Steve Williams couldn’t breathe. The former athlete had cardiomyopathy, which occasionally choked his lungs with fluid, making him gasp for air. But this felt different; Williams felt like he was dying. He was raced to an Orange County hospital, and shortly after checking in, his heart stopped. For 30 minutes, ER workers compressed his chest in an attempt to revive him. At one point, his wife Mary remembers being called into his room to say goodbye to her husband of 24 years. It seemed Williams was a dead man.

Incredibly, doctors rebooted Williams’ heart — but for three days, he was in an induced coma, his body packed in ice to minimize brain damage. When he woke up, his mental facilities were intact, but his body was ravaged. His liver was congested, fluid reappeared in his lungs, and his heart’s right and left ventricles were practically destroyed, making it hard for blood to circulate throughout his body. Without a heart transplant, he would soon die.

Donor hearts, however, are scarce; each year, only about 1 in 10 patients that need a transplant worldwide receives the life-saving surgery. Williams’ best shot at survival was to have his heart almost completely removed and replaced with a total artificial heart — a synthetic machine that stands in for a living, beating organ. Williams would be among a handful of patients who receive artificial hearts every year. Right now, they serve as life support for people who are about to have transplants. But if the device’s manufacturers have their way, one day soon mechanical hearts will replace our faulty biological ones forever.

Luckily, Williams had landed in one of the few places in the world that could perform the extreme procedure — he’d been transferred to the Cedars-Sinai Heart Institute in Los Angeles. But the proposal was harrowing: his chest cavity would be cracked, critical arteries severed, and the heart he’d lived with for 53 years pulled out of his body.

“Scared is such a simple word; we were totally blindsided,” Mary told me.

“But there was really no other choice for me,” Williams says.

The mechanical heart offered by Cedars-Sinai is manufactured by the Arizona company SynCardia. It has a simple design: a pair of fist-sized artificial ventricles that attach to the atria, the heart’s blood collection chambers; the aorta, the body’s largest artery; and the pulmonary artery, which connects the heart and lungs. Two tubes — with the circumference of garden hoses — attach the polyurethane ventricles to an air pump outside the body, which sends roughly 120 short bursts of air per minute into the machine. That air forces blood in and out, replicating a rapid heartbeat. The device must be constantly plugged into a power outlet or connected to a battery pack. Without electricity, the heart quickly shuts down; unless power is restored, the patient dies.

Williams agreed to have a mechanical heart installed as a temporary measure while waiting for a donor organ. In April of 2014, the day before his surgery, doctors introduced Williams to someone recovering from the same operation. The patient was tethered to an air compressor that sat at his bedside and made a perpetual thump-thump-thump-thump sound so loud it could be heard from across the room. Two tubes protruded from an incision on his stomach. The scene was unsettling, but Williams wasn’t fixated on the tubes, the pounding sound, or the man’s pulsating chest. He mainly noticed how healthy he looked.

Almost two-thirds of SynCardia total artificial heart recipients can get out of bed and walk two weeks after surgery, and the majority survive long enough to get a transplant. As odd as it might seem, Williams thought temporarily replacing his central organ with plastic looked promising.

Williams’ surgery went smoothly. He was discharged with a “Freedom Driver,” a toaster-sized battery and air pump designed by SynCardia that fits snuggly into a backpack and lets people return home. (Until 2010, most mechanical heart recipients, no matter how healthy they were, stayed connected to large, relatively immobile batteries and were confined to hospitals.)

The operation and the driver allowed Williams to resume a somewhat normal life. He saw his son graduate from high school, for instance. He takes daily walks on the beach, gardens in his backyard, and more than a year after he nearly died, remains in relatively good health.

“I was a 50-year-old guy that typically would be dead, and my wife would be the sad woman with two kids living off my insurance policy,” Williams says, as his “heart” labors away at his feet outside an Orange County Starbucks. “That’s what I have to say to myself to remember how lucky I am.”

But living with an artificial heart has its downsides: Williams is constantly accompanied by a caretaker, typically his wife, in case the device malfunctions; he is forever connected to a battery or plugged into a power outlet; the large doses of blood thinners he takes make his body run cold; and he can’t submerge himself in water. Then, there are the more impalpable challenges: he hasn’t heard silence in over a year — just the constantly beating sound of the air pump — and he draws stares in public. (Williams stopped seeing movies in theaters out of respect for other viewers; the noise from his artificial heart would bother most audiences.)

“It’s a love-hate relationship you have with these devices; you’re thankful you’re alive, but it’s a compromise to have them,” Williams says. “It’s human nature to want things to go back to the way they used to be. Sometimes they never do.”

