Fig. 1.

Human ether-a-go-go-related gene (hERG)-blocking drugs in the presence of high estrogen concentrations enhance arrhythmogenicity. Top: using the model described in Yang et al. (249), the authors simulated the late follicular phase of the reproductive cycle when estrogen levels are highest. An ectopic stimulus that was delivered (left) failed to initiate reentry. However, when the late follicular phase was simulated in the presence of the hERG-blocking drug E-4031 (middle), the premature stimulus led to the initiation of reentry. Reentry was not initiated when E-4031 administration was simulated in the presence of high testosterone levels (bottom). Epi, epicardial; M, M cell; Endo, endocardial; DHT, dihydrotestosterone. Figure is from Yang et al. (249), used with permission.