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

Indications for Thrombolysis in ST-Elevation Myocardial Infarction (STEMI)

Thrombolysis is indicated in STEMI patients with symptoms of ischemia lasting less than 12 hours and persistent ST-segment elevation when primary PCI cannot be performed in a timely manner (within 120 minutes of STEMI diagnosis). 1

Primary Indications

Thrombolysis should be administered according to the following criteria:

• Time from symptom onset:

  • Within 12 hours of symptom onset 1
  • Preferably within the first 1-2 hours of symptom onset, when the greatest mortality benefit is observed 2

• ECG criteria:

  • Persistent ST-segment elevation
  • New left bundle branch block presumed to be ischemic in origin 1

• PCI availability:

  • When primary PCI cannot be performed within 120 minutes of STEMI diagnosis 1
  • For patients <75 years with large anterior infarction presenting within 2 hours, PCI delay should not exceed 90 minutes 3

Administration Protocol

When thrombolysis is the chosen reperfusion strategy:

• Timing: Initiate as soon as possible after STEMI diagnosis, preferably in the pre-hospital setting 1
• Agent selection: Use a fibrin-specific agent (tenecteplase, alteplase, or reteplase) 1
• Dosing:
  • Tenecteplase: Single IV weight-based bolus (30-50 mg based on weight) 1, 4
  • Alteplase: 90-minute weight-based infusion 1
  • Reteplase: Two 10-U IV boluses given 30 minutes apart 1

Adjunctive Therapy

The following medications should accompany thrombolytic therapy:

• Antiplatelet therapy:

  • Oral or IV aspirin 1
  • Clopidogrel in addition to aspirin 1, 5

• Anticoagulation: Required until revascularization or for duration of hospital stay (up to 8 days) 1

  • Enoxaparin IV followed by SC (preferred over UFH) 1
  • Unfractionated heparin as weight-adjusted IV bolus followed by infusion 1

Post-Thrombolysis Management

After thrombolysis administration:

• Transfer: All patients should be transferred to a PCI-capable center immediately after fibrinolysis 1
• Rescue PCI: Indicated immediately when fibrinolysis has failed (<50% ST-segment resolution at 60-90 min) 1
• Routine angiography: Recommended between 2-24 hours after successful fibrinolysis 1
• Emergency angiography: Indicated in patients with heart failure/shock or recurrent ischemia 1

Absolute Contraindications to Thrombolysis 1

• Any prior intracranial hemorrhage
• Known structural cerebral vascular lesion
• Known malignant intracranial neoplasm
• Ischemic stroke within 3 months (except acute ischemic stroke within 4.5 hours)
• Suspected aortic dissection
• Active bleeding or bleeding diathesis
• Significant closed-head or facial trauma within 3 months
• Intracranial or intraspinal surgery within 2 months
• Severe uncontrolled hypertension
• For streptokinase, prior treatment within previous 6 months

Relative Contraindications 1

• History of chronic, severe, poorly controlled hypertension
• Significant hypertension on presentation (SBP >180 mm Hg or DBP >110 mm Hg)
• History of prior ischemic stroke >3 months
• Dementia
• Known intracranial pathology not covered in absolute contraindications
• Traumatic or prolonged (>10 min) CPR
• Major surgery (<3 weeks)
• Recent internal bleeding (within 2-4 weeks)
• Noncompressible vascular punctures
• Pregnancy
• Active peptic ulcer
• Current oral anticoagulant therapy

Special Considerations

• Late presenters (>12 hours): Benefit from thrombolysis not established in patients presenting >12 hours after symptom onset 1
• Early presenters (<2 hours): May have particular benefit from thrombolysis compared to primary PCI, with potentially lower mortality (2.2% vs 5.7%) and less cardiogenic shock (1.3% vs 5.3%) 2
• Bleeding risk: Thrombolysis increases risk of bleeding, including intracranial hemorrhage 4
• Post-cardiac arrest: Primary PCI is recommended over thrombolysis in patients with resuscitated cardiac arrest and ECG consistent with STEMI 1, 6

Pitfalls to Avoid

• Delaying thrombolysis when primary PCI cannot be performed in a timely manner
• Failing to transfer patients to PCI-capable centers after thrombolysis
• Administering thrombolysis in the presence of absolute contraindications
• Using non-fibrin-specific agents when fibrin-specific agents are available
• Neglecting to provide adjunctive antiplatelet and anticoagulant therapy
• Delaying rescue PCI when thrombolysis has failed

Thrombolysis remains a vital reperfusion strategy when timely primary PCI is not available, particularly in the first hours after symptom onset when its efficacy is highest.