METHODS
The patients, who were recently diagnosed with COPD in the Chest Diseases Outpatient Clinics of the Harran University Faculty of Medicine, were enrolled in the study. The exclusion criteria consisted of the presence of diabetes mellitus, hypertension, chronic or acute heart failure, moderate or severe valvular heart disease, hyperthyroidism, anemia, sleep disorders, ECG signs of incomplete or complete bundle branch block. The local ethics committee approved the study, which was conducted in full compliance with the Declaration of Helsinki. The signed informed consent were obtained from all patients.
Tests for Pulmonary Function and Diffusing Capacity of the Lung Carbon Monoxide (DLCO) as recommended by the American Thoracic Society (ATS) were performed in all patients 12. The assessment of pulmonary function was performed with at least three forced expiratory maneuvers in 90° upright position with the nose closed, and the best value was recorded. The measurements of Forced Vital Capacity (FVC), Forced Expiratory Volume in 1 second (FEV1), and the ratio of FEV1 / FVC were recorded. The current guideline was used for COPD diagnosing and staging [1]. Accordingly, a post-bronchodilator FEV1 / FVC < 70% in the presence of clinical findings indicates persistent airflow limitation and is essential for diagnosing COPD. The GOLD (Global Obstructive Lung Disease ) stage of COPD is categorized as stage 1 (mild) when post-bronchodilator predicted  FEV1 is equal to or greater than 80%, stage 2 (moderate) when between 50% and less than 80%, stage 3 (severe) when between 30% and less than 50%, and stage 4 (very severe) when less than 30%. Accordingly, the current study population was categorized into two groups as Group I, including the mild and moderate COPD patients, and Group II, including the severe and very severe COPD patients. The single-breath method via the Morgan Benchmark transfer test was used for the quantification of DLCO.
A 12-lead basal ECG with a 0.16–100 Hz filter range, 25 mm/s speed, and 10 mm/mV height both at rest and in the supine position was obtained from all patients on admission. The automatically reported axes of QRS and T wave were used to calculate the frontal QRS-T angle by using the formula: Frontal QRS-T angle = │QRS axis – T axis│. When the angle was greater than 180o, its subtraction from 360o was used for the calculation, as previously reported 13. Figure 1 depicts an example of the frontal QRS-T angle calculated as explained.
Blood samples for laboratory tests, including complete blood count and biochemical parameters consisting of serum electrolytes, liver enzymes, urea, and creatinine, were obtained from all patients on admission.