In this study, we enrolled 72 consecutive patients from two different centers who visited the Dermatology Clinic with the diagnosis of LP. The control group was selected in a 1:1 ratio from 70 patients in an age and sex matched manner. The criteria for exclusion in the patient group included the following: any kind of inflammatory diseases, chronic obstructive pulmonary disease, coronary artery disease, valvular heart disease, cardiomyopathy, pulmonary hypertension, abnormal serum electrolyte values, treatment with an antiarrhythmic drug, prior pacemaker implantation, bundle branch block or atrioventricular or intraventricular conduction abnormalities on electrocardiogram (ECG), history of permanent or paroxysmal atrial fibrillation, pericarditis, chronic systemic diseases including renal failure, anemia, thyroid disease, poor echocardiographic imaging quality, and/or presence of infectious disease within 1 week of laboratory and echocardiographic assessment. All the patients were in sinus rhythm. The participants' weights and heights were measured, and their body mass indexes (kg/m²) were calculated. Their blood pressures were measured after a 5-minute rest and again after 10 minutes, and the average of the two measurements was recorded. Two-dimensional and Doppler echocardiographic measurements were performed. Serum triglycerides, LDL-cholesterol, glucose levels, and high sensitive C-reactive protein (hsCRP) levels were assessed in samples collected between 8 a.m. and 9 a.m. after a 12-hour fasting period. The study conformed to the standards set by the Declaration of Helsinki, and ethical approval was obtained from the Medical Ethical Committee of Fırat University (Reference No: 02/12/2014-20-22). Written informed consent was obtained from each participant.

All subjects underwent 12-lead ECG recording (Nihon Kohden Corporation, Tokyo, Japan) after a 20-min resting period in the supine position at a paper speed and amplitude of 50 mm/s and 2 mV/cm, respectively. The P-wave duration was measured manually by using calipers and a 10X magnifying lens for evaluation of the electrocardiographic deflections in all simultaneously recorded 12 leads of the surface ECG by two investigators who were blinded to the participants. In each lead, the mean values for the three complexes were calculated. The onset of the P-wave was defined as the junction between the isoelectric line and the beginning of P-wave deflection and the offset of the P-wave as the junction between the end of the P-wave deflection and the isoelectric line. The P_max measured in any of the 12 leads of the surface ECG was considered to be the longest atrial conduction time. The difference between the maximum (P_max) and minimum (P_min) P-wave durations was calculated and it was defined as P-wave dispersion (Pd=P_max–P_min). In order to improve accuracy, all measurements were performed with calipers and a magnifying lens to define ECG deflections, as described previously.10)

Continuous ECG recording was performed from a single lead. Tissue Doppler echocardiography was performed using transducer frequencies of 3.5-4.0 MHz, adjusting the spectral pulsed Doppler signal filters until a Nyquist limit of 15-20 cm/sec was achieved. The monitor sweep speed was set at 50-100 mm/sec to optimize the spectral display of myocardial velocities. In the apical four-chamber view, the pulsed Doppler sample volume was subsequently placed at the level of left ventricular lateral mitral annulus, septal mitral annulus, and right ventricular tricuspid annulus. Tissue Doppler pattern was characterized by a positive (i.e., above baseline) myocardial systolic wave (S) and two negative (i.e., below baseline) diastolic waves—early (E) and atrial (A). Efforts were made to align the pulsed wave cursor in order to maintain the Doppler angle of incidence as close to zero as possible in relation to the direction of these walls. E deceleration time and isovolumetric relaxation time (IVRT) were measured. IVRT was defined as the interval between the end of the aortic outflow and the beginning of the mitral inflow signal. Atrioventricular annulus motions were recorded simultaneously with electrocardiogram in lead II during sinus rhythm to analyze the temporal relationship between atrial electrical phases and myocardial motion. The intervals from the onset of P-wave on surface ECG to the beginning of A-wave (PA), representing atrial electromechanical delay (Fig. 1) were obtained from lateral mitral annulus, septal mitral annulus, and right ventricular (RV) tricuspid annulus and designated as lateral PA, septal PA, and RV PA, respectively. The timing of mechanical activation of each reference point, namely, lateral mitral, septal mitral, and RV tricuspid annuli depends on the distances of these points from the sinus node. The difference between septal PA and RV PA was defined as intra-right atrial mechanical delay (septal PA-RV PA); the difference between lateral PA and septal PA was defined as intra-left atrial mechanical delay (lateral PA-septal PA); and the difference between lateral PA and RV PA (lateral PA-RV PA) was defined as inter-atrial mechanical delay.14)

All statistical analyses were performed by using SPSS package program ver.10.0 (SPSS Inc., Chicago, IL, USA). Continuous variables were reported as means±standard deviation and categorical variables were reported as percentages. Student's t-test was used for comparison of normally distributed variables and Mann-Whitney U-test was used for non-normally distributed variables. Categorical variables were compared by the χ² test or Fisher's exact test as appropriate. Pearson's correlation analysis was used for correlations. p values less than 0.05 were considered to be statistically significant.