Review Question - QID 104209

This woman with the sudden onset of symptomatic tachycardia has an electrocardiogram demonstrating supraventricular tachycardia. The most appropriate next step in management is administration of intravenous adenosine.

Adenosine is a short-acting AV nodal blocking agent. Rapid administration of 6mg IV adenosine in a stable patient whose electrocardiogram shows SVT may slow the sinus rate, increase AV delay, or cause a transient block in AV conduction. This may terminate an SVT or slow the rate enough to determine the cause of the SVT based on the electrocardiogram (i.e., SA nodal origin vs. atrial origin vs. AV nodal origin). When vagal maneuvers such as carotid massage or Valsalva maneuver fail to terminate an SVT, adenosine is indicated. The ACLS algorith dictates 6mg as the initial dose. If this is not effective, a subsequent dose of 12mg can be given.

Sohinki et al. describe SVT and its management. They note that vagal maneuvers are an appropriate first step in hemodynamically stable SVT. However, such maneuvers have only a 25% success rate. When these fail, the preferred initial agents are adenosine or nondihydropyridine calcium channel blockers.

Diaz-Parra et al. study adenosine use for SVT in a pediatric emergency department. They find that most episodes of SVT require treatment with more than one dose of adenosine and at higher doses than described in clinical guidelines.

Figure A shows an electrocardiogram demonstrating supraventricular tachycardia. Note the narrow QRS complex, absence of discernible P waves, and rate of approximately


Incorrect Answers:
Answer 2: Amiodarone is an anti-arrhythmic medication typically used in the management of atrial fibrillation or wide complex rhythms such as ventricular tachycardia. It is not indicated for the management of supraventricular tachycardias.

Answer 3: Intravenous fluid resuscitation and observation would not be sufficient management for this patient with supraventricular tachycardia. Active intervention is indicated to convert this patient's rhythm.

Answer 4: Intravenous nifedipine is a dihydropyridine calcium channel blocking medication. While non-dihydropyridine calcium channel blockers such as diltiazem may be effective for supraventricular tachycardia, the dihydropyridine class act more prominently on vascular smooth muscle and are not effective in the management of dysrhythmias.

Answer 5: Sedation and synchronized cardioversion would be indicated if this patient were to become hemodynamically unstable, or display other high risk symptoms such as chest pain or altered mental status. However, this patient is hemodynamically stable on presentation and should be managed initially with medication.

Bullet Summary: For patient with supraventricular tachycardia in whom vagal maneuvers have not been effective, the most appropriate next step in management is administration of intravenous adenosine.