Initial goals are to (1) quickly identify if pt is candidate for reperfusion therapy, (2) relieve pain, and (3) prevent/treat arrhythmias and mechanical complications.
- Aspirin should be administered immediately (162-325 mg chewed at presentation, then 75-162 mg PO qd), unless pt is aspirin-intolerant.
- Perform targeted history, examination, and ECG to identify STEMI (>1 mm ST elevation in two contiguous limb leads, ≥2 mm ST elevation in two contiguous precordial leads, or new LBBB) and appropriateness of reperfusion therapy (percutaneous coronary intervention [PCI] or IV fibrinolytic agent), which reduces infarct size, LV dysfunction, and mortality.
- Primary PCI is generally more effective than fibrinolysis and is preferred at experienced centers capable of performing the procedure rapidly (Fig. 119-1), especially when diagnosis is in doubt, cardiogenic shock is present, bleeding risk is increased, or symptoms have been present for >3 h.
- Proceed with IV fibrinolysis if PCI is not available or if logistics would delay PCI >1 h longer than fibrinolysis could be initiated (Fig. 119-1). Door-to-needle time should be <30 min for maximum benefit. Ensure absence of contraindications (Fig. 119-2) before administering fibrinolytic agent. Those treated within 1-3 h benefit most; can still be useful up to 12 h if chest pain is persistent or ST remains elevated in leads that have not developed new Q waves. Complications include bleeding, reperfusion arrhythmias, and, in case of streptokinase (SK), allergic reactions. Enoxaparin or heparin (60 U/kg [maximum 4000 U], then 12 [U/kg]/h [maximum 1000 U/h]) should be initiated with fibrinolytic agents (Fig. 119-2); maintain activated partial thromboplastin time (aPTT) at 1.5-2.0 × control (~50-70 s).
- If chest pain or ST elevation persists >90 min after fibrinolysis, consider referral for rescue PCI. Coronary angiography after fibrinolysis should also be considered for pts with recurrent angina or high-risk features (Fig. 119-2) including extensive ST elevation, signs of heart failure (rales, S3, jugular venous distension, left ventricular ejection fraction [LVEF] ≤35%), or systolic bp <100 mmHg.
The initial management of NSTEMI (non-Q MI) is different (Chap. 120. Unstable Angina and Non-ST-Elevation Myocardial Infarction). In particular, fibrinolytic therapy should not be administered.