Inferior STEMI With Hypotension and Bradycardia
At 14:20, a 61-year-old male is brought to your ambulance by his wife after 45 minutes of crushing substernal chest pain radiating to the jaw and both shoulders. He is pale, diaphoretic, and nauseated. He has a history of hypertension and an ulcer but no prior myocardial infarction. Vital signs: BP 92/58, HR 52 and regular, RR 20, SpO2 96% on room air, glucose 8.1 mmol/L. He is alert but anxious. A 12-lead ECG shows 2 mm ST elevation in leads II, III, and aVF, 1 mm ST depression in I and aVL, and a PR interval that is progressively lengthening before a dropped beat. You carry aspirin, nitroglycerin, fentanyl, atropine, and a pacing-capable monitor. The PCI center is 25 minutes away; the nearest ED is 8 minutes away but has no cath lab.
1. Interpret the ECG and identify the most dangerous medication for this patient.
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The ECG shows an acute inferior STEMI, likely with right ventricular involvement, plus second-degree AV block of the Wenckebach type. The most dangerous medication is nitroglycerin: in right ventricular infarction and hypotension, nitrates reduce preload and can cause profound hypotension or cardiac arrest. Avoid morphine for the same reason and because it may worsen bradycardia; fentanyl is a better analgesic. Give aspirin 300 mg chewed if there is no allergy, oxygen only if SpO2 is below 94%, and establish IV access. Do not give beta-blockers. The bradycardia and hypotension should first be treated with a fluid bolus because right ventricular output is preload-dependent.
2. How do you manage the hypotension and bradycardia?
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Give a 250 mL isotonic crystalloid bolus and reassess; repeat up to 500-1000 mL if there are signs of right ventricular failure and no pulmonary edema. For symptomatic bradycardia, give atropine 0.5 mg IV every 3-5 minutes to a maximum of 3 mg. If atropine fails or the patient becomes unstable, start transcutaneous pacing at 60-70 per minute and titrate to perfusion; sedation for pacing is difficult in hypotension, so use cautious fentanyl. If pacing is ineffective and the patient is peri-arrest, follow the cardiac arrest protocol. Avoid nitrates and diuretics. Reassess blood pressure after each intervention and watch for pulmonary edema, which would make further fluids dangerous.
3. Where should he go, and is prehospital fibrinolysis indicated?
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Transport to the PCI center 25 minutes away because primary PCI is the preferred reperfusion strategy and the nearest ED cannot provide it. Prehospital fibrinolysis is not indicated when PCI can be achieved within 120 minutes and there are no contraindications; it would also be risky with his age and ulcer history. Notify the PCI center en route with the ECG, vital signs, and treatments. If he arrests, follow ACLS and consider the nearest ED. Aspirin and fentanyl can be given en route; do not delay transport for on-scene procedures.