METHODS

After obtaining approval from the local ethics committee (2018/177), we enrolled 30 patients with GDM aged between 18 and 45 years and 30 healthy pregnant women without GDM matched with age and gestational weeks.
All pregnant women were screened for GDM with a laboratory-based screening test using blood glucose levels. Screening for GDM is generally performed at 24–28 weeks of gestation 13. GDM was determined by 50 g and 100 g oral glucose challenge tests (OGTT) according to the current guidelines 14. Exclusion criteria included chronic conditions (hypertension, diabetes before pregnancy), eclampsia or pre-eclampsia, ECG rhythm other than sinus rhythm (atrial fibrillation, atrial flutter, atrioventricular (AV) blocks, complete bundle branch block) history of myocardial infarction, chronic obstructive pulmonary disease, asthma, obstructive sleep apnea syndrome, heart failure (ischemic, dilated, hypertrophic), moderate to severe valvular insufficiency or stenosis, history of paroxysmal atrial fibrillation, history of percutaneous coronary intervention (PCI), drug use which may affect cardiac electrical conduction, chronic renal failure, rheumatic and endocrine disease and insufficient echocardiographic image. Medical history, drugs used, pregnancy week, smoking status, laboratory findings (hb, glucose values), and blood pressure values were noted. Body mass index (BMI) was calculated (with the following formula: BMI: weight (kg)/ square of height (in meters)). ECG and echocardiography records of the participants were taken.
The ECGs of the patients were recorded at a rate of 50 mm/sec and amplitude standardization of 20 mm/mV (Nihon Kohden Cardiofax; Japan). While recordings, subjects were permit breathe normally, forbid to hold their breath or speak. ECG analyses were made by Tomax brand digital caliper (150 mm). P wave measurement calculated by averaging the 3 P waves examined in all leads. The beginning of the P wave was considered as the point where the P wave separated from the isoelectric line of the first deviation, and the end of the P wave was taken as the point where it intersects with the isoelectric line again. The PWD was calculated as the difference between the longest and shortest P-wave times in the 12 leads. ECG parameters were measured by the same processor.
Echocardiography was performed on all subjects using a Philips EPIQ 7 device (Philips Medical Systems, Bothell, WA, USA). The patients were examined in the left supine position. Parasternal long axis, short axis, apical four-chamber, and two-chamber images were taken and evaluated using M-mode, 2-D, continuous wave Doppler, pulsed wave Doppler, and tissue Doppler methods according to the criteria of the American Society of Echocardiography 15. All echocardiography was performed by the same processor. One-lead ECG recordings were taken continuously during the echocardiography procedure. Tissue Doppler echocardiography was performed using a transducer with a frequency of 2.5 MHz’s. The pulsed Doppler sample volume was placed in the septal mitral annulus, lateral mitral annulus, and right ventricular tricuspid annulus in 4-chamber view. Systolic wave (Sm) amplitude, early diastolic wave (Em) amplitude, and late diastolic wave (Am) amplitude were determined. Atrial conduction time times (PA) were calculated by the time interval from the onset of the P wave on the ECG to the onset of the late diastolic flow (Am wave) on echocardiography (Figure.1); from the lateral mitral annulus (PA lateral), septal mitral annulus (PA septum), and right ventricular tricuspid annulus (PA tricuspid). The difference between (PA lateral-PA tricuspid) was defined as interatrial electromechanical delay (EMD); the difference between (PA septum-PA tricuspid) was defined as intraatrial EMD, and the difference between (PA lateral-PA septal) was defined as intraleft atrial EMD.
Statistical analyses were performed using SPSS version 20.0 (IBM, Chicago, USA). The conformity of the variables to the normal distribution was examined using Shapiro–Wilk test. Normally distributed numerical variables were compared by independent -T test, and the non-normally distributed variables were compared using Mann–Whitney U test. Categorical variables were compared using the Chi-square test. Spearman’s correlation (for non-normally distributed data) and the Pearson correlation test (for normally distributed data) were used for correlation analysis. Comparisons with a p value below 0.05 were considered statistically significant.