Show Explanatory Sources

This patient has a regular narrow-complex tachycardia (ie, supraventricular tachycardia [SVT]) causing hemodynamic instability with hypotension and signs of poor perfusion (cold extremities).  Common causes of regular narrow-complex tachycardia include sinus tachycardia, atrial tachycardia, atrial flutter (can be regular or irregular), atrioventricular reentrant tachycardia (AVRT), and atrioventricular nodal reentrant tachycardia (AVNRT).

All patients with persistent tachyarrhythmia, either narrow or wide complex, causing hemodynamic instability (eg, severe hypotension, signs of shock, ischemic chest discomfort, mental status changes, acute pulmonary edema) should undergo immediate synchronized cardioversion due to the risk of rapid clinical deterioration.  Synchronized cardioversion involves delivering an electric shock synchronized to the QRS complex.  Whenever possible, awake and alert patients should receive adequate sedation and analgesia (eg, midazolam and fentanyl) prior to cardioversion.

In patients with a regular narrow-complex tachycardia who are hemodynamically stable, adenosine or vagal maneuvers (eg, Valsalva maneuver, squatting) can be considered.  However, these interventions would not be appropriate in this patient who is hemodynamically unstable.

(Choices A and D)  Amiodarone is typically the drug of choice for hemodynamically stable patients with monomorphic ventricular tachycardia, and procainamide is the drug of choice for hemodynamically stable patients with preexcited atrial fibrillation (both wide-complex tachycardias).  These antiarrhythmic drugs can worsen hypotension and should not supercede cardioversion as the first step in a hemodynamically unstable patient.

(Choice B)  Intravenous beta blockers (eg, metoprolol, esmolol) or nondihydropyridine calcium channel blockers (eg, verapamil, diltiazem) are commonly used for attempted rate control of rapid atrial fibrillation or flutter.  They are also sometimes used for attempted rate control of other forms of SVT that are refractory to initial therapy.  However, these drugs should not be used in patients with hemodynamic instability.

(Choice C)  Intravenous fluid resuscitation can improve blood pressure transiently.  However, it does not resolve the underlying cause of hypotension and may unnecessarily delay definitive management.

(Choice F)  Unsynchronized cardioversion (defibrillation), which provides a high-energy shock at a random point in the cardiac cycle, is used during cardiac arrest in patients who have a shockable rhythm (ie, ventricular fibrillation, pulseless ventricular tachycardia).  Administering an unsynchronized shock in other circumstances (eg, in this patient with a pulse who has a regular narrow-complex tachycardia) is not appropriate as it can induce ventricular fibrillation.

Educational objective:
Patients with persistent tachyarrhythmia (narrow or wide complex) causing hemodynamic instability with a pulse should undergo immediate synchronized cardioversion.