There are few people alive in the world who have no natural heartbeat. Fewer than 2,000 patients have received an entirely artificial heart in the device’s three decades of existence, and most patients haven’t used the machines for long. As with Williams, mechanical hearts are typically just a bridge to an eventual transplant.

But that may change. A handful of companies, including SynCardia, are trying to get regulatory approval to market the first permanent mechanical heart for wide-scale use, which would replace a patient’s biological organ over the remaining course of their lifetime. “Think along the lines of knee replacements and hearing aids,” says Piet Jansen, chief medical officer for the French company Carmat, which is running an early clinical trial for a long-term mechanical heart. “At some point we will have an implantable blood pump that [permanently] replaces a sick heart.”

If it works, the technology could save a lot of lives. More than 5 million people in the US have heart failure, according to the CDC, and many need a new organ to survive. The lucky few that get a transplant often face complications such as rejection of the donated heart, infection, and vital organ failure. Mechanical hearts can be more reliable, and some predict they are the future of treating total heart failure.

But the technology raises also practical and ethical questions. It’s unclear whether plastic and metal hearts can ever truly replicate their biological counterparts, which pump 2,000 gallons of blood every day, service 60,000 miles of blood vessels (more than double the circumference of the world), and work without a hitch year after year.

Living with an artificial heart is also hard on patients, and once the surgery begins, it’s irreversible. “You’ve cut out a big chunk of the heart, and you’ve cut out the parts that are necessary to sustain life,” says Stuart Finder, a health care ethicist at Cedars-Sinai. “Once you start the intervention, you can never go back.”

The heart is just a pump, and for the past half-century bioengineers have doggedly tried to replicate the biological machine with a mechanical one. Success has always been just beyond their grasp.

In the 1960s, scientists promised to develop a total artificial heart by the end of the decade, to cure end-stage biventricular heart failure. The proposal intrigued Congress, which funneled hundreds of thousands of dollars into the newly created Artificial Heart Program at the National Heart, Lung, and Blood Institute. While it seemed relatively easy to craft an effective blood pump, designing one that agreed with the human body and worked for decades without fail was much harder.

One of the first prototypes, built in the 1970s, had an unlikely power source: plutonium-238 — a byproduct of nuclear weapons manufacturing. The element generates thermal energy for close to a century through radioactive decay; in theory, it could keep recipients alive well into old age.

The “atomic heart,” however, had some obvious drawbacks. Even when functioning properly, patients would be exposed to high levels of radiation. And what if it malfunctioned? Would enough radiation seep into the patient or harm their loved ones? Co-workers? Neighbors? A member of a federal assessment panel even wondered if terrorists could kidnap mechanical heart recipients, dissect them, and turn them into weapons.

Despite protest from researchers, the atomic heart was ultimately killed before it was implanted in anyone. But it did pave the way for the first clinically tested permanent mechanical heart: the Jarvik-7. The Jarvik’s design was simple: two man-made ventricles, connected to an external air pump, expand and contract the artificial organ, propelling blood throughout the body — much like Williams’ artificial heart today.

In 1982, Barney Clark, a 61-year-old dentist with end-stage congestive heart failure, agreed to have a Jarvik-7 installed. He didn’t expect to live long, but was willing to endure the operation for the sake of science. On December 2nd, after nine hours of surgery, Clark woke up with two plastic ventricles and titanium in his chest. He was the first human to live without a natural heartbeat.

Clark’s body had a hard time accepting the implant. He bled internally and suffered multiple strokes; his mental health deteriorated. In TV interviews, he stared off-camera with a distant look in his eyes, a washing machine-sized air compressor called “big blue” working tirelessly beside him. On a few occasions he supposedly asked doctors to unplug the device and let him die.

Then, on a snowy day in March of 1982, after multiple organs failed, Clark experienced brain death. His artificial heart, which beat nearly 13 million times over 112 days, was shut down. Four more Jarvik hearts were implanted after Clark’s, and each produced equally grim results. The device caused kidney failure, hemorrhaging, stroke, and seizure. Sociologist Renee Fox documented the Jarvik experiments in her 1992 book Spare Parts. One Jarvik recipient endured such heavy internal bleeding after his surgery, Fox writes, that half of his total blood volume had to be replaced. The patient later compared the device to a “threshing machine” in his chest cavity.

