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One of my earliest memories of my cousin is — is kind of vague. I remember the two of us together, it was somewhere in India, and we were each flying these thin, paper kites. I was using the tension from my kite string to try and cut his string, and he was doing the same thing to me. It’s something called kite fighting. My last memory of my cousin is much clearer, though. It was a dinner in Boston’s Back Bay around July of 2012. And I remember that meal so clearly because it was actually our last dinner together. You see, a week later, my cousin died of cardiac arrest. He was at work, and he collapsed outside of an office building, while he was leaving. He was taken to Massachusetts General Hospital, and I happened to be there, in the hospital, on call that night. I’d just arrived there, and I got a page from the Emergency Department, asking me to call about my cousin, which I thought was really strange. So, I returned the page and the resident asked if I was sitting down, which is never a good sign. He told me that my cousin had suffered a cardiac arrest. He’d been brought to Mass General, and they’d tried to resuscitate him for 45 minutes, but they couldn’t. My cousin was 34 years old.

It’s hard to tell this story, but I wanted to share it because it was my introduction to something that almost everyone in medicine has seen and feared: cardiac arrest. Nearly 400,000 cases of cardiac arrest happen outside of hospital settings every year in the U.S., and around 80 percent of them lead to death.   When it affects young people, like my cousin, it’s even more shocking.

Especially because, well, it doesn’t have to be that way.

From the Freakonomics Radio Network, this is Freakonomics, M.D.

I’m Bapu Jena. I’m an economist and I’m also a medical doctor. Each episode, I dissect an interesting question at the sweet spot between health and economics.

Today on the show: cardiac arrest is so common. Death from cardiac arrest is, too. How can we prevent more of those deaths? We’ll explore one possible solution that involves something we all use every day —

David FREDMAN: How could we use this new thing that everyone was carrying around?

— and another that challenges our preconceived notions.

 Prachi SANGHAVI: We’re actually trying to take a simpler approach.

When someone has a cardiac arrest, meaning, their heart has stopped pumping blood, for any number of reasons, you can’t really waste any time. Of course, the first thing anyone should do is call 9-1-1. And then, ideally, you’d start administering cardiopulmonary resuscitation, or CPR. Even better: if there’s an automated external defibrillator, or A.E.D., nearby, you use that. It’s a device that uses a shock to reset certain fatal heart rhythms. But what are the odds that one of those machines is within reach? Or that there’s even someone, anyone, around who knows how to do CPR?

David FREDMAN: I was at home putting my daughters to sleep, and all of a sudden, the phone rang.

Our first guest today is from Stockholm, Sweden. I’ll let him introduce himself.

FREDMAN: My name is David. My surname is Fredman, spelled with just an E. So, that’s the Swedish little spelling of it.

David is a cardiology nurse. We’ll get into his work a bit more in a second. But back to that time when he was putting his daughters to sleep. When the phone rang, it wasn’t a call but actually a notification, alerting him that his neighbor was suffering a cardiac arrest.

FREDMAN: And I rushed off and ran over between our houses and made my way to my neighbor. And I was — well, like, 30 seconds before the, the firefighters arrived. So, I helped them in, and the neighbor was unconscious in the living room, and we performed CPR together. I think we were there for, like, six, seven minutes before the first ambulance arrived. And then I actually tended to the spouse in this case, like bringing up a glass of water.

The neighbor survived, probably in part because David was able to respond so quickly. The call that David received is actually from an app he helps run called HeartRunner. For now, it operates only in Sweden and Denmark.

FREDMAN: I’m the operations manager or “heart of operations” of the company, Heart Runner. We are a med-tech company, founded in Sweden, originating from the idea of alerting volunteers using their smartphones.

As I mentioned, David was once a full-time cardiology nurse. He went on to earn a Ph.D. from the prestigious Karolinska Institute in Sweden. David didn’t come up with the idea for the notification system — that was his Ph.D. adviser, Dr. Leif Svensson, and his colleagues, in the early 2000s.

