The first person to receive a heart transplant from a pig lived for two months. The second and third already were brain-dead -- experiments announced on Tuesday that are a key step before trying again in the living. Regulators are considering whether to allow a small number of Americans who need a new organ to volunteer for rigorous studies of animal-to-human transplants, after a historic first attempt earlier this year. The latest experiments -- one performed last month and one last week -- offer something of a rehearsal for anticipated trials. Researchers removed hearts from genetically modified pigs, put them on ice and flew them hundreds of miles to New York University. There surgeons sewed the hearts into the chests of a deceased man and woman.
New York researchers transplanted pig hearts into two brain-dead people over the last month, the latest in a string of developments in the long quest to one day save human lives with animal organs.
The experiments announced Tuesday come after a historic but failed attempt earlier this year to use a pig's heart to save a dying Maryland man — sort of a rehearsal before scientists try again in the living.
Among the lessons: Practice with the deceased is important.
"We learned so much from the first one that the second one is much better," said Dr. Nader Moazami, who led the operations at NYU Langone Health. "You stand there in awe" when the pig heart starts to beat in a human body.
This time around, Moazami's team mimicked how heart transplants routinely are done. Once last month and once last week, researchers traveled to a facility housing genetically modified pigs, removed the needed hearts, put them on ice and flew them hundreds of miles back to New York.
They used special new methods to check for any worrisome animal viruses before sewing the heart into the chest of each deceased recipient — a Vietnam veteran from Pennsylvania with a long history of heart disease and a New York woman who'd benefited from a transplant earlier in life.
Then came three days of more intense testing than living patients could tolerate — including frequent biopsies of the organ — before doctors disconnected life support.
Dr. Nader Moazami, right, and cardiothoracic physician assistant Amanda Merrifield, center, and other members of a surgical team prepare for the transplant of a genetically modified pig heart into a recently deceased donor at NYU Langone Health on July 6, 2022, in New York.
Already the Food and Drug Administration is considering whether to allow a small number of Americans who need a new organ to volunteer for rigorous studies of either pig hearts or kidneys. NYU Langone is among three transplant centers planning trials — and has a meeting planned with the FDA in August to discuss requirements.
Testing in the deceased could help fine-tune how the first trials in the living are designed, said Dr. David Klassen of the United Network for Organ Sharing, which oversees the nation's transplant system.
"They serve as an important sort of stepping stone," said Klassen, who wonders if researchers next might consider tracking the organs for a week or so in a donated body rather than just three days.
One of the deceased recipients, Lawrence Kelly, had suffered heart disease for most of his life and "he would be so happy to know how much his contribution to this research will help people like him" in the future, his longtime partner Alice Michael told reporters Tuesday.
Animal-to-human transplants, what scientists call xenotransplantation, have been tried for decades without success, as people's immune systems almost instantly attacked the foreign tissue. Now, pigs are being genetically modified so their organs are more human-like — increasing hope that they might one day help fill a shortage of donated organs. More than 100,000 people are on the national waiting list for a transplant, most of them kidney patients, and thousands die every year before their turn comes.
The most ambitious attempt so far came in January, when doctors at the University of Maryland Medical Center transplanted a pig heart into a dying 57-year-old. David Bennett survived for two months, evidence that xenotransplantation was at least possible. But initial testing missed that the organ harbored an animal virus. What caused Bennett's new heart to fail and whether that virus played any role still isn't known, the Maryland researchers recently reported in the New England Journal of Medicine.
Months earlier, the NYU team and researchers at the University of Alabama at Birmingham separately were testing pig kidney transplants in the deceased, people who'd donated their bodies for science.
NYU's recent heart experiments will add to the evidence as the FDA decides whether to allow formal studies in living patients.
But NYU Langone's Dr. Robert Montgomery, a kidney transplant surgeon who received his own heart transplant, said continuing careful experiments in the deceased is critical to figuring out the best methods "in a setting where a person's life isn't at stake."
"This is not a one-and-done situation. This is going to be years of learning what's important and what's not important for this to work," said Montgomery, who has a list of almost 50 people who've called desperate to volunteer for a pig kidney transplant.
The FDA hasn't signaled how soon it might decide whether to allow such studies. At a recent two-day public meeting, the agency's scientific advisers said it was time to try despite a long list of questions. They include how best to modify the pigs, as several biotech companies — including Revivicor, which supplied the NYU organs — are pursuing different options.
It's not even clear which organ to attempt first in a clinical trial. If a pig kidney fails, the patient can always survive on dialysis. Yet some of the FDA's advisers said starting with the heart might be better. Experiments with pig kidneys in deceased humans showed the organs produced urine. But still unknown is whether pig kidneys do another important job — processing medications — the same way human kidneys do.
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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute's Department of Science Education. The AP is solely responsible for all content.
