Abstract 2698: Men are Unstable, But Women are Incoherent: Gender Differences in Repolarization
Women in MADIT II were sicker than men but had less VT/VF. Abnormal cardiac repolarization appears to contribute to the risk for VT/VF, but little is known regarding the effect of gender on repolarization. We have previously shown that an increase in the ratio of QT variability to heart rate variability is predictive of VT/VF in males but not females. We hypothesized that in women with structural heart disease, an unstable relationship between the heart rate and the QT (“low coherence”), would be predictive of VT/VF in females. Methods: MADIT II study patients not in atrial fibrillation or paced had resting digitized recordings at study entry. Spectral analysis of heart rate and QT time series was performed; coherence was indexed as the transfer function between the power spectra. Incidence of VT/VF was determined by ICD interrogation. Results: There were 817 usable recordings (146 females); 463 received ICDs (86 females). The mean coherence in both genders was similar overall (0.267 men; 0.275 women) and in the lowest quartile (0.155 men; 0.151 women). Females in the lowest coherence quartile were more likely to experience VT/VF (Hazard Ratio [HR] of 4.8, 95% confidence interval [CI] 1.5 to 14.0, p=0.007) compared to females not in this quartile. VT/VF risk for males was not significantly different in between the lowest coherence quartile (HR=1.2, CI=0.7 to 2.0) and the remaining males. Conclusions: In postinfarction patients with a depressed ejection fraction, decreased coherence between the heart rate and QT interval is predictive of VT/VF in females but not males. These data point to important gender differences in either the substrate or the trigger for VT/VF in women versus men.