Vagal maneuvers should be performed with the patient in the supine position. Patients can be taught to perform a Valsalva maneuver by forcefully exhaling against a closed airway for 10 to 30 seconds, equivalent to at least 30 Another vagal maneuver based on the classic diving reflex consists of applying an ice-cold, wet towel to the face.85 IIa B-R Flecainide or propafenone is reasonable for ongoing management in patients without structural heart disease or ischemic heart disease who have symptomatic SVT and are not candidates for, or prefer not to undergo, catheter ablation.45,46,107 112 See Online Data Supplement 2. Several RCTs have demonstrated the efficacy of daily therapy with propafenone (450 mg/day to 900 mg/day) or flecainide (100 mg/day to 300 mg/day) to prevent recurrences of SVT in symptomatic patients.45,46,107 112 In 1 RCT, the probability of 12 months of effective (defined as <2 attacks of arrhythmia) and safe treatment was 86% for propafenone and 93% for flecainide.109 However, flecainide and propafenone have a risk of proarrhythmia in patients with structural heart disease or ischemic heart disease, so these drugs are contraindicated in these patient groups.113 These drugs, though often effective, have potential side effects and as such should be reserved for patients for whom beta blockers, diltiazem, or verapamil are ineffective or cannot be prescribed. I B-NR Synchronized cardioversion is recommended for acute treatment in patients with hemodynamically stable SVT when pharmacological therapy is ineffective or contraindicated.87,95 See Online Data and 10. Synchronized cardioversion is highly effective in terminating SVT (including AVRT and AVNRT), and when the patient is stable, this is performed after adequate sedation or anesthesia.94 Most stable patients with SVT respond to pharmacological therapy, with conversion success rates of 80% to 98% for agents such as verapamil, diltiazem, or adenosine. 