1. Division of Nephrology, Dialysis and Hypertension, Policlinico S. Orsola-Malpighi, 40138 Bologna, Italy
2. Cardiology Unit, Policlinico S. Orsola-Malpighi, 40138 Bologna, Italy
3. Pediatric Cardiac Surgery Unit, Policlinico S. Orsola-Malpighi, 40138 Bologna, Italy
4. Nephrology and Dialysis Unit, Ospedale Santa Maria delle Croci, 48121 Ravenna, Italy