What is the usefulness of invasive EP study (without catheter ablation of the accessory pathway) or noninva- sive EP study for predicting arrhythmic events (includ- ing SCD) in patients with asymptomatic pre-excitation? 4. What are the efficacy and effectiveness of invasive EP study with catheter ablation of the accessory pathway as appropriate versus noninvasive tests with treatment (including observation) or no testing/ablation as appro- priate for preventing arrhythmic events (including SCD) and improving outcomes in patients with asymptomatic pre-excitation? Figure 11. Ongoing management of focal atrial tachycardia. Colors correspond to Class of Recommendation in Table 1; drugs listed alpha- betically. Pt indicates patient; and SHD, structural heart disease (including ischemic heart disease). IIb C-LD Oral beta blockers, diltiazem, or verapamil may be reasonable for ongoing management of orthodromic AVRT in patients with pre- excitation on their resting ECG who are not candidates for, or prefer not to undergo, catheter ablation.46,287 See Online Data and 12. 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. 