Jeremy Laurance: 'How much should we spend on saving the lives of the elderly?'

My aunt Margaret has elected to take the biggest gamble of her life this week. Aged 80, she has a heart problem for which the only remedy is surgery. But surgery carries high risks. The doctor looking after her told me last week that for someone in her condition, the mortality rate is 15 per cent. So she has a slightly less than one in six chance of dying on the operating table or in recovery. That is like playing Russian roulette. Would you take such a gamble? Would I?

My aunt, a tiny woman who weighs just seven stone, didn't hesitate when the options were put to her. Of course she would have the operation. Why ever not? She had emergency heart surgery 15 years ago and was not expected to live then, but here she still is. She was a lot sicker then than now, she said, so why should there be a problem?

I remember that previous occasion. The surgeon – Sir Magdi Yacoub, as it happens – had telephoned my father as Margaret was being wheeled into theatre to warn him, as the closest relative, that it was touch and go. My father packed a black tie before making the journey to London to see her. None of us expected her to pull through, but she defied the odds then and she doesn't see why she shouldn't defy them again now.

The problem now is the same as it was before – a failed aortic valve. This means that the blood being pumped out by her heart is falling back into it instead of circulating around her body. When the lungs can't get enough blood, they fill up with fluid making her breathless. The result is that simple things like walking or lifting a shopping bag are exhausting.

Replacing an aortic valve was a standard operation even in the mid-1980s, but Margaret was not a standard patient. She has had lupus, an autoimmune disease, for the past 40 years, which was treated with high doses of steroids that damaged her heart and sight (she is registered blind). One effect is that she is very low in platelets, the constituent of the blood responsible for clotting, which makes it difficult to stop the bleeding after surgery. All in all, her medical history makes hers a risky case.

I have tried to raise this with her gently but she is firm. Her mind is made up. The cardiologist who examined her said that if it was his mother, he would advise her to go home and live a quiet life within the limits that the illness imposes – in other words, doing little and staying put. Margaret's response was robust. "I would rather snuff it than be a semi-invalid," she told me. "And anyway, I'm not his mother."

So here she is, laughing, feeding me cake and telling me of the foibles of the doctors and nurses, of the quality of the hospital food (not bad), of the health of the other patients, and I'm thinking – she's enjoying this. She likes being the unusual patient – for more than a decade she "lent her body" regularly to St Thomas' hospital, to be prodded by students – and she likes testing the limits of medical skill. But I wonder, in an age of league tables and targets, where mortality rates may soon determine careers, whether she would have been granted her wish for surgery had different criteria prevailed. Imagine a surgeon anxious about his record, sizing her up and thinking, "This is just not worth the risk".

It may be happening already, for resource reasons, not reasons of risk. How much should we spend on saving the elderly? The Wanless report on the future funding of the NHS showed that half of all spending on health occurs in the last year of life, but that the amount falls with increasing age. The last year of life of someone dying in their eighties is on average cheaper than the last year of life of someone dying in their fifties. Why should that be? One reason may be that we do less for the elderly than for the middle-aged.

It's a hell of a risk to take but I think my aunt deserves her chance. By the time you read this I may be weeping – or rejoicing. But she will have made her own decision and not had it made for her. For that, at least, we shall be thankful.