1. Cardiology Department, Centro Hospitalar e universitario de Coimbra � Polo Hospitais da Universidade de Coimbra, Praceta Prof. Mota Pinto, 300 � 075 Coimbra, Portugal
2. Cardiology Department, Hospital do Divino Esp�rito Santo, Avenida D. Manuel I, Matriz, 9500 � 370 Ponta Delgada, Portugal
3. Department of Physiology and Cardiothoracic Surgery, Faculty of Medicine, University of Porto, Alameda Prof. Hern�ni Monteiro, 4200 � 319 Porto, Portugal