Intravascular Ultrasound Preferred for Atherosclerosis Imaging

Compared to other techniques, intravascular ultrasound (IVUS) is much better than other imaging modalities for monitoring atherosclerotic change in the coronary arteries, according to recent research. Scientists are now investigating whether the method may be used to predict the risk of a heart attack or other cardiovascular event.

Studies indicate this may be the case, according to Prof. Clemens von Birgelen in his inaugural address at the University of Twente (Enschede, The Netherlands). Results of IVUS measurements also raise the question of whether patients with demonstrated coronary disease should be treated with more powerful cholesterol-lowering statins to reverse atherosclerosis.

Narrowed coronary arteries caused by atherosclerosis can be visualized using traditional cardiac catheterization, but the technique only shows the space blood flows through the lumen, and not the diseased vascular wall surrounding it. By using a specialized catheter with an ultrasound sensor, IVUS also creates images of the calcifications (i.e., the plaque), and allows various components of the plaque (not only calcium) to be identified, as well as fat and connective tissue. Prof. Von Birgelen reported that this additional information is important for assessing disease progression--plaque progression. Plaque initially leaves the lumen unaffected and grows outward. The blood vessel as a whole becomes wider, leading to a significantly increased risk of heart attack. However, plaques may also decrease in volume while the lumen diameter remains the same, something that can only be determined using IVUS.

Various studies have shown a relationship between plaque growth and cardiovascular events, such as heart attacks. "Plaque progression measured using IVUS could become a valuable ‘surrogate marker' for cardiovascular events,” stated Prof. Von Birgelen. In his address, he also highlighted the relationship between plaque progression and cholesterol. Decreasing cholesterol through intensive statin therapy not only slows plaque formation, but also reverses it. This is reason enough for the professor to question the current target value for low-density lipoprotein (LDL) cholesterol of 2.5 for patients with coronary disease; at that value, over half of patients still have plaque growth. Prof. Von Birgelen wants to determine whether or not a large group of patients is receiving suboptimal treatment for reducing plaque.

IVUS also plays an important role in the treatment of narrow coronary arteries, for example, during balloon dilation and the placement of a so-called stent. New types of stents are being constructed with integrated regulated drug release to prevent the formation of scar tissue in the stent, thereby decreasing the odds of recurrence.

Prof. Von Birgelen is currently performing research on these new stents at the University of Twente, and will soon be launching the so-called TWENTE study at the Medisch Spectrum Twente hospital, in which approximately 1,400 patients will be treated with one of two promising drug eluting stents to compare the clinical results. "During some PCI procedures, IVUS is essential for properly guiding the implantation,” stated Prof. Von Birgelen, who is a cardiologist on staff at the Thorax Center of the Medisch Spectrum Twente in Enschede. He believes that good invasive imaging of the coronary arteries will remain important in future to safeguard the quality of care for heart patients.


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