Dr Richard Charles, Emeritus Consultant Cardiologist at Liverpool Heart and Chest Hospital and Chair of Creavo Medical Technologies’ Medical Advisory Board
October is Sudden Cardiac Arrest (SCA) awareness month – a campaign to address a major health problem which, although affecting 100,000 people a year in the UK, is widely misunderstood.
The fundamental distinction to make at the outset is that SCA is very different from a heart attack. A heart attack is caused by impeded blood flow through the heart, whereas SCA is usually caused by a structural or electrical problem with the heart – the result of an underlying condition. It is imperative, therefore, that we find a way of identifying those at risk before a serious cardiac event occurs.
Some of those that suffer SCA will have a recognised history of heart problems, such as coronary disease or disease of the heart muscle (cardiomyopathy). But for about half of those affected, SCA is in fact the first indication that there is something wrong with their heart. As such, developing techniques to screen patients, and identify people who may be at risk of SCA, could save many lives.
Some methods have been investigated over the years for such screening, mainly focusing on those with a recognised history. Some have been reasonably effective at identifying SCA in certain groups – but none have been robust enough to go into daily practice.
Innovations in screening
One area being explored is magnetocardiography (MCG) – a technology which existed previously in SQUID devices, but which Creavo Medical Technologies has developed for use at a patient’s bedside. MCG provides a unique look at the electromagnetics of the heart – and there is hope that it could be used initially in people with recognised underlying cardiac diseases, but then also, due to its simplicity and ready availability, incorporated into cardiac screening.
The primary purpose of Creavo’s device, Corsens, is to act as an aid to help physicians rule out acute myocardial ischaemia in patients who present with symptoms consistent of chest pain of cardiac origin in the emergency department. Identifying these patients early reduces patient anxiety and can save the hospitals valuable time, resources and bed space.
But now, we are considering how the technology might benefit the arrhythmia field – exploring whether it could be used to risk-stratify patients for SCA. One option could be to use MCG to examine those who fulfil the criteria for an implanted defibrillator (ICD) and assess common characteristics, compared to healthy hearts.
Improving our understanding of the need for an ICD
Many patients who have an ICD implanted never actually need a therapeutic shock. A study of the ICD registry in Israel, for example, found that only 1-2% of people with an ICD actually had a therapeutic shock in the ensuing 30 months. We also know that only around 20-30% of people who meet the guidelines for having an ICD actually have one implanted.
So, on the one hand we have a group of people with expensive and intrusive devices that are never ultimately required and, on the other, people who will potentially die of SCA who didn’t have a defibrillator fitted.
If we were able to refine and improve our understanding of which patients are most likely to need a shock, this would help reduce the cost to the health service and target care where it is most needed.
A key benefit of Corsens is that it visualises the heart’s magnetic field, producing a trace, magnetic field map and measurements. The hope is that it could allow us to better identify the characteristics of the ‘ultra-high risk’ patients amongst those who fulfil the current requirements to have an ICD implanted.
We are planning to use the device to perform studies into those patients who fulfil the current consensus guideline criteria for an ICD implant, to see whether any common features can be identified which could help us improve our risk stratification understanding. If we can assure ourselves that the metal in their chest is not affecting our MCG reading, this could also be supplemented by a study of people with an ICD who have already had a shock.
There are other studies that we are interested in linking up with. For example, a large scientific research project is being conducted in Belgium amongst people at risk of cardio-metabolic disease (such as people with diabetes). The objective of the study is to assess if it is possible to predict those at risk of heart failure – introducing MCG to the equation could deliver some illuminating results.
If such studies among those with ICDs or other high-risk groups were successful, we could then begin to look at using MCG to screen a much wider population of people.
At the same time, we are exploring using MCG for very specific groups, including children with genetic heart problems such as Brugada Syndrome – which are much rarer than SCA but just as devastating. We are involved in a study into Brugada Syndrome at St George’s University Hospital, to gauge whether MCG can identify those at risk.
A fight against SCA on many fronts
A huge amount of work has been done in recent times to raise awareness of SCA and move towards more effective screening. With MCG, we have the potential to screen for foetal and early infancy cardiac problems, right through to inherited and degenerative diseases. Implantable defibrillator devices remain the last line of defence to prevent death, and, by ensuring that the right people have them, we could save tens of thousands of lives each year.