How 3 factors impact CPR survival rates
3 factors that impact CPR survival rates
Updated
When done correctly, cardiopulmonary resuscitation, or CPR, has the potential to save lives. This technique is used in medical emergencies such as cardiac arrest to maintain the flow of oxygen-rich blood to the brain and throughout the rest of the body. CPR is often performed leading up to emergency medical services’ arrival and until a normal heart rhythm is restored.
For patients who go into cardiac arrest outside of a hospital, there are several factors that increase their chances of making it to the hospital and recovering well enough to be safely discharged. These factors include having the event witnessed by a bystander or emergency medical services and receiving CPR as soon as possible. Researchers have found that survival rates have increased over the last 40 years among those who received CPR up to one year following an out-of-hospital cardiac arrest.
Citing research analyzing CPR survival rate data collected across 88 studies from around the world, ACLS Medical Training looked at how three key factors impact survival rates. These three factors are then broken down into how they impact survival to hospital admission, after discharge from the hospital, and then one month and one year afterward.
Bystander versus EMS CPR
Updated
- Survival to admission:
--- Bystander CPR: 26.3%
--- EMS CPR: 36.3%
--- Unspecific CPR: 29.6%
- Survival to discharge:
--- Bystander CPR: 22.8%
--- EMS CPR: 25.5%
--- Unspecific CPR: 21.1%
- One-month survival:
--- Bystander CPR: 11.3%
--- EMS CPR: 10.7%
--- Unspecific CPR: 7.7%
- One-year survival:
--- Bystander CPR: 12.8%
--- EMS CPR: 12.3%
--- Unspecific CPR: 7.9%
When someone's heart can't circulate blood on its own, performing CPR can be critical until the patient gets to the hospital. Emergency medical service responders are trained to perform CPR at a rate of 30 compressions per two rescue breaths. EMS responders are essentially acting in place of the heart—each compression manually pushes blood through to the brain and other tissues. Even partially restoring blood flow can increase the chances of resuscitation.
Though bystander CPR has a lower survival rate than EMS responders, it can still improve the chances of survival. The American Heart Association encourages adults and even children to learn hands-only CPR, which is performing 100 to 120 chest compressions per minute with no mouth-to-mouth breaths. Research has found that higher quality CPR training and initiating CPR as soon as possible after a collapse significantly improve long-term survival outcomes.
Whether the cardiac arrest was witnessed by anyone
Updated
- Survival to admission:
--- Witnessed: 36.4%
--- Not witnessed: 36.6%
--- Mixed: 23.7%
--- Unspecific events: 28.2%
- Survival to discharge:
--- Witnessed: 23.2%
--- Not witnessed: 24.7%
--- Mixed: 21.6%
--- Unspecific events: 19.2%
- One-month survival:
--- Witnessed: 10.5%
--- Not witnessed: 4.4%
--- Mixed: 8.2%
--- Unspecific events: 8.9%
- One-year survival:
--- Witnessed: 13.2%
--- Not witnessed: not applicable
--- Mixed: 8.3%
--- Unspecific events: not applicable
In a randomized clinical trial of 874 patients, those whose cardiac arrest was witnessed by a bystander had more than twice the rate of survival than those whose cardiac arrest was not—but with some caveats.
Although bystanders performed CPR on 32% of patients, early bystander CPR was not associated with increased survival. The researchers found that early bystander CPR didn't always improve survival either because CPR was not performed properly or its effectiveness decreased after a few minutes. These findings emphasize the importance of raising public awareness about CPR training and early notification of paramedics by bystanders.
Location where CPR was performed
Updated
- Survival to admission:
--- Oceania: 33.5%
--- Europe: 25.7%
--- North America: 20.5%
--- Asia: 15.6%
- Survival to discharge:
--- Oceania: 16.2%
--- Europe: 11.7%
--- North America: 7.7%
--- Asia: 4.5%
- One-month survival:
--- Oceania: 16.0%
--- Europe: 9.0%
--- North America: 6.5%
--- Asia: 12.8%
- One-year survival:
--- Oceania: 11.5%
--- Europe: 9.2%
--- North America: 4.0%
--- Asia: 5.3%
Comparing post-CPR survival rates in Europe, North America, Asia, and Oceania (a region that includes Australia and Polynesia), researchers found that there is a higher rate of survival in Western countries. The popularity of CPR classes among the general public is more recent in most Asian countries than in Europe and the U.S., so the quality of bystander CPR may be lower there. South Korea and China have a much higher prevalence of CPR training than other Asian countries, thus survival rates may be higher there.
The threshold for starting CPR by paramedics is also lower in some non-Western countries. These factors may lead to lower survival rates for out-of-hospital cardiac arrest in Asia. Promoting awareness about the importance of CPR training is something governments and health authorities can do to improve outcomes for patients who have out-of-hospital cardiac arrests.
This story originally appeared on ACLS Medical Training and was produced and distributed in partnership with Stacker Studio.
