Background: Few studies have reported electrocardiogram data collected during the neonatal period. The aim of this study was to evaluate electrocardiographic parameters in healthy neonates during the first postnatal hour. Methods: Electrocardiogram samples taken during the first hour of life from newborns born at our hospital were analyzed in this prospective observational study. Demographic data and possible electrocardiogram changes were studied. The results were statistically analyzed. Results: A total of 260 patients were included during the study period. Among these, 50% were male (n = 130), the mean gestational age was 38.1 ± 1.4 weeks, and the mean birth weight was 3.2 ± 1.4 kg. In the electrocardiograms obtained, low atrial rhythm was detected in 0.3% of the patients (n = 1). Right axis deviation was observed in 1.5% of the patients (n = 4), and left axis deviation was observed in 1.2% of the patients (n = 3). An abnormal P-axis was found in one patient (0.3%), and an abnormal QRS-T angle was found in one patient (0.3%). No statistically significant differences were observed in the other parameters. Conclusion: Physiologic electrocardiographic findings can be observed during the first postnatal hour. Further studies are needed to clarify the interpretation of the electrocardiogram findings.

Introduction: Transposition of the great arteries (TGA) is one of the most common cyanotic congenital heart diseases in the neonatal period, and arterial switch operation (ASO) is the standard surgical treatment. Postoperative low cardiac output syndrome remains an important cause of morbidity. This study evaluated the association between serial vasoactive–inotropic score (VIS) measurements and postoperative intensive care unit (ICU) length of stay in neonates with TGA undergoing ASO. Methods: This retrospective study included neonates with TGA who underwent ASO and were followed in a tertiary Pediatric Cardiac Intensive Care Unit between 1 August 2020, and 1 August 2022. ICU length of stay was analyzed as a continuous primary outcome. Prolonged ICU stay, defined as the upper quartile of ICU length of stay in the study cohort (≥9 days), was evaluated as a secondary exploratory outcome. VIS values were recorded at ICU admission and at 24, 48, and 72 h after surgery. Associations between VIS parameters and continuous ICU length of stay were assessed using Spearman’s rank correlation. ROC analysis and logistic regression were performed for prolonged ICU stay. Results: A total of 60 neonates were included, and 15 patients (25%) had a prolonged ICU stay. Admission VIS values were similar between groups. However, VIS values at 24 and 48 h were significantly higher in the prolonged ICU stay group (p = 0.005 and p = 0.001, respectively), whereas no significant difference was observed at 72 h. VIS at 48 h showed the strongest correlation with ICU length of stay (Spearman’s r = 0.52, p < 0.001), followed by ΔVIS48 (r = 0.48, p = 0.001) and VIS at 24 h (r = 0.44, p = 0.002). In secondary exploratory analyses, VIS at 48 h demonstrated a numerically higher AUC than VIS at 24 h (0.82 vs. 0.74). ΔVIS48 was associated with prolonged ICU stay in multivariable logistic regression (OR, 1.18 per unit increase; 95% CI, 1.05–1.33; p = 0.006). Firth’s penalized logistic regression yielded a similar estimate (OR, 1.15; 95% CI, 1.03–1.30; p = 0.012). Conclusions: In neonates with TGA undergoing ASO, higher VIS during the first 24–48 postoperative hours, particularly an increase from admission to 48 h, was associated with longer ICU stay. These findings support serial VIS assessment as a marker of early postoperative clinical trajectory. Cohort-derived VIS thresholds should be considered exploratory and require external multicenter validation before clinical application.