Between 350,000 and 400,000 Americans die every year from sudden cardiac death. And while the “sudden” part makes it seem like it came from out of the blue, there actually can be warning signs – and lifesaving measures people can take.

“When I talk about sudden cardiac death with patients, I tell them: This is a real health issue, and there are a lot of folks at risk,” said Dr. Russ Bailey, a clinical cardiac electrophysiologist with Novant Health Heart & Vascular Institute in Charlotte. “Our job – our obligation – is to try to identify patients who are at a higher risk and have this conversation about a defibrillator as a protective approach.

Dr. Russ Bailey

“The stories patients see in the media will mention someone on a golf course or at a restaurant who suddenly collapsed and died of a ‘massive heart attack.’ That's almost never the case.”

Bailey had much more to say on the topic.

What exactly is “sudden cardiac death”?

The terminology is similar to “heart attack,” and they are easy to get mixed up. The lay press commonly mixes up the terminology, and the public consequently thinks they’re synonymous.

Let's start with the term “heart attack.” What cardiologists mean by “heart attack”: A coronary artery has had a sudden limitation of blood flow. That’s usually due to long-standing cholesterol plaque buildup, which suddenly changes and limits blood flow downstream to the heart muscle.

A heart attack means a coronary vessel is not delivering enough blood to an area of the heart muscle. Someone having a heart attack might show symptoms of chest pain or tightness, shortness of breath. Those are the classic symptoms. And unless that's relieved quickly, those patients suffer permanent damage to the heart muscle, which impacts heart pumping function.

Fortunately, most patients don't die of a heart attack, although a small percentage do.

Sudden cardiac death in my world – as an electrophysiologist dealing with rhythm issues – means the abrupt onset of such a chaotic rhythm that the heart is no longer stimulated to contract in a nice, rhythmic way. It just quivers. The muscle is stimulated so chaotically that it's no longer pumping.

And those patients promptly develop either profound dizziness or very quickly pass out. And unless something is done to interrupt that rhythm and return it to normal in a hurry – and we’re talking seconds to minutes – those patients don't survive.

So, the things people do to ward off heart disease – exercising, eating healthfully, not smoking – don’t help prevent sudden cardiac arrest?

Let's talk about it the other way around – in terms of risk factors for developing sudden cardiac death.

At the top of the list is prior damage to the heart muscle. And that can be caused by multiple processes, but the most common is a prior heart attack. That heart attack may have been a month ago, or it may have been 15 years ago. So, prior heart damage is the biggest risk factor we know for developing one of these sudden chaotic rhythms.

Patients with normal heart pumping function, with rare exceptions, are generally at very low risk of developing these problems.

People at high risk are those who've had a prior heart attack or cardiomyopathy – a weakness of the heart muscle from other reasons, including long-standing, poorly controlled high blood pressure – and prior diagnosis of heart failure, which we think of most commonly as being low-pumping function.

Also, patients can have weakness of the heart muscle because of severe valve disease. And there's, unfortunately, a group of patients who have weakness of the heart muscle for reasons we can’t clearly identify.

The things folks can do to reduce their risk would be those things that would minimize their chance of developing heart damage. So, to your question, controlling blood pressure, stopping smoking, knowing your cholesterol and keeping it well-managed through diet or prescription medications, exercise, managing blood pressure and diabetes if they have that – all of these things reduce risk.

Someone who experiences sudden cardiac arrest will likely not survive?

Right – unfortunately. Unless they happen to have a defibrillator (an implanted device that sends an electrical shock to the heart to restore a normal heartbeat) in place, 95% of those patients don't survive to meaningful recovery. Some will survive with profound neurologic deficits, but only about 5% will return to baseline functional status if they survive. Read more about implanted defibrillators here.

Does that mean that everyone who suffers cardiac arrest might have known there was a chance it might happen because there was a prior heart attack or some other heart trouble?

Well, many people do die without a prior diagnosis. There are, unfortunately, lots of folks walking around who don't know they've had a cardiac event – what we used to call a “silent heart attack.” They may think they had bad indigestion six months or a year ago, and it was actually a heart attack they never knew about.

A population that is at risk and needs regular assessment and follow-up are patients who have had a known event. That’s who we want to reach. We know they had some degree of prior damage, but from a functional standpoint, they're feeling OK, they're doing well. But it doesn't mean they’re at low risk for it happening. Anyone who’s walking around with what’s known as low ejection fraction – or low EF – is in a higher-risk group.

Everyone who's had a heart attack is at higher risk for low ejection fraction. We want to know who they are. They should want to know who they are; they may not have been assessed in years.

How often should somebody in that category be assessed?

No less than an annual follow-up with their primary care physician and periodically with a cardiologist, and that may be annually, as well.

What does that annual visit involve?

It could simply be an EKG. Or, it may be a reassessment of that ejection fraction with an echocardiogram, which uses sound waves to produce images of the heart for a doctor to evaluate. If they've developed any new symptoms, it might include reassessment of their coronary arteries either when stress testing or other imaging or even catheterization.

And certainly, any new symptoms – chest pain, breathing problems, palpitations, dizziness, passing-out episodes – should lead to an earlier reassessment.