blood test used to determine whether a heart is suitable for donation may be leading to unnecessary rejections, and its use should be reviewed. This is the conclusion of a new study published in the journal Circulation: Heart Failure.

Heart failure occurs when the heart is unable to pump enough oxygen-rich blood around the body to help other organs function.

According to the Centers for Disease Control and Prevention (CDC), in the United States, around 5.7 million Americans have heart failure.

In some cases, heart failure can be treated with lifestyle changes - such as a healthy diet, exercise, and quitting smoking - and medications. For end-stage heart failure, however, a heart transplant may be the only option.

According to the United Network for Organ Sharing (UNOS), as of June 10, 2016, there are 4,147 people in the U.S. waiting for a heart transplant.

However, according to Dr. Snehal R. Patel, assistant professor of medicine at Albert Einstein College of Medicine's Montefiore Medical Center in New York, NY, more than half of these patients will not receive a transplant.

"A lot of focus has been on finding ways to sign up more people as organ donors, but there is also a problem in that only an average of 1 in 3 donor hearts are placed," he adds.

In many heart transplant centers, the blood of potential donors is routinely tested for levels of troponin I - a protein that is released in response to heart damage.

Dr. Patel explains that if troponin I levels are high, then a donor heart will often be rejected out of concern that the organ is too damaged to function following transplantation - regardless of whether the heart appears healthy.

Donor troponin I levels do not affect recipient survival

For their study, the researchers assessed the outcomes of 10,943 heart transplant recipients aged 18 and older using data from UNOS. All donor hearts had normal pumping function, the authors note.

The team set out to determine whether there are any differences in outcomes for patients who received a heart from a donor with high troponin I levels.

At 30 days, 1 year, 3 years, and 5 years after heart transplantation, the researchers found no significant differences in survival between recipients whose donors had high troponin I levels and those whose levels were normal.

There was also no association between donor troponin I levels and risk of recipient death 1 year after transplantation, the researchers report.

Additionally, donor troponin I levels made no difference to recipients' incidence of primary graft failure - loss of pumping action that occurs within 30 days of transplantation - and cardiac allograft vasculopathy - a form of heart disease that can limit long-term survival following heart transplantation.

Based on their findings, Dr. Patel and colleagues believe heart transplant centers should make decisions about whether a heart is suitable for transplantation based exclusively on donor troponin I levels.