Over 18,000 qualified donor hearts were discarded in 2011, according to the findings of a group of Stanford researchers led by Dr. Kiran Khush, an assistant professor of cardiovascular medicine.

The group recently released a study revealing that, each year, surgeons are becoming more and more selective about what hearts they accept — despite the fact that there is a national shortage of donor hearts and an increasing number of patients needing heart transplants.

It is estimated that while over 20,000 patients a year could potentially benefit from heart transplants, only 1,949 patients were able to receive such operations in 2011.

The study lays out several reasons for the rising percentage of heart rejections. Increasingly strict and frequent inspections of heart transplant centers deter surgeons from choosing hearts that are not perfect. However, the growing usage of medical devices that enhance the conditions of patients waiting for heart transplants is also a factor.

In 1995, donor heart acceptance rate was 44 percent, but in 2006, the number fell to 29 percent. Since then, the percentage has increased marginally and was measured at 32 percent in 2010.

The study also concluded that different regions of the United States have varying acceptance criteria for donor hearts, which means that hearts discarded in one region of the country would be accepted in other regions.

“There are a lot of criteria that vary from surgeon to surgeon and center to center,” Khush said.

“With factors like mild thickening of the heart muscle, as can be seen in donors with high blood pressure or drug abuse, it is really up to the transplant center or the surgeon,” he added.

The Northeast, for instance, had a higher usage of donor hearts when compared to the Pacific Northwest, which has a fewer amount of transplant centers.

According to Khush, this data, as well as the fact that only one third of donor hearts were accepted between 1995 and 2010, suggests a growing need for the development of a standard, nationwide criteria for the acceptance of donor hearts.

Contact Batuhan Berk Balci at bbalci ‘at’ Stanford.edu.