Please could you give a brief introduction to heart attack centres?
Heart attack networks are designed to facilitate the rapid transfer of heart attack patients to centres with facilities that allow the manual unblocking of the coronary artery with angioplasty. These heart attack centres are often open 24 hours a day to treat heart attack patients around the clock and are staffed with dedicated teams and equipment.
Why are patients sent to specialist heart attack centres?
When a heart attack is due to a blocked artery it is vital that the artery is unblocked as soon as possible. This can be done with clot busting drugs (fibrinolysis) or manually via a minimally invasive procedure called angioplasty.
Randomised trial data has consistently demonstrated that angioplasty is associated with fewer deaths than fibrinolysis. Heart attack centres have therefore been set up to have dedicated equipment and staff that are trained in angioplasty to try and deliver the best possible therapy to patients most efficiently.
Please could you outline the surgical procedure some patients receive at these centres – primary angioplasty?
When a patient suffering a heart attack arrives at a heart attack centre they are transferred into an operating theatre to undergo angioplasty. This is a minimally invasive procedure that can be performed via an artery in the wrist or the top of the leg.
During this procedure small calibre tubes (called catheters) are passed up the main blood vessel of the body to the heart. Pictures are then taken of the arteries supplying blood to the heart to determine which artery is blocked.
Once identified a very fine wire is threaded through the catheter into the artery and through the blockage. The artery is then opened up and a stent (a metal scaffold) placed across the narrowing to keep the artery open. This procedure can be done rapidly and the relief of chest pain is often immediate.
Why did research based on “real-world” data suggest that patients given an angioplasty don’t tend to do better than those given drug treatment alone?
Randomised trials, in which doctors do not decide on the therapy given to the patient, have found that angioplasty is much more successful than drug treatment alone. But research based on “real-world” data has suggested that patients given an angioplasty don’t tend to do better.
We found that this is because in real life, doctors faced with a very sick patient tend to give them the most effective possible treatment. As a result more sick patients were sent to primary angioplasty and less sick patients were given fibronolysis and the benefit of angioplasty was being masked.
This phenomenon – termed allocation bias – is good medical practice but can make ‘real world comparative effectiveness’ research unreliable. When we adjusted for this bias we confirmed that angioplasty is the best choice for heart attack patients.
However, adjusting for this bias is difficult because doctors may base their decisions on many features that are difficult to document. As a result, decisions regarding the therapy of heart attack patients should be tested in the most reliable way, namely a randomised trial, and should not rely on registries.
Please can you explain the difference between this research based on “real-world” data and the randomised trials that have found that angioplasty is more successful than drug treatment alone?
In randomised trials patients are randomly assigned to a therapy and the decision of which therapy is out of the control of the treating doctor. This allows a more objective assessment of the competing therapies (fibrinolysis and angioplasty in this case). Whilst these trials are less susceptible to bias, they are difficult to conduct, are expensive, and may not be properly representative of patient populations.
In ‘real world’ registries, patients are allocated according to physician preference. They cover wide patient populations, are argued to be more generalizable because they can interrogate a therapy in subgroups excluded from randomised trials and may be favoured for reasons of ethics or feasibility. Registries and meta-analyses of them may therefore become more common. However, several factors may influence the choice of therapy for a heart attack patient seen by a doctor and these are difficult to record accurately. As a result these studies are more susceptible to bias and misleading results.
Which research is more accurate?
Randomised control trials give a more objective and less biased assessment of competing treatments and should remain the gold standard. Findings from ‘real world’ registry data should be interpreted by physicians and patients cautiously and confirmed in randomised trials before firm conclusions can be made about the merits of a therapy.
What does this research teach us about specialist heart attack centres?
There has been some debate in the cardiology community about whether it is worthwhile to run specialist heart attack centres, despite evidence from clinical trials that they save lives. This study resolves an important question. The global push towards dedicated heart attack centres is well founded and we must strive to make sure everyone suffering from a heart attack has access to the best emergency treatment.
What do you think the future holds for heart attack centres?
The aim should be to enable everyone to have rapid access to a heart attack centre in the event of a heart attack.
Where can readers find more information?
About Dr Sayan Sen
Dr Sayan Sen is an Interventional Cardiology Fellow at Imperial College Healthcare NHS Trust. Having qualified from University College London Medical School with honours in 2003 he trained as a junior Doctor at the Hammersmith Hospital and University College hospital in London before being appointed a cardiology registrar in 2006.
Dr Sen’s main clinical interests are complex coronary intervention and structural heart disease. His research interests include the assessment of novel technologies to guide treatment of cardiac patients.
In 2009 he was awarded a prestigious MRC clinical research fellowship to study the effect of coronary stenoses, coronary bypass grafts and aortic valve disease on coronary hemodynamics.
He has won several prizes for his research which has been published in Circulation and the Journal of the American College of Cardiology. He has been invited to present his work at the American Heart Association, American College of Cardiology and the European Society of Cardiology congresses.