When patients complain of chest pain, they have to undergo a time-consuming and expensive set of tests to find out if the cause is something to do with the heart or some other problem, such as in the muscles, lungs or esophagus.
Study lead author Julian Borissoff, a postdoctoral research fellow at Boston Children's Hospital and Harvard Medical School, says in a statement that if testing the DNA fragments proves to be effective, then "they may improve medical care in terms of identifying patients at risk sooner," which means they could be treated sooner.
While he and his colleagues were able to show that DNA fragments have potential as blood markers for narrowed heart arteries, they say further studies are now needed to prove that these markers are sufficiently specific and sensitive to be of clinical use.
DNA Fragments Released Into Bloodstream When Heart Arteries Become CalcifiedCertain DNA fragments in the blood can be a sign that heart arteries have become narrow and hardened due to calcified build up (advanced atherosclerosis), since under these conditions the blood vessels become chronically inflamed and release small particles of DNA into the bloodstream.
The DNA particles are shed by neutrophils: important immune cells that play a vital role in many diseases, and which become inappropriately active during the advanced stages of atherosclerosis.
Once they become inappropriately active, the neutrophils can undergo apoptosis (cell suicide) or release stretches of DNA called neutrophil extracellular traps (NETs), a method usually reserved for trapping pathogens.
These bits of extracellular DNA are thought to be toxic to cells and strong promoters of inflammation and blood vessel blockages.
Thus Borissoff and colleagues wanted to find out more about the DNA particles and how they might link to narrowed heart arteries and other heart risks such as the likelihood of blood vessel blockages (eg from a clot).
CT Images of Calcified Heart Arteries Linked with DNA Fragments In BloodFor their study they examined CT (computed tomography) images of heart arteries of patients with chest pain who were suspected of having coronary artery disease. There were 282 patients in all, aged from 34 to 83.
They scrutinized the images for signs of hardened or calcified build up in the arteries that supply blood to the heart.
The patients also gave blood samples which the researchers tested for bits of DNA.
The results indicated that blood samples with higher levels of DNA particles were from patients whose CT images showed they also had high levels of calcified build up in their coronary arteries.
The researchers conclude that the DNA particles are potential markers of disease and suggest they may even one day help spot patients with severely narrowed heart arteries, to the extent of predicting how many vessels are affected and whether the patient is at high risk of a serious heart problem or even death.
They suggest larger studies that follow more patients over a longer time are now needed to find out more precisely how these markers might spot patients at risk for coronary artery disease.
About half the patients in their study were followed for 18 months or more.
DNA Particles Themselves May Contribute to Atherosclerosis and ThrombosisThe researchers say it is plausible that the DNA particles themselves promote atherosclerosis and raise the risk of dangerous blockages in blood vessels (thrombosis or blood clot).
"The more the ongoing cell death, which is normal with inflammation, the more DNA enters the circulation and more plaque builds up," explains Borissoff, adding that:
"Cells get damaged, and the products released from the damaged cells can cause even more damage and inflammatory responses."
The team is now doing further tests to find out which DNA particles are the most sensitive and to see how their levels change under different circumstances, such as during a treadmill test, at different stages of calcified build up, or even after treatment for a heart attack.
Funds from the Netherlands Heart Foundation helped pay for the study.
Written by Catharine Paddock PhD