This week I’m utilizing Genius as a way to annotate this post and give readers information that maybe didn’t fit into the article, but provides further insight. Click here to see the article with annotations.

The most common cause of death in the United States is heart disease. However, in the last 50 years, the prognosis for those living with heart disease has greatly improved, thanks in part to medical devices. From 1950 to 1996, the rate of death from cardiovascular disease dropped by more than 50 percent.

Many of these devices wouldn’t be possible without animal models. FDA requires that like these be tested in nonclinical trials before they approve it for humans, which includes using animal models to assure the material won’t react poorly with tissue and that the device will operate as intended. Let’s look at some of the lifesaving devices available for those with heart disease that were made possible by animal testing and research.

Cardiopulmonary bypass

Lindbergh_perfusion_pump_in_Putnam_Gallery,_2009-11-24

A perfusion pump created by Charles Lindbergh and Alexis Carrel.

Before the invention of the cardiopulmonary bypass (CPB), it was almost impossible to perform heart surgery. The only way doctors could operate was to slow down the heart using hypothermia. Hence, the need for something that could breathe and pump blood throughout the body – a heart-lung machine.

The first forays into CPB include efforts by Charles Lindbergh and Alexis Carrel in the 1930s to build a perfusion pump that would sustain the body during heart surgery. In their research, they were able to keep cat and bird organs alive for up to 21 days. Though the technology became obsolete by the 1950s, other medical innovations were built off of the knowledge gained from the perfusion pump.

Around the same time Lindbergh and Carrel were working on their perfusion pump, a medical student named Michael E. DeBakey created a “roller pump” – something that would help provide continuous blood flow during operations. The roller pump later played a critical role in the heart-lung machine. Because of his work as an inventor and surgeon, DeBakey became known by many as the “greatest surgeon ever.” DeBakey was also FBR’s board chair for many years.

One of the researchers who made the most progress with CPB was John Gibbon. By 1937, he successfully kept several cats alive for a week or more after CPB. With the help of Thomas Watson, the president of IBM, Gibbon created models with which he could conduct research in dogs. By 1952, 9 out of 10 dogs survived operations. One of his clinical trials with an 18-year-old woman was the first successful open-heart surgery in a human using the heart-lung machine.

In 1952, the first widely used heart-lung machine was created, modeled after Gibbon’s. Since then, CPB has given doctors the opportunity to perform surgeries that would have otherwise been too dangerous or impossible and given people a second chance at life. In addition to that, while rare and expensive, open-heart surgery does occur on dogs and cats – allowing our companions to benefit from research for human health.

 

Artificial heart

Total artificial hearts have become invaluable devices for people who otherwise wouldn’t be able to function while waiting for a donor heart. When the heart can’t pump enough blood to the body, and the damage is so severe that heart transplant is the only viable option, people are kept alive on a total artificial heart.

The first artificial heart was made by Vladimir Demikhov in 1937, and was tested in a dog. But it wasn’t until 1957 that Dr. Willem Kolff and Dr. Tetsuzo Akutsu were able to implant a total artificial heart into a dog that lived for an hour and a half. Starting in 1971, Kolff and his team – veterinarian Don Olson, medical engineer Robert Jarvik and surgeon William DeVries – began research on artificial hearts in calves at the University of Utah. A calf named “Alfred Lord Tennyson” lived for 268 days on the Jarvik 5 Total Artificial Heart.

 

Heart valves

Artificial heart valves are devices used to replace natural valves when there is a serious defect, like a congenital malformation or infection, which can result in heart failure or stroke. The valves can be mechanical or made out of tissue from pigs, cows or horses.

With the development of the heart-lung machine, surgeons were able to operate on the heart safely, which made it possible for them to consider replacing heart valves that were defective. In the late ‘50s, Lowell Edwards and Albert Starr developed a replacement heart valve that was similar in structure to a human heart valve, testing it first in dogs. The ball-and-cage design they pursued worked well in several dogs, so they moved to clinical trials.

However, to prevent clots, patients with ball-and-cage valves had to take blood thinners for the rest of their lives. In the 1960s, a French surgeon named Alain Carpentier looked at the possibility of using animal valves to replace diseased human valves, which would eliminate the need for blood thinners. He used mostly pig heart valves, and treated them with a chemical that helped prevent the body from rejecting the valves.

Currently, the most common types of heart valves in use are mechanical ones, like leaflet or tilting disc, as well as biological, from animals or donated tissue.

 

Pacemakers

St_Jude_Medical_pacemaker_with_ruler

Implantable cardiac pacemakers like these ensure that the heart keeps beating normally.

Pacemakers are small devices that use electrical impulses to regulate heartbeat.

In the 1930s, Albert Hyman was the first to coin the term cardiac pacemaker. But it wasn’t revisited until 1941 –and even then, it was almost by accident. Two researchers in Toronto, Canada, Wilfred Bigelow and John Callaghan experimented with using hypothermia as a way to slow down the heart so that heart surgery could take place. However, the pair discovered that rewarming the dogs didn’t start the heart up again quickly enough, so they stimulated the sinoatrial node, the pacemaker of the heart. The electric pacemaker came about in 1949 as a result of those experiments. Designed and built by Canadian electrical engineer John Hopps, it was tested in dogs and rabbits.

The implantable pacemaker wasn’t far behind. In another happy accident, Wilson Greatbatch, a professor at the University of Buffalo, put the wrong sized resistor into a heart rhythm recording device, which made it emit heartbeat-like pulses. After work to make the pacemaker smaller, he was able to demonstrate that it could take control of a dog’s heartbeat.

The pacemaker has been incredibly important for those who need it in the short term or long term – whether they’re walking on two legs or four. In the late ‘60s, a repurposed human pacemaker was implanted into a dog with heart problems. Now, however, most pacemakers implanted in pets are unused and donated by medical device companies, with 300 to 500 implants taking place per year. Worldwide, about three million people live with pacemakers. Recently, the FDA approved use of the first leadless pacemaker.

In the past fifty years, treatments for those with cardiac problems have come a long way – and are still improving. The contributions animals have made in developing and testing medical devices are incredibly important. For many, animal testing and research has meant the difference between life and death.

A special thanks to Macallan Penberthy for her help with the research for this blog.

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