Biology Technology

Living with no pulse, How doctors reinvented the heart

Living with no pulse, How doctors reinvented the heartThe ancient Egyptians believed, as some modern people do, that the mind exists in the heart instead of the brain. I guess they would claim that anesthesia works on the heart and the changes seen in the brain are unrelated to consciousness. There is proof, however, that consciousness does not reside in the heart: Living conscious people with only electric motors for hearts!

… As many as five million Americans suffer some form of heart failure, but only about 2,000 hearts a year become available for transplant. The obvious solution to that scarcity is to build an artificial heart, and how hard could that be? The heart’s just a pump, after all, and people have been making pumps since the Mesopotamians invented the shadoof to raise river water 3,000 years before the birth of Christ. Doctors started thinking seriously about replacing the heart with a machine around the time Harry Truman was president.

To understand why they still haven’t succeeded, pick up a two-pound barbell and start curling it. Two pounds: nothing. But see how long you can keep it up. Twenty minutes? An hour? Two? Your heart does that all day and all night–35 million beats a year–for as long as you live, without ever taking a rest. Manufacturing a metal and plastic heart capable of beating that way for more than about 18 months has so far proved impossible. …

Building a heart that mimics nature’s lub-dub may be as comically shortsighted as Leonardo da Vinci designing a flying machine with flapping wings. Nature is not always the best designer, at least when it comes to things that humans must build and maintain. So the newest artificial heart doesn’t imitate the cardiac muscle at all. Instead, it whirs like a little propeller, pushing blood through the body at a steady rate. After 500 million years of evolution accustoming the human body to blood moving through us in spurts, a pulse may not be necessary. That, in any case, is the point of view of the 50-odd calves, and no fewer than three human beings, who have gotten along just fine with their blood coursing through them as evenly as Freon through an air conditioner. …

The continuous-flow heart solves the biggest problem with artificial hearts: longevity. One little turbine like the ones Cohn showed me has been running continuously in a lab for eight years and shows no sign of wearing out. Another advantage is that it runs on a battery no bigger than a videocassette. The patient can wear it in a kind of shoulder holster–cumbersome, but not as bad as sitting day and night beside a hissing compressor the size of a dishwasher. …

And here’s where the story gets spooky. In November 2003, Frazier installed the newly approved HeartMate II to assist the failing heart of a young man from Central America who barely spoke English. His family members spoke none. So none of them fully understood Frazier’s instructions to return to the hospital frequently for follow-up. The young man walked out of the hospital and disappeared.

When he finally showed up eight months later, Frazier held a stethoscope to his chest and was stunned to hear no heartbeat at all. None. Even more-sensitive instruments would have found nothing resembling a pulse. The young man’s heart continued to flutter weakly, but it had effectively shut down. Although the HeartMate II had been designed to assist the heart, not replace it, in this case it seemed to be doing all the work: not just helping the left ventricle push oxygenated blood to the body, but pushing the blood hard enough to flow through the body, then back through the useless heart to the lungs, through the useless heart again, and into the pump to complete the loop and begin the process all over again. The reason the young man had never come back for follow-up, he told Frazier, was that he’d felt perfectly fine.

Thoratec won FDA approval of the HeartMate II in 2008, and surgeons have now installed continuous-flow LVADs alongside the hearts of some 11,000 people worldwide (among them former vice president Dick Cheney). But cases like that of the Central American man remain extremely rare. Newspapers reported that Cheney had no pulse, but in fact he and most other recipients continue to experience, as Cohn describes it, “cyclic fluctuations of pressure with each heartbeat.” Even though such fluctuations might be detectable only by an intra-arterial monitoring line hooked to a pressure transducer, they remain present. Patients walk around with videocassette-size batteries hanging under their armpits, their hearts still beating. Frazier, who invited Billy Cohn to join him at the Texas Heart Institute in 2004, has installed many LVADs. He showed me a video of one of his patients playing basketball and another participating in a hip-hop dance contest.

One of the most surprising things about the LVAD is that it does something the medical community had thought impossible: It reverses heart failure. Until the past few years, damage to the heart was thought to be permanent. But it seems that by relieving strain, an LVAD lets some hearts damaged by, for instance, heart attacks repair wall tissue and grow healthy again. Often the LVAD can be removed. “It’s like putting a cast on a broken ankle,” Cohn says. “You take it off when it’s healed. We had no idea that could happen.”

Some hearts, though, can’t be healed. And for those who continue to worsen even with an LVAD, the only choices are the increasingly hard-to-come-by transplant, or replacement with a machine. The experience of Frazier’s Central American patient told Frazier and Cohn that it was theoretically possible to replace hearts entirely with continuous-flow pumps. But that raised the kind of questions nobody had ever before had to consider. Our bodies have evolved to have blood move through us in pulses. Was a pulse necessary for reasons we couldn’t yet imagine? One possible snag that occurred to Cohn was the lymphatic system. Unlike blood, the ducts that move lymph through the body have no motor of their own. They surround arteries and get their motion from the pulse of the blood. “It was a good theory,” Cohn laughs. “So far, though, we haven’t found any evidence that continuous flow creates problems with the lymph.” …

“I remember going in and out that first day, and when Tim told me my family was coming from Switzerland, I knew it wasn’t good,” she said as we sat in a warm living room decorated with her daughters’ artwork. She extended her wrist for me to hold. It was warm, but might otherwise have been that of a dead woman: no pulse.

Reger’s heart doesn’t seem to be getting better, but it could hardly get worse. Like the heart of Frazier’s Central American patient, Reger’s has all but given up. Logically, she should be dead. Instead, she feels fine, caring for her daughters and walking a pedometer-measured two miles a day. So far, living without a pulse has caused no problems with her lymph or anything else.

A few people continue to walk around with no pulse at all. One of them was living comfortably in upstate New York. The little quilted backpack held two lithium-ion batteries and the HeartMate II’s computerized controller, which are connected by cable through a hole in Reger’s side. Needless to say, she has never left her backpack on a bus. “My cousin once disconnected me, though, by mistake,” she said. “I was showing her how to change the battery. She disconnected one, and then–I was distracted for a second–the other. I yelled, ‘You can’t do that!’ and then passed out. The device blares at you. She reconnected it, and I came back. I was probably out for 10 seconds. She was completely freaked out. She wanted to go right back to Switzerland.”

Reger and the Central American patient proved that humans could survive, indeed thrive, with no pulse.

via PopSci

The pumping action of walking, swinging the arms and pumping the legs, a few miles a day keeps the lymph moving daily to clean out the junk from around the body’s cells, and this works without a pulse, apparently.

Related posts


This site uses Akismet to reduce spam. Learn how your comment data is processed.

Notify of
Do NOT follow this link or you will be banned from the site!