Cardiovascular disease (CVD) from atherosclerosis accounts for 29 percent of deaths worldwide and ranks second only to infectious and parasitic disease. Deaths from CVD are often premature, and millions of nonfatal events result in disability.
In the United States alone, atherosclerosis affects 1 in 4 persons, causing approximately 42 percent of all deaths. Approximately half of these are due to atherosclerotic coronary heart disease (CHD), which is mainly driven by complications such as myocardial infarction and stroke.
Atherosclerosis is a slow, progressive disease that may start in childhood. In some people, the disease progresses rapidly during the third decade, while in others, the disease doesn't become dangerous until the fifth or sixth.
Exactly how atherosclerosis begins or what causes it remains unknown, but some theories have been proposed, including damage to the endothelium by elevated cholesterol and triglycerides in the blood, hypertension and cigarette smoking. Unfortunately, patients with atherosclerosis are often unaware of the disease until they have a heart attack or stroke.
Now, patients at risk may soon be identified earlier because of a new diagnostic tool.
Dr. Tara Schiller from the International Institute for Nanocomposites Manufacturing at WMG, along with colleagues from the Baker and Monash University, have found that near-infrared autofluorescence is associated with the presence of intraplaque hemorrhage and heme degradation products, particularly bilirubin. The researchers made this discovery by using a mouse model, which uniquely reflects plaque instability as seen in humans, and human carotid endarterectomy samples.
Fluorescence emission computed tomography detecting near-infrared autofluorescence allows in vivo monitoring of intraplaque hemorrhage, establishing a preclinical technology to assess and monitor plaque instability as well as potential plaque-stabilizing drugs. In other words, by increasing the wave length of the infrared radiation currently used to detect fatty deposit build up in arteries to near-infrared wavelengths, the researchers were able to selectively identify plaques with internal bleeding, usually associated with high-risk bleeding.
Raman spectroscopy caused the fluorescence, which was thought to be a mixture of heme products formed during degradation of red blood cells but were only observable in unstable plaques with internal bleeding, not in more stable fatty deposits, thereby improving selectivity when looking for high-risk deposits.
Previously, researchers used low wavelength (300-400 nm) fluorescence technology to assess plaque composition, detecting fluorescence signals of collagen, elastin and oxidized low-density lipoprotein, typically as components of the lipid core. However, this technology was limited by poor specificity, as low wavelength fluorescence is not exclusively emitted by lipid core associated materials, as well as poor signal-to-noise ratio and weak tissue penetration caused by hindering tissue autofluorescence and strong photon absorption.
Near-infrared autofluorescence imaging is a novel technology that allows identification of atherosclerotic plaques with intraplaque hemorrhage and ultimately may help detect high-risk plaques in patients. Although further clinical trials are needed, this method of imaging technique to assess unstable fatty arterial plaques could be used to monitor the effectiveness of drugs used to prevent heart attacks or strokes.
