One RCT supports the use of verapamil for prevention of orthodromic AVRT in patients with pre-excitation on their resting ECG (manifest There are no RCTs supporting the use of oral beta blockers or diltiazem for prevention of recurrent AVRT, although clinical experience suggests the drugs are effective, with a favorable side effect profile.287 Patients with pre-excitation may develop AF during an episode of AVRT and be exposed to increased risk of rapid conduction over the accessory pathway while receiving beta blockers, diltiazem or verapamil, so these agents must be used with caution.269 The decision to treat with these agents should follow a discussion of risks with the patient. Although evidence of poor anterograde conduction via the accessory pathway may be reassuring, rapid conduction in AF has been described even in the setting of intermittent anterograde conduction.291 IIb C-LD Oral digoxin may be reasonable for ongoing management of orthodromic AVRT in patients without pre-excitation on their resting ECG who are not candidates for, or prefer not to undergo, catheter ablation.292 See Online Data Supplement 12. One small study reported the usefulness of oral digoxin in prevention of recurrent orthodromic AVRT in patients without pre-excitation on their resting ECG (concealed accessory pathway).293 Digoxin has been used clinically for many years, but the low efficacy indicates its use would be best limited to patients who are not candidates for catheter ablation or prefer pharmacological therapy and have failed to respond to other antiarrhythmic drugs. III: Harm C-LD Oral digoxin is potentially harmful for ongoing management in patients with AVRT or AF and pre-excitation on their resting ECG.271 See Online Data Supplement 12. Digoxin shortens the refractory period of the accessory pathway, such that AF may induce ventricular fibrillation.271 Even if AF has never been documented, AVRT may degenerate into AF. 