14.4 Acute Coronary Syndrome

Acute coronary syndrome (ACS) is a plaque event until you prove a mimic, and a destination decision before it is a drug mnemonic. Domain 4.B.1 of the August 2026 Board of Certification for Emergency Nursing (BCEN) Certified Flight Registered Nurse (CFRN) outline tests ACS because Dalton's law steals coronary oxygen on climb and because the wrong pad cannot open the artery. Get a 12-lead, start the reperfusion clock, put defibrillator pads on, and fly to percutaneous coronary intervention (PCI).

ST-elevation versus non-ST-elevation ACS

Twelve-lead, right-sided, and posterior walls

ST-elevation myocardial infarction (STEMI) is ST elevation in two contiguous leads, or a recognized equivalent, plus a compatible story. It is an immediate reperfusion disease. Non-ST-elevation ACS (NSTE-ACS) is non-ST-elevation myocardial infarction (NSTEMI) plus unstable angina: ischemia without persistent ST elevation. High-risk NSTE-ACS—ongoing pain, instability, dynamic ST depression, shock—still belongs in a catheterization laboratory, not a clinic observation chair.

Record the 12-lead before you congratulate yourself on a “normal” three-lead. Add right-sided and posterior leads when the inferior or posterior wall is in play. V4R is the right-ventricular lead. V7–V9 catch posterior infarction that looks like ST depression and a tall R wave in V1–V3. A missed posterior STEMI is a missed reperfusion clock.

MONA is outdated as a bundle

Morphine, oxygen, nitroglycerin, aspirin (MONA) is a historical packing list, not a protocol. Treat each item on its own merits.

PDE5 timing is a sending-history question: sildenafil-type drugs in about the last 24 hours, tadalafil-type drugs in about the last 48 hours. That is emergency-cardiology teaching, not a BCEN statute. If the last dose is unknown and the patient is hypotensive, do not add nitroglycerin to find out.

Inferior ST elevation plus hypotension is RV infarct until the right-sided lead or the receiving cardiologist says otherwise. The stiff RV needs preload. Give fluids, not nitroglycerin and not morphine that drops venous return. Clear lungs and jugular venous distention with inferior elevation are the cabin clue. Chapter 9 already sorted this as cold-and-dry right-sided failure; here you prevent the nitroglycerin that creates that shock.

Reperfusion clock, sending drugs, and pads

First medical contact to a laboratory that can open the artery

STEMI is a system clock: first medical contact to balloon, or a planned fibrinolytic strategy only when PCI cannot be reached in time and the sending team has already chosen that path. Do not invent prehospital lytics in a rotor that is twenty minutes from a catheterization laboratory. NSTE-ACS still has a clock when the patient is unstable.

Heparin and a P2Y12 inhibitor (clopidogrel, ticagrelor, prasugrel) follow the sending physician and receiving interventionalist. Do not double-load a second agent because a pocket card says so. Confirm what was given, when, and whether the receiving laboratory wants a drip continued.

Put defibrillator pads on before lift. The cabin is a terrible place to find skin under a packaged torso while the patient is in ventricular fibrillation. The aircraft must have a working defibrillator; if it does not, you are not a STEMI platform. Watch for ventricular fibrillation, ventricular tachycardia, and sudden complete heart block in an inferior infarct. Rhythm lectures live in Chapter 15.2; the flight habit is pads on and a charged plan.

Cabin hypoxia, shock, and the chapters this hands off to

Dalton's law drops the partial pressure of inspired oxygen (PIO2) as cabin altitude rises even if fraction of inspired oxygen (FiO2) is unchanged. A coronary that is already two-thirds occluded does not tolerate a 6,000-foot climb on room air. Raise FiO2 or request a lower cabin. Treat shivering and uncontrolled pain because they waste oxygen, but do not treat pain with automatic morphine.

If the pump fails—cool, wet, hypotensive, narrow pulse pressure—you have left uncomplicated ACS and entered cardiogenic shock. That physiology, the first pressor, and the wet-versus-dry sort are Chapter 9. If drugs cannot restore output, mechanical circulatory support (MCS)—intra-aortic balloon pump (IABP), Impella, extracorporeal membrane oxygenation (ECMO)—is Chapter 15. Recognize the need early enough to call a PCI or MCS center before you lift toward a clinic.

• Get a 12-lead, including V4R and posterior leads when inferior or posterior wall ischemia is possible.
• Give aspirin if it has not been given; give oxygen only if hypoxic; give nitroglycerin only if pressure, RV, and PDE5 history allow.
• Inferior plus hypotensive means fluids, not nitroglycerin.
• Pads on; continue sending heparin or P2Y12 rather than freelance a second load.
• Fly to PCI; hand shock to Chapter 9 and devices to Chapter 15; raise FiO2 because altitude steals coronary oxygen.

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