IIb C-LD Oral digoxin may be reasonable for ongoing management in patients with symptomatic SVT without pre-excitation who are not candidates for, or prefer not to undergo, catheter ablation.99 See Online Data Supplement 2. Evidence for the use of digoxin is limited. One small study randomized patients with SVT to digoxin (0.375 mg/day), propranolol (240 mg/day), and verapamil (480 mg/day), with 1 week of placebo washout between drug regimens.99 Overall, episodes and duration of SVT (ascertained by diary and weekly 24-h Holter) were similar, and all 3 medications were well tolerated.99 However, the dose of digoxin used was higher than that commonly used in clinical practice today, and in view of the risk of toxicity, digoxin should be reserved for patients who cannot take beta blockers, diltiazem, or verapamil or a class Ic agent (flecainide or propafenone) and must be used with caution in the presence of renal dysfunction. In some clinical studies, digoxin levels >1.2 ng/mL were associated with worse clinical outcomes, while levels <0.8 ng/mL were considered optimal; therefore, caution is advised.116 Recommendations for Ongoing Management of SVT of Unknown Mechanism (Continued) COR LOE Recommendations Page et al 2015 ACC/AHA/HRS SVT Guideline e519 success rates comparable to conventional approaches yet with significant reduction in fluoroscopy times.145 148 2.5.3. Mapping and Ablation With No or Minimal Radiation Fluoroscopy has historically been the primary imaging modal- ity used for EP studies. The use of ionizing radiation puts patient, operator, and laboratory staff at risk of the short- and long-term effects of radiation exposure. Attention to optimal fluoroscopic technique and adoption of radiation-reducing strategies can minimize radiation dose to the patient and oper- ator. 