Initial Treatment for Supraventricular Tachycardia

Immediate Assessment and Treatment Algorithm

The American College of Cardiology, American Heart Association, and Heart Rhythm Society recommend beginning with vagal maneuvers immediately in all hemodynamically stable patients with SVT, followed by intravenous adenosine if vagal maneuvers fail, and proceeding directly to synchronized cardioversion in any hemodynamically unstable patient 1, 2
If hemodynamically unstable, proceed directly to synchronized cardioversion without attempting vagal maneuvers or medications, as recommended by the American College of Cardiology 1, 2, 3
The American College of Cardiology, American Heart Association, and Heart Rhythm Society recommend vagal maneuvers as Class I, Level B evidence for acute SVT treatment in hemodynamically stable patients 1, 2

The modified Valsalva maneuver is the most effective vagal technique, with significantly higher success rates than standard carotid sinus massage, and is recommended by the American College of Cardiology 1, 2
The technique for the modified Valsalva maneuver involves the patient bearing down against a closed glottis for 10-30 seconds while supine, then immediately lying flat with legs elevated, as described by the American College of Cardiology 1, 2

If vagal maneuvers fail, adenosine is the next intervention, with 90-95% effectiveness for terminating SVT, and is a Class I, Level B recommendation from the American College of Cardiology, American Heart Association, and Heart Rhythm Society 1, 2, 4
Adenosine should be administered as a rapid IV bolus via peripheral line, with electrical cardioversion equipment immediately available, as recommended by the American College of Cardiology 1, 2

The American College of Cardiology, American Heart Association, and Heart Rhythm Society recommend immediate synchronized cardioversion for any hemodynamically unstable patient, and after failed pharmacotherapy in stable patients 1, 2
Synchronized cardioversion should be performed after adequate sedation/anesthesia in stable patients, as recommended by the American College of Cardiology 2

The American College of Cardiology warns against using AV nodal blocking agents in patients with wide-complex tachycardia or known accessory pathways, as these can precipitate ventricular fibrillation 3
The American College of Cardiology recommends avoiding verapamil and diltiazem in patients with systolic heart failure, and wide-complex tachycardia of uncertain etiology, due to the risk of hemodynamic collapse 4, 3

The American Heart Association recommends immediate synchronized cardioversion with an initial biphasic energy of 50-100 J for hemodynamically unstable patients with SVT, and to increase the dose stepwise if the initial shock fails 5
The American College of Cardiology suggests alternative vagal maneuvers, such as carotid sinus massage, for hemodynamically stable patients with SVT 5

The American Heart Association recommends a 6 mg rapid IV push of adenosine through a large peripheral vein, followed by a 20 mL saline flush, for hemodynamically stable patients with SVT, with a success rate of 90-95% for AVNRT and orthodromic AVRT 5
The American College of Cardiology advises adenosine dosing adjustments, including reducing to 3 mg for patients taking dipyridamole, carbamazepine, or with transplanted heart, and larger doses may be needed with theophylline, caffeine, or theobromine 5
The American Heart Association warns that adenosine is contraindicated in asthma patients, as it can cause severe bronchoconstriction, and to always have resuscitation equipment available when administering adenosine 5

The American College of Cardiology notes that automatic tachycardias, such as ectopic atrial tachycardia, multifocal atrial tachycardia, and junctional tachycardia, are not responsive to cardioversion and require rate control with AV nodal blocking agents 5