Effect of estrogen on ventricular repolarization in menopausal patients with syndrome X and effects of nicorandil

Syndrome X may exhibit myocardial ischemia and is associated with estrogen deficiency. We sought to assess the possible role of estrogen in modulating the characteristics of ventricular repolarization by measurement of QT int erval and QT dispersion in patients with syndrome X, We prospectively used 12-lead electrocardiograms and echocardiograms to study 52 consecutive meno pausal patients with syndrome X (group subdivided into subgroup 1a, 32 pati ents who received nicorandil, an adenosine triphosphate-sensitive potassium ion channel opener; subgroup 1b, 20 patients without dosing nicorandil). F or comparisons, a control group consisted of age-matched and echocardiograp hic left ventricular mass index-matched 20 healthy menopausal women. Baseli ne QT intervals and QT dispersion were similar between the 2 groups (subgro up 1a and controls). After administration of estrogen, there was significan t prolongation of maximal QTc intervals and reduction in QT or QTc dispersi on compared with baseline in patients with syndrome X. The changes returned to baseline after nicorandil administration. Control subjects had no chang es with administration of estrogen. Thus, estrogen modulates characteristic s of ventricular repolarization, which appears to be mediated by blocking a denosine triphosphate-sensitive potassium ion channel. The effects of estro gen on QT intervals may be different between menopausal women with or witho ut syndrome X, (C) 1999 by Excerpta Medico, Inc.