Treatment of cardiac arrhythmias during pregnancy: safety considerations.

Maternal and fetal arrhythmias occurring during pregnancy may jeopardise the life of the mother and the fetus. When arrhythmias are well tolerated and patients are minimally symptomatic, conservative therapy, such as observation and rest or vagal manoeuvres, should be employed. When arrhythmias cause debilitating symptoms or haemodynamic compromise, antiarrhythmic drug therapy is indicated. Although no antiarrhythmic drug is completely safe during pregnancy, most are well tolerated and can be given with relatively low risk. Physiological changes that occur during pregnancy mandate caution when administering antiarrhythmic drugs, with close monitoring of serum concentration and patient response. Drug therapy should be avoided during the first trimester of pregnancy if possible, and drugs with the longest record of safety should be used as first-line therapy. Several therapeutic options exist for most arrhythmias in the mother and fetus. Of the class IA agents, quinidine has the longest record of safety during pregnancy, and is generally well tolerated. Procainamide is also well tolerated, and should be a first line option for acute treatment of undiagnosed wide complex tachycardia. All IA agents should be administered in the hospital under cardiac monitoring due to the potential risk of ventricular arrhythmias (torsade de pointes). The IB agent, lidocaine (lignocaine), has local anaesthetic role but is also generally well tolerated as an antiarrhythmic agents. Phenytoin should be avoided due to the high risk of congenital malformations and limited role as an antiarrhythmic drug. Of the IC agents, flecainide has been shown to be very effective in treating fetal supraventricular tachycardia complicated by hydrops. Beta-Blockers are generally well tolerated and can be used with relative safety in pregnancy, although recent data suggest that they may cause intrauterine growth retardation if they are administered during the first trimester. Amiodarone, a class II agents with characteristics of the other antiarrhythmic drug classes, has been reported to cause congenital abnormalities; it should be avoided during the first trimester and used only to treat life-threatening arrhythmias that fail to respond to other therapies. Adenosine is generally safe to use in pregnancy, and is the drug of choice for acute termination of maternal supraventricular tachycardia. Digoxin has a long track record of treating both maternal and fetal arrhythmias, and is one of the safest antiarrhythmics to use during pregnancy. Direct current cardioversion to terminate maternal arrhythmias is well tolerated and effective, and should not be delayed if indicated. The use of an implantable cardioverter-defibrillator should be considered for women of childbearing potential with life-threatening ventricular arrhythmias.