Invasive Imaging Techniques Used to Assess Atherosclerosis

Intravascular ultrasound (IVUS)

The IVUS technique, developed in the 1990s, involves the sending and receiving of ultrasound waves which are emitted from a catheter introduced into an artery. The catheter rotates at about 1800 revolutions per minute producing a detailed picture of the lumen and wall, including the atheromatous plaques, at those sites visualised by the catheter. This technique may be used to examine arterial wall thickness (intima-media thickness or IMT). Assessments of IMT have proved to be an extremely reliable surrogate marker for examining the progression of atherosclerosis and for assessing cardiovascular risk. Drug efficacy can be assessed using this method by measuring changes in atheroma and lumen area, before and after treatment.

The image below shows an example where an atheroma, evident by IVUS, remains undetected by angiography as a result of coronary remodelling.¹ On the left, the angiogram is normal. However, 2 sites in the left anterior artery, indicated by arrows, show a varying extent of atherosclerosis by IVUS. The more distal site (top right) has little disease, but the more proximal site (bottom right) has a large crescentic atheroma. The lumen size at both sites is similar because of remodelling, resulting in a false-negative angiogram.

Click to enlarge

*Reproduced from Circulation 2001;103:604–616, with permission from Lippincott Williams & Wilkins.

Coronary angiography

Coronary angiography, introduced in 1958, uses X-rays to examine the blood vessels or chambers of the heart. A catheter is inserted into a blood vessel and the tip is positioned either in the heart or in the coronary arteries supplying the heart. A contrast medium or dye is injected into the artery which is then visible by X-ray. The X-ray images obtained are called coronary angiograms and enable visualisation of the lumen of the overall coronary bed.

The coronary angiogram shown here shows a narrowing or stenosis of the coronary artery as a result of atherosclerosis.

Click to enlarge

*Photograph M172/354 (CVS 12): BSIP VEM/Science Photo Library.

Reference:
1. Nissen SE, Yock P. Intravascular ultrasound: novel pathophysiological insights and current clinical applications. Circulation 2001;103:604–616.

^ Top