1. Department of Cardiothoracic Surgery and Physiology, Faculty of Medicine, University of Porto, Porto, Portugal
2. Department of Cardiology, Centro Hospitalar de Vila Nova de Gaia, Vila Nova de Gaia, Portugal
3. Department of Cardiothoracic Surgery, Centro Hospitalar de Sao Joao, Porto, Portugal
4. Institute of Public Health of Porto, Rua das Taipas 135, Porto 4050-600, Portugal