Barney clark heart6/20/2023 “When we pinch our thumb and it goes from pink to white and immediately back to pink, this means blood is flowing through the body. How, in such a future, would we determine if a person were alive or dead? “That is very easy,” says William (Billy) Cohn, a surgeon at the Texas Heart Institute, bringing my existential philosophizing to a halt. I try to imagine a world full of people with no pulse. Since its FDA approval in January 2010, close to 20,000 people – including former US Vice President Dick Cheney – have received a HeartMate II, 20 of whom have been living with the device for more than eight years. 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 – up to ten years. Like the Hemopump, it doesn’t replace the heart but rather works like a pair of crutches for it. Meanwhile, at the Texas Heart Institute, the HeartMate II is being developed. The Impella is the smallest heart pump in use today – it’s not much bigger than a pencil – 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. It has a motor so small it sits inside the device at the end of the catheter, rather than outside of the body. Abiomed’s newest heart prototype, Impella, uses similar technology boosted by leaps in modern engineering. And the Hemopump lives on in spirit of newer devices. The patient’s 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. Because of this, there is no ejection of the blood in spurts. It was the world’s first ‘continuous flow’ pump: Rapidly spinning turbines create a flow like water running through a garden hose, meaning the blood flow is continuous from moment to moment. When the screw inside the pump spun, blood was pumped from the heart to the rest of the body. The result was the Hemopump, a device as big as a pencil eraser. Perhaps, he thought, this principle could be applied to pumping blood. Wampler saw men using one such device to pump water up a river bank. In 1976, during voluntary medical mission work in Egypt, cardiologist Dr. 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. The Archimedes’ screw was an ancient apparatus used to raise water against gravity. Today, scientists are working on a new wave of artificial hearts with one crucial difference: they don’t beat. That’s the cause of the gentle movement you feel when you put your fingers to your wrist or your chest – your pulse, which corresponds with the beating of your heart. The result is what’s 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. 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. And in the early 2000s, Massachusetts-based company Abiomed unveiled a new heart that (unlike the SynCardia) was designed to be permanent – a total replacement heart for end-stage heart failure patients who were not candidates for transplant and couldn’t be helped by any other available treatment. Another widely used artificial heart, a direct descendent of the Jarvik-7, is the SynCardia. The device has been tweaked and renamed many times at the time of writing, it was the world’s only FDA-approved total-replacement artificial heart device used as a bridge-to-transplant for patients. 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. A second patient was implanted in 1984 and died after 620 days. Their first patient was a 61-year-old dentist called Barney Clark, who lived on the Jarvik-7 for 112 days. 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. It had wheels, was as big and heavy (although not as tall) as a standard household refrigerator, and was normally connected to sources of compressed air, vacuum and electricity. 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 – mainly adult men. 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. Perhaps the most influential device was kick-started by Willem Kolff, the physician-inventor who produced the first kidney dialysis machine. One solution that researchers have pursued since the late 1960s is an artificial heart.
0 Comments
Leave a Reply. |