In many reports, the response to intravenous drug therapy was evaluated by EP study rather than in the clinical envi- In the clinical setting, if the diagnosis is uncertain, vagal maneuvers may be attempted to better iden- tify the mechanism of SVT. Digoxin has not been well studied for focalAT. Intravenous class Ic drugs (eg, flecainide, propafenone) may be moder- ately effective in treating focal AT in the acute setting, as reported in earlier, small observational studies, although intravenous forms of IC drugs are not available in the United States. In patients with an implanted cardiac pacing device, it may be possible to perform overdrive pacing through the device, although close monitoring is required to prevent any significant adverse effect, such as pacing-induced AF or other atrial arrhythmias. Equipment should be available to provide support for cardioversion of AF if needed. Ibutilide Contraindicated when QTc >440 ms ; 1 mg over kg); if <60 kg, then 0.01 mg/kg Can repeat 1 mg once, if the arrhythmia does not terminate within QT prolongation, torsades de pointes, AV block Prolonged QT interval History of torsades de pointes Avoid other QT interval prolonging drugs Concurrent administration of high-dose magnesium has been associated with enhanced efficacy and safety119,120 Note: For this reference table, drugs are presented in alphabetical order within the drug classes, not by COR and LOE. *When 1 drug is used in combination with other drugs, appropriate dosing adjustments should be made with consideration of at least additive effects during dosage titration. All potential drug drug interactions are not included in this list. For a more detailed list of drug drug interactions, clinicians should consult additional resources. 