# Situation: A 62-year-old man arrives at the emergency department of a provincial hospital with 2 hours of crushing chest pain. The 12-lead electrocardiogram (ECG) shows ST elevation in leads II, III and aVF. The hospital has no cardiac catheterization laboratory, and the nearest center that performs percutaneous coronary intervention (PCI) is 4 hours away by ambulance. His pain continues. Blood pressure is 104/66 mmHg (baseline 112/70 mmHg), heart rate 64/min, and he denies taking any erectile dysfunction drug. A right-sided ECG shows ST elevation in lead V4R. Sublingual nitroglycerin 0.4 mg is ordered. What should the nurse do?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=630021  
> language: ko  
> subject: Nursing Practice V — Care of Clients with Maladaptive Patterns of Behavior; Care of Clients with Life-Threatening Conditions, Acute Multi-Organ Problems, High Acuity and Emergency Situations

## 문제

Situation: A 62-year-old man arrives at the emergency department of a provincial hospital with 2 hours of crushing chest pain. The 12-lead electrocardiogram (ECG) shows ST elevation in leads II, III and aVF. The hospital has no cardiac catheterization laboratory, and the nearest center that performs percutaneous coronary intervention (PCI) is 4 hours away by ambulance.

His pain continues. Blood pressure is 104/66 mmHg (baseline 112/70 mmHg), heart rate 64/min, and he denies taking any erectile dysfunction drug. A right-sided ECG shows ST elevation in lead V4R. Sublingual nitroglycerin 0.4 mg is ordered. What should the nurse do?

## 보기

1. Give intravenous morphine in place of the nitroglycerin
2. Hold the dose and report the right-sided lead findings **✔ 정답**
3. Give the dose, since his systolic pressure is above 90 mmHg
4. Give the dose after raising his legs to support venous return

**정답: 2**

## 해설

ST elevation in V4R with an inferior infarction indicates right ventricular infarction. The right ventricle then depends on preload, and nitrates can cause severe hypotension, so nitroglycerin is held even though the systolic pressure is above 90 mmHg. The nurse reports the finding so that the physician can adjust therapy.

## 심화 해설

Clinical reasoning

Inferior-wall ST elevation in leads II, III, and aVF points to an acute inferior myocardial infarction. The additional finding of ST elevation in lead V4R on a right-sided ECG is the key discriminator: it indicates that the infarction extends into the right ventricle. In right ventricular infarction, the right ventricle loses its ability to pump effectively, so left ventricular filling becomes highly dependent on venous return, or preload. Nitroglycerin is a venodilator that reduces preload. In this setting, even a modest reduction in preload can sharply lower cardiac output and trigger severe hypotension. The patient’s current systolic pressure of 104 mmHg does not make nitrate administration safe, because the danger is not the absolute number but the vulnerable preload-dependent state of the right ventricle. The correct nursing action is to hold the nitroglycerin and promptly report the V4R finding so the provider can adjust therapy.

Why “systolic above 90 mmHg” is not enough

A common exam trap is to apply the usual nitrate safety rule—give nitroglycerin if systolic blood pressure is above 90 mmHg. That rule applies to left ventricular infarction without right ventricular involvement. In right ventricular infarction, the physiology changes. The right ventricle is stiff and failing, so it cannot compensate for reduced venous return. Nitroglycerin lowers preload, which further reduces right ventricular output, which then reduces left ventricular filling and systemic blood pressure. The result can be a rapid, difficult-to-reverse hypotensive episode. Therefore, the blood pressure threshold is overridden by the right-sided ECG finding.

Why the other options are incorrect

Option 1 suggests substituting intravenous morphine for nitroglycerin. Morphine may be used for ongoing ischemic chest pain, but it is not a replacement for nitroglycerin in this decision pathway, and it carries its own risk of hypotension and respiratory depression. The immediate priority is not to choose another vasoactive drug but to recognize the contraindication and communicate it. Option 3 gives the nitroglycerin based only on the systolic pressure, ignoring the right ventricular infarction. Option 4 proposes raising the legs to support venous return before giving nitroglycerin. Although leg elevation can transiently increase preload, it does not neutralize the vasodilatory effect of nitroglycerin and is not a safe workaround. Watch out! Nitrate administration in right ventricular infarction is a preload-removal maneuver in a preload-dependent state; no positioning trick makes it safe.

Evidence from the literature

A systematic review and meta-analysis examined adverse events from nitrate administration during right ventricular myocardial infarction [1]. The review notes that both the American Heart Association and European Society of Cardiology guidelines recommend avoiding nitrates when right ventricular infarction is present because decreasing preload in the setting of already compromised right ventricular ejection fraction may reduce cardiac output and precipitate hypotension. The meta-analysis pooled data from newer studies totaling 1050 patients and found that the topic merits systematic review because the original cohort study underlying the recommendation was small. The clinical implication remains consistent with the guideline stance: nitrates are held when right ventricular infarction is identified. A general pharmacologic treatment review similarly emphasizes that nitroglycerin carries a risk of hypotension in right ventricular infarction and is contraindicated in patients taking sildenafil [2]. In this scenario, the patient denies erectile dysfunction drug use, so the sildenafil contraindication is not the issue; the right ventricular infarction itself is the reason to withhold the drug.

Nursing priority and exam focus

The nursing priority is safety. The nurse must recognize that a right-sided ECG finding changes the pharmacologic plan. Key point! In inferior MI with V4R elevation, hold nitroglycerin regardless of systolic blood pressure, because the right ventricle is preload-dependent. The nurse should report the finding before giving the ordered dose. This is a classic licensure examination scenario that tests whether the candidate can override a routine order when a new assessment finding creates a contraindication. The correct sequence is: recognize the right ventricular infarction, hold the nitrate, and communicate the finding to the provider.References (research sources)

- [1]Adverse events from nitrate administration during right ventricular myocardial infarction: a systematic review and meta-analysis.Meta-analysis/systematic reviewWilkinson-Stokes M, Betson J, Sawyer S (2023) · DOI: 10.1136/emermed-2021-212294

- [2]General pharmacologic treatment of acute myocardial infarction.Research articleShannon AW, Harrigan RA (2001) · DOI: 10.1016/s0733-8627(05)70192-9

## 임상 시나리오

Nitroglycerin in Right Ventricular InfarctionHold nitrates when V4R shows ST elevation
Inferior MI with ST elevation in V4R indicates right ventricular infarction. The RV becomes preload dependent, so any reduction in venous return can cause severe hypotension.

Nitroglycerin is a venodilator that lowers preload. Even with systolic BP above 90 mmHg, it is held in RV infarction because the risk is not the absolute BP but the vulnerable preload state.

CautionDo not apply the usual nitrate safety rule for left ventricular MI. In RV infarction, nitroglycerin can sharply reduce cardiac output and trigger profound hypotension. Report the V4R finding immediately.

## 핵심 개념

- **Right Ventricular Infarction** — Myocardial infarction involving the right ventricle, often complicating inferior MI, characterized by preload dependence and risk of hypotension with nitrates.
- **V4R Lead** — A right-sided precordial ECG lead used to detect right ventricular involvement; ST elevation in V4R is highly suggestive of RV infarction.
- **Preload** — The degree of ventricular stretch at end-diastole; RV infarction makes cardiac output heavily dependent on maintaining adequate preload.
- **Nitroglycerin** — A venodilator that reduces preload; contraindicated in RV infarction due to risk of profound hypotension.

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