Max George has revealed that he will now have emergency surgery sooner than expected because his heart rate has 'failed to pick up.'
The singer, 36, is suffering from a 2:1 atrioventricular block and revealed last week that he would be spending Christmas in hospital as he awaits an operation.
In a health update on Monday, he explained that after having a full chest scan, he might be heading into surgery 'way sooner' and could be home for the festive period.
Sharing an update to Instagram, Max could be seen wearing a hospital gown in the back of an ambulance.
He wrote: 'Had a little day trip today. Full cat scan on my heart. Not something I'd choose to do again!'
'As I mentioned yesterday, I have a 2:1 block in my heart. Unfortunately my heart rate hasn't picked up at all in almost a week.'
Max added: 'Because of this, we don't have too much time to wait so it looks like I'm going to be in surgery way quicker than the doctors first thought. I may even be home for Christmas!
'Still a pretty scary time right now and the last few nights have been really rough, but I wanted to say that I'm absolutely humbled by all your messages of support.
'Both people I know and those I don't. It's given me a much needed boost and my family have been overwhelmed with support, which means more to me than anything.'
An Atrioventricular block is a disorder that occurs when electrical impulses are delayed or blocked from reaching the ventricles.
The cause has been a 'mystery' and Max, who has battled alcoholism in the past, previously said: 'We've cancelled out a few things, like alcohol for example I've not had a drink for four-and-a-half years so it's not that'.
He told his followers: 'I hope you are having a good night, spoke to the nurse earlier and good news is I get to have a scan earlier than I thought'.
'So that's really really good, and it's called a 2:1 block, that's what we know at the moment, going to try and find out the cause before determining how we treat it, wether a pacemaker, defibrillator, or something else'.
Looking on the bright side he quipped: 'So that's where here I am at, feeling OK tonight, City game didn't help much' - after his beloved Manchester City lost to United.
In a health update on Monday, he explained that after having a full chest scan, he might be heading into surgery 'way sooner' and could be home for the festive period.
He wrote: 'Had a little day trip today. Full cat scan on my heart. Not something I'd choose to do again!... Unfortunately my heart rate hasn't picked up at all in almost a week'
An Atrioventricular block is a disorder that occurs when electrical impulses are delayed or blocked from reaching the ventricles.
A pacemaker is a small, battery-powered device that prevents the heart from beating too slowly. Surgery is needed to install it and the operation is generally carried out under local anaesthetic.
Following his health scare last week, Max shared to Instagram: 'Hey everyone, Yesterday I felt really unwell and was taken in to hospital. Unfortunately after some tests they've found that I have some issues with my heart.'
'I have a lot more tests to determine the extent of the problems and what surgery I will need to get me back on my feet.
'It's gonna be a difficult few weeks / months... and Christmas in a hospital bed wasn't exactly what I had planned! But, as always, I'm surrounded with love and support by my wonderful partner Maisie [Smith], her family,my family and friends..and I'm 100% in the best place.
'Although this is a huge shock and no doubt a set back, it's something I'll take on with all I've got! I count myself very lucky that this was caught when it was.
This week, Max, who has battled alcoholism previously, admitted he is 'very lucky that his heart problem was caught when it was' as he shared the health scare
Max shared to Instagram: 'Hey everyone, Yesterday I felt really unwell and was taken in to hospital'
He added: 'Apologies if I bore you with updates in the coming weeks..I've probably got a month in a bed and there's not THAT much to do! Let's do this! Much love, Max x'
Shortly after his announcement, Max posted a light-hearted jibe from his hospital bed about Manchester City loss in Wednesday night's football game.
Lying in bed with a heart monitor across his chest, he joked: 'So I think they are officially trying to kill me off... come on boys.'
Max has been open about his battle with binge drinking and alcoholism over the years, previously admitting he drank '10 pints and three bottles of wine in one night'.