Testosterone and dihydrotestosterone (DHT) attenuate drug-induced lengthening of ventricular repolarization, but it is unknown whether they influence drug-induced torsades de pointes (TdP). We tested the hypothesis that DHT reduces the incidence and severity of drug-induced TdP. Male New Zealand white rabbits underwent orchiectomy and were implanted with 2 subcutaneous sustained-release pellets containing DHT 50 mg (100 mg, n = 23) or placebo (n = 20). After 7 days, hearts were excised, mounted, and perfused with modified Krebs-Henseleit solution. The atrioventricular node was destroyed manually. Dofetilide 100 nM was perfused for 30 minutes. Median (Q 1 , Q 3 ) serum DHT concentrations were higher in DHT-treated rabbits [314.0 (232.5, 388.6) vs. 32.5 (28.5, 36.2) ng/dL, P < 0.0001]. The incidence of TdP in the DHT and placebo groups was 6/23 (26%) versus 8/20 (40%), respectively ( P = 0.33). In hearts that developed TdP, the median (Q 1 , Q3) number of episodes was lower in the DHT group [2 (2, 3.5) vs. 18.5 (12.5, 20.5), P = 0.01]. The median time to first TdP episode was longer [18.5 (17.3, 21.3) vs. 10.5 (12.5, 20.5) minutes, P = 0.01], and the TdP burden (median total number of TdP beats per heart) was lower in the DHT group [11.5 (9.5-46.5) vs. 271 (99.3-440.3) beats, P = 0.007]. Pre-dofetilide Fridericia-corrected QT intervals were shorter in the DHT group [377 (366, 390) vs. 385 (378, 401) ms, P = 0.02]. Maximum Fridericia-corrected QT interval during dofetilide perfusion was shorter in the DHT group [399 (390, 410) vs. 414 (399, 442) ms, P = 0.007]. In conclusion, DHT diminishes the severity of dofetilide-induced TdP.
Keywords: QT interval; beat-to-beat variability; dihydrotestosterone; dofetilide; isolated perfused heart; rabbit; torsades de pointes.
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