Max George, of boy band The Wanted, has said he needs surgery for a heart condition, "way quicker than the doctors first thought".
Taken into hospital on Wednesday, the singer, 36, had a scan on Monday and then posted: "We don't have too much time to wait."
He had been diagnosed with "a 2:1 block in my heart", George said, where the heart beats more slowly or with an abnormal rhythm because of a problem with the electrical pulses.
It was "a pretty scary time right now and the last few nights have been really rough" but he hoped to be out of hospital by Christmas.