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Arrhythmias During Pregnancy
Arrhythmias of any type may occur during pregnancy. Patients who have a condition that predisposes them to develop arrhythmias may have their initial episodes during pregnancy, and patients who already have arrhythmias may have them continue during pregnancy. Some patients with supraventricular tachycardias (SVTs) have a reduction in the frequency of episodes while pregnant, and others have an increase. This chapter first provides an overview of arrhythmias in pregnancy and the drugs used to treat them and then discusses specific types of arrhythmias.
Overview: Arrhythmias
There are three physiologic mechanisms of arrhythmia: automaticity, reentry, and triggered activity. The physiologic changes of pregnancy enhance the probability of firing of an automatic focus and predispose to reentry. Increased catecholamine levels promote automaticity and shorten the refractory period of myocardial tissues, which also predisposes to reentry. By increasing the length of reentrant circuits, cardiac dilation predisposes to reentry as well.
The mainstays of modern diagnostic and therapeutic management of arrhythmias—electrophysiologic evaluation and ablation—could be performed during pregnancy, but they are rarely warranted because most arrhythmias can be diagnosed noninvasively and treated medically until after delivery.
In assessing a patient with arrhythmias, it is important to evaluate for causative factors, including structural heart disease, which usually can be diagnosed with an echocardiogram; electrolyte abnormalities; and hyperthyroidism. In pregnant patients, pulmonary emboli also should be considered. Channelopathies (a group of congenital disorders of the ion channels that predispose patients to arrhythmias) may first present during pregnancy. Most often, they can be diagnosed with a 12-lead electrocardiogram (ECG).
For the most part, arrhythmias during pregnancy are treated in the same way as in nonpregnant patients. Digoxin; beta blockers; and antiarrhythmic drugs, such as flecainide, propafenone, and amiodarone, can be used with reasonable safety.
Antiarrhythmic drugs may sometimes have to be administered to a pregnant woman to treat fetal tachycardia. Sotalol, flecainide, and amiodarone may be used for this purpose. Amiodarone is usually reserved for resistant cases because of the potential for fetal thyrotoxicity.
Specific Arrhythmias: Diagnosis and Management
Specific arrhythmias include atrial fibrillation, atrial flutter, bradycardia, channelopathies, palpitations, premature contractions, tachycardia, SVT, VT, and Wolff-Parkinson-White (WPW) syndrome.
Atrial Fibrillation
Atrial fibrillation is rare in pregnancy, and typically it is associated with a causative factor, such as hyperthyroidism or structural heart disease. Unless associated with mitral stenosis, it is usually well tolerated. Atrial fibrillation in pregnant women is treated in a manner very similar to that in nonpregnant patients. Rate control, if necessary, can be achieved with intravenous (IV) verapamil. Verapamil is preferable to diltiazem because it has a good safety profile in pregnancy. There are limited data on diltiazem and reports of embryopathy in animal studies. For chronic rate control, oral verapamil or beta blockers can be used (avoid using atenolol in the first trimester). Digoxin is safe to use but not very effective; generally, it is used only as a second- or third-line drug in patients with left ventricular dysfunction. Anticoagulation with heparin is mandatory to prevent embolic events. Cardioversion should be undertaken as soon as practical. Propofol can be used safely for anesthesia during cardioversion. If long-term antiarrhythmic therapy is needed to maintain sinus rhythm, flecainide, sotalol, or amiodarone can be used. There is considerable experience using these drugs to treat fetal tachycardia, and they seem well tolerated by both the mother and baby. Amiodarone has the potential for fetal thyrotoxicity.
The difficult part of managing pregnant patients with either atrial fibrillation or atrial flutter is anticoagulation. Warfarin is generally contraindicated during pregnancy, particularly during weeks 6 to 12, because of embryopathy. The newer anticoagulants, non–vitamin K antagonist oral anticoagulants (NOACs), are probably contraindicated because they are small molecules that can cross the placenta. There have been accidental exposures of pregnant women to NOACs, but the data are very limited. At present, the best option is to use IV heparin or therapeutic doses of enoxaparin.
CHADS 2 -VASc is a measure that helps predict the likelihood that a patient will have a stroke; the letters or contributing factors in the acronym stand for c ongestive heart failure, h igh blood pressure, a ge, d iabetes, and s troke (double weight). Women with normal hearts and low CHADS 2 -VASc scores may not require anticoagulation throughout pregnancy, but they should receive it for a least 1 month after cardioversion because all guidelines (American Heart Association [AHA], American College of Cardiology [ACC], and Heart Rhythm Society [HRS]) recommend postcardioversion anticoagulation for all patients with atrial fibrillation with a duration of 48 hours or more. The AHA/ACC/HRS guidelines suggest the same anticoagulation regimen for patients with atrial flutter as for those with atrial fibrillation.
Atrial Flutter
Atrial flutter is rare in pregnancy and is usually associated with congenital heart disease. Atrial flutter in pregnant women is treated in a manner very similar to that in nonpregnant patients. Rate control, if necessary, can be achieved with IV verapamil. Verapamil is preferable to diltiazem because it has a good safety profile in pregnancy, but there are limited data on diltiazem, and there are reports of embryopathy in animal studies. For chronic rate control, oral verapamil or beta blockers can be used (again, avoid using atenolol in the first trimester). Digoxin is safe to use but not very effective; generally, it is used only as a second- or third-line drug in patients with left ventricular dysfunction. Anticoagulation with heparin is mandatory to prevent embolic events. Cardioversion should be undertaken as soon as practical. Propofol can be used safely for anesthesia during cardioversion. If long-term antiarrhythmic therapy is needed to maintain sinus rhythm, flecainide, sotalol, or amiodarone can be used. There is considerable experience using these drugs to treat fetal tachycardia, and they seem well tolerated by both the mother and baby. Amiodarone has the potential for injury to the fetal thyroid gland.
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