This Soft Artificial Heart May One Day Shorten the Heart Transplant List

ETH Zurich
ETH Zurich

If the heart in the Functional Materials Laboratory at ETH Zurich University were in a patient in an operating room, its vital signs would not be good. In fact, it would be in heart failure. Thankfully, it's not in a patient—and it's not even real. This heart is made of silicone.

Suspended in a metal frame and connected by tubes to trays of water standing in for blood, the silicone heart pumps water at a beat per second—a serious athlete's resting heart rate—in an approximation of the circulatory system. One valve is leaking, dripping onto the grate below, and the water bins are jerry-rigged with duct tape. If left to finish out its life to the final heartbeat, it would last for about 3000 beats before it ruptured. That's about 30 minutes—not long enough to finish an episode of Grey's Anatomy

Nicolas Cohrs, a bioengineering Ph.D. student from the university, admits that the artificial heart is usually in better shape. The one he holds in his hands—identical to the first—feels like taut but pliable muscle, and is intact and dry. He'd hoped to demonstrate a new and improved version of the heart, but that one is temporarily lost, likely hiding in a box somewhere at the airport in Tallinn, Estonia, where the researchers recently attended a symposium.

Taking place over the past three years, the experimental research is a part of Zurich Heart, a project involving 17 researchers from multiple institutions, including ETH, the University of Zurich, University Hospital of Zurich, and the German Heart Institute in Berlin, which has the largest artificial heart program in Europe.


Heart failure occurs when the heart cannot pump enough blood and oxygen to support the organs; common causes are coronary heart disease, high blood pressure, and diabetes. It's a global pandemic, threatening 26 million people worldwide every year. More than a quarter of them are in the U.S. alone, and the numbers are rising.

It's a life-threatening disease, but depending on the severity of the condition at the time of diagnosis, it's not necessarily an immediate death sentence. About half of the people in the U.S. diagnosed with the disease die within five years. Right now in the U.S., there are nearly 4000 people on the national heart transplant list, but they're a select few; it's estimated that upwards of 100,000 people need a new heart. Worldwide, demand for a new heart greatly outpaces supply, and many people die waiting for one.

That's why Cohrs, co-researcher Anastasios Petrou, and their colleagues are attempting to create an artificial heart modeled after each patient's own heart that would, ideally, last for the rest of a person's life.

Mechanical assistance devices for failing hearts exist, but they have serious limitations. Doctors treating heart failure have two options: a pump placed next to the heart, generally on the left side, that pumps the blood for the heart (what's known as a left ventricular assist device, or LVAD), or a total artificial heart (TAH). There have been a few total artificial hearts over the years, and at least four others are in development right now in Europe and the U.S. But only one currently has FDA approval and CE marking (allowing its use in European Union countries): the SynCardia total artificial heart. It debuted in the early '90s, and since has been implanted in nearly 1600 people worldwide.

While all implants come with side effects, especially when the immune system grows hostile toward a foreign object in the body, a common problem with existing total artificial hearts is that they're composed of hard materials, which can cause blood to clot. Such clots can lead to thrombosis and strokes, so anyone with an artificial heart has to take anticoagulants. In fact, Cohrs tells Mental Floss, patients with some sort of artificial heart implant—either a LVAD or a TAH—die more frequently from a stroke or an infection than they do from the heart condition that led to the implant. Neurological damage and equipment breakdown are risky side effects as well.

These complications mean that total artificial hearts are "bridges"—either to a new heart, or to death. They're designed to extend the life of a critically ill patient long enough to get on (or to the top of) the heart transplant list, or, if they're not a candidate for transplant, to make the last few years of a person's life more functional. A Turkish patient currently holds the record for the longest time living with a SynCardia artificial heart: The implant has been in his chest for five years. Most TAH patients live at least one year, but survival rates drop off after that.

The ETH team set out to make an artificial heart that would be not a bridge, but a true replacement. "When we heard about these problems, we thought about how we can make an artificial heart that doesn't have side effects," he recalls.


Using common computer assisted design (CAD) software, they designed an ersatz organ composed of soft material that hews closely to the composition, form, and function of the human heart. "Our working hypothesis is that when you have such a device which mimics the human heart in function and form, you will have less side effects," Cohrs says.

To create a heart, "we take a CT scan of a patient, then put it into a computer file and design the artificial heart around it in close resemblance to the patient's heart, so it always fits inside [the body]," Cohrs says.

But though it's modeled on a patient's heart and looks eerily like one, it's not identical to the real organ. For one thing, it can't move on its own, so the team had to make some modifications. They omitted the upper chambers, called atria, which collect and store blood, but included the lower chambers, called ventricles, which pump blood. In a real heart, the left and right sides are separated by the septum. Here, the team replaced the septum with an expansion chamber that is inflated and deflated with pressurized air. This action mimics heart muscle contractions that push blood from the heart.

