University of Iowa researcher identifies 'Grinch effect' in heart, lung transplants
Researchers contend matching donors, recipients by heart and lung size vs. weight and height has better outcome
At his worst, Josh Burdette couldn’t stand after sitting without pausing to catch his breath. Going to the bathroom was among the most difficult tasks of his day.
He needed extra oxygen to function.
The then-29-year-old’s body was rejecting the new lungs he had received through an emergency transplant five years earlier and, without a second transplant, death was imminent.
“I ended up getting really depressed,” said Burdette, 31, of Cedar Rapids. “It was a pretty scary ordeal. The scariest part was knowing all the risks that were involved.”
The University of Iowa Hospitals and Clinics, at that time, had never done a “re-transplant” involving lungs, and doctors were intended to send Burdette back to his first surgeon. But as Burdette’s condition worsened, plans changed.
Two years ago, on Feb. 2, 2012, Burdette became the UIHC’s first re-transplant patient using a pair of “oversized” lungs.
“They told me the lungs were larger for my body … but it was a risk they were willing to take,” he said. “It was my blood type, and it was available, and I wasn’t going to last much longer.”
On the eve of his two-year re-transplant anniversary, Burdette said he’s doing well. In fact, he feels great and sometimes forgets how close he came to not being here.
Michael Eberlein, UI assistant professor of internal medicine, said that makes sense. Even though Burdette’s new lungs previously might not have been considered a transplant match, subsequent research has revealed a better way of matching organ donors with recipients, Eberlein said.
“Our research has shown that transplantation of oversized lungs does not compromise patient survival,” he said.
In fact, research by Eberlein and Robert Reed, assistant professor of medicine at the University of Maryland School of Medicine, has linked oversized transplants – up to a point – with improved survival rates.
In lungs, for example, such matches have been associated with a 30 percent lower risk of death one year after transplant.
And, Eberlein said, the new matching metric often increases the pool of possible donors for patients awaiting transplants.
“I think Josh had a better shot of getting a lung transplant because of our lung-size metric and because our research on organ-size matching in thoracic transplantation gave us the knowledge and confidence to accept an oversized lung,” Eberlein said.
The 'Grinch' effect
In a study published earlier this month in the Journal of the American College of Cardiology, Eberlein and Reed contend that matching donors and recipients by heart and lung size instead of by weight and height could produce better outcomes.
That’s because two people who weigh the same or are the same height could have vastly different organ sizes, possibly requiring the smaller donor organ to strain in a recipient’s body.
The researchers dubbed this the “Grinch” effect – referring to the Dr. Seuss character whose heart was “two sizes too small.”
With heart donations, for example, recipients commonly are listed for a donor weight 30 percent above or below their own, Eberlein said. But research has shown that gender also plays a significant role in successful organ matches.
“For the same body weight, a female will have a 20 percent smaller heart than a male,” Eberlein said. “The sex mismatch has been associated with a worse survival rate at one year and later.”
Eberlein and Reed’s new metric for matching organs donors with recipients compares CT scans and MRIs with information about a person’s sex, height, weight and age.
“The math behind it is simple,” he said. “And the method gives you a significantly more accurate heart size.”
Using a data base of 32,000 heart transplants recorded between 1989 and 2011, researchers looked back at optimal matches and mismatches according to their new metric. What they found was a 30 percent higher chance of dying in the first year for mismatched patients.
“The study highlights the detriments of under-sizing a transplanted heart,” he said. “But if you take the normal metrics, it’s not apparent that a heart is undersized.”
In response to concerns about how a new metric might affect a donor’s wait time, Eberlein said, he thinks access to organs actually could increase in some cases.
“It would not lead to any limits or fewer transplants or someone being bypassed,” he said. “It would just lead to size optimization with the effect of improving outcomes.”
'They saved my life'
The current way of matching heart and lung donors with recipients was accepted as the standard of care years ago, based on the best information available at the time, Eberlein said. But he’s pushing for an industrywide change.
“There are more novel and newer ways to do this, and we would advocate for the transplant community to update its size-matching method,” he said.
Eberlein said he and his UIHC colleagues have been calculating donor options using the new organ-size metric for more than a year.
Burdette said he’s proof that it works.
“They saved my life,” he said.
Burdette’s lungs mysteriously started to fail at age 23 in 2006 when he was living in California. After several trips to the emergency room and numerous misdiagnoses, he slipped into a coma and awoke with his first set of new lungs.
“It was a crazy, out-of-nowhere thing,” he said.
Doctors weren’t able to determine what caused the lung failure, but Burdette’s second set of lungs have allowed him to move on without the need for more answers.“Half the time I don’t think about it,” he said. “You get to feeling so good after that fact that you feel normal and you forget.”