FREDMAN: He had an event where he was actually taking the bus to his work at one of the hospitals here in Stockholm. And the bus was somehow delayed. The driver got off and nobody actually knew what’s going on. And after a while, the bus drove off and just rushing in behind is an ambulance. And at the bus stand, there was a lady having a cardiac arrest. And that’s when Leif sort of, “Well, how could I have been alerted or made aware that my skills in CPR were needed just nearby?”

Leif and his colleagues wondered: Could they use smartphones — which were new at the time, but becoming more popular — to save lives?

FREDMAN: How could we use this kind of new thing that everyone was carrying around? Was it possible to engage private individuals in lifesaving attempts using a smartphone?

First, they tweaked technology already in place that warned truck drivers of local weather issues. Then, they changed the algorithm so that when an emergency call came in about a cardiac arrest, the dispatcher would send out an ambulance and trigger this unique bystander alert system. The goal was to notify people near the crisis as it was happening, with the hope that they could respond faster than an ambulance.

FREDMAN: We know that if you perform CPR on a cardiac arrest patient, the likelihood of survival increases dramatically. And the earlier you do it, the higher the chance of survival.

Just because they built this technology — didn’t mean it would work. Would you drop everything to help a stranger in the vicinity because your phone told you to do so?

David, Leif, and a group of other researchers decided to test the system out. They recruited thousands of volunteers who knew CPR. If someone nearby had a cardiac arrest, they could be notified, and respond. Then patients who had a cardiac arrest were divided into two groups, at random. They either had alerts sent to one of these volunteers or not.

FREDMAN: By using cell phone technology we could alert individuals and and ask them to leave what they were doing, and go to another location and perform CPR.

The study looked at rates of CPR performed in 667 patients who had an out-of-hospital cardiac arrest. It turns out the patients who had the alerts sent to volunteers were about 29 percent more likely to receive bystander CPR than patients who didn’t. The study, which was published in the New England Journal of Medicine in 2015, wasn’t large enough to detect differences in survival associated with the intervention. But we’d expect increases in CPR rates of this magnitude to improve survival when applied to larger numbers of people.

The researchers didn’t just stop at this study, though. They went further.

FREDMAN: That’s when the innovations company from the university Karolinska Institute approached us and said, “Well, we can help you with the establishment of the company.”

The company — HeartRunner — was officially set up in 2016, and as of today about 244,000 volunteers are registered on the app. Research has shown that nudges like this have increased rates of bystander A.E.D. use, not to mention survival rates among people who suffer cardiac arrests.

There are other companies that are trying to do what HeartRunner does. In the U.S., there’s PulsePoint. There’s GoodSAM in the U.K. But Sweden and Denmark are a bit different culturally than the U.S., even the U.K., because they generally have higher levels of social trust. When the GoodSAM app was studied in the U.K., it had far lower usage rates. In London, for instance, less than 2 percent of app notifications were accepted. David’s study in Sweden found that about two-thirds of calls led to bystander action.

FREDMAN: We spend lot of time and efforts on communicating with the volunteers to keep them motivated. And I know that in Denmark, they spend lots of money and resources on keeping the volunteers alert, keeping them motivated and asking them to take refresher courses. And they really communicate. And will bang on the drum that, “Well, you are important. And if you do something, you might help your neighbor.”

Tools like the HeartRunner app sound so promising. Just think about all the lives that could be saved if people knew to help their neighbor. Of course, there are challenges. Not everyone knows CPR, or regularly refreshes their skills if they do. In Denmark, you learn CPR when you get your drivers’ license.  That’s not the case here in the U.S., although 40 states and the District of Columbia do require CPR training to graduate high school. Not to mention, what about entering someone’s home? How willing would you be to allow a stranger into your home before a first responder? Maybe in an emergency, but it’s hard to know for sure. In Sweden, David says an ethics committee approved their research work, giving the okay for the volunteers to enter homes when notified.

FREDMAN: It was well-monitored in the first years and even after, and we don’t have any reports of incidents about theft or criminal activities. And so, we’re really lucky. But of course, it’s not only about informing the volunteers about enrolling and alerting them. It’s also about when you call 9-1-1 or 1-1-2, about your spouse who is in cardiac arrest, it’s not the ambulance who will be there first. It might be your neighbor.

