In our experience, propafenone was highly effective and well-tolerated without proarrhythmia or adverse effects in any infants. We feel it should be considered early in the treatment of this uncommon tachycardia. If CAT persists despite propafenone, we would proceed to amiodarone singly or in combination with propafenone. In our experience, all infants were tachycardia-free on 24-hour Holter recording during effective chronic drug therapy. Therapy can be discontinued within 4 to 6 months in most patients. In the absence of structural heart disease, the prognosis of CAT is good with adequate therapy.