Access to a potentially life-saving treatment for heart patients is a postcode lottery, a study suggests.
Pacemakers can stop sudden cardiac death
A University of Southampton study in the British Medical Journal Online looked at the use of defibrillators which are implanted inside the heart.
It was found that the English regions with the highest heart disease death rates use the lowest number of devices.
The researchers blame a lack of funding and trained staff, and a failure to identify eligible patients.
Around 100,000 people die in the UK each year from sudden cardiac death.
Most of these deaths occur when the heart's rhythm suddenly goes out of sync, causing the heart to stop.
The condition can be treated by fitting a type of pacemaker called an implantable cardioverter defibrillator (ICD).
They device works in the same way as an external defibrillator, delivering an electric shock to restore the heart's normal function.
The researchers looked at the use of ICDs in regions across England between 1998 and 2002.
And they said that although use of the devices had increased significantly, England still lags behind the rest of Europe and the US in its use of ICDs.
Shortage of specialists
And they say an "inverse care law" is effectively in operation, with the areas where there are most at risk having the least access to effective treatment.
The study found that the South West and Trent regions implanted most ICDs.
But the West Midlands and North West - which have the highest proportion of heart disease sufferers - implanted the lowest number.
The research team, led by Dr Julie Parkes of the Health Care Research Unit at the University of Southampton, also questioned ICD centres across England to ask why they felt there were regional disparities.
The most common reasons given by the centres were a lack of resources for the £20,000 devices, a lack of staff trained to implant ICDs and poor identification and referral of patients to centres.
Writing in the BMJ Online, the researchers said all the centres surveyed expected to see an increase in demand for ICDs in the future.
They said ICD centres needed more funding and better planning to ensure the inequalities in access were eradicated.
Dr Parkes told the BBC News Website: "If people aren't getting these devices, they are missing out on effective treatment."
Dr Mark Mason, a consultant cardiologist at Harefield Hospital, said: "Cost is a factor in the number of these devices which are implanted.
"But the current guidelines from the National Institute of Clinical Excellence (NICE) were out of date when they were published in 2000.
"They were due to be revised within three years, but we are still waiting."
Dr Mason said doctors working in local hospitals were often the ones referring patients to have ICDs fitted.
But he said they were often not cardiologists and had often not seen the latest research outlining who was suitable for the treatment.
He suggested the regional variation in ICD provision was linked to the number of heart specialists.
"I'm sure that the data on the number of cardiologists available would show that areas of greater deprivation - and higher levels of heart disease - would be those with the least number of specialists."