Oral Contraceptive Use and the ECG: Evidence of an Adverse QT Effect on Corrected QT Interval

BACKGROUND: A prolonged corrected QT (QTc) interval is a marker for an increased risk of sudden cardiac death. We evaluated the relationship between oral contraceptive (OC) use type of OC and QTc interval. METHODS: We identified 410782 ECGs performed at Northern California Kaiser Permanente on female patients between 15 and 53 years from January 1995 to June 2008. QT was corrected for heart rate using log-linear regression. OC generation (first second and third) was classified by increasing progestin androgenic potency while the fourth generation was classified as antiandrogenic. RESULTS: Among 410782 women 8.4% were on OC. In multivariate analysis after correction for comorbidities there was an independent shortening effect of OCs overall (slope = -0.5 ms; SE = 0.12 P < 0.0002). Users of first and second generation progestins had a significantly shorter QTc than nonusers (P < 0.0001) while users of fourth generation had a significantly longer QTc than nonusers (slope = 3.6 ms SE = 0.35 P < 0.0001). CONCLUSION: Overall OC use has a shortening effect on the QTc. Shorter QTc is seen with first and second generation OC while fourth generation OC use has a lengthening effect on the QTc. Careful examination of adverse event rates in fourth generation OC users is needed. (c)2013 Wiley Periodicals Inc.