Can we predict sudden cardiac arrest?

Can we predict sudden cardiac arrest?

The following is a full transcript of our recently recorded conversation with University of Notre Dame Professor of Cardiology, David Playford (pictured).

In this conversation, Prof Playford outlined the various, sophisticated methods used to determine if someone is at risk of a cardiac event – such as a heart attack or sudden cardiac arrest.

His concluding message: no method of risk detection is conclusive.  To save lives, we need to be prepared to respond in the event that a cardiac event occurs.  


“I’m David Playford.  I’m a cardiologist.  I’m the Professor of Cardiology at the University of Notre Dame.  Apart from being a clinical cardiologist, I’m also an imaging specialist, a researcher, and I also have an artificial intelligence program.

“I want to talk a little bit today about cardiovascular risk, what we can do to try and pick cardiovascular risk, and how we can find a way to be prepared for it, potentially.”

What is cardiovascular risk?

“So, when I’m thinking about cardiovascular risk, I’m thinking first of all, about the traditional risk factors.

“Some of these risk factors include high blood pressure, high cholesterol, smoking, diabetes, and a family history of heart disease.

“What do I mean by each of these?

“High cholesterol has a few different meanings.  There’s something called familial hypercholesterolemia, which means you’re born with a very high cholesterol caused by a genetic abnormality, and then very high cholesterol persists throughout life.

“The longer you’re exposed to very high cholesterol level, the more likely it is to cause cholesterol build-up in the walls of the arteries.  As that increases, the chance of heart attack also goes up.

“Familial hypercholesterolemia can be detected by a genetic test – but, a lot of people who have this, feel perfectly well, and are unaware they’ve got a problem until someone goes looking for it in them individually.

“Second thing we would look at, is whether the cholesterol may be relevant in context of other risk factors.

“In cardiology, we try not to look at things on their own, out of context.  We try to look at things in context of how things match together, in association with other risk factors.

“We do a risk factor assessment, using a series of probabilities I suppose, where we link one risk factor with another and see how they interact, to increase somebody’s chance of potentially having a heart attack in the future.

“We have various different scoring systems that we use.  The bottom line is, the trouble is, even if we do this carefully, we really assess someone’s risk in detail, we can never exactly predict what’s going to happen in the future.  We just give our best estimate I suppose, based on the information we have available.

“Just briefly talking about other risk factors, high blood pressure is a well-known risk factor, not just for heart attacks but also strokes and other heart events.

“High blood pressure is defined by a blood pressure above 140mm of mercury systolic.  In fact, and optimal blood pressure, a perfect blood pressure I suppose, sits around 125mm – a lot lower than the cut point we use “to diagnose in the first place. We often use treatments to try and get the blood pressure down to normal levels, particularly if the risk overall of a future event is high.

“(There are) about other risk factors as well.  Type II diabetes is a well-known risk factor for heart disease.  Those who have high blood pressure and high cholesterol also have risk factors for diabetes as well.  Type II diabetes, once it has been identified, is really something we need to treat to minimise the chance of causing significant cholesterol build-up in the arteries.

“Talking about a family history of coronary heart disease, that kind of history isn’t necessarily just related to cholesterol.  There could be other genetic abnormalities that somebody’s born with, that can increase the risk of developing heart disease.”

Can you predict a heart attack or sudden cardiac arrest? 

“Once we have all of this knowledge, we know the blood pressure, we know the cholesterol, we know the smoking history, we know the history of diabetes and their genetic family history – even then, it’s really hard to pick necessarily who’s going to go on to have a heart attack in the future.

“We have newer forms of cardiac imaging that are really very good now in being able to pick coronary disease, or whether there’s cholesterol build-up in the arteries.

“The test I’m talking about is coronary CT, or cardiac CT.

“The calcium score, you may have heard of already, is one of the commonly-used test now to see if there is long-term cholesterol build-up in the arteries.

“Calcium scoring gives us the ability to actually measure how much calcium there is in the walls of the arteries.  A calcium score of zero basically means there is no calcium build-up, which is a sign there hasn’t really been much exposure of the arteries to cholesterol over time.

“Older individuals, say someone who is over the age of 65 or 70; if there’s zero calcium, then that pretty much excludes significant heart disease.  That’s really reassuring.

“In a younger person – let’s say someone between the age of 40 and 50 – a calcium score of zero doesn’t really give that much reassurance because there hasn’t been enough time yet to expose the arteries to high cholesterol.  It’s possible there may be cholesterol build-up but without any calcium there yet.

