Abstract 13719: Long Qt Associated Ventricular Tachycardia Caused by Sex Hormone Therapy

Abstract

Introduction: Increasing number of patients are currently receiving hormonal therapies for a variety of conditions. Modulation of cardiac repolarization by sex hormones resulting in VT remains controversial. Anastrozole is an aromatase inhibitor (ANI), used as an anti-estrogen medication in women with breast cancer or as replacement therapy for hypogonadism. Arrhythmias associated with ANI are extremely rare and hence ANI is considered relatively safe to use. Case Presentation: We report two cases receiving ANI who presented with VT and long QT (LQT). Case 1, 71 year old female with breast cancer on ANI recently started on levofloxacin 750 mg qd, presented with monomorphic VT. Post-conversion ECG showed sinus rhythm (SR) QT 0.48s/QTc 0.56s. Case 2, 50 year old male with hypogonadism on ANI and clomiphene (CL) presented with monomorphic VT, post conversion ECG showed SR with QT 0.65s/QTc 0.59s. Both patients had normal electrolytes and coronaries. Discussion: Studies have shown that levofloxacin is not associated with significant LQT, however, a relationship between its concentration and the extent of LQT has been demonstrated. LQT in our first case can be explained by an increase in levofloxacin level resulting from inhibition of CYP by ANI. CL is a HERG inhibitor however has not been shown to prolong QT. ANI lower the estradiol level which blocks the membrane trafficking of KCNH2 channels, potentially lengthening the QT. LQT in the second case can be explained by the additive effect of both HERG and KCNH2 inhibition. Conclusion: Although reported as safe, ANI hormone therapy can be arrhythmogenic if combined with agents that potentially affect potassium currents. We recommend QT monitoring in such patients to prevent lethal arrhythmias.