Female Gender as Independent Risk Factor of Torsades De Pointes During Acquired Atrioventricular Block

Background:
Female gender increases the risk of torsades de pointes (TdP) in the long QT syndrome, and this increased risk is assumed to be due to their longer QT interval.

Objective:
The purpose of this study was to study the interplay between gender, duration of the QT interval, and risk of TdP during AV block.

Methods:
We studied 250 patients (48% women) with AV block. QT interval was measured at the time of most severe bradycardia. We then constructed different receiver operating characteristic curves for the QTc of males and females for predicting TdP.

Results:
As expected, patients with TdP had longer QTc intervals than did patients with uncomplicated AV block (564 ± 81 ms vs 422 ± 62 ms, P o.001). This correlation between longer QTc and higher risk of TdP was true for both genders. However, the QT of females with TdP was shorter than the respective value for males with TdP. Despite similar severity of bradycardia, the QT was shorter for females (QT 672 ± 88 ms vs 727 ± 57 ms for females with TdP vs males with TdP, P ¼ .022). The QTc/TdP risk curve for females was shifted to the left in comparison to the pertinent graph for males. Female gender was an independent predictor of TdP.

Conclusion:
Women are at increased risk for developing TdP during AV block, but this increased risk is independent of their longer QT interval. Females develop TdP with QT intervals that are not necessarily arrhythmogenic for males.