August 01, 2014
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Oral contraceptive use had no beneficial, harmful effect in patients with long QT syndrome

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In a new study, researchers observed that use of oral contraceptives did not affect cardiac events related to long QT syndrome.

Previous research indicated that the high progesterone content of oral contraceptives may produce favorable effects on cardiac events among women with long QT syndrome, according to the study background.

Researchers studied 174 women included in the Rochester, N.Y.-based LQTS Registry who responded to a questionnaire about oral contraceptive use. The time period for the survey began with date of menarche and ended at age 40 years, excluding periods of pregnancy.

The primary endpoint was occurrence of one or more syncopal events or aborted cardiac arrest.

After adjusting for baseline QTc interval, cardiac events before menarche, age at menarche onset, number of births, LQT1 vs. LQT2 genotype and time-dependent beta-blocker use, there was no difference in the risk for cardiac events during the periods of oral contraceptive use compared with periods of nonuse (HR=1.01; 95% CI, 0.71-1.44).

The researchers also found no effect of oral contraceptive use on risk for recurrent cardiac events in any of the following analyzed subsets: long QT syndrome genotype (LQT1 vs. LQT2), QTc (<500 vs. ≥500), cardiac events (none vs. one or more) and age at menarche (13 years or younger vs. older than 13 years; P>.2 for all subsets.)

“Our study results are not consistent with the animal studies that suggested a protective role for progesterone,” the researchers wrote. “One of the many reasons for the discrepancy could be that the pathways by which these hormones affect cardiac repolarization in the cardiac ion channels are different among different species, that is, between rabbits, guinea pigs and humans.”

Another possibility, they wrote, is that much higher concentrations of progesterone and estrogen than which are found in oral contraceptives are required to observe any cardiac effect in humans.

Disclosure: The study was funded by the NIH and the NHLBI. The researchers report no relevant financial disclosures.