establish the mechanism.

• Mechanical causes should be corrected.

• Antithrombotic treatment should be reviewed, particularly adherence, interruption, and possible hyporesponsiveness.

• The patient should receive appropriate ACS management and secondary prevention.

Mechanism-directed PCI

Large thrombi may embolize during PCI. Routine manual catheter thrombus aspiration in contemporary primary PCI for STEMI has not shown a mortality benefit and may increase stroke risk, although it may still be useful in selected patients.

Antiplatelet therapy

Antiplatelet treatment is central to the prevention and treatment of arterial thrombosis because arterial thrombi contain a high proportion of platelets. DAPT after stent implantation has contributed to the reduction in stent thrombosis, particularly when combined with appropriate high-pressure stent deployment.

In patients after STEMI, DAPT with aspirin plus a P2Y12 receptor antagonist—clopidogrel, prasugrel, or ticagrelor—is recommended for 12 months when there is no high bleeding risk or bleeding complication.

Treatment failure may reflect:

• Nonadherence

• Premature discontinuation

• Reduced clopidogrel bioavailability

• Hyporesponsiveness to aspirin or clopidogrel

• Interruption for surgery or bleeding

When DAPT is interrupted because of noncompliance, bleeding, or urgent surgery, the risk of major adverse cardiovascular events and stent thrombosis is highest shortly after interruption, particularly during the first 7 days.

Anticoagulants

Anticoagulants are not a universal substitute for DAPT after coronary stenting. Their use should be based on an established indication and balanced against bleeding risk.

In patients with ACS or chronic coronary syndrome who require long-term oral anticoagulation, combined antithrombotic therapy may include a full-dose oral anticoagulant with clopidogrel, with or without aspirin as part of triple antithrombotic therapy. Combining antithrombotic agents increases major bleeding risk. Some analyses suggest that dual antithrombotic therapy may be associated with more myocardial infarction and stent thrombosis than triple therapy, particularly in patients with diabetes; consequently, the duration of triple therapy must be individualized according to thrombotic and bleeding risks.

Low-dose rivaroxaban has reduced recurrent ischaemic events and stent thrombosis when added to antiplatelet therapy in selected patients with ACS or stable atherosclerotic disease, but it increases major bleeding. The source material does not establish this strategy as routine treatment for a patient with stent thrombosis.

Long-term secondary prevention

Secondary prevention after STEMI includes:

• Long-term antiplatelet therapy, usually aspirin

• DAPT for 12 months when appropriate

• ACE inhibitor or angiotensin receptor blocker, and an aldosterone antagonist when indicated by heart failure, reduced left ventricular ejection fraction, or a large regional wall-motion abnormality

• Chronic beta-blocker therapy for at least 1 year after STEMI

• Modification of atherosclerotic risk factors

• Consideration of low-dose colchicine, 0.5 mg once daily, particularly after recurrent atherosclerotic events despite guideline-directed therapy

Routine long-term nitrate therapy does not appear to reduce mortality, although nitrates may be used for recurrent angina or as part of heart-failure treatment.

Perioperative prevention and management

Timing of noncardiac surgery

The period immediately after stent implantation carries the greatest risk of thrombosis. The first 4–6 weeks after implantation of either a bare-metal stent (BMS) or DES are particularly vulnerable. If possible, noncardiac surgery should be avoided during this interval.

Guidance on postponement of elective surgery includes:

Elective surgery after more than 180 days may be considered in chronic coronary disease treated with a DES when the risk of delaying surgery exceeds the risk of stent thrombosis. The perioperative decision should be individualized and multidisciplinary.

The increased perioperative risk appears to decline with time. Observational data indicate that risk is especially high during the first 6 months after stent placement, and is particularly pronounced when PCI was performed for myocardial infarction.

Perioperative antiplatelet management

If surgery cannot be avoided:

• DAPT interruption should be minimized.

• Aspirin should generally be continued when a P2Y12 inhibitor is stopped, except when bleeding would be catastrophic, such as in selected neurosurgical or spinal procedures.

• The P2Y12 inhibitor should be restarted as soon as possible after surgery.

• Elective surgery should be delayed after the last dose of clopidogrel for 5 days, prasugrel for 7 days, and ticagrelor for 3–5 days.

• Decisions should involve cardiology, surgery, anaesthesia, and other relevant specialties.

Intravenous cangrelor may be considered as a bridging strategy because it is a reversible P2Y12 receptor antagonist, but evidence in patients undergoing cardiac or noncardiac surgery remains limited. Intravenous eptifibatide or tirofiban have also been used as bridging approaches, although rigorous testing and outcome data are lacking.

Other perioperative cardiovascular medications

Patients receiving chronic beta-blocker therapy should continue it through surgery when clinically feasible. Beta-blocker withdrawal should be avoided, and treatment should not be initiated on the day of surgery. Perioperative initiation may be considered in carefully selected very high-risk patients, ideally sufficiently before surgery to assess safety and tolerability.

Statins should be continued in patients already taking them. Starting statin therapy is reasonable before vascular surgery, whereas the benefit of initiating therapy before other high-risk operations remains uncertain. In a statin-naïve perioperative loading strategy, atorvastatin 80 mg within 18 hours before surgery followed by 40 mg daily for 7 days did not reduce major adverse events.

Guideline recommendations

Key recommendations derived from the available guidance are summarized below:

Prognosis and follow-up

Stent thrombosis is infrequent with contemporary stenting and DAPT, with an approximate first-year incidence of 1%, but it is associated with ACS and may cause severe recurrent ischaemia or infarction. Risk is increased after STEMI, complex PCI, interruption of DAPT, and in the presence of mechanical or anatomic abnormalities.

Very-late thrombosis remains a concern after DES because impaired endothelialization may extend the period of risk beyond the first year. Although reported rates are approximately 0.2%–0.5% annually after the first year, the source material does not establish a significant increase in late morbidity or mortality attributable to these events.

Follow-up should include:

• Verification of antiplatelet adherence and access to medication

• Review of bleeding and interruptions in therapy

• Assessment of ongoing thrombotic and bleeding risks

• Evaluation for diabetes, renal failure, heart failure, and other clinical risk factors

• Review of the PCI anatomy and procedural details

• Confirmation that any mechanical cause identified by intracoronary imaging has been corrected

• Continued secondary prevention after myocardial infarction

• Careful planning before any future noncardiac surgery

The timing and duration of DAPT or combined anticoagulant–antiplatelet therapy should be revisited whenever bleeding, surgery, recurrent ischaemia, or a new indication for anticoagulation develops.