The next step was to 3D-print a negative mold of the heart in ABS, a thermoplastic commonly used in 3D printing. It takes about 40 hours on the older-model 3D printers they have in the lab. They then filled this mold with the "heart" material—initially silicone—and let it cure for 36 hours, first at room temperature and then in an oven kept at a low temperature (about 150°F). The next day, they bathed it in a solvent of acetone, which dissolved the mold but left the printed heart alone. This process is essentially lost-wax casting, a technique used virtually unchanged for the past 4000 years to make metal objects, especially bronze. It takes about four days.

The resulting soft heart weighs about 13 ounces—about one-third more than an average adult heart (about 10 ounces). If implanted in a body, it would be sutured to the valves, arteries, and veins that bring blood through the body. Like existing ventricular assist devices and total artificial hearts on the market, it would be powered by a portable pneumatic driver worn externally by the patient.


In April 2016, they did a feasibility test to see if their silicone organ could pump blood like a real heart. First they incorporated state-of-the-art artificial valves used every day in heart surgeries around the world. These would direct the flow of blood. Then, collaborating with a team of mechanical engineers from ETH, they placed the heart in a hybrid mock circulation machine, which measures and simulates the human cardiovascular system. "You can really measure the relevant data without having to put your heart into an animal," says Cohrs.

Here's what the test looked like.

"Our results were very nice," Cohrs says. "When you look at the pressure waveform in the aorta, it really looked like the pressure waveform from the human heart, so that blood flow is very comparable to the blood flow from a real human heart."

Their results were published earlier this year in the journal Artificial Organs.

But less promising was the number of heartbeats the heart lasted before rupturing under stress. (On repeated tests, the heart always ruptured in the same place: a weak point between the expansion chamber and the left ventricle where the membrane was apparently too thin.) With the average human heart beating 2.5 billion times in a lifetime, 3000 heartbeats wouldn't get a patient far.

But they're making progress. Since then, they've switched the heart material from silicone to a high-tech polymer. The latest version of the heart—one of which was stuck in that box in the Tallinn airport—lasts for 1 million heartbeats. That's an exponential increase from 3000—but it's still only about 10 days' worth of life.

Right now, the heart costs around $400 USD to produce, "but when you want to do it under conditions where you can manufacture a device where it can be implanted into a body, it will be much more expensive," Cohrs says.

The researchers know they're far from having produced an implantable TAH; this soft heart represents a new concept for future artificial heart development that could one day lead to transplant centers using widely available, easy-to-use design software and commercially available 3D-printers to create a personalized heart for each patient. This kind of artificial heart would be not a bridge to transplantation or, in a few short years, death, but one that would take a person through many years of life.

"My personal goal is to have an artificial heart where you don't have side effects and you don't have any heart problems anymore, so it would last pretty much forever," Cohrs says. Well, perhaps not forever: "An artificial heart valve last 15 years at the moment. Maybe something like that."

10 Things You Should Know About Asthma Kozielczyk Kozielczyk

To anyone with asthma, the feeling of an attack is unmistakable. Patients have compared an asthma attack's feeling of breathlessness, caused by inflammation in the lungs and airways, to being smothered by a pillow or having an elephant sit on their chest. Medical experts have already figured out some aspects of asthma, like how to diagnose and treat it, but other components, like what causes asthma and how to cure it, remain unclear. From the triggers people encounter at work to the connection to allergies, here are some facts about asthma symptoms and treatments you should know.

1. Asthma attacks are related to allergies.

The physical process that occurs when someone has a sneezing fit during pollen season is similar to what happens during an asthma attack. But while the former causes discomfort, the latter produces potentially life-threatening symptoms. When people with allergies are exposed to an allergen like pollen, they produce antibodies that bind to that allergen. This signals the body to release the chemicals that cause allergic symptoms. In most people, the symptoms are limited to the head, such as a runny nose or watery eyes, but in people with asthma, they're felt in the lungs. If the lungs are inflamed, the airways that carry air swell up and fill with mucus, constricting airflow and causing common asthma symptoms like coughing, wheezing, and shortness of breath. Such asthma attacks can be fatal when patients can’t get enough air to their lungs.

2. Asthma is the most prevalent chronic disease among children.

Asthma is common, affecting 25 million in the U.S. alone, and of those patients, about 7 million are children. Most people with the disease develop it during childhood. Asthma is the most prevalent chronic illness among kids, and each year, students miss 13.8 million school days because of it.

