# Situation: A 70-year-old woman with rheumatic heart disease is in the coronary care unit. An echocardiogram shows moderate mitral stenosis. She has had palpitations for about 4 days, and the monitor shows atrial fibrillation (AF) with a ventricular rate of 150–160/min. She has not been taking an anticoagulant. At 14:00 her blood pressure is 94/58 mmHg (earlier 112/70 mmHg). She is newly confused about where she is and reports pressure in her chest. The rhythm is unchanged. Which intervention should the nurse prepare for?

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> url: https://mymerci.kr/pages/nclex_q.php?qn_id=630023  
> 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 70-year-old woman with rheumatic heart disease is in the coronary care unit. An echocardiogram shows moderate mitral stenosis. She has had palpitations for about 4 days, and the monitor shows atrial fibrillation (AF) with a ventricular rate of 150–160/min. She has not been taking an anticoagulant.

At 14:00 her blood pressure is 94/58 mmHg (earlier 112/70 mmHg). She is newly confused about where she is and reports pressure in her chest. The rhythm is unchanged. Which intervention should the nurse prepare for?

## 보기

1. Three weeks of anticoagulation, then elective cardioversion
2. Transesophageal echocardiogram before any cardioversion
3. An intravenous diltiazem bolus for rate control
4. Synchronized cardioversion right away **✔ 정답**

**정답: 4**

## 해설

Instability is judged by signs of poor perfusion, not by a single systolic cut-off: acute altered mental status and ischemic chest discomfort make this rapid AF unstable even though the systolic pressure is above 90 mmHg. An unstable tachycardia with a pulse is treated with immediate synchronized cardioversion. The rule of anticoagulating for 3 weeks, or excluding atrial thrombus by transesophageal echocardiogram, applies to planned cardioversion of AF lasting 48 hours or more in a stable client.

## 심화 해설

Unstable tachycardia: the decision is about perfusion, not a single blood pressure number

The client has rapid atrial fibrillation with a ventricular rate of 150–160/min. The key change is not the rate itself—it is that she has become hemodynamically unstable. Her blood pressure fell from 112/70 mmHg to 94/58 mmHg, and she now has acute altered mental status plus ischemic chest discomfort. Instability in tachyarrhythmia is defined by signs of poor end-organ perfusion, not by an absolute systolic cutoff such as 90 mmHg. A confused patient with chest pressure and a falling pressure is showing evidence that the brain and myocardium are not being adequately perfused.

The underlying mechanism explains why rapid AF becomes dangerous. In atrial fibrillation, the atria quiver rather than contract effectively, so the normal “atrial kick” that contributes to late diastolic ventricular filling is lost. When the ventricular rate is very high, diastolic filling time shortens further, stroke volume drops, and cardiac output falls. In a patient with rheumatic mitral stenosis, this is even more problematic: the stenotic mitral valve already limits left ventricular filling, so the combination of lost atrial contraction and a short diastolic interval severely compromises forward flow. The result is hypotension, cerebral hypoperfusion, and myocardial ischemia—exactly what this client is demonstrating.

Key point! For an unstable tachycardia with a pulse, the treatment is immediate synchronized cardioversion. Synchronization means the shock is delivered on the R wave to avoid the vulnerable period of the cardiac cycle, which reduces the risk of precipitating ventricular fibrillation. This is a time-sensitive intervention; the goal is rapid restoration of an organized rhythm so that atrial contraction and adequate ventricular filling can resume.

The other options describe appropriate steps for a stable patient with atrial fibrillation lasting 48 hours or longer. In that situation, the concern is that a thrombus may have formed in the left atrial appendage because of stasis from ineffective atrial contraction. Cardioversion in the presence of an atrial thrombus can dislodge the clot and cause a stroke. Therefore, stable patients are either anticoagulated for 3 weeks before elective cardioversion, or they undergo a transesophageal echocardiogram (TEE) to rule out atrial thrombus immediately before cardioversion. Those precautions do not apply when the patient is unstable, because the immediate threat of cardiovascular collapse outweighs the thromboembolic risk. The 3-week anticoagulation rule and the TEE-first strategy are for planned cardioversion in a stable client, not for emergency cardioversion in an unstable one.

Intravenous diltiazem for rate control is also a reasonable intervention in atrial fibrillation, but it is appropriate for a stable patient. Rate control lowers the ventricular response gradually and allows time for anticoagulation decisions. In an unstable patient, waiting for pharmacologic rate control delays definitive treatment and may allow further deterioration. The priority is synchronized cardioversion.

| Feature | Stable AF | Unstable AF |
| --- | --- | --- |
| Perfusion status | Adequate; no acute altered mental status, chest pain, or shock | Poor perfusion: confusion, ischemic chest pain, hypotension, signs of shock |
| Immediate treatment | Rate control (e.g., diltiazem, beta-blocker) or rhythm control with anticoagulation precautions | Immediate synchronized cardioversion |
| Anticoagulation before cardioversion | Required if AF lasts 48 hours or more: 3 weeks of anticoagulation or TEE to exclude thrombus | Not required before emergency cardioversion; thromboembolic risk is addressed after stabilization |
| Priority | Prevent thromboembolism and control symptoms | Restore perfusion and prevent cardiac arrest |

Watch out! A systolic pressure above 90 mmHg does not automatically mean the patient is stable. The nurse must assess the whole clinical picture—mental status, chest pain, urine output, skin perfusion, and trend of blood pressure. This client’s pressure is falling and she has new neurologic and cardiac symptoms, which makes her unstable despite the number being above the classic threshold. Rapid AF with a pulse and any sign of hemodynamic compromise is a synchronized cardioversion scenario.

## 임상 시나리오

Unstable Tachycardia: Immediate Synchronized CardioversionPerfusion signs, not a single BP number, drive the decision
In rapid atrial fibrillation with a ventricular rate of 150–160/min, instability is defined by signs of poor end-organ perfusion—acute altered mental status, ischemic chest discomfort, falling blood pressure—not by an absolute systolic cutoff such as 90 mmHg.

For an unstable tachycardia with a pulse, the intervention is immediate synchronized cardioversion. The shock is timed to the QRS complex to avoid the vulnerable T wave period.

The 3-week anticoagulation rule or transesophageal echocardiogram to exclude atrial thrombus applies only to planned cardioversion of AF lasting 48 hours or more in a stable client.

CautionDo not delay cardioversion for anticoagulation or echocardiogram when the client is unstable. Mitral stenosis worsens hemodynamic compromise because the stenotic valve already limits left ventricular filling, and the loss of atrial kick further reduces stroke volume.

## 핵심 개념

- **Unstable tachycardia** — Tachyarrhythmia causing signs of poor end-organ perfusion such as altered mental status, ischemic chest discomfort, hypotension, or shock; treated with immediate synchronized cardioversion when a pulse is present.
- **Synchronized cardioversion** — Delivery of a shock timed to the QRS complex to terminate unstable tachyarrhythmias with a pulse, avoiding the vulnerable T wave period.
- **Atrial fibrillation** — Chaotic atrial electrical activity causing loss of effective atrial contraction and irregularly irregular ventricular rhythm; rapid ventricular rates reduce diastolic filling time and cardiac output.
- **Mitral stenosis** — Narrowing of the mitral valve orifice that impedes left ventricular filling; exacerbates hemodynamic compromise during rapid atrial fibrillation.
- **Atrial kick** — Contribution of atrial contraction to late diastolic ventricular filling; lost in atrial fibrillation, reducing stroke volume especially at high heart rates.

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