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Long QT Syndrome and Pregnancy
Abstract & Commentary
By John P. DiMarco, MD, PhD, Professor of Medicine, Division of Cardiology, University of Virginia, Charlottesville. Dr. DiMarco is a consultant for Novartis, and does research for Medtronic and Guidant.
Source: Seth R, et al. Long QT Syndrome and Pregnancy. J Am Coll Cardiol. 2007;49:1092-1098.
Seth and his colleagues report on the effects of pregnancy in women with the long QT syndrome (LQTS). The International Long QT Syndrome Registry enrolls patients and family members with LQTS in a longitudinal observational study. In this report, women of child bearing age who had either a known LQTS related gene mutation or carried a clinical diagnosis of LQTS on the basis of a QTc greater than 470 msec were categorized as either having one or more live births (n = 564) or as being nulliparous (n = 520). The child bearing age range was considered to be ages 15 through 40 years of age. The women in the live-birth category were subdivided into those who gave birth before 1980 (n= 173) and after 1980 (n = 391) to reflect the availability of beta blocker therapy for treatment of LQTS. The cardiac risks associated with pregnancy were analyzed by peripartum time intervals immediately before, during, and after a live birth in 9-month segments. A post-postpartum time interval was defined as the time after the immediate postpartum 9-month interval until the date of last follow-up or age 41. If a woman had more than one child, the time intervals for each pregnancy were analyzed. The outcomes analyzed were LQTS-related death, aborted cardiac arrest and syncope. Results of standard genetic tests for LQTS mutations were available in 153 patients. Of these, 82 had LQT1, 59 LQT2, and 12 LQT3 mutations.
When nulliparous women were compared with women who had a live birth, the nulliparous women had a shorter average follow-up time, a higher event rate before age 15 and a higher use of beta blockers at age 15 than the other 2 groups. The authors cite multiple potential explanations for these findings. The remainder of the article dealt only with those women who had a live birth after 1980. Cardiac event rates were relatively stable in the intervals more than 9 months before first pregnancy, the pre-pregnancy 9-month interval, and during pregnancy. There was a significant rise in the annualized cardiac event rate in the 9 months immediately postpartum and then a decrease in the post-post partum interval. The annualized cardiac event rate in the 9-month postpartum period was 0.23 events per year. For the entire group, the hazard ratio during pregnancy was 0.28, during the postpartum period 2.7, and in the post-postpartum period 0.91. Among women in whom genotype data were available, the high rate of postpartum events was primarily due to events in the women with the LQT2 genotype. Of the 391 women who had live births after 1980, 104 were using beta blockers at conception, 116 at the time of childbirth, and 128 at 9 months after giving birth. Beta blockers were associated with a reduction in annualized cardiac event rate with an annualized rate of 3.7 events per year in the absence of beta blockers vs 0.8 events per year with beta blockers. A Cox proportional hazard survival analysis indicated a hazard ratio of 0.34 (0.14 to 0.84) associated with beta blocker therapy.
The authors conclude that the 9-month postpartum period is associated with a significant increased risk of experiencing a cardiac event in women with LQTS and this increase in risk is most noticeable in subjects with the LQT2 genotype. Thus, beta adrenergic blocker should be continued in LQTS patients before, during, and after pregnancy.
Cardiologists are often asked to help manage women with LQTS during pregnancy. This paper from the International Long QT Syndrome Registry demonstrates that pregnancy itself does not place the patient at unusually high risk, but that the early postpartum period is associated with increased risk. The reasons for this are uncertain. There are physiologic and hormonal changes that occur after pregnancy during this period that may contribute. In addition, however, the observation that LQT2 patients were at higher risk suggests that environmental stimuli associated with early childbearing may also be an important factor. LQTS type 2 patients are more likely to have sudden auditory stimuli events serve as triggering events. Such events and sleep deprivation might well be common in mothers caring for a young infant.
Also, the data presented here argue that beta blockers should be continued peripartum in patients with long QT syndrome, particularly if they have a known LQT2 genotype.