3. Asthma may be inherited.

Doctors aren’t entirely sure what causes asthma, but they know it sometimes runs in families. A 2010 study found that people with one parent with the condition were nearly twice as likely to have it themselves, and people with a parent and a grandparent with asthma were four times more likely to develop it. Because asthma is connected to allergies, a genetic disposition toward allergies, known as atopy, may explain some inherited asthma cases.

4. Asthma is surprisingly easy to diagnose.

One of the simplest ways to diagnose asthma is through a lung function test. If a patient is reporting asthma symptoms (coughing, chest tightness, a feeling of not getting enough air), their doctor may check the strength of their exhalations before and after having them use an inhaler. If their breathing improves with the medicine, they likely have asthma. An X-ray of the patient’s chest can also be used to reach an asthma diagnosis.

5. Kids who grow up around germs are less likely to have asthma.

A person’s environment early in life may also play a role in whether or not they develop asthma. People who grew up in rural areas, around animals, and in large families are less likely to have asthma than those who did not. One possible explanation is the hygiene hypothesis: According to this theory, kids who were exposed to germs and pathogens while their immune systems were developing are better equipped to deal with allergens, while kids who were sheltered from germs may be more likely to have an exaggerated (and in the case of asthma, potentially deadly) immune response to harmless substances. The hygiene hypothesis hasn’t been proven, however, and it’s definitely not an excuse to expose children to infections in an attempt to strengthen them against asthma attacks in the future.

6. Asthma triggers are everywhere.

To manage their symptoms, doctors tell asthma patients to limit exposure to their triggers when possible. Common asthma triggers include irritants and allergens like dust, tobacco smoke, car exhaust, mold, pet dander, and smoke from burning wood. Triggers that don’t come from the environment, like colds, sinus infections, acid reflux, and hyperventilation brought on by stress, can be even harder to avoid.

7. There's one asthma trigger patients shouldn't avoid.

Physical activity causes fast breathing, which can provoke asthma attacks in some people with the condition. There’s even a type of asthma called exercise-induced bronchoconstriction that specifically describes people who suffer from these kinds of attacks. But the risks of living a sedentary lifestyle outweigh those of exercising carefully, even with asthma. Instead of cutting out cardio altogether, doctors work with patients to come up with an exercise plan that’s safe for them. This might include warming up and using an inhaler before working out, practicing cool-down activities afterward, and wearing scarves or masks to limit exposure to irritants that may also trigger asthma symptoms.

8. There are two types of asthma treatments.

Long-term controllers and quick-relievers are the two types of medications used to treat asthma. Immediate medicines like short-acting beta agonists and anticholinergics relax muscles in the airways when flare-ups occur, and they’re typically administered directly to the lungs with an inhaler. Long-term medications help keep asthma symptoms under control over time are taken as often as once a day, regardless of whether symptoms are present. They include inhaled long-acting beta agonists and corticosteroids, biologic injections, and theophylline and leukotriene modifier pills and liquids. All of these medications suppress asthma symptoms by either relaxing muscles, reducing swelling, or preventing inflammation in the airways.

9. Asthma can be an occupational hazard.

Occupational asthma develops when a patient’s triggers come from their work environment. According to the National Institutes of Health, wood dust, grain dust, animal dander, fungi, and various chemicals are some of the most common asthma triggers that patients encounter in the workplace. Bakers, farmers, laboratory workers, millers, and woodworkers predisposed to asthma are all at higher risk.

10. There's no cure for asthma, but symptoms can lessen over time.

Though asthma is treatable, there’s no cure for the chronic illness. Some people, however, do appear to grow out of the condition after suffering from it as kids. It’s possible for asthma symptoms to become less severe and go into remission as patients get older, but once someone is diagnosed with asthma, the risk of an episode never goes away completely. Changes in hormone levels are a factor that could possibly bring asthma symptoms back in patients who haven’t experienced an attack in years.

7 Facts About the Measles

Abid Katib, Getty Images
Abid Katib, Getty Images

The measles used to be one of the world’s most common childhood diseases. Since the introduction of the measles vaccine, however, the disease is rarely seen in the U.S. But people still have reason for concern about symptoms like the telltale measles rash: In 2018, there were 349 reported cases of the measles across 26 states and Washington, D.C. The year before, 120 people contracted the disease. Here are seven things to know about measles symptoms and treatments.

1. Everyone used to get the measles.

There was a time not so long ago when exhibiting measles symptoms was a near-ubiquitous part of childhood. In the 4th century CE, Chinese alchemist Ko Hung wrote of the differences between smallpox and measles, and the disease was described in the 9th century by the famous Persian physician Rhazes. There were major epidemics of the disease in the 11th and 12th centuries [PDF].

