{"id":4590,"date":"2015-06-05T05:36:39","date_gmt":"2015-06-05T05:36:39","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=4590"},"modified":"2015-06-05T05:42:06","modified_gmt":"2015-06-05T05:42:06","slug":"researchers-quest-for-an-artificial-heart","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/researchers-quest-for-an-artificial-heart\/","title":{"rendered":"Researcher’s quest for an artificial heart"},"content":{"rendered":"
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\"shutterstock_198620987\"<\/span><\/a><\/span><\/dt>\n
Image by Ociacia\/ Shutterstock<\/span><\/dd>\n<\/dl>\n

The need to mend broken hearts has never been greater. In the USA alone, around 610,000 people die of heart disease each year. A significant number of those deaths could potentially have been prevented with a heart transplant but, unfortunately, there are simply too few hearts available.<\/span><\/p>\n

In 1967 the South African surgeon Christiaan Barnard performed the world\u2019s first human heart transplant in Cape Town. It seemed like a starting gun had gone off; soon doctors all around the world were transplanting hearts.<\/span><\/p>\n

The problem was that every single recipient died within a year of the operation. The patients\u2019 immune systems were rejecting the foreign tissue. To overcome this, patients were given drugs to suppress their immune system. But, in a way, these early immunosuppressants were too effective: they weakened the immune system so much that the patients would eventually die of an infection. It seemed like medicine was back to square one.<\/span><\/p>\n

Early Mechanisms<\/strong><\/span><\/p>\n

One solution that researchers have pursued since the late 1960s is an artificial heart. Perhaps the most influential device was kick-started by Willem Kolff, the physician-inventor who produced the first kidney dialysis machine. Kolff invited a fellow medical engineer, one Robert Jarvik, to work with him at the University of Utah, and the result was the Jarvik-7. Made up of two pumps, two air hoses and four valves, the Jarvik-7 was more than twice as big as a normal human heart and could only be implanted in the biggest patients \u2013 mainly adult men. It had wheels, was as big and heavy (although not as tall) as a standard household refrigerator, and was normally connected to sources of\u00a0compressed air, vacuum and electricity.<\/span><\/p>\n

In 1982, Jarvik and Kolff won approval from the US Food and Drug Administration to use it in human patients and implanted it that same year. Their first patient was a 61-year-old dentist called Barney Clark, who lived on the Jarvik-7 for 112 days. A second patient was implanted in 1984 and died after 620 days. History records a total of five patients implanted with the Jarvik-7 for permanent use, all of whom died within 18 months of the surgery from infections or strokes.<\/span><\/p>\n

The device has been tweaked and renamed many times; at the time of writing, it was the world\u2019s only FDA-approved total-replacement artificial heart device used as a bridge-to-transplant for patients. Another widely used artificial heart, a direct descendent of the Jarvik-7, is the\u00a0SynCardia<\/span><\/a>. And in the early 2000s, Massachusetts-based company\u00a0Abiomed<\/span><\/a>\u00a0unveiled a new heart that (unlike the SynCardia) was designed to be permanent \u2013 a total replacement heart for end-stage heart failure patients who were not candidates for transplant and couldn\u2019t be helped by any other available treatment.<\/span><\/p>\n

But all these versions of artificial heart devices, whether they are meant to support the heart or replace it completely, are trying to copy the functions of the heart, mimicking the natural blood flow. The result is what\u2019s called a pulsatile pump, the flow of blood going into the body like a native heart, at the average of 80 spurts a minute needed to sustain life. That\u2019s the cause of the gentle movement you feel when you put your fingers to your wrist or your chest \u2013 your pulse, which corresponds with the beating of your heart.<\/span><\/p>\n

Today, scientists are working on a new wave of artificial hearts with one crucial difference: they don\u2019t beat.<\/span><\/p>\n

Pulseless Hearts<\/span><\/p>\n

The Archimedes\u2019 screw was an ancient apparatus used to raise water against gravity. Essentially, it is a screw in a hollow pipe; by placing the lower end in water and turning it, water is raised to the top. In 1976, during voluntary medical mission work in Egypt, cardiologist Dr. Richard K. Wampler saw men using one such device to pump water up a river bank. He was inspired. Perhaps, he thought, this principle could be applied to pumping blood.<\/span><\/p>\n

The result was the Hemopump, a device as big as a pencil eraser. When the screw inside the pump spun, blood was pumped from the heart to the rest of the body. It was the world\u2019s first \u2018continuous flow\u2019 pump: Rapidly spinning turbines create a flow like water running through a garden hose, meaning the blood flow is continuous from moment to moment.<\/span><\/p>\n

Because of this, there is no ejection of the blood in spurts. There is no \u2018heartbeat\u2019. The patient\u2019s own heart is still beating but the continuous flow from the device masks their pulse, meaning it is often undetectable at the wrist or neck.<\/span><\/p>\n

