NUGGET : The £12,000 device has the same kind of effect as a traditional defibrillator used to shock hearts into starting after they have failed
A breakthrough device just an inch and a half in diameter could save the lives of thousands of Britons at risk of dying from cardiac arrest.
People who suffer from life-threatening disturbances to their heartbeat - known as arrythmia - could now be given the Subcutaneous Implantable Defibrillator, or S-ICD, after it was found to be a major success in clinical trials.
The £12,000 defibrillator is implanted under the skin and delivers a shock if the rhythm of the heart is disturbed, to get it back to the regular beat.
The 1.5" system delivers a bigger kick-start to the heart than conventional devices in response to life-threatening rhythm disturbances.
And it also offers new hope to sufferers as previous devices had the risk of complications from infection from the leads which connect them to the heart.
Around 70,000 people every year die in the UK from sudden cardiac death caused by arrhythmia, a disturbance or irregularity of the heartbeat.
Implanted defibrillators provide round-the-clock protection for hundreds of thousands of patients with heart problems, with at least 30,000 implanted in the UK, but many more go untreated.
Dr Andrew Grace, consultant cardiologist at Papworth Hospital, Cambridge, who helped develop and test S-ICD, said it was a major advance.
He said 'This could completely change the use of implantable defibrillators.
'At present the potential complications are a barrier. Some patients turn them down, and some of them do die as a result of rhythm disturbances that could have been detected and treated with an internal device.'
The new battery-operated S-ICD system has just one wire going across the chest under the skin, connected to the device implanted beneath the skin on the side which contains the electronic components to deliver the shock.
The added distance from the heart means a more powerful shock can be delivered than from conventional devices - about 2.5 times stronger.
It also means the S-ICD is less likely to pick up electrical 'noise' from the heart which can trigger unnecessary shocks, known as false positives, which can be 'traumatising' for patients.
The breakthrough by an international team of researchers is reported today in the prestigious New England Journal of Medicine.
The findings from three clinical trials show the Subcutaneous Implantable Defibrillator (S-ICD) detected and successfully treated all 12 episodes of severe rhythm disturbance over a 10-month period.
Conventional ICDs require placement of at least one lead in the heart - usually threaded through a vein - which sense dangerous changes in heart rhythm and deliver a lifesaving shock.
But the leads on these devices may cause infections in patients who then need treatment or even further surgery to remove them, said Dr Grace.
'This deters some patients from having them implanted, and may mean doctors are less willing to recommend them' he added.
The clinical trial data shows the S-ICD is as effective as conventional devices at delivering electrical impulses to restore normal rhythm in almost all episodes of induced disturbances.
The S-ICD also successfully detected all 12 episodes of ventricular tachyarrhythmia in 55 patients using it in a 'real-life' trial.
There were two minor infections over the 10-month trial period.
The journal report says S-ICD could overcome some of the complications and lead failure caused by conventional devices.
'These benefits would be especially important for young patients, in whom leads may fail during the decades that therapy is needed' it says.
Made by US-based Cameron Health, the S-ICD lasts around five years before replacement is necessary.
Dr Grace has started using S-ICD for patients at high risk, including young people with a family history of sudden cardiac death.
Previous research suggests they are 98 per cent effective at preventing sudden death, with drug treatment being far less benefical.
Dr Grace said NHS guidelines recommend their use in around 6,000 patients a year, yet only 4,000 were getting them.
'The number who could benefit is much, much higher than this. The question is where do you draw the line?
'If there is a low-risk device available then it's likely we'll eventually be treating many more patients who are at risk of sudden cardiac death but don't currently fit the criteria for an implantable defibrillator' he said.