A blood test can show whether a new heart is tolerated by the recipient and not rejected. This has been shown in a thesis from the University of Gothenburg, Sweden.  This means that heart transplant recipients can often avoid having tissue samples taken from their heart.
This thesis reveals how small DNA fragments from the donor heart in the patient's blood can be used to rule out rejection. The study includes 94 patients, both adults and children. The DNA fragments are analyzed using a new method (droplet digital PCR).
“The results are so clear that the new method will start to be used on patients, including those who have already had a heart transplant. We see in the study that DNA levels were usually very low, and that levels rose during rejection. This means that we can rule out rejection with a simple blood test,” says Pediatric Cardiologist Jens Böhmer, who wrote the thesis at Sahlgrenska Academy at the University of Gothenburg.
Tissue samples from the heart
Today, the routine is to regularly take small tissue samples (biopsies) from a transplanted heart. It is usually performed 10 to 12 times during the first year. This is to enable early detection of rejection, a life-threatening complication. 
“Biopsies are very unpleasant and carry a risk for the patient. In addition, children undergo general anesthesia to take these samples,” says Jens Böhmer.
Today, taking biopsies from transplanted hearts is not only expensive, it also means that the recipient of a new heart has to travel, often long distances. In Sweden, heart transplants are performed in Gothenburg and Lund.
Blood tests at the healthcare center
The sample tubes used stabilize the DNA in the blood sample, allowing heart transplant patients to have their blood sample taken at their own healthcare center instead. The sample can then be sent by regular mail for analysis.
“We have analyzed samples from all over the country and also Iceland without seeing any differences in quality. So now we have opened the door for patients to be monitored remotely,” says Jens Böhmer.
The new blood test appears to work at least as well as similar tests available in the US, and it is significantly cheaper. As the current biopsies are also more expensive, the test could save a lot of money within public healthcare.
Doctoral thesis: Surveilling Hearts - A New Biomarker for the Non-Invasive Diagnosis of Rejection after Heart Transplantation, https://hdl.handle.net/2077/83358