Management of Myocardial Infarction
For STEMI, immediate primary PCI within 90-120 minutes of first medical contact is the definitive treatment, while NSTEMI requires risk stratification with early invasive strategy (within 24 hours) for high-risk patients and immediate intervention (within 2 hours) for those with hemodynamic instability, refractory angina, or life-threatening arrhythmias. 1, 2
Initial Assessment and Immediate Management
Obtain a 12-lead ECG within 10 minutes of first medical contact to differentiate STEMI from NSTEMI, as this single test determines the entire treatment pathway 2. Look specifically for ST-segment elevation ≥1mm in two contiguous leads, new left bundle branch block, or STEMI equivalents including hyperacute T-waves, true posterior MI (ST depression V1-V4 with ST elevation in V7-V9), or multilead ST depression with ST elevation in aVR suggesting left main disease 2.
Administer aspirin 162-325 mg (chewed) immediately unless contraindicated 1, 2. This is a Class I, Level B recommendation that should occur as soon as MI is suspected, even before ECG confirmation 1.
Initiate continuous ECG monitoring with defibrillator capacity given the high risk of ventricular arrhythmias in the acute phase 2.
Avoid routine oxygen therapy unless oxygen saturation is <90%, as unnecessary oxygen can cause harm 2.
STEMI Management: The Time-Critical Pathway
Reperfusion Strategy Selection
Primary PCI is the preferred reperfusion strategy and must be performed within specific time windows: ≤90 minutes at PCI-capable centers or ≤120 minutes with transfer 1, 2. This applies to all patients with symptoms <12 hours duration and persistent ST-segment elevation 1.
Transport patients directly to the catheterization laboratory, bypassing the emergency department entirely 1, 2. This direct transfer approach is a Class I, Level B recommendation that saves critical minutes 1.
If primary PCI cannot be performed within these time windows, initiate fibrinolytic therapy within 12 hours of symptom onset in patients without contraindications 1. The benefit of reperfusion is highly time-dependent, with greatest mortality reduction occurring within the first 3 hours 3.
Antithrombotic Regimen for Primary PCI
Administer a potent P2Y12 inhibitor before or at the time of PCI: prasugrel (60 mg loading dose) or ticagrelor are preferred over clopidogrel 1, 2, 4. Prasugrel is specifically FDA-approved to reduce thrombotic cardiovascular events including stent thrombosis in ACS patients managed with PCI 4.
Give unfractionated heparin IV bolus at 100 U/kg (60 U/kg if glycoprotein IIb/IIIa inhibitors are used) 2. Alternatively, enoxaparin IV followed by subcutaneous dosing is preferred over UFH for fibrinolytic therapy 1.
Use radial access and drug-eluting stents as standard of care 2. Radial access reduces bleeding complications compared to femoral access.
Continue dual antiplatelet therapy (DAPT) for 12 months: aspirin 75-100 mg daily plus P2Y12 inhibitor unless contraindications such as excessive bleeding risk exist 1, 2. This is a Class I, Level A recommendation 1.
Fibrinolytic Therapy Protocol (When PCI Unavailable)
Initiate fibrinolytic therapy as soon as possible after STEMI diagnosis, preferably in the pre-hospital setting 1. Use a fibrin-specific agent: tenecteplase, alteplase, or reteplase (Class I, Level B) 1.
Administer aspirin and clopidogrel in addition to the fibrinolytic 1. Clopidogrel is specifically indicated with aspirin for STEMI patients managed medically 5.
Anticoagulation is mandatory: enoxaparin IV followed by subcutaneous (preferred over UFH) or weight-adjusted UFH bolus followed by infusion 1.
Transfer all patients to a PCI-capable center immediately after fibrinolysis 1. This is non-negotiable even if fibrinolysis appears successful.
Perform angiography and PCI of the infarct-related artery between 2-24 hours after successful fibrinolysis 1. This routine invasive strategy improves outcomes compared to conservative management.
Rescue PCI is indicated immediately when fibrinolysis has failed (<50% ST-segment resolution at 60-90 minutes) or at any time with hemodynamic/electrical instability or worsening ischemia 1.
NSTEMI Management: Risk-Stratified Approach
Immediate Invasive Strategy (Within 2 Hours)
Proceed immediately to coronary angiography for:
- Refractory angina despite maximal medical therapy 2
- Hemodynamic instability or cardiogenic shock 2
- Life-threatening arrhythmias 2
- Acute heart failure 2
These patients represent STEMI equivalents in terms of pathology and high risk, requiring the same urgency as STEMI 6.
Early Invasive Strategy (Within 24 Hours)
High-risk NSTEMI patients require coronary angiography within 24 hours 2. High-risk is defined as GRACE score >140 or TIMI risk score >4 2.
Approximately 30% of NSTEMI patients have total coronary occlusion and represent a high-risk subgroup that benefits from early intervention 6.
