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Introduction: The standard 12-lead electrocardiogram (ECG) remains a widely used tool in the basic cardiac evaluation of children and adolescents. With the emergence of inherited arrhythmia syndromes, the period of cardiac repolarization has been the focus of attention. So far, data on cardiac repolarization and its normal variants in healthy children are scarce. This may cause uncertainties in the differentiation between pathologies and normal variants. As abnormal autonomic regulation seems to be a major influencing factor on cardiac repolarization, this study aimed to evaluate the parameters of cardiac repolarization of children in extremely good physical shape to obese children to improve knowledge about cardiac repolarization in these subgroups of pediatric patients that are vastly affected by the alterations of autonomic regulation. Methods: A total of 426 pediatric volunteers (84 lean, healthy controls; 130 obese healthy pediatric volunteers; and 212 elite athletes) were enrolled in the study, and the parameters of cardiac repolarization were determined in 12-lead ECG. Results: Most importantly, there were no pathological findings, neither in the healthy controls nor in the obese or athletes. Athletes showed overall shorter corrected QT intervals than children from the other groups. This is also true if a correction of the QT interval is performed using the Hodges formula to avoid bias due to a tendency to lower heart rates in athletes. Athletes showed the shortest Tpeak-to-end ratios between the groups. The comparison of athletes from primarily strength and power sports versus those from endurance sports showed endurance-trained athletes to have significantly longer QT intervals. Conclusions: This study suggests that neither obesity nor extensive sports seems to result in pathological cardiac repolarization parameters in healthy children. Therefore, pathology has to be assumed if abnormal repolarization parameters are seen and might not be simply attributed to the child's habitus or an excellent level of fitness.

Objectives: To validate the physical and psychological effectiveness of cardiac pacing in pediatric patients with breath-holding spells (BHS) and prolonged asystole. Materials and Methods: The records and clinical data of all the patients with BHS who presented to our center in the period of 2001-2013 were reviewed. All patients who received cardiac pacemaker implantation for prolonged asystole during BHS were included. In addition, the parents were asked to fill out a standardized quality of life (QOL) questionnaire. Results: Seven patients were identified. The mean onset of symptoms was 7 month (1-12 months) of age, documented asystole was 12-21 seconds, and a permanent cardiac pacemaker device was implanted at a mean age of 23 months (8 months-3.9 years). No pacemaker related adverse events were recorded. Follow up showed immediate resolution from spells in four cases (4/7). Two patients (2/7) showed significant reduction of frequency and severity of spells, with complete elimination of loss of consciousness (LOC). One patient (1/7) with an additional neurologic disorder continued to have minor pallid BHS and eventually switched from pallid to cyanotic spells without further detection of bradycardia or asystole in holter examination. QOL questionnaire revealed significant reduction in subjective stress levels of patients (P = 0.012) and parents (P = 0.007) after pacemaker implantation. Conclusion: Cardiac pacing using appropriate pacemaker settings seems effective in the prevention of LOC and reduction of the frequency of BHS. Our results imply a reduction of subjective stress levels of patients and parents as well as an increased quality of everyday life. After all, randomized controlled trials of the influence of cardiac pacemaker implantation on subjective stress levels in patients with BHS are needed.

We report the use of the Abbott three-dimensional mapping system (EnSite Precision) for the placement of an atrial pacemaker lead in a patient after modified Fontan procedure. The mapping system was used for the identification of a promising pacing site in the complexly modified right atrium and to visualize the successful placement of an atrial lead at the same spot.