However, in view of the reported 5% to 10% risk of AV block, catheter ablation is generally reserved for highly symptomatic patients in whom drug therapy has been ineffective or not tolerated (Table 8). Many practitioners use cryoablation as an alternative to radiofrequency ablation.132 Given that it is often difficult to distinguish junctional tachycardia from AVNRT on the ECG, EP study with the goal of ablation may be a helpful diagnostic and potentially therapeutic intervention. Junctional tachycardia may be observed during and after slow-pathway ablation of AVNRT, because of irritation of the compact AV node.406 This iatrogenic junctional tachycardia is transient and generally benign and can be distinguished from AVNRT through pacing maneuvers at EP study.396,405 It is crucial to recognize this phenomenon at the time of EP study because attempts to ablate the junctional tachycardia are unnecessary and could result in AV block. AVNRT. Higher initial doses of adenosine are needed in chil- dren than in adults, with children receiving from 150 mcg/kg Digoxin and propranolol have simi- lar efficacy in infants with SVT without pre-excitation.416 Digoxin is avoided in the presence of pre-excitation because its use in infancy has been associated with SCD or ventricu- Amiodarone, sotalol, propafenone, or flecainide can be used for refractory SVT in infants. In older children presenting with SVT, beta-blocker therapy is most often the initial therapy used. Because of the rare occurrence of adverse events with flecainide, including in patients without structural heart disease, ischemic heart disease, or ventricular dysfunction, flecainide is not used as a first-line medication in Figure 16. Abrupt loss of pre-excitation during exercise testing. During exercise treadmill testing, this patient abruptly lost pre-excitation at a heart rate of 117 bpm. 