What is the immediate management of acute myocardial infarction (AMI) at home or outside a medical facility?

Immediate Management of Acute Myocardial Infarction at Home or Outside a Medical Facility

Call emergency services (112 or 911) immediately—do not attempt self-transport, as ambulances equipped with defibrillators and trained personnel significantly improve survival, particularly during the critical early phase when cardiac arrest is most likely. 1

Critical First Actions (Before EMS Arrives)

Patient Positioning and Initial Assessment

• Have the patient sit or lie down in a comfortable position to reduce cardiac workload 2
• Do not leave the patient unattended—the most critical period for cardiac arrest is the very early phase 1
• If trained, assess for signs of cardiac arrest and be prepared to initiate CPR if the patient becomes unresponsive 2

Immediate Medication Administration

• Administer aspirin 160-325 mg orally immediately (chewed for faster absorption) unless the patient has a known aspirin allergy 2, 1
• Give sublingual nitroglycerin (0.4 mg tablet or spray) if available, unless systolic blood pressure is below 90 mmHg or heart rate is below 50 or above 100 beats per minute 2, 1
• Nitroglycerin can be repeated every 5 minutes up to 3 doses total if chest pain persists and blood pressure remains adequate 2
• Do not give oxygen unless the patient appears severely short of breath or cyanotic—routine oxygen in non-hypoxic patients may be harmful 1, 3

Pain Management

• If you are a healthcare provider with access to opioids, administer intravenous morphine (2.5-5 mg) or diamorphine (2.5-5 mg) titrated against pain with an antiemetic such as metoclopramide 10 mg IV 2, 1
• If IV access is unavailable, intramuscular administration is acceptable 2

Emergency Medical Services Response

What EMS Should Provide

• Immediate 12-lead ECG acquisition and interpretation (or transmission to hospital) within 10 minutes of arrival to identify ST-segment elevation or new left bundle branch block 2, 1
• Continuous cardiac monitoring with defibrillator immediately available 2, 1
• Oxygen only if oxygen saturation is below 90% 1, 3
• Additional aspirin if not already given 2, 1
• Sublingual or IV nitroglycerin for ongoing chest pain (if blood pressure permits) 2
• IV opioid analgesia (morphine or nalbuphine) with antiemetic 2, 1

Critical Time Targets

• EMS should minimize time at the scene—advanced skills must not prolong on-scene time 2
• Direct transport to a PCI-capable hospital if ST-elevation is identified, bypassing the emergency department to go straight to the catheterization laboratory 2
• Total time from emergency call to reperfusion therapy (call-to-needle or call-to-balloon) should be under 90 minutes, with 60 minutes being ideal 2, 1

Pre-Hospital Thrombolytic Therapy Considerations

When to Consider Pre-Hospital Thrombolysis

• If transport time to a PCI-capable facility exceeds 120 minutes and the patient has clear ST-elevation on ECG, pre-hospital thrombolytic therapy by trained physicians or paramedics can save substantial time and reduce mortality 2
• This requires ECG confirmation of ST-segment elevation ≥1 mm in contiguous leads or new left bundle branch block 2
• Recording an ECG before giving thrombolysis is an important safeguard—patients with normal ECGs or isolated ST-depression should not receive thrombolytics 2

Contraindications to Check Before Thrombolysis

• Active bleeding or known bleeding disorder 2
• Recent major surgery or trauma 2
• History of intracranial hemorrhage or stroke 2
• Severe uncontrolled hypertension 2

Transport Decisions

Hospital Selection

• Transport directly to a hospital with 24-hour emergency cardiac care capability and PCI facilities if transport time is reasonable 2, 4
• Critically ill patients (cardiac arrest, repetitive ventricular arrhythmias, severe bradycardia, or shock) should be taken to a tertiary hospital with catheterization and cardiac surgery facilities even if this requires slightly longer transport time 2
• Do not transport to a physician's office—go directly to the hospital 4, 3

For General Practitioners at the Scene

• Stay with the patient until the ambulance arrives 2
• Request an emergency (999/911) response rather than an "urgent" response to ensure the next available emergency ambulance attends 2
• Administer opioid analgesia (diamorphine up to 5 mg or morphine up to 10 mg IV) with antiemetic (metoclopramide 10 mg) 2
• Give aspirin and nitroglycerin as described above 2
• In rural settings with prolonged transport times, consider initiating thrombolytic therapy before transfer if trained and protocols are in place 2, 3

Critical Pitfalls to Avoid

Common Mistakes That Delay Treatment

• Do not wait for the patient's private physician—prolonged consultation efforts are inappropriate if they delay specific therapy 2
• Do not delay treatment for insurance authorization or administrative procedures 4, 3
• Do not send the patient home or to a clinic for evaluation—symptoms may represent life-threatening MI even if they seem atypical 1
• Do not give routine oxygen to non-hypoxic patients—this may increase myocardial injury 3

Recognizing Atypical Presentations

• Be alert for atypical symptoms, particularly in elderly patients, women, and diabetics: throat pain, jaw pain, neck pain, isolated fatigue, dyspnea, or syncope without chest pain can all represent MI 1
• Severe epigastric pain or unexplained indigestion should trigger immediate ECG and MI protocol activation 4, 3

Medication Cautions

• Avoid nitroglycerin in patients with suspected right ventricular infarction (often seen with inferior wall MI)—it can cause profound hypotension 3
• Do not give beta-blockers or calcium channel blockers in the pre-hospital setting if there are signs of heart failure, bradycardia, or heart block 3
• Morphine may delay absorption of oral antiplatelet agents, but pain relief remains a priority 3

Expected Outcomes Based on Treatment Timing

Time-Dependent Mortality Benefit

• Treatment within the first hour ("golden hour") saves 65 lives per 1,000 patients treated 1
• Treatment in hours 2-3 saves 27 lives per 1,000 patients 1
• Treatment within 6 hours provides maximum benefit, with definite benefit extending to 12 hours 4
• Treatment beyond 12 hours offers little benefit in most patients unless there is evidence of ongoing ischemia 4