By Per-Eric Hawthorne
Producer, Intensive Scares: Heart Ache
When you go into hospital for heart surgery you do not expect to get brain damage. But that is exactly what is happening to thousands of people a year in Britain.
Andrew Weston's marriage has suffered since his heart surgery
Their characters change. Frequent symptoms include anger, depression, memory loss, confusion, problems with coordination and difficulties in doing more than one thing at a time.
Andrew Weston is a 33-year-old traffic warden from Reading. After his triple heart bypass surgery to treat an inherited heart condition, Andrew's life changed completely. His character changed.
"I get very, very angry", he told the BBC programme Intensive Scares: Heart Ache.
"The anger really comes along at the slightest little thing that happens."
Difficulties at home
Andrew's uncontrollable anger is starting to interfere with the professionalism of his job, but its effects are far worse at home, where his wife and three children feel the brunt of his anger.
"One day, when I was at home, I just couldn't take it no more. The way I felt, I broke down.
"I lost my temper. I smashed the cooker. I did a lot of things I shouldn't have done. And then I realised that there was something really wrong and I had to get it sorted out."
For a long time Andrew didn't realise that his mood swings had been caused by his heart surgery. Andrew also experiences deep depressive episodes and frequent memory losses.
His heart surgery may have saved his life, but it has put his whole marriage in jeopardy.
Severe memory loss
Mo Thornton had heart bypass surgery ten years ago and her memory has been severely damaged by the surgery. If her husband Pete tells her something, two minutes later she will have completely forgotten what he said.
She had to give up working and is virtually housebound, because she keeps getting lost when she leaves the house alone.
"I used to order thousands of lines at the shop I worked at. Now I can't even remember what's in my own grocery cupboard."
Mo has to write endless lists to try and remind herself what tasks she has to do each day. It is tremendously frustrating.
"I get very confused and panicky, because I know I should be doing something. Or getting something. And I can't remember what it is."
Then there is Yvonne Kezthelyi who can remember the beginning of a journey and the end but completely forgets what happens in the middle.
Joe Xuereb cannot remember the order of complicated chess moves
Or Joe Xuereb who used to play chess for Malta but is now beaten by relative novices because, although he can remember all the right moves and combinations in his chess game, he plays them in the wrong order.
Intensive Scares: Heart Ache looks at how heart surgery has dramatically affected the lives of four ordinary people, and follows two further patients as they go through heart bypass surgery where the surgeons try out different techniques to minimise the likelihood of brain damage.
But most of this brain damage can be prevented.
And it is a British team led by world renowned Professor Stanton Newman, at UCL Middlesex, that has led the research in this field.
He became aware that the problem is caused by "microemboli" - tiny bits of matter which break away from within the arteries during surgery and travel towards the brain.
"Microemboli" can break away from arteries during surgery
"Imagine that it's a bit like kettle fur lining the inside of your arteries", explains Professor Newman.
"These are deposits which can be quite dangerous for the brain because if you clamp on them, they can go up into the brain and cause damage.
"What we're talking about, in a sense, is very tiny little strokelets, tiny little bits of damage to the brain where the supply of blood has been blocked."
Hundreds of tiny areas of the brain can die off in one operation.
But with various surgical techniques - such as using arterial filters in heart-lung machines, scanning arteries with an ultrasound probe before clamping them, minimizing the handling or "palpating" of heart and major arteries - surgeons can greatly reduce the incidence of this sort of brain damage in their patients.
And research continues.
Professor Newman's team is now looking at similar brain damage in other operations, like hip and knee surgery, and carotid artery surgery.
Intensive Scares: Heart Ache will be broadcast on Thursday 14 August at 21:00 BST on BBC One.