The Use of Cardiac Drugs During Pregnancy

Atrial Fibrillation and Atrial Flutter

These arrhythmias usually require treatment with an atrioventricular (AV) nodal blocking agent to slow the rate. For acute situations, intravenous (IV) verapamil (class C) is the drug of choice. Long term, beta blockers such as metoprolol or oral verapamil (both class C) are best. Digoxin (class C) is not as effective and should be used only in rare situations when heart failure is present and beta blockers are ineffective or cannot be used. To prevent recurrences, an antiarrhythmic, such as flecainide (class C) or sotalol (class C), can be used; because both are proarrhythmic drugs, they should not be used in women with left ventricular dysfunction. In these cases, amiodarone (class D) is less likely to be proarrhythmic, but it should be used cautiously because of concerns for fetal thyroid dysfunction. Anticoagulation should be initiated. Acutely, IV heparin (class B) can be used; long term, low-molecular-weight heparin given subcutaneously (class B) is now the standard. In general, warfarin (class X) should not be used.

Supraventricular Tachycardia

For the acute treatment of patients with SVT, IV adenosine (class C) is quite effective; it is the most commonly used treatment in both pregnant women and the general population. If adenosine fails or arrhythmias recur, IV verapamil (class C) can be used.

For long-term prevention of SVT recurrences, AV nodal blocking agents are the drugs of choice. Digoxin (class C) has been used for many years and is effective. The dose generally should be increased during pregnancy because of increased renal clearance. Beta blockers also are effective. Metoprolol (class C) is widely used, but propranolol (class C) or labetalol (class C) can be used as well. As noted earlier, atenolol (class D) has been associated with fetal growth restriction when given in the first trimester. The calcium channel blocker verapamil (class C) is also effective.

In the rare cases when an antiarrhythmic drug is needed, flecainide (class C) or sotalol (class C) can be used. Amiodarone (class D) is used in pregnancy to treat fetal tachycardia, but it should be used only as a last resort because of concerns for fetal thyroid dysfunction.

Ventricular Tachycardia

Idiopathic VT can be treated with beta blockers (class C) or verapamil (class C). If these drugs are unsuccessful, antiarrhythmics such as flecainide (class C) or sotalol (class C) could be tried. Amiodarone (class D) may be considered. However, it may not be necessary to eliminate all nonsustained VT.

Ventricular tachycardia associated with LV dysfunction is usually quite intermittent, and if the patient has an implantable cardioverter-defibrillator, it may not need to be treated. If there are recurrent episodes of VT, amiodarone (class D) is the best option.

Adenosine (class C), which is given intravenously, transiently blocks conduction through the AV node. It can be used diagnostically if the diagnosis of a tachycardia is uncertain. If the patient is in atrial flutter with two-to-one conduction, adenosine may bring out the flutter waves and allow a correct diagnosis. It also may be used as a diagnostic tool in wide complex tachycardias. SVT with aberrancy will usually break. Idiopathic VT may convert to sinus rhythm. Usually, adenosine has no effect on VT associated with structural heart disease.

Quinidine (class C) is rarely used today, but it may be a good option in extremely rare cases, such as VT storm in Brugada syndrome.

Pronestyl (class C) is still available for IV use and occasionally may be helpful in pregnant patients.

In current practice, lidocaine (class C) is rarely used in treating patients with ventricular arrhythmias; the lidocaine-like drug tocainamide has been used to treat idiopathic VT of pregnancy, but it is no longer available.

Left-Sided Systolic Heart Failure

To treat left-sided systolic heart failure, diuretics are used to relieve pulmonary congestion and edema, and beta blockers are used to help prevent recurrences. In nonpregnant patients, carvedilol is the most commonly used drug, but there is little experience with it in pregnancy, so metoprolol is probably the best choice. Digitalis can be used to treat symptoms. As noted earlier, ACE inhibitors and ARBs, both of which are mainstays of therapy in nonpregnant patients, should not be used.

Right-Sided Diastolic Heart Failure

To treat right-sided diastolic heart failure, diuretics are used. Beta blockers and verapamil are sometimes used, but there is little evidence that they are effective. Similarly, there is no convincing evidence that digitalis is helpful. Long-acting nitrates such as isosorbide dinitrate are also sometimes helpful in relieving symptoms.