Catheter ablation is associated with a success rate of approximately 95% and a 3% risk of major complications when patients are followed up for 6 months to Other documents advise EP study in asymptomatic athletes who engage in moderate- or high-level IIa B-NR SR 4. Observation, without further evaluation or treatment, is reasonable in asymptomatic patients with pre-excitation.301,306 309 See Online Data Supplements 11 15. Most observational cohort studies suggest that the great majority of adult patients with asymptomatic pre-excitation who do not undergo an ablation of the accessory pathway have a benign course with few clinically significant arrhythmic events occurring over time. This supports the recommendation that observation without medical therapy or ablation is a reasonable alternative because the risk of SCD is small and is seen mainly in children.254,301,306 309 The choice to observe asymptomatic patients should be preceded by the patient being informed of the small risk of life-threatening arrhythmias developing in the absence of treatment, along with the success rate and complications associated with catheter ablation of the accessory pathway. Page et al 2015 ACC/AHA/HRS SVT Guideline e539 6.3. Risk Stratification of Symptomatic Patients With Manifest Accessory Pathways: Recommendations 7. Atrial Flutter See Figure 17 for a schematic depicting classification of atrial flutter/ATs; Figure 18 for the algorithm for acute treatment of atrial flutter; and Figure 19 for the algorithm for ongoing management of atrial flutter. 7.1. Cavotricuspid Isthmus Dependent Atrial Flutter Atrial flutter is a macroreentrant atrial arrhythmia character- ized by regular atrial rate and constant P-wave morphology. When the atrial flutter circuit involves the cavotricuspid isth- mus (CTI), it is labeled CTI-dependent atrial flutter. 