“What we tend to use with younger individuals is CT coronary angiography, a contrasting injection that’s usually given in one of the arms, then fills the coronary arteries.  A cat scan then is taken while it’s filling the coronary arteries.  We can really see in detail, what the wall of the artery looks like, and whether there’s any cholesterol build-up there.  It’s a really good way of picking early cholesterol build-up in the arteries, or atherosclerosis.

“That gives us a really good picture overall whether there is coronary risk present – and that’s very helpful for making a decision on whether we should treat somebody to prevent a future heart attack from occurring.

“I’ve talked about risk factors, I’ve talked about coronary CT – but even with this information, we still don’t know really exactly what’s going to happen in someone’s future.  We can give an estimate, we can give a prediction of risk – but we can’t absolutely know what’s going to happen.”

What is the most effective way to help someone survive sudden cardiac arrest?

“One statistic that’s really important in making a decision on what to do, is what happens if somebody has a heart attack.

“50 per cent of all first heart attacks are fatal.  This is a really scary statistic, but I’m sure you may actually know someone who has had a heart attack that they didn’t survive from.

“What we’re trying to do is increase the chance of somebody’s survival, even in the unfortunate circumstance where they have a heart attack.

“The first thing we can do if we possibly can, is to prevent the heart attack from occurring.  We treat risk factors, we do whatever we can to minimise risk.

“But even if we do that, there are some people that we just couldn’t pick it.  We just didn’t know they were going to have a heart attack.  Those are the people we want to try and identify.

“If that individual has a heart attack, we want to be prepared.  We want every tool that we have available, to be able to potentially deal with that if that occurs.”

“In the event of somebody having a heart attack as you I’m sure know, the right thing to do is to call (emergency services).  If somebody presents with chest pain, they have this classic central discomfort, or sudden unexplained breathlessness, collapse – then (emergency services), call an ambulance, get to hospital as fast as possible, and then we can administer the appropriate treatments.

“The other thing I want to mention is about what happens if somebody collapses, so somebody goes unconscious.  If somebody goes unconscious in the setting of a heart attack, usually that’s a cardiac arrest that’s occurred.

“If a cardiac arrest occurs, the best way to improve that person’s survival is defibrillation.  That’s to give them a shock as early as possible, to get their heart back to normal again.

“The way that needs to be done is with a defibrillator.  You probably have seen around in shopping centres, in airports and in public places, there’s a lot of AEDs, that’s automated external defibrillators, that are available specifically to cover this possibility, if somebody has a heart attack, becomes unconscious, they go into cardiac arrest.  The defibrillator is designed to be able to give them a shock as fast as possible, to try to restore normal rhythm.

“The danger here, is that first of all, the defibrillator may not be where the person is that has the cardiac arrest.   Sometimes, trying to find that defibrillator or trying to get access to it in a timely fashion is a problem.

“Really, the holy grail would be to some way, find a method of defibrillating people, where the defibrillator is available where the person is.  That’s obviously a logistics challenge, but that would be the ideal, and to cover all the eventualities so that really, nobody is missed.”

What can we do about cardiovascular risk?

“50 per cent of all first heart attacks are fatal.

“This is a very sobering statistic.  But it’s important because, before a heart attack occurs, the individual doesn’t know they’ve got a problem.  They may be totally unaware of it.

“If the individual hasn’t really been able to anticipate if the problem is going to happen, they haven’t been able to take evasive action to prevent it from happening.

“The real issue here is that coronary artery disease can be a silent killer, in the sense that the individual who has the problem doesn’t know that they’ve got something brewing under the surface, until something happens.

“There are ways we can try to prevent this, to predict risk; we have various tools available such as cat scanning and risk assessments et cetera, that are really very good at being able to identify risk – but we can’t pick everyone.

“We want to be able to prevent premature death.

“The way we try to do this, apart from trying to control risk factors, and decrease the overall likelihood of a cardiovascular event, because we can’t prevent all cardiovascular events, we’re trying to get people more prepared.”

“The way to be more prepared is to have access to emergency facilities.

“Everyone knows about ringing emergency services if somebody collapses – but it takes time for an ambulance to arrive.

“In those critical minutes, the first three minutes, somebody can die before the ambulance actually arrives.

“So, having emergency defibrillation available onsite, at the point where the event occurs, it can be absolutely life-saving.

“The capacity to defibrillate somebody, to get them out of their cardiac arrest and save their life, could make a massive difference to the overall survival of people who have out-of-hospital cardiac arrest.”


RELATED ARTICLE: Cardiac arrest isn’t someone else’s problem