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9.3 Pregnancy

Pregnancy may confer an increased susceptibility to a variety of arrhythmias, even in the absence of underlying heart disease.513 Pregnancy is also associated with an increased risk of arrhythmia exacerbation, such as more frequent and refractory tachycardia episodes, in patients with a pre-existing arrhythmic substrate.514 An important consideration is that adverse maternal and fetal outcomes have been reported as a result of SVT in pregnancy.515 Although there is potential toxicity to the fetus with certain pharmacological and nonpharmacological therapies, safe options exist to allow for treating most cases of maternal SVT effectively. The literature on therapeutic options for the management of arrhythmias in pregnancy is generally limited to single case reports or small series and favors the use of older antiarrhythmic agents because of more abundant reports on the safe use of these drugs. Experience with use of drugs in pregnancy also comes from treating a variety of maternal and fetal conditions, not maternal SVT alone. Although all medications have potential side effects to both the mother and the fetus at any stage of pregnancy, if possible, drugs should be avoided in the first trimester, when risk of congenital malformations is greatest. The lowest recommended dose should be used initially, accompanied by regular monitoring of clinical response.

9.3.1 Acute Treatment: Recommendations

IIb B-NR 2.  Oral dofetilide may be reasonable for prevention of recurrent AT or atrial flutter in ACHD patients.447,474,487,488

See Online Data Supplement 20. Two small observational studies on the use of oral dofetilide for ACHD patients report a high rate of acute conversion of AT or atrial flutter, with longer-term efficacy of the drug (defined by either complete suppression or partial improvement of symptoms) ranging from 70% to 85%. The benefit was tempered by an association with torsades de pointes in 10%.471,484 Although many patients continued to experience recurrence, these episodes were better tolerated and were of limited duration.471,484 Because of the potential risk of proarrhythmia, dofetilide is usually a second-line medication after failure of beta blockers and sotalol. Initiation of oral dofetilide is recommended during 72-hour inpatient monitoring. IIb B-NR 3.  Amiodarone may be reasonable for prevention of recurrent AT or atrial flutter in ACHD patients for whom other medications and catheter ablation are ineffective or contraindicated.447

See Online Data Supplement 20. An observational study reported efficacy of amiodarone in maintaining sinus rhythm, although side effects were noted frequently, including thyroid disorders or AV block.447 The risk of significant side effects increases with chronic use and with higher dosages; using the minimal effective chronic dosage is recommended. Observational studies reported thyroid disorders in 13% to 36% of ACHD patients receiving amiodarone; risk factors for thyrotoxicosis include female sex, cyanotic heart disease, low body mass index, prior Fontan procedure, or dosages >200 mg daily.511,512 Amiodarone is recommended for short-term use or for patients for whom alternative therapy is not an option for prevention of recurrent AT. III: Harm B-NR 1.  Flecainide should not be administered for treatment of SVT in ACHD patients and significant ventricular dysfunction.419

See Online Data Supplement 20. There are no RCTs on the use of flecainide in ACHD patients and ventricular dysfunction. One retrospective study collected data on 579 young patients, 369 of whom received flecainide for the treatment of SVT. Efficacy for the treatment of SVT was 71%. Among 12 patients with cardiac arrest while receiving flecainide for SVT, 8 had congenital heart disease, and 7 of 8 had either mild to moderate ventricular dysfunction or systemic right- or single-ventricle anatomy. The risk associated with flecainide treatment of SVT associated with congenital heart disease appears to be highest among patients with complex heart disease or ventricular dysfunction.

Recommendations for Ongoing Management of SVT in ACHD Patients (Continued) COR LOE Recommendations

Recommendations for Acute Treatment of SVT in Pregnant Patients COR LOE Recommendations

I C-LD 1.  Vagal maneuvers are recommended for acute treatment in pregnant patients with SVT.235,516

See Online Data Supplement 20. For acute conversion of SVT, vagal maneuvers, including Valsalva and carotid sinus massage, can be performed quickly and should be the first-line intervention to terminate SVT. These maneuvers should be performed with the patient in the supine position. Vagal maneuvers typically will not be effective if the rhythm does not involve the AV node as a requisite component of a reentrant circuit. There is no “gold standard” for proper Valsalva maneuver technique, but in general, the patient raises intrathoracic pressure by bearing down against a closed glottis for 10 to 30 seconds, equivalent to at least 30 mm Hg to 40 mm Hg.82,84 Carotid massage is performed after absence of bruit has been confirmed by auscultation, by applying steady pressure over the right or left carotid sinus for 5 to 10 seconds.83,84 Another vagal maneuver based on the classic diving reflex consists of applying an ice-cold, wet towel to the face85; in a laboratory setting, facial immersion in water at 10°C (50°F) has proved effective in terminating tachycardia, as well.86 One study involving 148 nonpregnant patients with SVT demonstrated that Valsalva was more successful than carotid sinus massage, and switching from 1 technique to the other resulted in an overall success rate of 27.7%.82 The practice of applying pressure to the eyeball is potentially dangerous and has been abandoned.

I C-LD 2.  Adenosine is recommended for acute treatment in pregnant patients with SVT.516

See Online Data Supplement 20. When vagal maneuvers fail to terminate SVT, adenosine is a first-line drug option for pregnant patients.516 Adverse effects to the fetus would not be expected, given that it is unlikely the drug will reach the fetal circulation because of adenosine’s short half-life.517 Maternal side effects, such as chest discomfort and flushing, are usually transient. The initial dose for adenosine is 6-mg rapid bolus IV. 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 3.  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

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