1. Cardiology Department of the Children's Memorial Health Institute; Warsaw; Poland
2. DOM-MED GP Practice; Pruszków; Poland
3. Department of Cardiac Arrhythmia of the Institute of Cardiology; Warsaw; Poland
4. Institute of Physics; University of Zielona Góra Zielona Góra Poland; Department of Cardiology-Intensive Therapy; Poznan University of Medical Sciences; Poland