Someone like David, himself.

FREDMAN: I I still see my neighbor. He’s still alive.  What we have done, what was a crazy idea, what we’ve been fighting for because no one really actually thought that this was achievable. Here I am, and it works.

There are a lot of stories about cardiac arrest, and each one can help us learn something. Sometimes because the patient also happens to be a researcher. Dr. Kevin Volpp is a doctor and economist at the University of Pennsylvania. You heard him recently on an episode of Freakonomics, M.D., on whether we can pay people to be healthier.

Kevin VOLPP: It happened on July 9th of 2021. I had been training for a half Ironman triathlon with one of my daughters. I was probably in the best shape I’d been in since I was 25 years old. And I felt great. And then one evening I was with one of my daughters at a sports tournament in Cincinnati, Ohio. And we’re at dinner and without any warning, all of a sudden, I just keeled over. Fortunately, my daughter and I were with two people. One was John White, who’s the squash coach at Drexel. The other is Gina Stoker, who’s the head squash pro at the Cynwyd Club.  And they were there with my daughter and some of her teammates to coach them at this tournament. Gina immediately called 9-1-1. My daughter later told me within 20 seconds, John realized I didn’t have a pulse and started CPR. And those two people taking action right away clearly played a big role in my surviving this incident.

The emergency medical technicians arrived less than five minutes after they were called. Still, it was touch-and-go.

VOLPP: I didn’t have a pulse for 14 minutes. That meant the E.M.T.s worked on me for nine minutes after they arrived, before they were able to get a pulse restarted. I had to be shocked three times. So, they were able to have me regain a pulse out in the field. I don’t remember going to dinner. I don’t remember keeling over. I get asked a lot, you know, my parents are both dead — like, people will say, “Did you see your parents? You know did you see bright flashing lights? Did you meet God?” And the answer to all that is “No,” at least, as far as I remember.

Kevin was taken to the University of Cincinnati hospital, where doctors discovered he had a blocked coronary artery, which means his cardiac arrest was likely the result of a heart attack. The event stunned Kevin. He was only 54 years old, well below the average age of men who experience their first heart attack, which is 65. Not only was he in amazing shape, he was also taking aspirin and a statin, a drug that reduces cholesterol, proactively. Kevin’s dad had suffered a heart attack, too.

VOLPP: Interestingly enough, of the 400,000 or so sudden cardiac arrests each year in the United States, a very large percentage of them happened without any warning, where people don’t have any symptoms. They just all of a sudden keel over.

All of this goes to show just how hard it can still be to prevent something like this. And, that a person’s baseline health matters too.

 VOLPP: I don’t want people to get the idea that, oh, here’s this guy who trained all the time and he had this cardiac arrest, so, “Why bother exercising because you might die anyway, right?” It’s more important to emphasize like, “Well, if he hadn’t trained all the time, he probably wouldn’t have survived.”

Kevin took two other lessons away from his cardiac arrest.

 VOLPP: It’s really important people around you know bystander CPR and activate E.M.S., emergency medical services.  And a lot of times people ask, “Well, you know, I don’t know what I’m doing. Maybe I’ll hurt somebody.” But believe me, if they don’t have a pulse, they’re going to be better off with you trying to do your best to keep their circulation going. And if they actually are awake and you weren’t successful in detecting it, they will let you know if you start pounding on their chest. And then availability of A.E.D.s is really critical. And now that they don’t cost very much, we certainly should see a lot more of them in commercial establishments than we sometimes do.

I wanted you to hear Kevin’s story because it’s a living testament to the importance of early CPR when someone’s had a cardiac arrest. So, training more people in CPR, getting them to use CPR quickly when needed, and increasing the availability of defibrillators are all important. But, what if there’s more that we can do? What if changing the fundamental way ambulances respond to cardiac arrests could also save lives? That’s coming up, right after this.

*          *          *

Before the break, we talked about how a bystander alert app may be one way to improve outcomes after a cardiac arrest, by getting CPR started earlier.

