The ability to promptly perform electrical cardioversion must be available should AF with rapid ventricular conduction occur. Before intravenous beta blockers, diltiazem, and verapamil were available, intravenous digoxin was commonly used for acute treatment of patients with orthodromic AVRT who had pre-excitation on their resting ECG270 ; this agent is rarely used now because other agents are available and digoxin may put patients at risk of ventricular fibrillation.271 III: Harm C-LD Intravenous digoxin, intravenous amiodarone, intravenous or oral beta blockers, diltiazem, and verapamil are potentially harmful for acute treatment in patients with pre-excited AF.269,271 275 See Online Data and 12. Patients with pre-excited AF should not receive intravenous digoxin, intravenous amiodarone, or intravenous/oral beta blockers, diltiazem, or verapamil because these medications may enhance conduction over the accessory pathway, increase the ventricular rate, and increase the risk of provoking a life-threatening ventricular arrhythmia.269,271 275 Digoxin increases the ventricular rate by shortening refractoriness of the accessory pathway, whereas amiodarone, beta blockers, diltiazem, and verapamil may increase the ventricular rate as a result of drug- induced hypotension with increased catecholamines. In addition, these medications may enhance conduction over the accessory pathway by slowing or blocking conduction through the AV node, preventing competitive concealed retrograde conduction into the accessory pathway. Recommendations for Acute Treatment of Orthodromic AVRT (Continued) COR LOE Recommendations Recommendations for Ongoing Management of Orthodromic AVRT COR LOE Recommendations I B-NR 1. Catheter ablation of the accessory pathway is recommended in patients with AVRT and/or pre-excited AF.103,254,276 282 See Online Data and 12. Several large series support the use of catheter ablation of the accessory pathway as first-line therapy in patients who have had AF and/or AVRT. These series report a success rate of approximately 93% to 95% and a 3% risk of major complications when patients are followed up (Table 8). 