Study population and data collection

This clinical protocol was approved by the institutional medical ethics committee and was conducted according to the ethical guidelines outlined in the Declaration of Helsinki. We evaluated 35 consecutive postmenopausal female patients with IOTVA who agreed to participate in the study. The participants received oestrogen replacement therapy (conjugated equine oestrogen, 0.625 mg/day for 3 months) from Renmin Hospital of Wuhan University. Thirty-five age-matched postmenopausal women without IOTVA who also agreed to participate in the study were used as a control group; these women were selected randomly from the municipal population registry in Wuhan City. Both groups underwent the following tests: physical examination; chest X-ray; laboratory values; echocardiography with wall motion analysis; electrophysiological study and/or 12-lead electrocardiographic monitoring to exclude others types of arrhythmia; and Doppler screening to exclude the presence of structural heart disease. Potential participants were excluded if they were aged > 70 years, had a disease other than IOTVA (including fever, coronary artery disease, others types of arrhythmia, hypertension, endocrine secretion, metabolic diseases, etc.) or if they had taken any medication within the previous 2 months.

Blood samples for analysis of basal hormone concentrations were obtained between 8:00 am and 9:00 am after an overnight fast. Concentrations of plasma sex hormones (including luteinizing hormone, oestradiol and progestogen) were measured using commercially prepared immunoassay kits according to the manufacturer’s instructions (ADVIA Centaur Immunoassay Assay System, Bayer, Germany). Serum potassium, sodium and calcium concentrations were measured with standard laboratory techniques on a Hitachi 912 Analyzer (Roche Diagnostics, Basel, Switzerland). PVCs were defined as identifiable premature QRS complexes (premature with respect to the P wave). Other multipart forms of PVCs, such as bigeminy (two consecutive PVCs), salvos (three consecutive PVCs) and ventricular tachycardia (four or more consecutive PVCs), were all included in the PVC count. The average PVC count (number of counts/24 hours) was assessed by 72-h, 12-lead electrocardiographic monitoring (GE Healthcare, Milwaukee, WI, USA). The 12-lead electrocardiogram (ECG) diagnostic criteria for idiopathic right outflow tract ventricular arrhythmias are a wide QRS complex tachycardia with a left bundle branch block pattern and an inferior axis . The 12-lead ECG diagnostic criteria for idiopathic left outflow tract ventricular arrhythmias are an S wave in lead I and an R-wave transition in leads V1 or V2; the absence of an S wave in leads V5 or V6 suggests a supravalvular location, whereas an S wave in leads V5 and V6 indicates an infravalvular location .

Statistical analysis

All values were expressed as means ± standard deviations or the percentage of incidence. The chi ² test or Fisher’s exact test was used to compare proportions. Student’s t test was used for comparisons between groups. The paired t test was used for comparisons before and after oestrogen replacement therapy. Statistical significance was assumed if P was less than 0.05.