But ultimately, even with early and high-quality CPR, the problem that caused the cardiac arrest to occur — whether it was a heart attack, an aberrant heart rhythm, or something else — needs to be addressed. For example, if someone went into cardiac arrest because of a heart attack — which is basically when a blockage in an artery prevents blood flow to the heart — the definitive treatment has to be in the hospital, nowhere else.

That’s where emergency medical services come in. Emergency medical technicians, or E.M.T.s, and paramedics work extremely hard and around the clock to help patients with medical emergencies. They stabilize patients and transport them to the hospital for immediate medical care. And even though they’re incredibly vital and efficient, sometimes those two goals — stabilizing patients and transporting them to the hospital as fast as possible — can be at odds.

And just to sort of set the stage here, there are two types of emergency medicine providers. Let’s start with basic life support, or B.L.S. Ambulances that use B.L.S. care have E.M.T.s on board who can administer basic care to keep a patient alive; things like a simple bag valve — a mask over a patient’s face — to provide airway support. That’s compared to advanced life support or A.L.S. ambulances. Those ambulances have paramedics on board, who can provide more invasive interventions. To stay with the example of airway support, they can intubate a patient, which is inserting a flexible tube down a patient’s throat to keep their airway open. But that’s not the only way in which these two ambulances differ.

Prachi SANGHAVI: Basic life support ambulances follow the scoop-and-run model, which means that they’re prioritizing rapid transport to the hospital, and advanced life support ambulances are often referred to as following the stay-and-play approach, which is more about providing more care at the scene, even if that means delaying getting to the hospital.

That’s Prachi Sanghavi.

SANGHAVI: I’m an assistant professor in the department of public health sciences at the University of Chicago.

The way in which basic and advanced life support ambulances tend to operate is a key distinction in Prachi’s mind. Basic life support ambulances really focus on getting patients to the hospital quickly, where definitive medical care can occur. Advanced life support ambulances may be inclined to spend more time at the scene. The question is: which of these approaches is better?

Prachi started looking into this when she was in graduate school at Harvard.

SANGHAVI: I became interested in ambulances after I heard a trauma surgeon complain about the introduction of advanced life support ambulances in low-income countries. And he was complaining because he thought they were expensive and without evidence.

What Prachi means is that there was no real proof that those advanced ambulances were any more effective than a basic, less costly type of ambulance.

SANGHAVI:  I thought that was an odd statement because they’re called “advanced” ambulances. So, you know, they might be expensive, but I thought, “Surely, they must save lives.” So, I started digging into this and I realized pretty quickly that he was right. I found it, you know, really intriguing that we use ambulances in these emergency settings, but we don’t really have any scientific evidence that supports them.

So, Prachi tried to find some proof herself, by looking at how these ambulances are used in the U.S., where they’re also pretty common.   She wanted to understand if the benefits of A.L.S. ambulances — and the advanced care that they could provide on the scene — were outweighed by the risks of spending time away from the hospital. She started by looking at data for Medicare.

SANGHAVI: We wanted to compare survival differences between cardiac arrest patients who had received an A.L.S. ambulance and those who received a B.L.S. ambulance. The most fundamental concern in an analysis like this is that the patients are different and they’re sicker in one type of ambulance, say the advanced life support ambulances.

In other words: if cardiac arrest patients treated by A.L.S. ambulances have worse outcomes, is it because of something different that the A.L.S. providers did? Or was it because those patients were sicker to begin with, and that’s why advanced ambulances were dispatched in the first place. Prachi interviewed dozens of E.M.S. agencies to try to get a fuller picture of how, exactly, ambulances were dispatched.

SANGHAVI: We concluded that the priority in cardiac arrest or for symptoms of cardiac arrest would always be to send out an A.L.S. ambulance. The B.L.S. ambulances are only dispatched when A.L.S. is, for whatever reason, not available. That told us that cases where only B.L.S. showed up were not necessarily less sick patients. We also compared the comorbidities and chronic conditions in the A.L.S. and B.L.S. groups. And in fact, we found that the B.L.S. patients were, on average, slightly sicker.

