1. University Hospital , Kraków , Poland
2. Jagiellonian University Medical College , Kraków , Poland
3. Institute of Cardiology, Faculty of Medicine, Jagiellonian University Medical College , Kraków , Poland
4. Department of Electrocardiology, The John Paul II Hospital , Kraków , Poland
5. Cardiovascular Division, Department of Medicine, Washington University School of Medicine , Saint Louis, MO 63110 , USA