Intravenous procainamide may be reasonable for acute treatment in pregnant patients with SVT.522 See Online Data Supplement 20. Intravenous procainamide has been used safely to treat a variety of maternal and fetal supraventricular and ventricular arrhythmias and can be effective when used for acute conversion.517,522 Procainamide is generally best avoided as long-term therapy because it can cause a lupus- like syndrome, unless other options are contraindicated or ineffective. IIb C-LD Intravenous amiodarone may be considered for acute treatment in pregnant patients with potentially life-threatening SVT when other therapies are ineffective or contraindicated.517,523 See Online Data Supplement 20. Although intravenous amiodarone has been administered safely during pregnancy, multiple adverse effects to the fetus have also been An important concern is the possibility of fetal hypothyroidism, reported in approximately 17% of cases.517,523 With an intravenous infusion for short-term use, side effects would be less of a concern, given that most toxicities are related to cumulative drug dose. Recommendations for Acute Treatment of SVT in Pregnant Patients (Continued) COR LOE Recommendations Recommendations for Ongoing Management of SVT in Pregnant Patients COR LOE Recommendations IIa C-LD The following drugs, alone or in combination, can be effective for ongoing management in pregnant patients with highly symptomatic SVT: See Online Data Supplement 20. If possible, antiarrhythmic drugs should be avoided in the first trimester, when risk of congenital malformations is greatest. Almost no reports exist on the use of newer antiarrhythmic drugs (such as dofetilide) during pregnancy, yet their use may be justified if the benefits outweigh the risk. The lowest recommended dose should be used initially, with dose adjustments made according to clinical response. 