A nurse is caring for a 75-year-old patient with a history of myocardial infarction being monitored in the cardiac unit. The patient suddenly develops ventricular tachycardia with a heart rate of 160 bpm on the cardiac monitor, remains conscious but complains of lightheadedness and nausea. What is the nurse's priority action?

Synchronized cardioversion is priority for ventricular tachycardia with hemodynamic compromise (chest pain, dizziness) to quickly restore normal rhythm. Other actions (oxygen, ECG, medication) are important but secondary in this unstable situation.

Clinical Context and Priority Setting

The patient is experiencing ventricular tachycardia (VT) with a heart rate of 160 bpm. Although the patient is currently conscious, the presence of lightheadedness and nausea indicates hemodynamic instability due to decreased cardiac output. In the NCLEX-RN framework, the priority is determined by the immediate threat to life and perfusion. A patient with an unstable tachyarrhythmia requires urgent electrical intervention to prevent deterioration into cardiac arrest. The clinical signs of instability—symptomatic hypotension, altered mental status, ischemic chest discomfort, or acute heart failure—dictate the need for immediate synchronized cardioversion, not a stepwise pharmacological approach .

Why Synchronized Cardioversion is the Priority

Synchronized cardioversion delivers a timed electrical shock that corresponds with the QRS complex to avoid the vulnerable T-wave period, which could otherwise precipitate a more lethal rhythm such as ventricular fibrillation. In the case of refractory wide complex tachycardia described in the provided evidence, pharmacological treatment with amiodarone failed to terminate the arrhythmia, and multiple standard synchronized cardioversion attempts were required, ultimately necessitating double sequential synchronized cardioversion . This underscores a critical principle: when a patient exhibits signs of instability, electrical therapy takes precedence over antiarrhythmic drugs, which have a slower onset and carry a proarrhythmic risk. Delaying cardioversion to administer medication or obtain a diagnostic 12-lead ECG allows for progressive clinical deterioration and is not the priority action.

Analysis of Incorrect Options

- Option 1 (Administer oxygen): While supplemental oxygen is an adjunctive measure for a patient with potential myocardial ischemia or hypoxia, it does not address the primary problem of a rapid, perfusing-but-unstable rhythm. Oxygen administration is a supportive intervention, not the definitive treatment for symptomatic VT, and should not delay electrical cardioversion.
- Option 3 (Obtain a 12-lead ECG): A 12-lead ECG is valuable for diagnosing the specific type of wide complex tachycardia, but it is a diagnostic procedure that consumes critical time. In an unstable patient, immediate treatment takes priority over a comprehensive diagnostic workup. The rhythm is already identified on the monitor as VT, and the presence of instability symptoms confirms the need for intervention without waiting for a 12-lead tracing.
- Option 4 (Administer prescribed antiarrhythmic medication): Antiarrhythmic agents such as amiodarone are appropriate for stable VT. However, these medications have a delayed therapeutic effect and carry significant risks, including QT prolongation and proarrhythmia. A case report highlights that combining class III agents like sotalol and amiodarone can lead to life-threatening polymorphic ventricular tachycardia . In the unstable patient, relying on pharmacological therapy exposes the patient to the risk of decompensation while waiting for the drug to take effect. Electrical cardioversion provides immediate rhythm termination, making it the safer and more effective choice.

Pathophysiology and Clinical Reasoning

Ventricular tachycardia at a rate of 160 bpm significantly shortens the diastolic filling time, which reduces stroke volume and cardiac output. This hemodynamic compromise leads to cerebral hypoperfusion, manifesting as lightheadedness, and mesenteric hypoperfusion, causing nausea. The underlying mechanism of VT in a patient with a history of myocardial infarction is often a reentry circuit around a scarred area of myocardium. The evidence from the cardiac MRI case demonstrates that structural abnormalities, even when not apparent on initial echocardiography, can serve as the substrate for malignant ventricular arrhythmias . The electrical shock of synchronized cardioversion depolarizes the entire myocardium simultaneously, interrupting the reentrant circuit and allowing the sinoatrial node to resume its role as the primary pacemaker. This immediate termination of the arrhythmia restores effective cardiac output and reverses the symptoms of instability.