Acute Myocardial Infarction: Initial Management Case Study
Clinical Scenario
You're the FY1 on call when a 62-year-old man presents to A&E at 2:15 AM with crushing central chest pain radiating to his left arm, started 45 minutes ago while watching television. He's sweating profusely, looks grey, and tells you he feels like he's going to die. His wife called 999. BP 145/90, HR 98, RR 22, SpO2 94% on room air.
Your Immediate Actions (First 10 Minutes)
Obtain a 12-lead ECG within 10 minutes of arrival—this is your most critical initial step to identify ST-elevation or new left bundle branch block requiring immediate reperfusion therapy. 1
Simultaneous Initial Interventions:
Aspirin 300mg chewable immediately (or 160-325mg if using non-chewable)—this reduces mortality and should never be delayed while awaiting ECG results 2, 1, 3
Oxygen via nasal cannula at 2-4L/min if SpO2 <90% or patient is breathless (this patient is at 94% and breathless, so yes) 2, 1
Sublingual GTN spray (400mcg) or tablet unless systolic BP <90mmHg or HR <50 or >100bpm (this patient's vitals allow it) 2, 1
Establish IV access and draw bloods (troponin, FBC, U&Es, glucose, lipids) 1
Attach continuous cardiac monitoring with defibrillator immediately available at bedside 1
Pain Management (Do Not Delay This)
Administer IV morphine 4-8mg (or diamorphine 2.5-5mg) with IV metoclopramide 10mg as antiemetic—inadequate analgesia increases sympathetic activation and worsens cardiac workload. 2, 1, 3 Titrate with additional 2mg doses every 5 minutes until pain relief achieved. 1
ECG Interpretation & Decision Point
If ST-Elevation ≥1mm in Contiguous Leads or New LBBB:
This patient requires immediate reperfusion therapy with a target "call-to-needle time" of 90 minutes maximum, ideally 60 minutes. 2, 1
Reperfusion Strategy Decision:
Primary PCI is preferred if available within 120 minutes of first medical contact and performed by experienced operators with surgical backup 1, 4
Thrombolytic therapy if PCI unavailable or delayed—greatest benefit within first hour (65 lives saved per 1000 patients) vs 4-6 hours (25 lives saved per 1000) 2, 1
Common thrombolytics: tissue plasminogen activator (tPA), streptokinase, or urokinase administered within 3 hours of symptom onset 3, 4
Critical Contraindications to Check Before Thrombolysis:
- Active bleeding or bleeding disorder
- Recent stroke (<3 months) or intracranial hemorrhage history
- Recent major surgery/trauma (<3 weeks)
- Suspected aortic dissection
- Severe uncontrolled hypertension (>180/110)
Note increased bleeding risk in: elderly >65 years, weight <70kg, hypertension, or when using tPA 1
Additional Medications to Administer
Heparin IV if giving thrombolytics (particularly with tPA) or if large anterior MI with risk of LV thrombus 1
Beta-blocker (e.g., metoprolol 25-50mg PO) unless contraindicated by heart failure, bradycardia, or hypotension 3
ACE inhibitor within 24 hours if no contraindications 3
Statin (high-intensity, e.g., atorvastatin 80mg) should be started immediately 4
If Non-ST Elevation MI (NSTEMI):
- Same initial management (aspirin, oxygen, nitrates, morphine, monitoring) 1
- Add dual antiplatelet therapy: aspirin + ticagrelor 180mg loading dose or clopidogrel 300-600mg 4
- Risk stratify using GRACE score
- Arrange urgent (not emergency) coronary angiography within 72 hours for high-risk patients 4
Critical Pitfalls to Avoid
Delaying ECG beyond 10 minutes—this is the single most important diagnostic test 1
Withholding aspirin while "waiting to be sure"—give it immediately unless clear contraindication 1
Inadequate analgesia—undertreated pain increases sympathetic drive and myocardial oxygen demand 2, 1
Missing the reperfusion window—every 30-minute delay in thrombolysis increases mortality; benefit is time-critical 2, 1
Giving thrombolytics without checking for ST-elevation or contraindications—can cause fatal intracranial hemorrhage 1
Forgetting antiemetic with opioids—vomiting increases vagal tone and can worsen bradycardia 2
Administering nitrates to patients with inferior MI and RV involvement—can cause catastrophic hypotension (check for ST elevation in V4R) 1
Monitoring in First 24 Hours
- Continuous cardiac monitoring—arrhythmias most common in first 24 hours, particularly ventricular fibrillation in first 4 hours 1, 5
- Serial troponins at 0,3,6 hours
- Repeat ECGs if pain recurs
- Monitor for complications: cardiogenic shock, acute mitral regurgitation, VSD, free wall rupture, pericarditis
What Happens Next?
- Transfer to CCU or monitored bed 5
- Echocardiography within 24 hours to assess LV function and complications 1
- Cardiac rehabilitation referral before discharge 2
- Secondary prevention: lifelong aspirin, statin, beta-blocker, ACE inhibitor 4
The key to this case is speed: ECG in 10 minutes, aspirin immediately, adequate analgesia, and reperfusion therapy within 90 minutes. 2, 1 Time is myocardium.