In 1988, after nearly a quarter of a billion dollars, the National Heart, Lung, and Blood Institute pulled funding from the Artificial Heart Program. The plastic-and-metal machines, it seemed, were incompatible with the human body, and the pursuit of the bionic man appeared to be over.

But not everyone gave up. While the device was impractical as a permanent replacement for the heart, a young heart surgeon from Arizona named Jack Copeland saw the potential to use artificial hearts as a bridge to transplant. In the mid-1980s he implanted a machine commonly referred to as the “Phoenix Heart” in a dying man. Controversially, Copeland didn’t have FDA approval or the person’s consent for the operation, but he saw no other options. “We didn’t have time to sit down and consider all of the implications,” he says. “We were trying to save his life, and that in the end that was the most important consideration.”

The urgency gave Copeland some legal protection, and to the chagrin of some medical ethicists, the FDA did not punish him. After the mechanical heart was installed, Copeland was impressed by its efficacy. “The guy did well on the device,” he recalls. “It worked a hell of a lot better than the heart that had been inside him.” The patient survived for 11 hours on the machine, but died shortly after getting a biological transplant.

A few months after implanting the Phoenix Heart, Copeland began using the Jarvik-7 as a bridge — this time with federal approval. In 1991 he co-founded CardioWest, which later became SynCardia. Its researchers obtained rights to the Jarvik heart and tweaked it. By 1993, after making minor changes to the old machine, Copeland and his colleagues had created a bridge-to-transplant device that was approved for a 10-year-long human trial.

Of the 81 people in the trial, 17 died after the artificial heart was installed. But the rest survived long enough to get a transplant — promising results considering that all the participants were considered at high risk of imminent death. Soon thereafter, the CardioWest device became the first and only FDA-approved artificial heart for a bridge to transplant.

Once widely rejected by the medical community, mechanical hearts have since become a viable temporary treatment for end-stage biventricular heart failure. “It’s like chemotherapy in the 1960s: people used to think it was crazy to give poison to someone who was dying, and now it’s routine,” says Francisco Arabia, a biological and mechanical heart surgeon, and surgical director of Cedars-Sinai’s mechanical circulatory support program. “There’s no doubt life is not the same with [a total artificial heart], but the human body can adjust to incredible things.”

On the sixth floor of Cedars-Sinai — where heart patients recover after surgery — a room hums with what sounds like a loud clock, each tick separated by exactly one half of one second. Kerrie Cancel De La Cruz, a 42-year-old mother from Texas with an ear-to-ear smile and a neck-to-chest scar, sits in the middle of a din coming from an air pump that keeps blood flowing through her 5-foot, 3-inch frame.

A large sticker that reads “Tink” in bold red letters is plastered across the pump. “I thought, you’re a ticker, but I’m not going to call you ticker,” she says to the machine. “I like Tinkerbell, so I named you Tink.” On a visit last April her walls were covered in family photos and a stuffed teddy bear hung off her bed. Flowers from her husband and a fellow artificial heart recipient wilted on her bedside table.

De La Cruz was born with a weak heart. At 18, she had a defibrillator implanted, and at 32, after giving birth to twins, developed atrial fibrillation, a disorder that causes an irregular heartbeat. Her skin turned pale grey, her stomach bloated with fluid, and she experienced such severe pain that it was hard for her to get out of bed. De La Cruz needed a new heart, but her small body and high level of antibodies made her an unlikely transplant candidate.

She was transferred to Cedars-Sinai in the spring of 2014, where Arabia explained that her best treatment option was a mechanical heart. The operation would increase her odds of survival seven-fold, while also helping her regain strength — which she would need in order to receive a donor transplant, Arabia said. Still, De La Cruz was reluctant. “At first I didn’t want it,” she recalls, tears welling up in her husky-blue eyes. “I was tired, I fought a lot. It felt like it was time for me to go.”

Patients like De La Cruz, who are out of options, often end up at Cedars-Sinai; the plush medical center adjacent to Beverly Hills performs more total artificial heart transplants than anywhere else in the country. When Arabia describes the operation, reactions are mixed, he says. A few patients — mostly men — are excited at the prospect of getting a “super heart,” but the majority don’t want the implant. It isn’t until they’re dying in the ICU that most people agree to it.

As Christiaan Barnard, the South African surgeon who performed the first human-to-human heart transplant in 1967 put it: “patients on the brink of death are between a lion and a crocodile.”

If the lion is a mechanical heart, a biological transplant is the crocodile: while it might be a better option, it still poses a grave threat. Taking a living heart from one person’s body and putting it into another person is a high-risk procedure with ample room for error. The donor heart first has to be methodically extracted from a very recently deceased body, transported hundreds, sometimes thousands of miles on ice, and installed in an entirely foreign vessel.

