Pharmacology in Emergency MedicineHigh-Dose Adenosine for Treatment of Refractory Supraventricular Tachycardia in an Emergency Department of an Academic Medical Center: A Case Report and Literature Review

BackgroundSymptomatic tachycardia is a common admission diagnosis in the emergency department (ED). This can be a life-threatening condition and requires immediate attention. Supraventricular tachycardia (SVT) is commonly treated with adenosine, and successful treatment is limited to atrioventricular (AV) node-dependent SVTs as adenosine causes a transient heart block. However, there are limited data available for instances when the recommended dosing regimen (6 mg, 12 mg, 12 mg) fails to terminate SVT.Case ReportA 33-year old man was evaluated in the ED with an electrocardiogram revealing a regular narrow complex tachycardia with a heart rate of 180 beats/min and a rhythm consistent with SVT. He reported experiencing 3 days of fatigue, myalgias, palpitations, and dyspnea on exertion, but was otherwise hemodynamically stable. Attempts at chemical cardioversion with standard doses of adenosine (6 mg, 12 mg, and 12 mg) were given without success. After consultation with the cardiology service, additional doses of 24 mg and then 36 mg of adenosine were administered. The last dose of 36 mg produced sustained conversion and return to a normal sinus rhythm. The patient later underwent radiofrequency ablation of a left-sided orthodromic reciprocating accessory pathway. After 3 months of medical management, the patient had an implantable cardiac defibrillator placed for prevention of sudden cardiac death.Why Should an Emergency Physician Be Aware of This?Each case of SVT demands immediate attention from an emergency physician. It is imperative that providers be aware of the limitations of adenosine and when it may be appropriate to deviate from standard dosing recommendations. This is in addition to collaborating with an expert in cardiac electrophysiology when initial management tactics are not successful.