# A client admitted 2 days ago for chest pain develops a regular wide-complex tachycardia at 170/min on the monitor. The QRS complexes are uniform in shape. The client is alert, reports palpitations, and denies chest pain or shortness of breath. BP 118/74 mm Hg (baseline 124/78), SpO2 97% on room air, skin warm and dry, capillary refill 2 seconds. Admission QTc was 420 ms; K 4.2 mmol/L and Mg 2.0 mg/dL this morning. A saline lock is in the right hand. Which actions should the nurse anticipate? Select all that apply.

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> subject: Medical Emergencies  
> category: PA

## Question

A client admitted 2 days ago for chest pain develops a regular wide-complex tachycardia at 170/min on the monitor. The QRS complexes are uniform in shape. The client is alert, reports palpitations, and denies chest pain or shortness of breath. BP 118/74 mm Hg (baseline 124/78), SpO2 97% on room air, skin warm and dry, capillary refill 2 seconds. Admission QTc was 420 ms; K 4.2 mmol/L and Mg 2.0 mg/dL this morning. A saline lock is in the right hand. Which actions should the nurse anticipate? Select all that apply.

1

Perform synchronized cardioversion before any drug therapy

2

Start a large-bore IV line in an antecubital vein

3

Prepare adenosine 6 mg rapid IV push followed by a saline flush

4

Obtain a 12-lead ECG while continuous monitoring continues

5

Administer magnesium sulfate 2 g IV over 15 minutes

6

Prepare verapamil 5 mg slow IV push over 2 minutes

## Explanation

The client has no hypotension, altered mental status, shock, ischemic chest pain, or heart failure, so this is a stable wide-complex tachycardia: obtain a 12-lead ECG, and because the rhythm is regular and monomorphic, adenosine through a proximal large-bore IV may be used diagnostically and therapeutically. Immediate synchronized cardioversion is the right action for the unstable presentation, not this one. Verapamil is a narrow-complex SVT drug that can cause collapse if the rhythm is ventricular, and magnesium is for polymorphic VT with a long QT.

## In-depth explanation

Quick answer
Anticipate a 12-lead ECG, adenosine 6 mg rapid push, and a large-bore antecubital IV (options 4, 3, 2).

Why this is correct
First decide stable versus unstable. BP 118/74 near baseline, alert, no chest pain or dyspnea, and warm skin mean no signs of instability, so there is time for a 12-lead ECG to define the rhythm. The AHA adult tachycardia algorithm allows adenosine for a stable wide-QRS tachycardia only when it is regular and monomorphic, which this rhythm is. Adenosine has a half-life of seconds, so it must go through a proximal large vein with a rapid flush; a hand saline lock is too distal.

Easy analogy or mental picture
Think of a fire alarm: if people are collapsing (unstable) you pull everyone out immediately (cardioversion); if everyone is calm (stable) you first check which room the smoke is coming from (12-lead) before choosing the extinguisher.

Memory hook
Unstable = shock it; stable + regular + monomorphic = look (12-lead) and try adenosine.

NCLEX decision rule
In any tachycardia, classify stability first; the same rhythm gets electricity when unstable and diagnostic evaluation plus drugs when stable.

Why the other choices are wrong
Synchronized cardioversion first (option 1) is correct only when the client shows hypotension, altered mental status, shock, ischemic chest pain, or acute heart failure, none of which is present. Verapamil (option 6) is tempting because it treats narrow-complex SVT, but in a wide-complex rhythm that may be ventricular it can cause severe hypotension. Magnesium (option 5) is tempting because it appears in tachycardia protocols, but it is for polymorphic VT (torsades) with a long QT; this rhythm is uniform, the QTc is 420 ms, and the Mg is normal.

References
1American Heart Association: CPR and ECC Algorithms (Adult Tachycardia With a Pulse)Stability assessment, adenosine only for regular monomorphic wide-QRS, cardioversion for unstable
2American Heart Association: CPR and ECC GuidelinesCurrent adult advanced life support recommendations for tachyarrhythmias

## Clinical scenario

Scenario
A monitored client develops a regular monomorphic wide-complex tachycardia at 170/min while alert, normotensive, and without chest pain, dyspnea, or signs of shock.

## Key concepts

- **Wide-complex tachycardia** — A heart rate above 100/min with a QRS duration of 0.12 seconds or more, which may be ventricular or supraventricular with aberrancy.
- **Monomorphic** — QRS complexes of identical shape beat to beat, as opposed to polymorphic complexes that vary, such as torsades de pointes.
- **Signs of instability** — Hypotension, acutely altered mental status, signs of shock, ischemic chest discomfort, or acute heart failure caused by the tachycardia.

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