The purpose of the study is to compare the effectiveness of two different methods of administering adenosine for the treatment of stable supraventricular tachycardia (SVT).

The American Heart Association 2015 guidelines recommend adenosine for non-hypotensive patients with regular narrow complex SVT. Adenosine is usually given as a rapid intravenous bolus of 6mg over 1-2 seconds, followed by a 20ml saline flush. If the first dose does not result in the termination of SVT to normal sinus rhythm (NSR) within 1-2 minutes, a repeat dose of 12mg can be given, and the dose may be repeated one more time, if necessary, for a total of three doses.

The double-syringe technique (DST) is the standard method for administering adenosine. However, recent studies suggest that the single-syringe technique (SST) may be simpler and potentially beneficial. This technique injects adenosine and saline simultaneously at the same time instead of two separate injections. The study aims to determine if the SST method is non-inferior to the DST method.

Inclusion Criteria:

• Age 18 to 80 years
• Presentation to the emergency department with narrow-QRS tachyarrhythmia
• Heart rate ≥150 beats/min
• No visible P wave or presence of retrograde P wave on ECG
• Not responsive to Valsalva maneuvers lasting 15 to 30 seconds
• Requiring adenosine administration

Exclusion Criteria:

• Wide-QRS tachycardia or irregular R-R interval on ECG
• Known allergy or contraindication to adenosine
• Recent ingestion of dipyridamole, carbamazepine, or theophylline
• Caffeine ingestion within the previous 2 hours