Recommendations for Management of Symptomatic Patients With Manifest Accessory Pathways COR LOE Recommendations I B-NR 1. In symptomatic patients with pre-excitation, the findings of abrupt loss of conduction over the pathway during exercise testing in (Level of Evidence: B-NR) or intermittent loss of pre-excitation during ECG or ambulatory monitoring297 (Level of Evidence: C-LD) are useful for identifying patients at low risk of developing rapid conduction over the pathway. C-LD See Online Data Supplements 11 15. An important consideration in the evaluation of patients with pre-excitation is determining 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 incapable 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.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, which 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- If noninvasive evaluation suggests that the accessory pathway conducts poorly in the anterograde direction, although risk of life-threatening events is likely lower, the EP study still may be useful because of patient symptoms. I B-NR 2. An EP study is useful in symptomatic patients with pre-excitation to risk-stratify for life-threatening arrhythmic events.254,256,298 300 See Online Data Supplements 11 15. 