A New Approach to Prevention and Treatment of Coronary Disease
About Coronary Artery DiseaseCoronary artery disease is generally caused by atherosclerosis, a condition resulting from the buildup of cholesterol and other materials that form plaques and restrict blood flow through the coronary arteries. In some cases, the coronary blockages grow slowly and only become evident when they prevent adequate flow of blood to the heart muscle during periods of increased exertion or stress. This lack of flow causes chest discomfort that is called angina pectoris. In other cases, the plaque can rapidly produce a complete blockage of an artery leading to a myocardial infarction (heart attack). This occurs when a plaque ruptures and its contents are exposed to blood, creating a thrombus (blood clot) that, in turn, leads to a rapid, complete blockage of an artery.
The Role of Lipid Core Plaques
In 1989, Geoffrey H. Tofler, Peter H. Stone, and Infraredx founder James E. Muller, introduced the concept that heart attacks occur when a "vulnerable" lipid-rich plaque ruptures, leading to thrombosis. The rupture of lipid-core plaques, a subset of lipid-rich plaques, have been shown in autopsy studies to be the cause of a majority of heart attacks. In addition it has already been proven that such plaques complicate coronary stenting.
The Challenge of Identifying Lipid Core Plaques
While the importance of lipid core plaques in the occurrence of coronary events has been known for some time, traditional imaging technologies lack the ability to reliably assist physicians in the detection of lipid-core plaques. A stress test will only detect blockages in an artery. An angiogram, which often follows a positive stress test , can quantitate the degree of narrowing of an artery, but cannot reveal plaque composition.
Intravascular imaging with ultrasound can display the structure of a plaque, but it is not an optimal method to determine its plaque composition. A method is needed that can display the structure of the plaque, and determine if it contains a lipid core.
Angiography (Top): Angiogram from a 67 year old female with positive family history but no personal history of CAD demonstrates only a focal 75% diameter stenosis in mid segment of a large caliber RCA. A more advanced imaging technology would have the potential to reveal additional information that could help shape diagnosis and treatment strategies.
Co-registered NIRS/IVUS Image (Bottom):
Grayscale IVUS demonstrates deep calcium at 6 o'clock, superficial calcium at 10 o'clock, and hypoechoic plaque at 2 o'clock. Even though the IVUS signal drops out, NIRS positively identifies cholesterol signals in the IVUS shadows at 10 and 2, but not at 6 o'clock. Although IVUS indicates the plaque burden is concentric, near infrared imaging shows that over 180 degrees of this is comprised of lipid core plaque.