Finding Bone
Formation in Carotid Plaques
Helps to Avoid Stroke
September / October 2002
Penn vascular specialists performed a study to determine
if calcified carotid plaques are associated with an increased
risk of stroke. "The clinical significance of calcification
in artherosclerotic plaques throughout the body is debated.
Our results indicate
that bone formation tends to occur in heavily calcified carotid
lesions devoid of ulceration and hemorrhage. Patients with
intensive calcification of carotid plaques had fewer symptoms
of stroke and transient ischemic attacks (TIA) then those
without calcification," says Emile
R. Mohler, III, MD,
director of the Vascular Medicine Program at the University
of Pennsylvania Health System.
Penn vascular specialists analyzed carotid endarterectomy
specimens from close to 150 patients who underwent vascular
surgery at Penn. "We compared the characteristics of
the plaque with the clinical characteristics of the patient.
Specifically, we were looking to see if the patient had a
history of TIA or stroke," explains Dr. Mohler.
The results, which were published in Stroke, May 2002, found
that stroke and TIA occurred less frequently in patients
with plaques with large calcified granules. Thirteen percent
of the patients had bone formation. This correlated with
large sheets of calcification and inversely correlated with
the ulcerated lesions, which tend to be associated with stroke.
In addition, the presence of bone also correlated with diabetes
and coronary disease.
Penn researchers further speculate that in addition to preventing
stroke, statin drugs may actually promote a stable plaque
through a reduction of cholesterol and allow for a larger
percentage of calcification.
Penn's data is consistent with previous studies of ultrasound
imaging of the carotids. These studies demonstrated that
when a patient has echolucent plaque (plaque that does not
have much calcium and is presumably filled with a lot of
cholesterol) there is a higher risk of stroke. "The
predominantly echolucent plaques tend to result in plaque
ulceration and are associated with embolization to the brain
that can cause stroke. Echorich plaques with negligible cholesterol
are more stable," says Dr. Mohler.
Noninvasive detection of coronary artery calcification with
Electron-Beam Computed Tomgraphy (EBCT) is useful in identifying
patients at high risk for cardiovascular events. "Although
EBCT accurately determines plaque burden it is not suitable
in determining the components of the plaque and therefore
which plaques are unstable. Carotid ultrasound is better,
but not perfect," adds Dr. Mohler.
In the future, Penn vascular specialists would like to identify
imaging techniques that allow them to determine if plaques
are stable or unstable. Ongoing Penn studies include examining
carotid plaque morphology with MRI imaging and examining
patients to determine which plaques are the most dangerous.
Learning more about the plaque changes will assist clinicians
in knowing whether intervening earlier with medications,
angioplasty stenting or other methods would improve patient
outcomes.
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