What is the management plan for a patient with myocardial infarction (MI), including medical therapy, reperfusion therapy, and secondary prevention measures?

Management of Myocardial Infarction

For ST-elevation myocardial infarction (STEMI), primary percutaneous coronary intervention (PCI) performed within 90-120 minutes of first medical contact is the definitive reperfusion strategy that reduces mortality and morbidity, with fibrinolytic therapy reserved only when PCI cannot be achieved within this timeframe. 1, 2

Initial Diagnosis and Immediate Actions

First Medical Contact (Within 10 Minutes)

• Obtain and interpret a 12-lead ECG within 10 minutes of first medical contact to identify ST-segment elevation ≥1 mm in contiguous leads or new left bundle branch block 1, 2
• Initiate continuous ECG monitoring with defibrillator capacity immediately 1, 2
• Administer aspirin 160-325 mg orally (chewable preferred) or 250-500 mg IV if unable to swallow as soon as possible—this is a Class I recommendation that reduces mortality 1, 2
• Provide supplemental oxygen only if oxygen saturation is <90%; routine oxygen in non-hypoxemic patients is not recommended 1
• Administer sublingual nitroglycerin for chest pain relief unless systolic blood pressure <90 mmHg or heart rate <50 or >100 bpm 1
• Give adequate analgesia with morphine sulfate or meperidine for pain control 1

Reperfusion Strategy Selection

Primary PCI (Preferred Strategy)

Primary PCI is the gold standard when it can be performed by an experienced team within 90-120 minutes of STEMI diagnosis 1, 2. The 2017 ESC guidelines emphasize this narrow time window because mortality benefit diminishes significantly with delays beyond 120 minutes.

Key logistical requirements:

• Transfer patients directly to the catheterization laboratory, bypassing the emergency department entirely 1
• PCI-capable centers must provide 24/7 service without delay 1
• Use radial artery access as the standard approach (reduces bleeding complications) 1, 2
• Implant drug-eluting stents routinely 1, 2
• Avoid routine thrombus aspiration or deferred stenting—these are contraindicated 1, 2

Fibrinolytic Therapy (When PCI Delayed)

If primary PCI cannot be performed within 120 minutes of STEMI diagnosis, initiate fibrinolytic therapy immediately, preferably in the pre-hospital setting 1, 2. This is particularly critical within the first 6 hours of symptom onset, where thrombolysis saves 35 lives per 1000 patients treated versus only 16 lives per 1000 when given 7-12 hours after symptom onset 1.

Fibrinolytic protocol:

• Use a fibrin-specific agent: tenecteplase (preferred for single bolus dosing), alteplase, or reteplase 1, 2
• Administer aspirin 160-325 mg orally or IV 1, 2
• Add clopidogrel 300 mg loading dose, then 75 mg daily 1, 2
• Provide anticoagulation with enoxaparin IV followed by subcutaneous (preferred over unfractionated heparin) or weight-adjusted unfractionated heparin bolus followed by infusion 1
• Continue anticoagulation until revascularization or for duration of hospital stay up to 8 days 1, 2
• Transfer all patients to a PCI-capable center immediately after fibrinolysis 1

Post-fibrinolysis management:

• Perform rescue PCI immediately if fibrinolysis fails (<50% ST-segment resolution at 60-90 minutes) or if hemodynamic/electrical instability develops 1
• Perform angiography with PCI of the infarct-related artery between 2-24 hours after successful fibrinolysis 1

Critical contraindication: Patients without ST-segment elevation should not receive thrombolytic therapy 1

Antithrombotic Therapy During Primary PCI

Antiplatelet Therapy

Administer a potent P2Y12 inhibitor before or at the time of PCI 1:

• Prasugrel 60 mg loading dose (preferred in most patients) or
• Ticagrelor 180 mg loading dose (preferred in patients with prior cerebrovascular disease or age ≥75 years) 3, 2
• Clopidogrel 300-600 mg loading dose only if prasugrel and ticagrelor are unavailable or contraindicated 1

The 2017 ESC guidelines strongly favor prasugrel or ticagrelor over clopidogrel because clopidogrel's effectiveness depends on CYP2C19 metabolism, and patients who are CYP2C19 poor metabolizers (2-14% of the population) form less active metabolite and have reduced antiplatelet effects 4. However, prasugrel should be avoided in patients with prior stroke or TIA due to increased bleeding risk 3.

Anticoagulation

• Unfractionated heparin 100 U/kg IV bolus (60 U/kg if glycoprotein IIb/IIIa inhibitors used) 2
• Enoxaparin or bivalirudin are acceptable alternatives 1
• Fondaparinux is contraindicated for primary PCI 1, 2

In-Hospital Management (First 24-48 Hours)

Monitoring and Risk Stratification

• Monitor continuously for at least 24 hours for arrhythmias and mechanical complications 1
• Perform routine echocardiography during hospitalization to assess left and right ventricular function, detect mechanical complications (papillary muscle rupture, ventricular septal defect, free wall rupture), and exclude left ventricular thrombus 2
• Limit physical activity for at least 12 hours 1

Medical Therapy

Continue dual antiplatelet therapy (DAPT):

• Aspirin 75-100 mg daily indefinitely 2
• Prasugrel 10 mg daily or ticagrelor 90 mg twice daily for 12 months unless excessive bleeding risk develops 1, 2

