Women awaiting heart transplants are dying at significantly higher rates than men.

Motherboard did a deep dive into how gender bias shapes heart disease diagnosis, treatment, and who ends up on the transplant list.

Perhaps the most alarming part of the piece is that the only FDA-approved artificial heart — the 70cc SynCardia temporary Total Artificial Heart, which is used to keep patients from dying of late-stage heart failure while they await transplants — is too big for most women.

Motherboard reporter Rose Eveleth explained:

"The most frequently used artificial heart is made by a company named SynCardia. In 1999, SynCardia’s 70cc total artificial heart was approved in Europe, followed by the FDA in 2004 and Canada in 2005. And that 70cc heart fits 'a majority of men and some women,' according to the SynCardia site. '88 percent of the 70cc heart goes to men, and 12 percent goes to females,' Don Isaacs, vice president of communications at SynCardia, told me.

"SynCardia also makes a smaller 50cc heart, which can fit patients like Kahala, whose bodies can’t fit the larger 70cc heart, but using it requires a special exemption. And while the larger heart has been FDA approved since 2004, the 50cc heart, SynCardia only got FDA approval for a study on the smaller heart last year. It hasn’t been approved for regular use. In order to use a smaller heart for a smaller patient, the doctor has to make their case to the FDA that they really truly need to use the heart to save a patient's life."

So how does the company get away with providing a heart that doesn't fit many female patients?

It might be easy to paint SynCardia as a villain in this story, but the issue is a bit more complicated. In a sense, SynCardia is simply abiding by the laws of supply and demand: Companies choose to make products that many people want, and the patients seeking artificial hearts are 80 percent male.

Motherboard spoke to Mario Deng, a cardiologist at UCLA Medical Center, about the statistics.

"According to Deng, about 10 percent of heart failure patients will develop advanced heart failure. Of that 10 percent, only 1 percent will get a heart transplant, and of that 1 percent, only 10 percent will need an artificial heart to bridge them between their failing heart and a new one. So when you get down to it, the market for artificial hearts is small."

Experts are unclear about where gender bias plays into the issue.

ATTN: has previously reported about studies that have shown doctor bias in how women are treated for a variety of physical ailments.

“Clearly there is a gender bias," Deng told Motherboard. "The question is, how does this gender bias happen? What are the decision-making processes and branching points where the female gender is not having the same access to care as the male? At all these stages of — let’s call it a heart failure patients 'career' — they make decisions towards a more proactive or less proactive path."

Eileen Hsich, the Associate Medical Director for Heart Transplants at the Cleveland Clinic, has dedicated several years to researching the transplant gender gap and also hasn't found any answers.

Researchers have also found that women are more likely to be rejected as heart donors than men.

"Donors whose hearts were declined for transplantation were significantly more likely to be female,” according to a 2015 study in the Journal of Transplantation. Rejected donors were also more likely to be older and Asian.

Another contributing factor is age.

Women typically get heart disease later in life, and finding a suitable transplant for older patients of either gender can prove challenging. In 2011, 55 people in the 65-and-older age bracket died waiting for transplants, The New York Times reported.

For his part, SynCardia spokesman Isaacs told Motherboard that the FDA's approval process made things challenging.

“If someone wanted to manufacture and market an artificial heart, it would take them about 10 years to get approval,” Isaacs said.

Still, the company submitted the smaller heart to the FDA in 2014 — a decade after the 70cc model was approved, Eveleth reported.

ATTN: reached out to SynCardia for comment and will update this post when we receive its response.

You can read the full piece on Motherboard to learn more.

[h/t Motherboard]