WEDNESDAY, Jan. 8, 2014 (HealthDay News) -- The "Grinch" effect
may be curbing survival rates in some heart transplant patients who
receive hearts that are too small for their bodies, a new study
Scientists at the University of Maryland School of Medicine and
University of Iowa School of Medicine said it may be due to the way
donors and recipients are matched up -- by weight -- and they
propose a new way to allocate hearts.
The researchers reviewed the records of more than 31,000 pairs
of heart donors and transplant patients -- surgeries that took
place over a 22-year period. They focused on heart size matching,
and compared outcomes based on body weight, predicted heart mass
and sex. Then they evaluated the risk of death following
transplantation after one year and five years.
Study author Dr. Robert Reed, an assistant professor of
pulmonary and critical care medicine at the University of Maryland,
said men who received women's hearts were 32 percent more likely to
die in the first year after transplantation due to the differences
in the size of the organ.
"The patients who received the smallest hearts were 25 percent more likely to die in the first year," Reed added.
Historically, cardiac surgeons have tried to match heart failure
patients with donors who weigh about the same -- weight is one of
the key criteria, said Dr. David Taylor, a professor of medicine at
the Cleveland Clinic Lerner College of Medicine.
"Since the beginning of heart transplantation, we've tried to match the donor with the size of the recipient with the presumption that the size of the heart matches the size of the recipient," said Taylor, who is also past president of the International Society for Heart and Lung Transplantation. But that protocol was established before modern imaging technologies existed, he said.
More recent imaging studies have revealed that a person's weight
doesn't necessarily correlate to his or her heart size, and that
height and sex play a bigger role, explained study author Reed.
"We just didn't know better that weight didn't equate to heart size," Reed said. The female heart is considerably smaller, even when a female and male patient weigh the same, he explained.
When a heart is too small for a transplant patient, it will work
harder and grow too big, the researchers added. While that was a
good thing in the Dr. Seuss character called the "Grinch," it's not
good for organ recipients, Reed said. It means the heart is
straining too much.
"The whole muscle of the heart is likely to be growing in what we call a bad soup. The environment it's growing in is a little bit inflammatory and not healthy for the heart," he explained.
More than 3,700 people worldwide undergo heart transplantation
each year, according to background information in study published
Jan. 8 in
JACC: Heart Failure.
Taylor, who was not involved with the study, said: "I think it's
a helpful study in that it does remind us that weight is not the
best marker of heart size, and if we want to match heart size we
should be more dogmatic about considering height and gender, too.
But any cardio surgeon worth their salt is already taking that into
Dr. Michael Acker, chief of cardiac surgery at the University of
Pennsylvania Health System, said he and colleagues look at dozens
of factors when seeking a donor for a particular patient. These
include age, height, weight and sex of the donor; how well the
donor heart is functioning; the donor's mode of death and if there
was trauma to the heart or evidence of infection.
"You have to do a risk-benefit analysis every time you accept or decline a donor," Acker said.
Reed said the study results have prompted him and his colleagues
to propose a new way of allocating organs. They believe it will
better match donors and recipients than the existing
weight-matching method -- a more refined method that does still
incorporate weight but also considers age, gender and height.
"It's not about pairing the perfect heart with the perfect person, it's about not giving too small of a heart," Reed said.
Acker said, however, that using a smaller heart might be the
best option for a transplant patient in some cases. "It's the wrong
thing to say we can now never do this. We don't want to limit our
donor pool any further."
Sometimes a smaller heart is the best choice because waiting for
a bigger, more appropriate-sized heart is a luxury the patient
can't afford, Acker said.
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