What is the immediate medical therapy for a patient diagnosed with Non-ST-Elevation Myocardial Infarction (NSTEMI)?

Immediate Medical Therapy for NSTEMI

The immediate medical therapy for a patient diagnosed with NSTEMI should include aspirin (162-325 mg loading dose), a P2Y12 inhibitor (preferably ticagrelor), anticoagulation with unfractionated heparin or low molecular weight heparin, intravenous nitroglycerin for ongoing chest pain, and early beta-blocker administration. 1, 2

Initial Pharmacological Management

Antiplatelet Therapy

1. Aspirin:

   • Administer 162-325 mg loading dose (non-enteric coated, chewed or crushed) as soon as possible after presentation 1, 2
   • Follow with 81 mg daily maintenance dose to minimize bleeding risk 1
   • Aspirin reduces 5-week vascular mortality by 23% in acute MI patients 1

2. P2Y12 Inhibitor (in addition to aspirin):

   • Ticagrelor: 180 mg loading dose followed by 90 mg twice daily (preferred for moderate to high-risk patients) 1
   • Clopidogrel: 300-600 mg loading dose followed by 75 mg daily (alternative) 2
   • Prasugrel: 60 mg loading dose followed by 10 mg daily (only after coronary anatomy is established and PCI is planned) 3
     • Contraindicated in patients with prior stroke/TIA
     • Not recommended for patients ≥75 years unless high-risk (diabetes or prior MI) 3

Anticoagulation

• Unfractionated heparin (UFH): IV bolus followed by continuous infusion, preferred when rapid reversal may be needed 2
• Low molecular weight heparin (LMWH) (e.g., enoxaparin): Generally preferred over UFH 2, 4
• Fondaparinux: Alternative in patients with high bleeding risk 1
• Bivalirudin: Direct thrombin inhibitor, alternative to heparin, especially in patients with heparin-induced thrombocytopenia 1

Anti-ischemic Therapy

1. Nitroglycerin:

   • IV nitroglycerin for ongoing chest pain 1, 2
   • Contraindicated if systolic BP <90 mmHg, severe bradycardia (<50 bpm), tachycardia (>100 bpm) without heart failure, or right ventricular infarction 1
   • Do not administer if patient has taken phosphodiesterase inhibitors (sildenafil within 24h, tadalafil within 48h) 1

2. Beta-blockers:

   • Administer early unless contraindicated 1, 2
   • IV beta-blockers should be avoided in patients with signs of heart failure, low cardiac output, increased risk of cardiogenic shock, or other contraindications 1

3. Calcium channel blockers:

   • Use for patients with ongoing ischemia despite nitrates and beta-blockers or in those who cannot tolerate beta-blockers 1, 2
   • Immediate-release dihydropyridine calcium channel blockers should not be administered without beta-blockers 1

Risk Stratification and Invasive Strategy

Risk Assessment

• Perform immediate risk stratification using validated tools like GRACE or TIMI Risk Score 2
• High-risk features requiring early invasive strategy (<24h):
  • Rise or fall in cardiac troponin compatible with MI
  • Dynamic ST- or T-wave changes
  • GRACE score >140 1

Timing of Invasive Strategy

1. Immediate invasive strategy (<2h) for very high-risk patients:

   • Hemodynamic instability or cardiogenic shock
   • Refractory angina despite medical treatment
   • Life-threatening arrhythmias or cardiac arrest
   • Mechanical complications of MI
   • Acute heart failure with refractory angina 1

2. Early invasive strategy (<24h) for high-risk patients:

   • Elevated cardiac troponin
   • Dynamic ECG changes
   • GRACE score >140 1

3. Invasive strategy within 72h for intermediate-risk patients:

   • Diabetes mellitus
   • Renal insufficiency (eGFR <60 mL/min/1.73 m²)
   • LVEF <40% or heart failure
   • Recent PCI or prior CABG
   • GRACE score >109 and <140 1

Common Pitfalls and Caveats

1. Bleeding risk:

   • Consider patient's weight, age, and renal function when dosing antithrombotic medications
   • Patients <60 kg have increased risk of bleeding with standard prasugrel dosing 3
   • Consider proton pump inhibitors in patients with history of GI bleeding 1

2. Timing of P2Y12 inhibitor administration:

   • For patients likely to undergo urgent CABG, consider delaying P2Y12 inhibitor administration
   • If CABG is planned, P2Y12 inhibitors should be discontinued (clopidogrel: 5 days, ticagrelor: 7 days, prasugrel: 7 days) prior to surgery 1

3. NSAIDs:

   • All NSAIDs except aspirin should be discontinued due to increased risks of mortality, reinfarction, hypertension, heart failure, and myocardial rupture 1

4. ACE inhibitors:

   • Oral ACE inhibitors can be useful within first 24h in patients without pulmonary congestion or LVEF ≤0.40
   • IV ACE inhibitors should be avoided within first 24h due to increased risk of hypotension 1

By following this evidence-based approach to immediate NSTEMI management, focusing on rapid administration of antithrombotic therapy, relief of ischemia, and appropriate risk stratification for invasive management, mortality and morbidity can be significantly reduced.