So, she could actually rule out that A.L.S. ambulances were being sent to sicker patients with cardiac arrest. She then ran two different analyses. In the first, she simply compared mortality outcomes of patients who received advanced versus basic care, and controlled for differences that might also affect mortality, things like age or certain chronic medical conditions.

SANGHAVI:  We found that patients who receive basic life support had 43 percent higher survival up to hospital discharge than the ones who received advanced life support.

That’s a pretty big deal. Prachi found evidence that the patients who received basic life support ambulances actually did better than those who got more advanced care.

SANGHAVI: And these differences persisted out to two years after the cardiac arrest. So, at two years, the basic life support patients had 74 percent higher survival than the A.L.S. patients.

One of the limitations of this first approach was that it’s possible that the differences Prachi observed were due to something else about these patients or their conditions that she just couldn’t measure. So, she conducted a second analysis where she relied on the fact that some areas use only B.L.S. ambulances. Prachi found that B.L.S. ambulances appeared beneficial in this case too — though the finding for cardiac arrest wasn’t statistically significant. It’s interesting, though, because, at a minimum, they weren’t any worse. She also found that patients with strokes and major trauma did better when a basic ambulance was dispatched.

SANGHAVI: For most people, this should be surprising. And I think the point is that the word “advanced” and “advanced” life support is really just about our expectations, but it doesn’t actually play out in the outcomes.

There are a few possible explanations for Prachi’s findings. To start, A.L.S. ambulances may spend more time at the scene rather than prioritize transport to the hospital. It also might have to do with the interventions A.L.S. providers perform.

SANGHAVI: For example, one of the most commonly discussed problems is advanced airway management, which requires skill and practice. It can come with severe consequences, including death, if it’s performed incorrectly and it can even get in the way of crucial procedures like chest compressions. There was a study in Pennsylvania, which looked at how often paramedics actually get to perform intubations in a real setting. And it came out to about one per year. In a hospital, anesthesiologists typically intubate, and they do it all day. They have lots of practice with it and it’s in a controlled environment, with you know, more people to help, more gear.

Prachi’s papers were published in 2015. For full disclosure, I was a co-author on these papers. Prachi’s work, which made for an impressive dissertation, was novel, rigorous, and it attempted to answer an important question: how do we design pre-hospital care? But, at the end of the day, it’s only one body of work and it’s still too early to conclude that basic life support is better than advanced care. And, of course, we haven’t yet seen randomized controlled trials of these issues, but maybe we should.

More generally, Prachi’s research raises important questions about the medical systems we set up, and why we continue to use them, especially when we don’t have hard evidence to back up whether they work or not.

SANGHAVI: We’re not asking people to take on more skills or do something more advanced, but we’re actually trying to take a simpler approach, an approach that doesn’t require the same set of technical skills. So, in theory, it shouldn’t be difficult to achieve from that perspective, but I think it’s just very difficult to change people’s minds and convince them that these advanced approaches are not quite achieving the outcomes that they think they are.  What it comes down to is: ambulances play this crucial role in these medical emergencies that actually are related with the leading causes of death. And so, it’s incredibly important what happens in that initial healthcare service before you get to a hospital.

Those healthcare services patients get before they get to the hospital? They’re often lifesaving, but they’re also sort of a black box. We know much less about pre-hospital care than we know about hospital care. Maybe there’s something else that could easily be changed in the pre-hospital setting — and have big effects on outcomes. Here’s Dr. Kevin Volpp again.

VOLPP: The restaurant where I had my cardiac arrest, despite being a large chain restaurant, which probably had seats for more than a hundred people, didn’t have an A.E.D. on site. And this is apparently quite common. There’s no national requirement that chains or other restaurants have A.E.D.s. At one point I did some back-of-the-envelope calculations, and it would probably add a penny to the average bill or something like that, if you had one $1,200 defibrillator in each of these restaurants. So, it’s not that this would be an expensive unfunded mandate, but there’s advocacy that’s needed to change some of these rules. A.E.D.s are intimidating because people think you have to be a medical professional to use one, and they don’t realize that anybody in the lay public could use one safely because it will tell you what to do.

