Electrocardiography
Standard 12-lead ECG were recorded on a Marquette MAC 12 system (Marquette Medical Systems, Inc. Milwaukee, WI) by trained technicians during the participant’s examination. Computerized analysis of the ECG data was performed using Minnesota and Nova code. PR prolongation on ECG was defined as PR interval >200ms. The population was divided into two groups based on the presence or absence of PR prolongation. Then two groups were divided into four groups according to the median of QRS axis in overall population. Among other parameters considered in the analysis were P-wave duration, heart rate, P-wave frontal axis, P-wave terminal force in V1 (PTFV1), QT interval and QRS duration. The QT interval was corrected by Bazett’s formula.