Occasionally a flaw in the donor heart will cause it to fail shortly after the transplant. Other times the transplant beats for a few months or years before giving out. “Human hearts are like a used car, they can have flaws, disease,” Arabia points out. Sometimes the patient’s body rejects the transplant — a painful process where the immune system attacks and kills the foreign organ. Nearly a quarter of heart transplant recipients show some signs of rejection within a year of surgery. To battle rejection, patients must take expensive and risky immunosuppressant medication. While the pills safeguard the new organ, they also increase the odds of infection, cancer, liver disease, and kidney failure.

Artificial hearts are different. Since they aren’t made of human tissue, rejection isn’t an issue, and defects are rare. “They work 100 percent of the time,” Arabia says. “You know what you’re getting.”

But they’re not without complications and downsides — both physical and emotional, as De La Cruz knows.

“This doesn’t only take from your body, it takes from your mind, spirit, and soul,” De La Cruz says.

Despite De La Cruz’s initial reservations, she had the operation. But in January, after a short stay at a temporary home in Los Angeles, she returned to Cedars-Sinai. While De La Cruz’s body accepted the mechanical implant, the Freedom Driver wasn’t strong enough to support her. She had to be hooked up to a more powerful air pump, forcing her to spend months living in a hospital room.

Each day she dreamt of resuming her old life: being home with her family; swimming in the Gulf of Mexico; eating and drinking freely (De La Cruz could only consume 1.5 liters of fluids each day, and had to stay away from sodium).

The ordeal was hard on her two children, particularly her youngest daughter, who’s in elementary school. “I shared the same room with her when I was home, and when I had to go back to the hospital, she said, ‘Mom, I really miss you, I can’t sleep,’” De La Cruz recalls, sitting cross-legged in her hospital bed. “When I asked her why, she said ‘because I can’t hear your heart beating.’”

“If you haven’t been through this, you don’t understand.”

Despite its drawbacks, SynCardia has helped hundreds resume a somewhat normal life while waiting for a donor transplant. Now, the company is preparing to leap forward: pending FDA approval, it plans to offer its total artificial heart — the same model De La Cruz and Williams have — as a permanent implant for patients in the US. If approved, the device will become available to a wider set of patients, including those not eligible for biological transplants.

Creating an effective long-term mechanical heart has been cardiac surgeons’ dream for decades, but the endeavor has been incredibly difficult and expensive. One company, called Abiomed, received FDA approval to use a permanent mechanical heart in 2006. The device was expensive and hard to implant. After clinical tests, only one person was fitted with the machine before the company abandoned the device.

One of SynCardia’s challenges is what appears to be a precarious financial situation. The Arizona firm registered for an IPO in September, hoping to raise money to pay off tens of millions of dollars in debt and expand into Latin America and Asia. “To serve as many patients that need the device, the company has to have the wherewithal to reach and treat them,” SynCardia CEO and president Michael Garippa says, referring to the IPO plan.

SynCardia withdrew its public offering in October and has since laid off some of its employees. Garippa blames the fumble on volatile market conditions.

The French company Carmat is developing an artificial heart, but it also faces an uphill battle. Unlike SynCardia’s machine, with its driver in a backpack, Carmat’s heart is almost fully implantable and is powered by small lithium batteries that can be worn on a belt or a holster under the arm. A layer of chemically treated cow-heart tissue — or “pseudo-skin” — coats the heart, wherever it touches blood, making it more biocompatible and reducing the need for blood thinners. It is still in early clinical trials.

Three people have been fitted with Carmat’s heart. The first patient survived two and a half months before the machine short-circuited — nearly three times longer than his projected survival. The second patient, who had the device installed last August, was able to return home roughly five months after operation, telling the newspaper Le Journal du Dimanche in April: “I have never felt so good.” Shortly after the interview, the machine’s motor malfunctioned and the patient died. The third patient, who was implanted six months ago, is still alive and well. Once a fourth person is fixed with the device and survives at least 30 days, the company can move beyond its early clinical trial and begin a second set of tests.

It’s clear that Carmat’s heart is still far from ready for the market. Aside from the two malfunctions, it weighs nearly three times more than an average human heart and is incredibly expensive. Nonetheless, the company estimates around 100,000 people in the United States and Europe could eventually benefit from the machine, which may usher in the next generation of mechanical hearts.

