title: The gray zone is always more dark.
authors.affiliation: Centro Cardiotoracico, Istituto Clinico Sant'Ambrogio, Gruppo Ospedaliero San Donato, Milan, Italy. Electronic address: mattia.glauber@gmail.com.
authors.forename: Mattia
authors.initials: M
authors.lastname: Glauber
authors.affiliation: Centro Cardiotoracico, Istituto Clinico Sant'Ambrogio, Gruppo Ospedaliero San Donato, Milan, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Lio
authors.affiliation: Centro Cardiotoracico, Istituto Clinico Sant'Ambrogio, Gruppo Ospedaliero San Donato, Milan, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Miceli