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. Thus, oral digoxin should not be used to treat patients with a manifest accessory pathway. Recommendations for Ongoing Management of Orthodromic AVRT (Continued) COR LOE Recommendations 6.2.2. Asymptomatic Patients With Pre-Excitation: Recommendations Recommendations for Management of Asymptomatic Patients With Pre-Excitation COR LOE Recommendations I B-NR SR 1. In asymptomatic patients with pre-excitation, the findings of abrupt loss of conduction over a manifest pathway during exercise testing in sinus rhythm294 297 (Level of Evidence: B-NR) SR or intermittent loss of pre-excitation during ECG or (Level of Evidence: C-LD) SR are useful to identify patients at low risk of rapid conduction over the pathway. C-LD SR See Online Data and 12. Noninvasive testing has been shown to identify patients at low risk of developing rapid conduction over the accessory pathway and life-threatening ventricular arrhythmias in response to AF. The noninvasive findings that identify a pathway not capable of maintaining rapid conduction during AF include intermittent loss of conduction over the accessory pathway on the resting ECG or during ambulatory monitoring, or abrupt loss of pre-excitation during exercise testing (Figure 16).294 297 The ECG should be evaluated closely to make certain the delta wave is truly absent, as accessory pathways, especially left lateral pathways, may demonstrate varying degrees of pre-excitation because of fusion between conduction over the accessory pathway and through the AV node. This may give the appearance of loss of pre-excitation if the subtle delta wave is not identified. Noninvasive tests have an approximately 90% positive predictive value and 30% negative predictive value for identifying pathways with life-threatening properties.294,295,297 IIa B-NR SR 1. 