If this is ineffective, up to 2 subsequent infusions of 12 mg may be administered. Higher doses of adenosine may be necessary in some cases; safe administration of up to 24 mg has been reported.518 I C-LD Synchronized cardioversion is recommended for acute treatment in pregnant patients with hemodynamically unstable SVT when pharmacological therapy is ineffective or contraindicated.516 See Online Data Supplement 20. Synchronized cardioversion has been reported to be safe at all stages of pregnancy. The electrode pads should be applied such that the energy source and trajectory are directed away from the uterus.519 Fetal monitoring during cardioversion (if time allows) and during the immediate postcardioversion period is recommended.519 Energy dosing for pregnant patients should be the same as in nonpregnant patients.520 9.3.2. Ongoing Management: Recommendations IIa C-LD Intravenous metoprolol or propranolol is reasonable for acute treatment in pregnant patients with SVT when adenosine is ineffective or contraindicated.516 See Online Data Supplement 20. Beta-adrenergic blocking drugs are considered the first-line option for a variety of arrhythmias in pregnancy because there are extensive reports on their safe use from treating a variety of maternal conditions over many decades. A slow infusion would be less likely to cause IIb C-LD Intravenous verapamil may be reasonable for acute treatment in pregnant patients with SVT when adenosine and beta blockers are ineffective or contraindicated.516 See Online Data Supplement 20. Intravenous verapamil has been used effectively for the acute treatment of SVT in pregnant women; however, there is a higher risk of maternal hypotension with intravenous verapamil than with adenosine.516 Reports on diltiazem use for acute SVT termination in pregnancy are more limited than for verapamil, yet similar effects are expected.517 IIb C-LD 2. Intravenous procainamide may be reasonable for acute treatment in pregnant patients with SVT.522 See Online Data Supplement 20. 