A prospective observational study suggests that an initial 12 mg of adenosine improves conversion rates without increased side effects.
Context
For hemodynamically stable patients with regular narrow-complex supraventricular tachycardia (SVT), current guidelines recommend 6 mg of adenosine as the initial pharmacological treatment, followed by 12 mg if the first dose fails to achieve rhythm conversion. However, retrospective studies consistently show better first-dose conversion rates when 12 mg is initially used instead of 6 mg.
In the first prospective observational study to examine this issue, researchers enrolled 142 hemodynamically stable adults with electrocardiography-confirmed SVT who presented to a single emergency department (ED) in Turkey. Patients received either an initial intravenous bolus of 6 mg or 12 mg of adenosine at the clinicians’ discretion.
Key Results
- The first-dose conversion rate was significantly higher with 12 mg than 6 mg (83% vs. 52%; number needed to treat, 4), and the benefit persisted in a matched cohort.
- The 12-mg group had fewer SVT recurrences during the ED stay (1% vs. 10%), but the difference did not reach statistical significance (P=0.06).
- Adverse effects occurred at similar rates in the two groups.
Comment
This study adds to mounting evidence suggesting that an initial 12 mg of adenosine improves conversion rates in SVT without increasing adverse effects. Until randomized data are available, clinicians might consider an initial 12-mg dose in selected patients, such as those with a history of SVT who have failed an initial 6-mg dose. Although not evaluated in this study, starting with 12 mg may also improve the patient’s experience: Given the transient but unpleasant side effects of adenosine, many patients would likely choose one brief episode of discomfort over two.