And the Hemopump lives on in spirit of newer devices. Abiomed\u2019s newest heart prototype,\u00a0Impella<\/span><\/a>, uses similar technology boosted by leaps in modern engineering. It has a motor so small it sits inside the device at the end of the catheter, rather than outside of the body. The Impella is the smallest heart pump in use today \u2013 it\u2019s not much bigger than a pencil \u2013 and as of March 2015 has been approved by the FDA for clinical use, supporting the heart for up to six hours in cardiac surgeries.<\/span><\/p>\n

Meanwhile, at the Texas Heart Institute, the\u00a0HeartMate II\u00a0<\/span><\/a>is being developed. Like the Hemopump, it doesn\u2019t replace the heart but rather works like a pair of crutches for it. About the size and weight of a small avocado, the HeartMate II is suitable for a wider range of patients than the SynCardia and has, on paper, a significantly longer lifespan \u2013 up to ten years. Since its FDA approval in January 2010, close to 20,000 people \u2013 including former US Vice President Dick Cheney \u2013 have received a HeartMate II, 20 of whom have been living with the device for more than eight years. All with an almost undetectable pulse.<\/span><\/p>\n

The Future of Heart Transplants<\/span><\/p>\n

I try to imagine a world full of people with no pulse. How, in such a future, would we determine if a person were alive or dead? \u201cThat is very easy,\u201d says William (Billy) Cohn, a surgeon at the Texas Heart Institute, bringing my existential philosophizing to a halt. \u201cWhen we pinch our thumb and it goes from pink to white and immediately back to pink, this means blood is flowing through the body. You can also tell if someone is still alive if they are still breathing.\u201d<\/span><\/p>\n

He admits that once more of these devices are implanted into patients we will need a standard method of determining such a person\u2019s vitals. Cohn imagines them wearing bracelets or even having tattoos to alert people to their pulseless state.<\/span><\/p>\n

I wonder how people will take to hearts that literally don\u2019t beat. Perhaps it will be the same as when patients were offered the first heart transplants: resistance, followed by acceptance due to overwhelming need.<\/span><\/p>\n

\u201cAny new procedure is going to have critics,\u201d says surgeon Denton Cooley. \u201cOn the day that Christiaan Barnard did the first heart transplant, the critics were almost as strong, or stronger, than the proponents of [artificial] heart transplantation,\u201d he says. \u201cA lot of mystery goes with the heart, and its function. But most of the critics, I thought, were ignorant, uninformed or just superstitious.\u201d<\/span><\/p>\n

Cooley performed the first US heart transplant in May 1968. And at 94 years old he still treasures the memory of the day, in 1969, when he implanted the first artificial heart into Haskell Karp and the \u201csatisfaction that came from seeing that heart supporting that man\u2019s life.\u201d<\/span><\/p>\n

\u201cI had always thought that the heart has only one function, and that is to pump blood,\u201d he says. \u201cIt\u2019s a very simple organ in that regard.\u201d<\/span><\/p>\n

This article originally appeared on\u00a0Mosaic<\/span><\/a>.<\/span><\/p>\n

Source: discovermagazine.com<\/span><\/a><\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

Image by Ociacia\/ Shutterstock The need to mend broken hearts has never been greater. In the USA alone, around 610,000 people die of heart disease each year. A significant number of those deaths could potentially have been prevented with a heart transplant but, unfortunately, there are simply too few hearts available. In 1967 the South […]<\/p>\n","protected":false},"author":6,"featured_media":4591,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[38,14],"tags":[],"class_list":["post-4590","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-curiosity","category-innovation"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/shutterstock_198620987.jpg",1000,800,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/shutterstock_198620987-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/shutterstock_198620987-300x240.jpg",300,240,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/shutterstock_198620987.jpg",750,600,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/shutterstock_198620987.jpg",750,600,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/shutterstock_198620987.jpg",1000,800,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/shutterstock_198620987.jpg",1000,800,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/shutterstock_198620987.jpg",1000,800,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/shutterstock_198620987.jpg",713,570,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/shutterstock_198620987.jpg",600,480,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/shutterstock_198620987.jpg",600,480,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/shutterstock_198620987.jpg",613,490,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/shutterstock_198620987.jpg",450,360,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/shutterstock_198620987.jpg",81,65,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/shutterstock_198620987.jpg",640,512,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/shutterstock_198620987.jpg",96,77,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/shutterstock_198620987.jpg",150,120,false]},"author_info":{"info":["Amrita Tuladhar"]},"category_info":"Curiosity<\/a> Innovation<\/a>","tag_info":"Innovation","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/4590","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=4590"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/4590\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/4591"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=4590"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=4590"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=4590"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}