In the years before the first licensed measles vaccine appeared in the U.S. in 1963, an estimated 90 percent of children caught the measles before they were 15. The disease was a leading cause of death for children—and in some places without access to vaccinations and medical care, it still is. Today, up to 5 percent of children in places without access to good medical care die of the measles annually.

The CDC estimates that prior to the existence of the measles vaccine, there were between 3 and 4 million measles cases in the U.S. per year, approximately 400 to 500 of them fatal—but vaccinations have reduced the prevalence of the disease by 99 percent. In some years, fewer than 100 people contract the disease in the U.S.

2. The measles virus is highly contagious.

The measles virus is considered one of the most contagious viruses around: Without vaccination, around 90 percent of people who are exposed to the virus will become infected.

The disease is caused by the spread of a type of virus called morbillivirus, which can be transmitted through the air via breathing, coughing, or sneezing. The virus can live in the air for up to two hours after an infected person coughed—meaning that you don’t necessarily need to be standing next to someone with the measles to get it from them.

3. It can cause more than just a measles rash.

A person exposed to measles will begin to show symptoms seven to 14 days after exposure. Common measles symptoms include coughing, congestion, fever, and most famously, a full-body skin rash. But a third of measles cases involve complications ranging from diarrhea to pneumonia, brain swelling, and coma. Pneumonia causes around 60 percent of fatalities when it comes to measles complications.

Children under 5 are particularly at risk of getting complications and dying from the disease. One in 10 will contract an ear infection, possibly leading to permanent hearing damage, and one in 20 will get pneumonia. One or two out of every 1000 kids who contract the measles will die, according to the CDC, many from pneumonia.

4. The measles vaccine is very effective.

The measles is combined with vaccines against two other diseases—mumps and rubella—and when administered as designed, it's incredibly effective. Experts recommend that children get their first dose of the MMR vaccine on their first birthday (but not before). Then, they should get the second dose before they enter kindergarten. If a child doesn’t get vaccinated before they’re 12, they should still get the vaccine: two doses a month apart. In most cases, those two doses of the vaccine should be enough to give you immunity for life (although some experts are now cautioning booster shots may be a good idea for some adults).

If you’re exposed to the virus and haven’t been vaccinated, an immediate dose of the vaccine can provide some protection from the disease, as long as you get it within 72 hours of exposure.

5. Measles is considered eliminated in the U.S. ...

Thanks to effective vaccinations, as of 2000, measles is no longer a threat in the U.S., according to the CDC’s standards. The disease is considered eliminated, which means that it hasn’t been continuously transmitted in a specific geographical location for at least a year. So even if there’s the occasional outbreak of cases, it’s considered eliminated because it’s not a constant threat anymore. In 2016, the World Health Organization declared the disease to be eliminated across the entirety of North and South America.

6. ... But you should still get vaccinated.

Measles isn’t prevalent in the U.S., but that doesn’t mean you can skip your vaccinations: Though home-grown measles has been eliminated, people in the U.S. still come down with it. That’s because measles is still a major issue elsewhere in the world, and travelers can bring it home with them, spreading it to unvaccinated populations in the U.S.

That includes babies. Children under 5 are one of the most vulnerable populations when it comes to measles infections, but babies aren’t generally vaccinated until they’re 12 months old (the CDC recommends that before international travel, “infants 6 months through 11 months of age should receive one dose of MMR vaccine” and then get a shot again when they’re a little older). That makes it incredibly important for everyone around them to be vaccinated, so that the disease can’t spread.

In addition to inoculating individuals against diseases, the measles vaccine operates on the principle of herd immunity. When nearly an entire population is vaccinated, it’s very hard for the disease to spread. That protects people who aren’t inoculated, like babies, or people whose bodies didn’t respond to the vaccine for whatever reason.

7. People still get measles in America.

Since measles was declared eliminated in 2000, there have been relatively few cases reported here, but a significant number of people have caught the disease in the past few years. In 2004, there were just 37 cases of measles reported in the U.S. Ten years later, in 2014, there were 667—most of whom were people who weren’t vaccinated. (That number was unusually high, and went down to 188 cases the next year.)

The CDC blames recent measles outbreaks on low rates of vaccination. One 2016 review of measles studies found that out of 970 measles cases, almost 42 percent of patients had opted out of getting the vaccine for non-medical reasons.

Europe has also seen a surge in measles cases in the last few years. Between 2016 and 2017, measles cases in Europe quadrupled, from 5273 cases to more than 21,000, according to the World Health Organization. Thirty-five of those 21,000 people died from the disease. This is bad news for Americans, too, since most U.S. measles cases can be linked back to travelers coming into the U.S. from places like Europe. So get your vaccinations!