Antithrombotic Therapy for NSTEMI
Dual antiplatelet therapy: aspirin plus P2Y12 inhibitor (clopidogrel, ticagrelor, or prasugrel) 2, 4, 5. Clopidogrel is FDA-approved for NSTEMI patients managed medically or with revascularization 5.
Anticoagulation with unfractionated heparin or low-molecular-weight heparin 2.
Management of Cardiogenic Shock and Heart Failure
Intra-aortic balloon counterpulsation is recommended for STEMI patients when cardiogenic shock is not quickly reversed with pharmacological therapy 1. The IABP serves as a stabilizing measure for angiography and prompt revascularization 1.
Early revascularization (PCI or CABG) is recommended for patients <75 years old with ST elevation or LBBB who develop shock within 36 hours of MI, if revascularization can be performed within 18 hours of shock 1, 2. This is a Class I, Level A recommendation 1.
For patients ≥75 years old with cardiogenic shock, early revascularization is reasonable for selected patients with good prior functional status who agree to invasive care 1.
Rapid volume loading with IV infusion should be administered to patients without clinical evidence of volume overload 1. Correct rhythm disturbances or conduction abnormalities causing hypotension 1.
For pulmonary edema: oxygen supplementation to arterial saturation >90%, morphine sulfate, and ACE inhibitors starting with low-dose short-acting agents (e.g., captopril 1-6.25 mg) unless systolic BP <100 mmHg 1.
Beta-blockers or calcium channel blockers should not be administered acutely to STEMI patients with frank cardiac failure evidenced by pulmonary congestion or signs of low-output state 1.
Long-Term Medical Therapy
Initiate high-intensity statin therapy as early as possible 2. This should begin during the acute hospitalization.
Start beta-blockers orally in patients with heart failure and/or LVEF <40% unless contraindicated 1, 2. This is a Class I recommendation for patients with reduced ejection fraction 1.
Maintenance aspirin 75-100 mg daily indefinitely 1, 2.
Add a proton pump inhibitor (PPI) in combination with DAPT for patients at high risk of gastrointestinal bleeding 1. This is a Class I, Level B recommendation 1.
Diagnostic and Monitoring Recommendations
Routine echocardiography during hospital stay is recommended in all patients to assess LV and RV function, detect early post-MI mechanical complications (ventricular septal rupture, papillary muscle rupture, free wall rupture), and exclude LV thrombus 1, 3.
Intra-arterial monitoring is recommended for management of STEMI patients with cardiogenic shock 1.
Special Populations and Critical Situations
For cardiac arrest with ST-elevation on post-resuscitation ECG, pursue primary PCI strategy 2.
Therapeutic hypothermia is recommended for comatose STEMI patients after out-of-hospital cardiac arrest due to ventricular fibrillation or pulseless ventricular tachycardia 2.
In asymptomatic patients, routine PCI of an occluded infarct-related artery >48 hours after onset of STEMI is not indicated 1. This is a Class III, Level A recommendation—meaning it should not be done 1.
Delayed PCI of a totally occluded infarct artery >24 hours after STEMI should not be performed in asymptomatic patients 1.
For patients on phosphodiesterase-5 inhibitors (e.g., tadalafil), nitrates are absolutely contraindicated for at least 48 hours after the last dose due to risk of severe, potentially fatal hypotension 3. Use morphine for pain control instead 3.
For patients weighing <60 kg on prasugrel, consider lowering the maintenance dose to 5 mg daily due to increased exposure to the active metabolite and increased bleeding risk 4.
Prasugrel is contraindicated in patients with prior TIA or stroke due to higher rates of intracranial hemorrhage 4.
Secondary Prevention and Rehabilitation
Identify all smokers and provide repeated advice on stopping with offers of follow-up support, nicotine replacement therapies, varenicline, and bupropion individually or in combination 1. This is a Class I, Level A recommendation 1.
Participation in a cardiac rehabilitation program is recommended 1. This improves long-term outcomes and quality of life 1.
Critical Pitfalls to Avoid
Never delay ECG acquisition beyond 10 minutes of first medical contact 2. This single delay can result in inappropriate triage and increased mortality.
Do not miss STEMI equivalents on ECG including hyperacute T-waves, true posterior MI, or multilead ST depression with ST elevation in aVR 2. These require the same urgent reperfusion as typical STEMI.
Recognize atypical presentations in women, elderly, and diabetic patients who may present without chest pain 2. These populations frequently have delayed diagnosis and worse outcomes.
Do not overlook high-risk NSTEMI patients who need urgent invasive management within 2 hours 2. Approximately 30% of NSTEMI patients have total coronary occlusion and represent STEMI equivalents 6.
Fondaparinux is not recommended for primary PCI 1. This is a Class III, Level B recommendation 1.
When possible, discontinue prasugrel at least 7 days prior to any surgery due to bleeding risk 4. Do not start prasugrel in patients likely to undergo urgent CABG 4.
Discontinuing DAPT, particularly in the first few weeks after ACS, increases the risk of subsequent cardiovascular events 4. If bleeding occurs, manage without discontinuing antiplatelet therapy if possible 4.