When Your Heart Turns Against You, Animals Are There to Help

You may know someone who takes blood thinners; over 3.2 million Americans have prescriptions. However, there are problems associated with these medications. Not only is a person who takes blood thinners unable to live life to the fullest, they must also be cautious about nearly all day-to-day physical activities.

Compared to someone with a healthy vascular system, a person on anticoagulants (also known as blood thinners) is at a much higher risk for bleeding out from even a minor injury such as a paper cut. This is the reality all patients with mechanical aortic valve replacements face.

Valve replacement is the go-to treatment for when the aortic valve does not function properly, causing blood flow to be restricted. This can happen for many reasons, but the most common ones are aortic stenosis and aortic calcification which can be fatal if not treated.

There are numerous surgical options including mechanical aortic valves and a variety of bioprosthetic valves (also known as tissue valves). Mechanical valves are sturdy but have many risks, which is why some patients prefer bioprosthetic valves.

Bioprosthetic valves are replacements made from animal or human tissue. Currently, the best bioprosthetic valve replacement method is the Ross procedure. This procedure is when the aortic valve is replaced with the patient’s own pulmonary valve (which is identical in structure to that of the aortic valve). Then the missing pulmonary valve is replaced with a valve from a donor. The Ross procedure is infrequent due to the high level of surgical skill required and also the lack of available organ donors. Another option is to replace the aortic valve with a human aortic valve, but once again, this is very rare due to a lack of donors.

Image Credit: Daniela Benoit

The other bioprosthetic options are bovine pericardium and porcine valves. A bovine pericardium valve is an aortic valve made from the tissue protecting a cow’s heart. The tissue is treated and made into a leather-like substance and then inserted into the patient’s heart. The other option, which is by far the most common bioprosthetic valve, is the porcine valve. This valve is the aortic valve from a pig’s heart, which is implanted into the patient.

Patients with bioprosthetic valves do not need to take blood thinners, which is the primary reason these are used over mechanical valves at times. However, there are other risks. Bioprosthetic valves do not last nearly as long as mechanical valves; it is almost certain that you will need to have another valve replacement. Obviously, each time a person is operated on it becomes more dangerous, so it is usually recommended that people over the age of 60 get a bioprosthetic valve and those under that age receive a mechanical valve. Hence, people with tissue valves are less likely to endure multiple surgeries in their shorter lifetimes. Although these are the guidelines for choosing a type of aortic valve replacement, every patient is different and it is ultimately the patient’s decision.

Dr. Tirone David, M.D., F.R.C.S.C, an esteemed cardiologist and professor at the University of Toronto, developed a procedure known as “the David Procedure” in 1989. This surgical approach allows a patient to avoid an aortic valve replacement by fixing the damaged tissue and leaving the valve untouched.

Dr. David says, “the beauty of [the David procedure] is that it restores [the patient’s] lifespan to normal.”

The advancement of aortic valve replacement surgery can be greatly attributed to the scientists, medical professionals and animals used in the study of the heart. Without pigs and cows, bioprosthetic valves, which do not require blood thinners, would not be an option for people around the world in need of an aortic valve transplant.

  • Over 3.2 million Americans have prescriptions for blood thinners and this carries a risk.
  • Compared to someone with a healthy vascular system, a person taking blood thinners is at a much higher risk for bleeding out from even a minor injury such as a paper cut. 
  • The need for blood thinners is also a challenge for patients outfitted with mechanical aortic valve replacements, a challenge that researchers are attempting to solve via cutting-edge design. 


Sider, Krista L et al. “Animal models of calcific aortic valve disease.” International journal of inflammation vol. 2011. August 2, 2022. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3150155/

Head, Stuart J et al. “Mechanical versus bioprosthetic aortic valve replacement” European Heart Journal, vol. 38, issue 28, July 21, 2017. https://academic.oup.com/eurheartj/article/38/28/2183/3746020

Yutzey, Katherine E et al. “Calcific Aortic Valve Disease” Arteriosclerosis, Thrombosis, and Vascular Biology vol. 34, issue 11, November 2014. https://www.ahajournals.org/doi/10.1161/atvbaha.114.302523

“Aortic Valve Stenosis” Mayo Clinic. July 6, 2022. https://www.mayoclinic.org/diseases-conditions/aortic-stenosis/diagnosis-treatment/drc-20353145

“Heart Valve Replacement: Which Type Is Best for You?” Cleveland Clinic. June 14, 2018. https://health.clevelandclinic.org/heart-valve-replacement-which-type-is-best-for-you/

Interview with Dr. Tirone David. Interview by Sofia Scartascini. July 21, 2022.

Tirone, David. “How to Decide Between a Bioprosthetic and Mechanical Valve”. September 28, 2020. https://pubmed.ncbi.nlm.nih.gov/33002585/

Peeters, Frederique et al. “Calcific Aortic Valve Stenosis: Hard Disease In the Heart: A biomolecular approach towards diagnosis and treatment.” European Heart Journal. July 21, 2018. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6055545/

Editorial Team

  • Chief Editor: Juhi Amin
  • Team Editor: Raunak Banerjee
  • Creative Team Senior Managers: Daniela Benoit, Bebe Lemanowicz
  • Creative Team Manager: Annika Singh
  • Social Media Team Managers: Spencer Lyudovyk, Yoojin Jeong
  • Image Credit: Daniela Benoit


Amber Snyder is an editorial intern for the NIH Record at the National Institutes of Health where she writes science and news articles and social media posts. She enjoys learning about science and educating others. She is currently pursuing her MA in Science Writing at Johns Hopkins University. She previously attended Sweet Briar College, where she studied biology and creative writing. In her free time, Amber enjoys reading and riding her horse, Sunny.

Content Expert

Dr. Tirone David, M.D., F.R.C.S.C, is an experienced cardiac surgeon and professor at the University of Toronto. He developed a procedure that is life-changing for those who have aortic aneurysms.  

About the Author

Sofia Scartascini

Sofia is an incoming senior at McLean High School in McLean, Virginia, is an avid writer and activist, who is passionate about biomedical science, storytelling, and literature. In her free time, Sofia loves to listen to music, spend time in nature, and hang out with her friends. She also enjoys a good discussion fueled by the abundance of new scientific knowledge.