Atherosclerosis

Atherosclerosis is the buildup of fat and cholesterol plaque in the nervous system. When this plaque builds up in the coronary arteries a partial or total blockage this will results inadequate blood flow and the heart muscle does not get an adequate blood supply. This is referred to as ischemic heart disease or coronary artery disease or CAD. Coronary artery disease is one of the leading causes of death in western societies. According to the American Heart Association, Coronary Artery Disease is the single leading killer of American men and women.

Coronary Artery Bypass Surgery – CABG

CABG is commonly pronounced as cabbage, is typically recommended when there is disease of the left main coronary artery or in three or more vessels, or if nonsurgical management has failed. Radiologic Technologist should be familiar with the basics of this procedure because it is a common indication for CT scan imaging, both in evaluating patients for possible Coronary Artery Bypass Graft surgery and for assessing graft patency after the surgery is performed. Arteries or veins taken from elsewhere in the patient’s body are grafted from one aorta to the other coronary arteries, to bypass atherosclerotic narrowing and results in improve the blood supply to the coronary circulation that supplying the myocardium. The terms single double, triple and quadruple are terms to refer the number of coronary arteries bypassed in the procedure. The arteries or veins used for the graft can be taken from different areas of the body.

Common choices of vessels for coronary
artery bypass grafting include the saphenous vein of the leg
(single arrow), the LIMA from the inside of the chest wall
(double arrow), and the radial artery of the forearm (not pictured).

The route choice is highly surgeon dependent. A common choice is the left internal mammary artery LIMA, also referred to as left thoracic artery LITA, which is grafted to the LAD.

Image (A) is an axial demonstrating the origin of the LIMA graft from the
left subclavian artery to the LAD coronary artery (LAD; arrow). Image (B) is a curved reformatted
image of the graft (arrows). Image (C) is a three-dimensional reformation of the
same graft. Images courtesy of the University of Michigan. (LCX = left circumflex artery.)

Another frequent choice is to use the saphenous vein from the leg.

Image (A) is an axial image demonstrating
the origin of the saphenous graft to the left circumflex artery.
Image (B) is three-dimensional reformatted image demonstrating
the graft. Images courtesy of the University of
Michigan.

Less frequently used for intravenous graft is the radial artery from the forearm or sometimes called the right internal mammary artery or the (RIMA), also called the right thoracic artery RITA. Vessels used for graft are redundant, which means that the body can compensate for their removal. Grafts may block in the months to years after bypass surgery is done. A graft is considered patent or open it there is flow though the graft without any significant graft stenosis this is greater than 70%.

Balloon Angiography and Coronary Stenting - Angioplasty

Balloon angiography and coronary stenting are less invasive than is CABG and these are the option for some patients. Angioplasty is a technique that is used to dilate an area of arterial blockage using a catheter with a small, inflatable, sausage shaped like balloon at its tip. However, angioplasty has some fault of certain standards or shortcomings. 1st, the opening areas of stenosis are typically made up of both atheroma, which soft, and plaque which is hard. The balloon may not be able to evenly expand areas with uneven degrees of hardness. 2nd, some of the areas compressed by the balloon, material the expanded channel can proliferate after the channel is expanded, which results in gradual restenosis of the blood vessels.

Coronary Artery Stent

Coronary artery stent where designed to bring under control the shortcomings of angioplasty techniques. One of the common type of stent is made of self expanding, stainless steel mesh. It is mounted on a balloon catheter in a collapsed from as shown in the picture below.

A common type of coronary stent is made
from stainless steel mesh. (A) Balloon catheter positions the
stent at the site of arterial stenosis, (B) inflation of the balloon
dilates the artery and expands the stent, and (C) the balloon
is collapsed and withdrawn, leaving the expanded stent in
position.

The function of the balloon is to push the stent against the inner portion of the vein when it is inflated with air. In many cases, a pharmacologic agent is coated to the stent to interfere the process of restenosis. These stent are called the drug-eluting stents, but however they are frequently referred to as coated or medicated stents. To reduce the chance of restenosis, this stents opens the disease segment into a rounder, bigger and smoother opening compared to angioplasty alone. However, stents cannot be used in all situations. For example, arteries that have extreme bends and very small vessels the stents are difficult to place and cannot be used. Like coronary grafts, radiologic technologist should familiar and can recognized coronary stents because they are a common finding on CT scan images.

Visualization of a right coronary artery stent
(arrow) on a curved MPR image. Image courtesy of the
University of Michigan.

Like for example, when the radiologic technologist is doing a calcium score, stents should be recognized so that they won’t be include in the images measured, as they will artificially increase the score.