What is the immediate management for a patient presenting with ST-Elevation Myocardial Infarction (STEMI) and how is the Thrombolysis In Myocardial Infarction (TIMI) score used to guide treatment?

TIMI Score and STEMI Management

The TIMI Score is NOT Used to Guide Initial STEMI Treatment

The TIMI (Thrombolysis In Myocardial Infarction) score is a risk stratification tool for non-ST-elevation acute coronary syndromes (NSTE-ACS), not for STEMI management. STEMI treatment decisions are based on time from symptom onset, anticipated delay to PCI, and immediate reperfusion strategy—not risk scores 1.

Immediate STEMI Management Algorithm

Initial Actions (Within 10 Minutes of Presentation)

• Obtain and interpret 12-lead ECG immediately to confirm ST-segment elevation >0.1 mV in at least two contiguous leads 1, 2
• Administer aspirin 150-325 mg orally or IV immediately unless contraindicated 1, 2, 3
• Place patient on continuous cardiac monitoring with defibrillator capacity 1, 2
• Establish IV access and give morphine 4-8 mg IV for pain control (additional 2 mg doses at 5-15 minute intervals as needed) 2, 4
• Do NOT give routine oxygen unless SaO2 <90% 1, 3

Reperfusion Strategy Decision (Time Zero = STEMI Diagnosis)

The choice between primary PCI and fibrinolysis depends entirely on time delays, not patient risk scores:

Primary PCI is Preferred When:

• PCI can be performed within 90-120 minutes of first medical contact 1, 2
• This is the definitive reperfusion strategy with Class I, Level A evidence 2
• Bypass the emergency department and transfer directly to catheterization laboratory when possible 1, 3

Fibrinolytic Therapy Should Be Given When:

• Primary PCI cannot be performed within 120 minutes of STEMI diagnosis 1
• Initiate fibrinolysis within 10 minutes of STEMI diagnosis, preferably in pre-hospital setting 1
• Use fibrin-specific agents: tenecteplase, alteplase, or reteplase 1, 5
• All patients receiving fibrinolysis must be transferred immediately to PCI-capable center after administration 1, 2

Antithrombotic Regimen (Given Before or During PCI)

P2Y12 Inhibitor Loading:

• Prasugrel 60 mg or ticagrelor loading dose before or at time of PCI 1, 2, 3
• Clopidogrel only if prasugrel/ticagrelor unavailable or contraindicated 1, 2
• For fibrinolysis patients: use clopidogrel (not prasugrel/ticagrelor) 1

Anticoagulation:

• Unfractionated heparin as weight-adjusted IV bolus followed by infusion for primary PCI 1, 3
• Enoxaparin IV followed by subcutaneous (preferred over UFH) for fibrinolysis patients 1
• Fondaparinux is contraindicated for primary PCI 1, 3

Post-Reperfusion Management

Rescue PCI Indications:

• <50% ST-segment resolution at 60-90 minutes after fibrinolysis 1
• Hemodynamic or electrical instability at any time 1
• Heart failure or cardiogenic shock develops 1, 2

Routine Angiography After Successful Fibrinolysis:

• Perform between 2-24 hours after successful fibrinolysis 1, 2

Long-Term Medical Therapy (Initiated Within 24 Hours)

• Dual antiplatelet therapy (DAPT) for 12 months: aspirin 75-100 mg plus prasugrel or ticagrelor 1, 2, 3
• Proton pump inhibitor (PPI) in combination with DAPT for patients at high GI bleeding risk 1, 2
• Oral beta-blocker for patients with heart failure or LVEF <40% (avoid IV beta-blockers in acute phase) 1, 3
• High-intensity statin started immediately 1
• ACE inhibitor within first 24 hours 1

Critical Pitfalls to Avoid

• Never delay reperfusion waiting for cardiac biomarkers in patients with ST-elevation on ECG 3, 5
• Avoid IV beta-blockers in acute STEMI due to risk of hypotension, acute heart failure, and bradycardia (Class III recommendation) 1, 3
• Do not give NSAIDs for pain due to increased mortality and myocardial rupture risk 3
• Prasugrel is contraindicated in patients with prior stroke/TIA and generally not recommended in patients ≥75 years or <60 kg 6
• Discontinue prasugrel at least 7 days before any planned surgery 6

Why TIMI Score is Irrelevant in STEMI

The TIMI risk score was developed for NSTE-ACS to stratify bleeding and ischemic risk 7. In STEMI, the presence of ST-elevation itself indicates complete coronary occlusion requiring immediate reperfusion regardless of other risk factors 5, 8. Treatment urgency is determined by the "time is muscle" principle—every minute of delay increases infarct size and mortality 1, 9.