Advanced X-rays called CT scans may be able to replace more invasive techniques to check whether heart devices called stents have become overgrown and need clearing, Dutch researchers said on Tuesday.
Stents are tiny wire-mesh tubes inserted into clogged arteries. In some cases, especially with older metal stents, the devices can themselves become clogged with scar tissue.

Older scanners were not capable at seeing inside a heart stent, but newer multislice computed tomography or CT scans were able to spot a blockage in nine out of ten patients, according to a small study published in the Journal of the American College of Cardiology.

"Multislice CT is a relatively simple examination associated with little discomfort," Dr. Jeroen Bax of Leiden University Medical Center in the Netherlands said in a statement.

Patients are injected with a high-contrast dye and then pass through a tunnel for about eight to 12 seconds, during which multiple pictures of the heart are taken.

These photographic ‘slices’ are then reconstructed into a 3D image.

Bax and colleagues believe the technology could spare some patients the discomfort of angiography, which requires the insertion of a thin tube called a catheter into a small opening in the groin and threading it through blood vessels to the artery that needs study.

Complications from angiography can include bleeding, pain or swelling where the catheter was inserted, and in rare cases, impaired kidney function.

Bax tested multislice imaging in 182 patients with 192 previously implanted stents. All had been recommended for testing because of symptoms suggesting narrowing inside the stent, such as chest pain or an abnormal electrocardiogram.

Out of the total, images from seven per cent or 14 of the stents were too blurry to read, either because of motion or problems with the metal inside the stents.

In the remaining 178 stents, CT scans correctly identified 19 out of 20 blocked stents.

The researchers said the CT scanner was 99 per cent accurate at ruling out problems.

"The implication of this finding is that if a narrowing is not detected, it is unlikely to be present, which potentially could avoid unnecessary catheterizations," Dr. Gilbert Raff of William Beaumont Hospital in Royal Oak, Michigan, said in a statement.

However, Raff noted that the study was small and it was done by highly trained experts, who still had trouble reading images from about seven per cent of stents.