stress, that is, when the heart rate is elevated.8 Because the mother’s heart rate increases significantly in the active pushing phase of labor, and ˜20% of women achieve 100% of their maximum age-predicted heart rate at this time,9 higher-risk women may benefit from epidural anesthesia, and assisted or operative delivery. However, the impact of mode of delivery and anesthesia on sympathetic activation and circulating maternal and fetal catecholamine levels is not well studied. In fact, there is little agreement between small published studies.9,10,11,12 TABLE 5.1.1 summarizes the suggestions for management of the pregnant woman with an inherited arrhythmia.
TABLE 5.1.1 MANAGEMENT OF THE PREGNANT WOMAN WITH INHERITED ARRHYTHMIA
pregnancy.1,33 The beta-blockers with proven efficacy in LQTS include nadolol, propranolol, metoprolol, and atenolol; however, atenolol should not be used in pregnancy, as it is associated with significant intrauterine growth restriction (pregnancy class D).34,35,36,37,38 Of the beta-blockers with demonstrated efficacy in LQTS, nadolol, propranolol, and metoprolol are pregnancy risk Category C. There is some evidence that metoprolol, particularly the shorter acting formulation with twice-a-day dosing, is inferior to nadolol or propranolol, particularly in individuals with a prior history of arrhythmia events.39 Overall, nadolol was found to be most effective and is considered the beta-blocker of choice overall, but especially in higher risk patients, including LQT2 mothers, women with QTc >500 ms, and individuals with a prior history of syncope or cardiac arrest.32,35,36,37,39 Nadolol dosing up to 1 to 1.5 mg/kg/d is the typical dose used in LQTS. If nadolol is poorly tolerated or not available, propranolol, another noncardioselective beta-blocker, can be considered.