“If we had a small, totally implantable artificial heart, all powered electromagnetically, that would be the standard, there’s no doubt,” Arabia says, noting that it may be a while before a reliable, self-contained artificial heart is available. “We want something we can implant and forget about, just like a normal human heart.”

Perhaps the biggest moral conundrum, though, has nothing to do with living with a mechanical heart, but dying with one. Unlike biological hearts, artificial ones can pump blood throughout the body and oxygen to the brain when the rest of the body breaks down. Death is dragged out — and may require the machine be shut off. “I’ve had patients where the liver and kidney failed, the skin turned yellow and died, and the only thing working normally was the brain,” Arabia says.

On a hot spring afternoon, Steve and Mary Williams drive a few miles from their modest Orange County home to the Pacific Ocean, where the couple regularly takes a two-mile walk on a meandering bike and pedestrian path. Steve misses surfing more than almost anything else, and coming to the beach keeps him grounded.

After pulling into a handicapped parking space, Williams unplugs his heart’s air-compressor from the car’s charger, straps on a backpack that weighs roughly 14 pounds, and steps into the Southern California sun. As he walks up a wheelchair ramp to the coastal path, a man in an army fatigue hat and board shorts yells: “What are you doing, you’re not handicapped!” Williams stops and locks eyes with the pedestrian. “I don’t have a heart,” he responds, noticeably flustered. “What’s your disability?”

Mary ushers him away before things can escalate. “He gets comments like that all of the time,” she tells me. A waitress once asked if Williams had monkeys inside of his backpack, due to the strange sound coming from it. Another person accused him of carrying a bomb.

Stares and comments are minor compared to other complications. Earlier this year Williams accidentally knocked the air pump onto the floor while preparing to take a sponge bath, and the battery stopped working. He took a few steps out of the bathroom, then crumpled onto the floor. A backup battery kicked in, jolting Williams awake. The fall and the jolt left him with superficial injuries: a chipped tooth and a large cut above his left cheekbone.

“I’m trying to live a normal life but it can be hard with this thing attached to me,” he says, his words slowed by a stroke he had after the operation. Williams keeps track of all the promising breakthroughs in the heart transplant field. We discuss scientists’ effort to create bioartificial hearts using stem cells, full body transplants, and bioengineers’ quest to develop a “continuous flow device,” which are small, implantable turbine-like pumps that send blood through the body at a steady stream, much like a hose or faucet. It’s controversial technology, but the machine has just one moving part, doesn’t experience much wear and tear, and is relatively quiet.

Today, Williams is stuck in a sort of limbo. If his heart had stopped beating 30 years ago, he probably would have died. If it stopped beating 30 years into the future, he might have a permanent and non-intrusive artificial heart. Or perhaps a perfect clone of his original organ. Instead, he has a mechanical heart that, while burdensome, keeps blood pumping to his organs and oxygen to his brain. It’s a hard life, yes, but Williams feels lucky to have it. “When people ask what it’s like I tell them, ‘Sure, I don’t have a heart, but I had a lot of problems with the heart I was born with. If I kept it I probably wouldn’t be here today.’”

At 6AM on April 9th, Williams was making coffee for Mary when his home phone rang. He answered tersely, bothered that someone was pestering him so early in the morning. The call, however, was one he had anxiously been awaiting for the past 51 weeks: a donor heart was being transported to Cedars-Sinai for him.

Williams and Mary raced to the hospital where he was prepped for surgery. At 1:30 the following morning, Williams had his artificial heart removed, was placed on a heart-lung bypass machine, and had a stranger’s biological organ installed in him.

The surgery went smoothly. He had crossed the bridge, so to speak.

“I’m just in shock still: I can’t believe I don’t have the artificial heart; I can’t believe there’s no noise; I can’t believe I don’t have to take the blood thinners,” he said a few weeks after the operation. “I should be dead at least three times from this whole ordeal, but I’m not. I’m just so grateful for everything.”

A few months later, the transplant was still holding up well. Williams plans on volunteering at Cedars-Sinai and helping artificial heart recipients adjust to their new lives.

And in July, after seven months of being monitored closely as an inpatient at Cedars-Sinai, De La Cruz also crossed the bridge. Her operation, though, didn’t go as smoothly as Williams’: De La Cruz’s body rejected the new organ and she went into kidney failure. She is now in and out of the hospital and may soon need a kidney transplant.

“This is exhausting; I was looking forward to getting the heart and trying to live a better life,” she said at the end of October. Despite the grim circumstances, De La Cruz maintains her optimism. “There are still things that can be done to give me the quality of life that I was hoping for… It will be better.”