# Stage 3 — Prioritize hypotheses. A 58-year-old client arrived by EMS with substernal pressure unchanged for 45 minutes at rest, spreading down the left arm, with new breathlessness. EMS gave chewable aspirin 324 mg. He smokes (30 pack-years) and has hypertension and hyperlipidemia. BP is 152/94, HR 102 and regular, RR 20, and SpO2 93% on room air (same as his clinic value last month); lungs are clear. His skin is pale, cool, and diaphoretic. The 12-lead ECG obtained 7 minutes after arrival shows ST elevation in II, III, and aVF with reciprocal ST depression in I and aVL, and no PR depression. Troponin is pending. Complete the diagram by selecting the condition the client is most likely experiencing, 2 actions the nurse should take to address that condition, and 2 parameters the nurse should monitor to assess the client's progress.

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> language: en  
> subject: System-Specific Assessments  
> category: ROR

## Question

Stage 3 — Prioritize hypotheses. A 58-year-old client arrived by EMS with substernal pressure unchanged for 45 minutes at rest, spreading down the left arm, with new breathlessness. EMS gave chewable aspirin 324 mg. He smokes (30 pack-years) and has hypertension and hyperlipidemia. BP is 152/94, HR 102 and regular, RR 20, and SpO2 93% on room air (same as his clinic value last month); lungs are clear. His skin is pale, cool, and diaphoretic. The 12-lead ECG obtained 7 minutes after arrival shows ST elevation in II, III, and aVF with reciprocal ST depression in I and aVL, and no PR depression. Troponin is pending. Complete the diagram by selecting the condition the client is most likely experiencing, 2 actions the nurse should take to address that condition, and 2 parameters the nurse should monitor to assess the client's progress.

Condition

Select 1
Acute pericarditis
Non-ST-elevation myocardial infarction
Acute inferior ST-elevation myocardial infarction
Unstable angina

Actions to take

Select 2
Give prescribed sublingual nitroglycerin now
Activate the cardiac catheterization team for PCI
Give prescribed high-dose ibuprofen and colchicine
Apply oxygen at 4 L/min by nasal cannula
Obtain a right-sided ECG with lead V4R

Parameters to monitor

Select 2
Pericardial friction rub on auscultation
Heart rhythm and AV conduction
Erythrocyte sedimentation rate
ST segments on serial ECGs
Fasting lipid panel

## Explanation

Persistent ischemic chest pain with ST elevation in II, III, and aVF and reciprocal depression in I and aVL is an acute inferior STEMI. The catheterization team is activated for primary PCI without waiting for troponin, and a right-sided ECG screens for right ventricular involvement. Serial ST segments show whether reperfusion is occurring, and rhythm and AV conduction are watched because the right coronary artery usually supplies the conduction system.

## In-depth explanation

Quick answer
Acute inferior STEMI. Activate the catheterization team for PCI and obtain a right-sided ECG with V4R. Monitor heart rhythm with AV conduction and ST segments on serial ECGs.

Why this is correct
ST elevation in the inferior leads with reciprocal depression in the high-lateral leads, plus 45 minutes of unrelieved ischemic pain, defines an inferior STEMI, usually from right coronary artery occlusion. Reperfusion by primary PCI is time-critical and does not wait for troponin. The right coronary artery also supplies the right ventricle and the AV node, so right-sided leads and rhythm monitoring are needed.

Easy analogy or mental picture
An inferior STEMI is a blocked water main under the floor of the house: the damage shows in the floor leads (II, III, aVF), with a mirror image on the opposite wall (I, aVL). Calling the plumber (cath lab) cannot wait for the damage report (troponin).

Memory hook
"II, III, aVF up + I, aVL down = inferior STEMI: cath lab now, look right (V4R), watch the rhythm."

NCLEX decision rule
When the ECG shows STEMI, choose immediate reperfusion and complication screening over tests that only confirm what the ECG already shows.

Why the other choices are wrong
Pericarditis causes diffuse concave ST elevation with PR depression and no reciprocal changes, so NSAIDs with colchicine, friction rubs, and ESR target the wrong problem. NSTEMI and unstable angina are defined by the absence of ST elevation, which this ECG has. Nitroglycerin can ease ischemic pain but does not open the artery, and in an inferior STEMI its use depends on the complete ECG assessment and provider direction, so it is not one of the two priority actions now. Oxygen is given for SpO2 below 90%, and this client's 93% matches his baseline. A lipid panel guides secondary prevention later, not the acute response.

References
1Acute ST-Segment Elevation Myocardial Infarction (STEMI) (StatPearls)Inferior STEMI with reciprocal changes needs immediate primary PCI; right-sided leads screen for RV involvement, and continuous rhythm monitoring is required

## Clinical scenario

Case update
The 7-minute ECG shows inferior ST elevation with reciprocal high-lateral depression in a client with persistent ischemic pain.

## Key concepts

- **Reciprocal ST depression** — Mirror-image ST depression in leads opposite an infarct, which supports a true STEMI over pericarditis.
- **Lead V4R** — A right-sided chest lead used to detect right ventricular infarction in inferior MI.
- **Primary PCI** — Emergency catheter-based opening of the blocked coronary artery, the preferred reperfusion for STEMI.

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