Oral contraceptive use and the risk of cardiac events in patients with long QT syndrome

Abstract

Background: In prior clinical studies of patients with long QT syndrome (LQTS), pregnancy was associated with fewer cardiac events (CEs) compared to before or after pregnancy. In recent animal studies involving rabbits with LQTS mutations, progesterone had favorable effects on CEs compared to estrogen. The effect of oral contraceptive therapy with its high progesterone/estrogen ratio on the risk of CEs in patients with LQTS has not been examined.

Objective: To study the effect of oral contraceptive use on the risk of CEs in patients with LQTS.

Methods: We studied 174 patients from the Rochester-based LQTS Registry who responded to a questionnaire about their oral contraceptive use. We used time-dependent Cox regression to estimate the hazard ratio for recurrent CEs when patients were using vs not using oral contraceptives during nonpregnancy periods. For this recurrent events analysis, the Prentice-Williams-Peterson model was used and the time origin was defined as the onset of menarche. We adjusted for the baseline corrected QT interval, history of CEs before menarche, age at menarche onset, number of births, time-dependent β-blocker therapy, and LQTS genotype.

Results: No differences in the risk of CEs for the times patients with LQTS were using vs not using oral contraceptives was found in the general population with LQTS (hazard ratio 1.01; P = .95) or in analyses of LQTS subsets (P > .2).

Conclusion: Oral contraceptive therapy use did not affect LQTS-related CEs in the study population. Oral contraceptives did not show beneficial or harmful effects in this patient group.

Keywords: Cardiac events; Estrogen; I(Kr) channels; I(Ks) channels; Long QT syndrome; Oral contraceptive therapy; Pregnancy; Progesterone; Sex hormones.