If pharmacological therapy is inefective or contraindicated, the merican College of Cardiology and the merican Heart Association recommend synchronized cardioversion in pregnant women with hemodynamically unstable SVT (Page, 2015). And although electrical cardioversion with standard energy settings is not contraindicated in pregnancy, vigilance is important. Barnes and colleagues (2002) described a case in which direct current cardioversion led directly to a sustained uterine contraction and fetal bradycardia. As an aside, pregnancy has no efect on the operation of implantable cardioverter-defibrillator devices (Boule, 2014).
If cardioversion fails or is unsafe because of concurrent thrombus, then long-term anticoagulation and heart rate control with medication are necessary (DiCarlo-1eacham, 2011). Other treatment options recommended by the American College of Cardiology and the American Heart Association (Page, 2015) include:
Intravenous metoprolol or propranolol when adenosine is inefective or contraindicated
Intravenous verapamil when adenosine and 3-blocking agents are inefective or contraindicated
Intravenous amiodarone with potentially life-threatening SVT and when other therapies are inefective or contraindicated.
Pregnancy may predispose otherwise asymptomatic women with WoffParkinson-White (WP) syndrome to exhibit arrhythmias. In a study of 25 women who had SVT diagnosed before pregnancy, three of 12 women with WPW syndrome and six of 13 without the condition developed SVT during pregnancy (Pappone, 2003). In some patients, accessory pathway ablation may be indicated. Driver and coworkers (2015) have provided a review.
This form of arrhythmia is uncommon in healthy young women without underlying heart disease. Brodsky and associates (1992) described seven pregnant women with new-onset ventricular tachycardia and reviewed 23 reports. Most of these women were not found to have structural heart disease. In 14 cases, tachycardia was precipitated by physical exercise or psychological stress. Abnormalities found included two cases of myocardial infarction, two of prolonged QT interval, and one of anesthesia-provoked tachycardia. They concluded that pregnancy events precipitated the tachycardia and recommended 3-blocking agents for control. As previously discussed (p. 964), arrhythmogenic right ventricular dysplasia will result occasionally in ventricular tachyarrhythmias (Lee, 2006). If unstable, emergency cardioversion is indicated, and standard adult energy settings are adequate Qeejeebhoy, 2011; Lin, 2015).
This conduction anomaly may predispose individuals to a potentially fatal ventricular arrhythmia known as torsades de pointes (Roden, 2008) . Two studies comprised of 502 pregnant women with long QT syndrome both reported a signiicant increase in cardiac events postpartum but not during pregnancy (Rashba, 1998; Seth, 2007). The normal rise in heart rate during pregnancy may be partially protective. Paradoxically, 3-blocking agents-preferably propranolol-lower the risk of torsades de pointes in patients with long QT syndrome and should be continued throughout pregnancy and the puerperium (Enriquez, 2014; Seth, 2007). Importantly, many medications, including some used during pregnancy such as azithromycin, erythromycin, and clarithromycin, may predispose to QT prolongation (Ray, 2012; Roden, 2004).