What are the indications and management for thrombolysis in ST-Elevation Myocardial Infarction (STEMI)?

Thrombolysis Indications and Management in STEMI

Thrombolytic therapy is indicated in all STEMI patients with symptoms of ischemia less than 12 hours duration and persistent ST-segment elevation when primary PCI cannot be performed in a timely manner (within 120 minutes of first medical contact). 1

Primary Indications for Thrombolysis in STEMI

• First-line indication: When primary PCI cannot be performed within 120 minutes after STEMI diagnosis 1
• Time window: Within 12 hours of symptom onset in patients without contraindications 1
• ECG criteria: Persistent ST-segment elevation or new-onset left bundle branch block 1
• Administration timing: Should be initiated as soon as possible after STEMI diagnosis, preferably in the pre-hospital setting 1

Contraindications to Thrombolysis

Thrombolytic therapy is contraindicated in patients with:

• Active internal bleeding
• History of cerebrovascular accident
• Intracranial or intraspinal surgery or trauma within 2 months
• Intracranial neoplasm, arteriovenous malformation, or aneurysm
• Known bleeding diathesis
• Severe uncontrolled hypertension 2

Thrombolytic Agent Selection and Administration

• Preferred agents: Fibrin-specific agents (tenecteplase, alteplase, or reteplase) 1
• Tenecteplase dosing: Individualized based on patient's weight, administered as a single bolus over 5 seconds 2
• Administration route: Intravenous only 2

Adjunctive Antithrombotic Therapy with Thrombolysis

1. Antiplatelet therapy:

   • Oral or IV aspirin (162-325 mg) 1, 3
   • Clopidogrel in addition to aspirin 1

2. Anticoagulation:

   • Required until revascularization or for duration of hospital stay (up to 8 days) 1
   • Preferred option: Enoxaparin IV followed by subcutaneous (superior to UFH) 1
   • Alternative: Unfractionated heparin as weight-adjusted IV bolus followed by infusion 1
   • Contraindicated: Fondaparinux is not recommended 1

Post-Thrombolysis Management

1. Transfer strategy:

   • All patients should be transferred to a PCI-capable center immediately after fibrinolysis 1
   • Angiography and PCI of the infarct-related artery (if indicated) is recommended between 2-24 hours after successful fibrinolysis 1

2. Rescue PCI indications:

   • Failed thrombolysis (<50% ST-segment resolution at 60-90 minutes) 1
   • Hemodynamic or electrical instability 1
   • Worsening ischemia 1
   • Heart failure or cardiogenic shock 1
   • Recurrent ischemia or evidence of reocclusion after initially successful thrombolysis 1

Special Considerations for Timing

• Early presenters (within 2 hours of symptom onset) may have particular benefit from thrombolysis compared to delayed primary PCI 4
• For patients <75 years with large anterior infarction presenting within 2 hours of symptom onset, primary PCI should be performed within 90 minutes of first medical contact 3
• If primary PCI cannot be performed within the recommended timeframe, thrombolysis should be initiated within 30 minutes of first medical contact 5

Post-Reperfusion Care

• Echocardiography during hospital stay to assess LV and RV function, detect mechanical complications, and exclude LV thrombus 1
• Cardiac rehabilitation program participation is recommended 1
• Smoking cessation support with nicotine replacement therapies, varenicline, and bupropion 1

Monitoring for Complications

• Bleeding: Avoid intramuscular injections and nonessential handling of the patient for the first few hours following treatment 2
• Arrhythmias: Have anti-arrhythmic therapy available for bradycardia and/or ventricular irritability 2
• Hypersensitivity: Monitor patients during and for several hours after infusion 2
• Cholesterol embolism: Has been reported with thrombolytic agents 2

Key Pitfalls to Avoid

1. Delayed administration: Thrombolytic efficacy decreases with time; administer as soon as possible after STEMI diagnosis
2. Inappropriate patient selection: Carefully screen for contraindications to minimize bleeding risk
3. Failure to transfer: All patients should be transferred to a PCI-capable center after thrombolysis
4. Missing failed thrombolysis: Monitor for signs of reperfusion failure and perform rescue PCI when indicated
5. Inadequate anticoagulation: Ensure proper anticoagulation is maintained after thrombolysis

The evidence strongly supports a reperfusion strategy that prioritizes timely treatment. While primary PCI is the preferred method when available within the recommended timeframe, thrombolysis remains a critical intervention when timely PCI is not feasible, with subsequent transfer to a PCI-capable facility for potential early intervention.