What is the ideal time frame for administering streptokinase in ST-elevation myocardial infarction (STEMI)?

Streptokinase Administration Timing in STEMI

Streptokinase should be administered within 30 minutes of hospital arrival in patients with STEMI when primary PCI cannot be performed within 120 minutes of first medical contact. 1

Timing of Streptokinase Administration

Key Time Parameters:

• Door-to-needle time: ≤30 minutes 1
• Symptom onset window: Within 12 hours (strongest evidence) 1
• Extended window: 12-24 hours only if there is ongoing ischemia, large area of myocardium at risk, or hemodynamic instability 1, 2

Administration Protocol:

• Standard dose: 1.5 million units
• Traditional infusion time: 30-60 minutes 1
• Some evidence supports accelerated regimens (20-30 minutes) with similar safety and potentially better efficacy 3, 4

Decision Algorithm for Streptokinase Use

1. Primary assessment:

   • Confirm STEMI diagnosis with ECG
   • Determine time from symptom onset
   • Assess contraindications to fibrinolytic therapy

2. Reperfusion strategy decision:

   • If PCI-capable hospital with FMC-to-device time ≤90 minutes: Choose primary PCI
   • If transfer to PCI-capable hospital with FMC-to-device time ≤120 minutes: Transfer for primary PCI
   • If PCI not available within 120 minutes: Administer streptokinase within 30 minutes of hospital arrival 1

3. Time window considerations:

   • ≤12 hours from symptom onset: Strong indication (Class I, Level A) 1
   • 12-24 hours with ongoing ischemia: Consider streptokinase (Class IIa, Level C) 1

   • 24 hours: Not recommended 2

Efficacy and Outcomes

• Mortality benefit is time-dependent, with greatest benefit when administered early
• Absolute mortality reductions:
  • 3% for patients presenting within 0-6 hours
  • 2% for patients presenting within 7-12 hours 1
• Total ischemic time (symptom-to-balloon time) ≥180 minutes is associated with increased in-hospital major adverse cardiac events 5

Important Considerations and Pitfalls

• Common pitfall: Delaying fibrinolytic therapy while waiting for transfer to PCI-capable facility when transfer times will exceed 120 minutes
• Caution: Streptokinase can cause hypotension in up to 44% of patients, but this is typically transient (resolves within 16±6 minutes) and does not appear to negatively impact outcomes 6
• Contraindication: Do not administer to patients with ST depression except when a true posterior MI is suspected or when associated with ST elevation in lead aVR 1
• Prior exposure: Streptokinase is highly antigenic and absolutely contraindicated within 6 months of previous exposure due to potential for serious allergic reactions 1

Adjunctive Therapy

• Aspirin (162-325 mg loading dose)
• Clopidogrel (300 mg loading dose for patients <75 years, 75 mg for patients ≥75 years)
• Anticoagulation (UFH, enoxaparin, or fondaparinux) for minimum of 48 hours 1

Remember that while the time window guidelines are important system goals, for any individual patient, every effort should be made to provide reperfusion therapy as rapidly as possible to minimize myocardial damage and improve outcomes.