That $1,200-per-A.E.D. figure Kevin cited? He’s right in that it’s not the most expensive medical device out there. It’s not nothing though, especially if you have multiple locations of a restaurant or business. Still, the importance of having A.E.D.s can’t be overstated. It’s a classic example of cost-benefit analysis. The N.I.H. has estimated that in the U.S., 1,700 lives a year are saved when bystanders use an A.E.D. In most states, A.E.D.s are required in certain areas, like schools, state-owned facilities, and gyms. But not all states, and not all types of crowded areas, despite the recommendations of health organizations. 1,700 lives saved a year is significant — especially if it’s your loved one. So, how many additional lives could be saved if A.E.D.s were required in more places? How much would that cost? And what would that be worth to society? Well, maybe one of you can send me an answer to that question.

I want to end this episode by going back to my cousin.

Thinking back, it’s hard not to wonder whether any of the interventions we talked about today could have saved his life. Maybe he would have survived if someone nearby had gotten an alert and started CPR sooner. Or, if there had been an A.E.D. inside the building near where he collapsed. Or if his cardiac arrest could have been prevented in the first place.

Unlike a lot of cardiac arrest victims, it turns out that my cousin did have some warning signs. Once, he had an episode where his heart was racing, beating abnormally fast. Another time, he actually collapsed in a classroom, out of nowhere. These signs, especially in a young person, have to be taken seriously, and they demand medical attention. I wish he’d been treated for his underlying heart condition, and that I never had to tell this story in the first place.

How we respond to cardiac emergencies depends a lot on the systems we have in place. We rely on other people — bystanders, first responders, E.M.T.s, — to jump in and help. A lot of the time, they make the difference. But it’s also about what we, as individuals, can do to help ourselves if we just know what to look for. So, here’s something to remember. A racing heartbeat isn’t typical. Passing out isn’t typical. Chest pain and sudden difficulty breathing aren’t typical. Having any of these doesn’t mean you have a problem with your heart, but that’s something to confirm, not to assume.

That’s it for today’s show. And coming up next week: Could a research method you’ve probably never heard of help answer some of medicine’s biggest questions?

George Davis SMITH: To try to obtain that level of certainty, you need to look across the whole field of evidence.

And then, what do we do — if we get the answers we need?

Sekar KATHIRESAN: It’s like surgery without a scalpel.

That’s next week on Freakonomics, M.D. If you want to learn more about the research I talked about today, that’s at There you can also find our complete archive, including this show’s pilot episode, which was about what happens to patients suffering from cardiac arrest when the Boston Marathon blocks ambulance access to hospitals. Spoiler alert: it’s not too good. Also, let me know what you thought about this episode. I’m at Thanks for listening.

Freakonomics, M.D. is part of the Freakonomics Radio Network, which also includes Freakonomics Radio, No Stupid Questions, and People I (Mostly) Admire. All our shows are produced by Stitcher and Renbud Radio. You can find us on Twitter and Instagram at @drbapupod. This episode was produced by Mary Diduch and mixed by Eleanor Osborne. Our senior producer is Julie Kanfer. Our staff also includes Alison Craiglow, Greg Rippin, Gabriel Roth, Rebecca Lee Douglas, Morgan Levey, Zack Lapinski, Ryan Kelley, Jasmin Klinger, Emma Tyrrell, Lyric Bowditch, Jacob Clemente, Alina Kulman, and Stephen Dubner. Our music was composed by Luis Guerra. If you like this show, or any other show in the Freakonomics Radio Network, please recommend it to your family and friends. That’s the best way to support the podcasts you love. As always, thanks for listening.

JENA: Nellie, can you hear anything in, in my background? Like, you don’t hear you don’t hear anybody Peloton-ing two doors down from me?

NELLIE: No, we’re good, we’re good.

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  • David Fredman, cardiology nurse and ‘heart of operations’ at Heartrunner.
  • Prachi Sanghavi, assistant professor of health services research at the University of Chicago.
  • Kevin Volpp, professor of medicine, medical ethics, and policy and founding director of the Center for Health Incentives and Behavioral Economics at the University of Pennsylvania.



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