Gated CT scan could predict risk of early death in diabetes patients
31 May 2011
A common test using a CT scan to determine calcified plaque
levels in the coronary artery may be useful in predicting early death in
individuals with diabetes, according to a study by Wake Forest Baptist
Medical Center. The study appears in the May issue of Diabetes Care.
“People with diabetes are already at high risk of developing heart
disease and experiencing an early death,” said Donald W. Bowden,
PhD, the director of the Center for Diabetes Research at Wake Forest
Baptist and lead investigator. “With this study, we’ve discovered
that we can identify a subset of individuals within this high risk
group who are at even higher risk, and the means to do this is
already widely available in the form of a computed tomography (CT)
scan — a relatively inexpensive and non-invasive test.”
At least 60% of diabetes patients — even those on dialysis
for kidney failure — ultimately die of a vascular event, such as
heart attack or stroke. However, Bowden said, questions about why so
many diabetes patients die early have remained unanswered in the
medical community’s understanding of the disease.
For the Diabetes Heart Study, Bowden and colleagues have been
following nearly 1,500 patients with diabetes in North Carolina for
about 13 years, gathering data on various aspects of the disease and
how it affects individual health. As original study participants
began to die, the researchers sought to understand why.
“When we reviewed the data last year, we were shocked by the
number of participants who had already died during this study,”
Bowden said. “We wanted to find out if there were any predictors of
who would succumb versus those who are still living. In a group of
people who are already at high risk, we were looking for a way to
identify which individuals were at even higher risk for early death,
with the goal of finding interventions or ways to focus medical care
and attention toward those individuals at highest risk.”
A high coronary artery calcium (CAC) score is known to be a
strong indicator of coronary heart disease. The score provides a
measure of how much coronary artery disease, or calcified 'plaque'
is present in the blood vessels of the heart. Plaque plays a major
role in heart attacks and other vascular events and can be measured
by taking a special 'gated' CT scan which, in comparison to typical
CT scans, uses very few X-rays, does not require any injections and
generally takes less than 10 minutes to perform. At Wake Forest
Baptist, the test costs just over $200 and some insurance companies
will cover the exam in appropriate situations.
Within the diabetes-affected population, there is a very wide
range of calcified plaque buildup in the arteries and the heart,
from individuals with none at all, to people whose entire vessels
are nearly completely calcified. The researchers separated more than
1,000 study participants into five groups, according to the amount
of calcified plaque they had in their blood vessels at the beginning
of the study. The health of those participants was then followed for
an average of 7.4 years before researchers compared the data from
those who died during the study to those who are still living.
“We saw a dramatic risk of dying earlier in the people with
highest levels of calcified plaque in their blood vessels,” Bowden
said. “When comparing the group with the highest amount of plaque to
the group that had the lowest amount of calcified plaque, the risk
of dying was more than six times greater in the group with high
levels of calcified plaque. The difference in risk that we revealed
is striking. It’s in a group of people who are already at risk, but
the CAC level really rather dramatically differentiates risk between
people within this high risk group. This finding could have novel
clinical implications.”
Diabetes is associated with many other medical problems, Bowden
said, so identifying a way to determine who is at highest risk and
who needs the most intensive medical monitoring and care is
especially important.
“The striking magnitude of the risk suggests very strongly that
other research samples should be evaluated, especially in
individuals with diabetes,” he said.