Initiate high-intensity statin therapy immediately:

• Target LDL-C <70 mg/dL (<1.8 mmol/L) or ≥50% reduction from baseline 3, 2

Start beta-blocker therapy:

• Administer IV beta-blocker within first 24 hours if no contraindications, followed by oral therapy 1
• Particularly important in patients with heart failure or LVEF <40% 2

Initiate ACE inhibitor within 24 hours:

• Indicated for patients with heart failure, LV systolic dysfunction, diabetes, or anterior infarction 1, 2

Nitroglycerin infusion:

• Continue IV nitroglycerin for 24-48 hours, titrating to blood pressure and heart rate 1

Anticoagulation for specific indications:

• Administer IV heparin followed by subcutaneous therapy in patients with large anterior MI or LV mural thrombus on echocardiography to prevent embolic stroke 1
• Consider anticoagulation for patients with anteroapical akinesis or dyskinesis 2

Special Situations

Cardiogenic shock:

• Perform emergency angiography and PCI immediately regardless of time from symptom onset 2
• Consider intra-aortic balloon pump or alternative left ventricular assist devices for hemodynamic support 2
• Consider PCI of non-infarct-related arteries during the index procedure 1

Cardiac arrest with STEMI:

• Proceed with primary PCI strategy in patients with ST-elevation on post-resuscitation ECG 1
• Initiate targeted temperature management early in patients who remain unresponsive after resuscitation 1
• Do not use pre-hospital cooling with rapid infusion of large volumes of cold IV fluid 1

Recurrent chest pain:

• Treat presumed pericarditis with high-dose aspirin 650 mg every 4-6 hours 1
• For suspected recurrent ischemia, administer IV nitroglycerin, analgesics, and antithrombotic medications (aspirin, heparin), and consider urgent coronary angiography with revascularization 1

Secondary Prevention and Long-Term Management

Antiplatelet Therapy

• Continue aspirin 75-100 mg daily indefinitely 1, 2
• Maintain DAPT (aspirin plus P2Y12 inhibitor) for 12 months after PCI unless contraindications develop 1, 2
• Add proton pump inhibitor in patients at high risk of gastrointestinal bleeding (history of GI bleeding, peptic ulcer disease, dual antiplatelet therapy with anticoagulation) 2

Lipid Management

• Continue high-intensity statin therapy with target LDL-C <70 mg/dL or ≥50% reduction if baseline LDL-C is 70-135 mg/dL 2
• Obtain fasting lipid profile within 24 hours of presentation 2

Lifestyle Modifications

• Provide smoking cessation counseling with pharmacological support 2
• Recommend cardiac rehabilitation program participation—this is a strong Class I recommendation that improves quality of life and reduces recurrent events 2
• Counsel on diet low in saturated fat and cholesterol, with goal of achieving ideal body weight 1

Risk Stratification Before Discharge

• Perform submaximal exercise testing at 4-7 days or symptom-limited testing at 10-14 days to assess functional capacity, evaluate medical regimen efficacy, and stratify risk for subsequent cardiac events 1
• Consider noninvasive testing for ischemia before discharge in patients who have not had coronary angiography and do not have high-risk clinical features 2

Critical Pitfalls to Avoid

• Never delay primary PCI to obtain additional imaging or consultations—time is myocardium 1
• Do not administer thrombolytic therapy to patients without ST-segment elevation—this increases bleeding risk without mortality benefit 1
• Avoid routine oxygen therapy in non-hypoxemic patients (SaO2 ≥90%)—this provides no benefit 1
• Do not use clopidogrel as first-line P2Y12 inhibitor when prasugrel or ticagrelor are available—these newer agents provide superior outcomes 1
• Avoid concomitant use of clopidogrel with omeprazole or esomeprazole—these significantly reduce clopidogrel's antiplatelet activity through CYP2C19 inhibition 4
• Do not perform routine PCI of an occluded infarct-related artery >48 hours after symptom onset in asymptomatic patients—this is contraindicated 1
• Avoid calcium channel blockers for acute MI management—they have not been shown to reduce mortality and may be harmful in certain patients 1
• Do not use glucocorticoids or NSAIDs for post-MI pericarditis—these are contraindicated 2

Special Population Considerations

Patients with renal insufficiency or elderly patients:

• Pay special attention to dose adjustments of antithrombotic medications 1
• Consider lower intensity DAPT regimens if bleeding risk is excessive 2

Patients on chronic oral anticoagulation:

• Minimize duration of triple antithrombotic therapy (warfarin + aspirin + P2Y12 inhibitor) to limit bleeding risk 2
• Consider 14 days of triple therapy for fibrinolysis patients, then transition to warfarin plus single antiplatelet agent 2
• Target INR 2.0-2.5 (lower than usual) when combining warfarin with DAPT 2

MINOCA (Myocardial Infarction with Non-Obstructive Coronary Arteries):

• Perform additional diagnostic tests to identify etiology (coronary spasm, spontaneous coronary artery dissection, thromboembolism, takotsubo cardiomyopathy) 1
• Tailor therapy based on underlying cause, which may differ from typical STEMI management 1
• Avoid intensified clopidogrel dosing in MINOCA patients—a post-hoc analysis showed possible harm with double-dose clopidogrel (HR 3.57) compared to standard dosing in this population 5