What is the treatment for myocardial infarction (heart attack)?

Treatment of Myocardial Infarction

Immediate reperfusion therapy is the cornerstone of myocardial infarction treatment: primary percutaneous coronary intervention (PCI) if achievable within 90-120 minutes, or fibrinolytic therapy if PCI cannot be performed within this timeframe, as this reduces mortality by 21% when initiated early. 1

Immediate Emergency Response (First 10 Minutes)

Time is myocardium—every minute of delay increases mortality. The greatest benefit occurs when treatment begins within the first hour of symptom onset, saving 65 lives per 1000 patients treated, compared to only 25 lives per 1000 when treatment starts 4-6 hours later. 2

Initial Actions Upon Patient Contact:

• Obtain 12-lead ECG within 10 minutes to identify ST-segment elevation ≥1 mm in contiguous leads or new left bundle branch block 3, 1
• Administer aspirin 160-325 mg orally immediately while awaiting ECG results—do not wait for confirmation 2, 1
• Give sublingual nitroglycerin for chest pain relief (not a substitute for opioid analgesia) 2, 1
• Provide oxygen via nasal prongs if hypoxemia is present 3, 1
• Establish continuous cardiac monitoring with defibrillator immediately available 3, 1

Pain Management:

• Administer intravenous diamorphine (up to 5 mg) or morphine sulfate (up to 10 mg) titrated against residual pain using small repeated doses 2
• Give intravenous antiemetic (metoclopramide 10 mg) routinely with opioids 2

Reperfusion Strategy Decision (Within 90 Minutes of First Medical Contact)

The "call-to-needle time" target is 90 minutes maximum, though 60 minutes is ideal for patients with readily diagnosed acute myocardial infarction. 2

Primary PCI (Preferred Method):

• Choose primary PCI if it can be performed within 90 minutes of first medical contact by experienced personnel 3, 1
• For high-risk patients (including anterior MI), transfer immediately to PCI-capable facility even if it means bypassing closer hospitals 3
• Administer unfractionated heparin, loading dose of aspirin, and prasugrel or ticagrelor for primary PCI 1

Fibrinolytic Therapy (When PCI Unavailable):

• Initiate fibrinolysis within 10 minutes of STEMI diagnosis if primary PCI cannot be performed within 120 minutes from first medical contact 1
• Thrombolytic treatment should be given within 90 minutes of alerting medical services in the absence of contraindications 2
• Administer enoxaparin, loading dose of aspirin, and clopidogrel 75 mg daily with fibrinolysis 1
• Pre-hospital thrombolysis by trained general practitioners is feasible and shows substantial time savings compared to in-hospital administration 2

Critical Caveat:

Do not give thrombolytics to patients with normal ECG or isolated ST-segment depression—these patients show no significant benefit and may be harmed. Only patients with ST-segment elevation or left bundle branch block benefit. 2

First 24-48 Hours Management

Intravenous Medications:

• Start intravenous nitroglycerin for 24-48 hours if no hypotension, bradycardia, or excessive tachycardia present 2, 3
• Begin early intravenous beta-blocker therapy followed by oral therapy if no contraindications (heart failure, hypotension, bradycardia) 2, 3
• Initiate anticoagulation with intravenous heparin, particularly for large anterior MI at high risk for left ventricular mural thrombus 3

Monitoring and Complications:

• Observe closely for recurrent chest pain, heart failure, and arrhythmias 2
• For recurrent ischemic chest pain: give intravenous nitroglycerin, analgesics, and antithrombotic medications (aspirin, heparin), then consider coronary angiography with revascularization 2
• For heart failure: administer intravenous furosemide and afterload-reducing agents 2
• For cardiogenic shock: insert intra-aortic balloon pump and perform emergency coronary angiography followed by PTCA or CABG 2
• For right ventricular infarction with hypotension: treat vigorously with intravascular volume expansion using normal saline and inotropic agents 2

Special Consideration for Anterior MI:

Anterior myocardial infarctions carry higher risk for left ventricular dysfunction, heart failure, and mural thrombus formation. 3 Perform echocardiography to evaluate LV function and detect complications. 3

Long-Term Medical Therapy (Indefinite Duration)

All patients require lifelong medical therapy to prevent recurrent events and reduce mortality:

• Aspirin 160-325 mg daily indefinitely 2, 3, 1
• Dual antiplatelet therapy (DAPT) for one year 1
• Beta-blocker therapy for minimum 6 weeks (ideally indefinitely) 2, 3, 1
• ACE inhibitor at selected dose, especially for anterior MI or left ventricular dysfunction 2, 3, 1

Lipid Management:

• For LDL cholesterol >130 mg/dL despite diet, initiate drug therapy with goal of reducing LDL to <100 mg/dL 2
• Instruct patients on diet low in saturated fat and cholesterol 2

Risk Stratification Before Discharge

Perform standard exercise testing before hospital discharge:

• Submaximal testing at 4-7 days or symptom-limited testing at 10-14 days 2
• This assesses functional capacity, evaluates medical regimen efficacy, and stratifies risk for subsequent cardiac events 2

Rehabilitation and Secondary Prevention

• Smoking cessation is essential—this is non-negotiable 2
• Achieve ideal body weight 2
• Participate in formal cardiac rehabilitation program 2
• Engage in 20 minutes of brisk walking exercise at least three times weekly 2

Critical Pitfalls to Avoid

Patient delay is the most critical time loss—40% of patients delay hospital presentation for more than 6 hours after symptom onset. 4 Advanced age, female sex, absence of chest discomfort, and symptom onset during evening/early morning hours (6 PM to 6 AM) are associated with prolonged delay. 4 Women ≥65 years have 2.39-fold higher odds of delaying >2 hours compared to all other patient groups. 5

Do not wait for cardiac biomarkers before initiating reperfusion therapy—blood sampling for serum markers should be done routinely but results should not delay treatment. 2

Calcium channel blockers have not been shown to reduce mortality in acute MI and may be harmful in certain patients—they are not recommended as routine therapy. 2