Washington, May 30 : Scientists have developed a new non-invasive
technique that may prove effective in uncovering early signs of heart
disease.

People who suffer a heart attack have non-calcified plaque, a build-up
of soft deposits embedded deep within the walls of the heart’s
arteries, undetectable by angiography or cardiac stress tests, and
prone to rupture without warning.

The new study led by a team from Beth Israel Deaconess Medical Centre
(BIDMC) used voxel analysis in combination with MDCTA (multi-detector
computed tomography angiography)

The technique was shown to be equally as effective as catheter coronary
angiography in identifying patients at risk for heart disease.

The researchers believe that the new results may help doctors monitor
the effects of medical treatment to reduce patients’ risk of
atherosclerosis and heart disease.

“The importance of quantifying plaque is critical because total plaque
burden is considered the most important predictor of coronary events,”
said the study’s senior author Dr Melvin Clouse, Emeritus Chairman of
the Department of Radiology and Director of Radiology Research at BIDMC
and Deaconess Professor of Radiology at Harvard Medical School.

“Furthermore, the rupture of soft non-calcified plaque has been implicated as the cause of heart attack,” he added.

Exercise stress testing and coronary angiography, the standard methods
for diagnosing atherosclerosis and heart attack risk, both work by
visualizing the lumen, the channel through which blood flows.

As lumen increases in size as plaque progresses, conventional
angiography and stress tests fail to provide a complete picture of
plaque accumulation.

The CT scanning method with 64 separate scans, provides a detailed
cross-sectional view of the blood vessel wall based on the amount and
volume of blockage present.

Its ability to differentiate plaque density makes it particularly
useful in distinguishing between stable plaque and unstable plaque.

“The latest MDCT scanners have made it possible to detect non-calcified plaque,” said Clouse.

The researchers analysed 41 normal and eight abnormal arterial cross
sections with non-calcified plaque selected from 10 patients undergoing
MDCTA.

“Voxel analysis estimates the volume of plaque in a blood vessel based on a range of volumetric densities,” said Clouse.

Within the selected volume, the number of voxels having a density
within the range of plaque is established, from which the volume of
plaque is then estimated. (In CT scans, voxel values are Hounsfield
units, which give the opacity of material to X-rays). The detailed
measurements, nearly 2,300 in total, provided physicians with a
detailed picture of the coronary arteries and surrounding areas.

“By plotting a voxel histogram across the arterial wall, we were able
to measure the amount of plaque, as well as the narrowing of the
artery,” Clouse added.

Clouse believes that using this new method, they would be able to
better assess the effects of medication treatment and lifestyle
interventions in treating atherosclerosis.

The findings are reported in the June 2008 issue of the American Journal of Roentgenology (AJR). (ANI)