Best and worst

United Bristol Healthcare 48 Plymouth Hospitals 51 Leeds Teaching Hospitals 54 University College London Hospital 170 South Manchester University Hospital 172 Walsgrave Hospital 182

The national average ratio is 100, with a figure above 100 indicating a higher death rate.

The study names United Bristol Healthcare - the hospital at the centre of the heart babies scandal - as having the lowest at 48.

Walsgrave Hospital in Coventry - run by the University Hospitals of Coventry and Warwickshire NHS Trust - has the highest at 182.

The guide has been compiled by the independent medical consultancy, Dr Foster, with the help of the Department of Health.

Biggest killer

Coronary heart disease is the UK's biggest killer, claiming 135,000 lives every year.

There are two procedures used to combat it. One takes a vein from the leg and uses it to bridge the blockage, while the other re-routes the mammary artery in the chest to achieve the same result.

There are some parts of the country where medical outcomes are unacceptably poor

Liam Fox Shadow health secretary

The death rates for by-pass operations show the greater the proportion of arterial grafts, the lower the mortality.

Nearly 90% of patients in the UK now get at least one mammary graft, but the proportions vary between different hospitals.

In some units, only 55% of patients get an arterial graft, while in others it is as high as 95%.

The guide is the first where death rates for NHS trusts have been published comparing the success rate for a single operation.

Analysed

Sir Brian Jarman, emeritus professor at Imperial College, analysed the figures separately.

He said: "This guide is a valuable tool for patients and GPs alike as it helps to identify variation in quality of hospital services.

"It also shows that the success rate of heart surgery is getting better all the time."

Overall, the survival rate for coronary artery by-pass grafts is around 97%. In the worst units it is around 95.5%, and in the best 98.5%.

Dr Roger Boyle warned against focusing on death rates.

Dr Roger Boyle, the National Heart Director, said it was important not to put too much emphasis on hospital mortality rates.

He told the BBC: "The worry is that by putting this huge emphasis on mortality rates it will tend to deter surgeons from taking on some of the higher risk, needy patients.

"The easiest way of getting the mortality rate down is to stop doing those patients.

"We have got to keep it balanced. I think what patients want is a safe system, but a caring system as well, and that part of it must not be forgotten."

Professor Sir Peter Morris, President of the Royal College of Surgeons said accurate data on surgical outcomes could potentially empower patients, and help surgeons make a case for improvements in facilities and support.

But he said the current figures were based data that commonly contained inaccuracies.

As such it would be unwise to place too great a reliance on this without further investigation."

Reasons

The figures are more bad news for Walsgrave Hospital, which received a daming inspection report two months ago.

John Richardson, of the University Hospitals Coventry & Warwickshire NHS Trust which runs the hospital, said: "Our figures are explainable by the number of emergency, elderly and very sick patients that we have been operating on in the past.

"These people are more likely to die, and they have made the figures the way they are.

"For people coming in for routine surgery there is no need to worry at all. Our figures are as good now as anybody elses in the country."

Improving performance

A spokesman for the Department of Health said while the tables showed some hospitals were not performing as well as others, they also showed surgical performance was improving across the NHS.

"We think increasing openness about data is involved in that," he said.

"But of course there are some hospitals whose progress has not matched up to that overall improvement.

"We expect trusts to look at their data, think carefully about why it may be different to the national improvement and - where the differences can't be accounted for in terms of case-mix or other issues - take action to improve their record as a matter of urgency."

The Conservative Party said the tables highlight the crisis in the NHS under Labour.

Shadow health secretary Liam Fox said: "They are bad enough in themselves, but there are some parts of the country where medical outcomes are unacceptably poor.

"What makes matters much worse is that, because Labour have removed the freedom of patients to move to other parts of the country for treatment, we now have areas of Britain where patients and their doctors are stranded in third-rate health ghettos."