When a 12-lead ECG confirms a narrow-complex supraventricular tachycardia with a regular rhythm, what is the appropriate next action?

In the case of a narrow-complex supraventricular tachycardia (SVT) with a regular rhythm, the appropriate next action is to attempt vagal maneuvers. Vagal maneuvers, such as the Valsalva maneuver or carotid massaging, are non-invasive techniques that can help to restore normal heart rhythm by increasing vagal tone, which can temporarily slow down the heart rate or convert the rhythm back to normal.

Using these maneuvers is vital in managing stable SVT because they can effectively interrupt the reentrant circuit responsible for the tachycardia without the immediate need for medication or more aggressive interventions. This approach is often the first-line treatment as it is low-risk and can be performed quickly in a pre-hospital or emergency setting.

The other options—defibrillation, administering IV fluids, and ordering an echocardiogram—are not indicated in this scenario. Defibrillation is typically reserved for cases of life-threatening arrhythmias such as ventricular fibrillation or pulseless ventricular tachycardia, not for stable SVT. IV fluids may be indicated in cases of hypovolemia or to hydrate a patient, but they do not directly address the immediate issue of a tach