Monika Kaldararova1, Peter Tittel2, Martin Zahorec3. 1. Department of Pediatric Cardiology, National Institute of Cardiovascular Diseases, Children's Cardiac Center, Bratislava, Slovakia. Electronic address: kaldararova@dkc-sr.sk. 2. Department of Pediatric Cardiology, National Institute of Cardiovascular Diseases, Children's Cardiac Center, Bratislava, Slovakia. 3. Cardiac Intensive Care Unit, National Institute of Cardiovascular Diseases, Children's Cardiac Center, Bratislava, Slovakia.