Successful ablation is often heralded by intraprocedural interruption of the arrhythmia and subsequent EP demonstration of bidirectional block across the ablated tissue. I C-LD Beta blockers, diltiazem, or verapamil are useful to control the ventricular rate in patients with hemodynamically tolerated See Online Data and 17. In some circumstances of persistent atrial flutter or in patients who have infrequent reasonably well-tolerated episodes of atrial flutter, a rate-control strategy may be chosen. In atrial flutter, the relatively slower atrial rate compared with AF often paradoxically results in more rapid AV nodal conduction because there is less concealed AV nodal conduction. Therefore, achieving adequate rate control can be difficult. Higher doses of beta blockers, diltiazem, or verapamil, and often a combination of agents, may be needed to achieve adequate rate control. Beta blockers are generally preferred in patients with heart failure. Avoidance of beta blockers, diltiazem, and verapamil in patients with pre-excited atrial flutter is recommended, given the potential for accelerated ventricular rates degenerating to ventricular fibrillation, as has been reported to occur rarely in similar patients with AF.274 I C-LD Catheter ablation is useful in patients with recurrent symptomatic non CTI-dependent flutter after failure of at least 1 See Online Data and 17. No prospective RCTs have compared the efficacy or safety of antiarrhythmic drugs with that of catheter ablation for non CTI-dependent atrial flutter. In general, catheter ablation of non CTI-dependent atrial flutter is substantially more difficult than ablation of CTI-dependent flutter because the anatomic circuits are complex, are often not anatomically defined, and can be difficult to locate. Knowledge of the prior surgical or ablation approach and detailed activation and entrainment mapping of the tachycardia are useful during attempts at ablation (Table 8). The location of the circuit determines ablation approach and risks. 