Dr Elijah Behr, Reader in Cardiovascular Medicine and Honorary Consultant Cardiologist and Electrophysiologist at the Cardiac Research Centre, St George’s University of London, UK, speaks with Cardio Debate & Radcliffe Cardiology about Prevention of Sudden Cardiac Death during the “Advances in the Pathogenesis and Management of Cardiovascular Disease” 2015 meeting organised by the Cardiovascular Sciences Research Centre of St George’s University and held at the Royal College of Surgeons of England in London, UK.
What is the role of implantable devices in inherited arrhythmogenic diseases?
The role for implantable devices really depends on the condition. There are some general principles though. The arrhythmia syndromes tend to affect young people, and therefore we need a very high threshold for which to implant young people with electronic devices because of the potential for long-term list of complications. So the first thing to say is only a small minority of arrhythmia syndromes require these devices and implants.
Secondly, the approach to risk stratification is very much dependent on the condition and so, for example, if we look at a condition called the Long QT syndrome, which we know very well and we have a lot of data on, we can actually do a certain amount of risk stratification that seems to be effective at determining which patients are at risk.
So, for example, we know that young boys are most at risk of the condition in the younger age groups. And if they’re having blackouts or if they’re having a very prolonged QT interval, or both, then they are more likely to benefit from an ICD implant.
And then conversely, in adults, young women seem to be at the greatest risk, there seems to be a hormonal shift, during puberty. But not all women with that condition require that sort of protection. Usually it’s if they have serious symptoms and if they’ve had a very prolonged QT interval on the ECG, or they are failing therapy already – so they’ve gone onto therapy and they’ve not succeeded.
And in the Long QT syndrome there are other therapies that may hold off the need for an ICD implant, for example sympathetic innervation of the heart.
We then move onto a different condition, the Brugada syndrome, where we have a lot less data on risk. And the stratification of risk with Brugada syndrome comes down to whether you have symptoms or whether you have no symptoms.
And unfortunately most people with the Brugada syndrome who die from the condition don’t have warning symptoms. So there is a large unmet gap there in terms of the patients who might need an ICD implant to protect them but we can’t predict them so well.
So the role for ICD implantation in Brugada syndrome is very clear in someone who has already had symptoms, but unlike in Long QT where you may be able to predict that somebody is going to be at greater risk in the long term, we have a lot of problems with that in Brugada syndrome. So the role for ICD implants there is very difficult at the moment, other than in the patients where it is very obvious to begin with.
What are the most recent advances in risk stratification of BRUGADA syndrome?
The potential advances in the Brugada syndrome in terms of risk stratification revolve around how we can examine the phenotype of the patient more accurately. And the easiest way to do that is to use the ECG because it is our easiest tool and there is certain evidence that if you see other features in the ECG they may indicate higher risk.
So if we abnormalities in the QRS complex, fragmentation of the QRS complex, or if we see ‘notching’ towards the end of the QRS complex in the inferior ECG leads known as early repolarisation pattern, then these seem to be associated with an increase in risk for cardiac arrest in the asymptomatic patient, of around three fold each.
So they be able to help us in determining whether we wish to implant an ISD in a patient, or not, who hasn’t had symptoms as yet.
In the individual we may also consider invasive risk stratification, and there has been a long-standing and contentious debate over the role of invasive electrophysiological study in the risk stratification of Brugada syndrome.
And the invasive ECG study has always been based around an attempt to induce stable ventricular arrhythmias in patients who have existing structural disease, for example having had a previous myocardial infarction.
It’s not particularly designed for interrogating a heart that where there isn’t serious structural abnormality. So there is an issue that this may be the wrong tool to be using in Brugada syndrome to begin with, but nonetheless it is being used.
And there are data that really strongly support the use of EP studies to induce arrhythmias and predict arrhythmias in patients, and then there is a large body of data that says that isn’t a useful predictor whatsoever.
The most recent meta-analysis suggest of these data suggest that there is a marginal benefit in the asymptomatic patient of being able to show induction of arrhythmia from the EP study, but it is only marginal so the predictor value is only small. And therefore you have to use it very carefully in the right patient to try and see if it will help your management. That’s my take on that latest data.
There will still be a lot of resistance to using it, as well as those people with great enthusiasm for it. I think that very tempered and very careful use of the tool is probably warranted, and that will probably be beneficial for our patients in the longer term.