Two-thirds of all heart attacks are caused by something known as vulnerable plaques, which are fatty lipid pool deposits in the inner layer of the arterial wall. But standard medical imaging tests such as MRIs, CT-scans, external ultrasound and coronary angiography often fail to detect them.
“Everybody hears about heart disease and heart attacks, yet vulnerable plaques are often the source — they are very insidious,” says Thomas Hughes, a professor of aerospace engineering and engineering mechanics at the Institute for Computational Engineering and Sciences (ICES) at The University of Texas at Austin.
New imaging technologies have yielded promising results. For example, virtual histology intravascular ultrasound (VH-IVUS) generates images of an artery cross section from an ultrasound catheter tracked through the vasculature. It can distinguish between low-risk artery wall thickening and a high-risk lesion. Once identified, current drugs such as statins prevent about 30 percent of vulnerable plaque heart attacks or strokes.
“Both detection and treatment of vulnerable plaque represent huge unmet clinical needs,” says Hughes. “If vulnerable plaque blocks flow to an area of the heart, it’s a heart attack; if it blocks a part of the brain, it’s a stroke.”
New studies propose supplementing statins with drugs delivered directly to diseased arteries to rapidly stabilize vulnerable plaques and prevent rupture. Hughes and his former Ph.D. student, Shaolie Hossain, created a 3-D model of a heart drug delivery system that demonstrates how the patient-specific imagery can be used to precisely deliver the supplemental drugs within each patient’s anatomy and physiology.
“Using this newly available information from a patient’s VH-IVUS, we can generate models showing the specific geometry of a patient’s arterial wall, as well as the fine junctures among arteries,” says Hossain. “The methodology will allow a physician to identify the location of the vulnerable plaque and inject a customized amount of the drug at a specific site tailored to the patient’s artery structure and blood flow features for the best outcome.”
To encourage use of the new technology, Hossain, now an ICES visiting research scholar and a research associate at the Methodist Hospital Research Institute, marshaled university resources to produce an instructional video on how to use it.
“Visualization is absolutely essential — there’s no question about it,” Hughes says.
With the help of sophisticated visualization expertise and techniques from the Texas Advanced Computing Center (TACC) and staff animators in the Faculty Innovation Center in the Cockrell School of Engineering, the 14-minute animation explains the underlying nature of vulnerable plaques and a clinical procedure for treatment with the goal of personalizing diagnostic and therapeutic interventions in patients. (The instructional video is available on YouTube.)
“Navigating ‘the great divide’ that often exists between clinicians and engineers or scientists can be challenging,” Hossain says. “We hope this video will help bridge this gap, and prove to be educational to the general public as well as get high school students excited about math and science.”
In addition to the animation, and also using TACC advanced computing resources, Hughes and Hossain developed a computational toolset and simulation capabilities to model important characteristics of the research such as fluid flow, drug release, nanoparticle properties, patient-specific geometries and bifurcations of vessels.
“To model these very complicated systems takes millions of equations over millions of time steps to do simulations, so the computational burden is enormous,” Hughes says. “For a computational institute like ICES, having an advanced computing center like TACC available is a platform for all of our research.”
The treatment represents a continuation of decades of work by Hughes and his students to develop effective patient-specific heart disease interventions. Cardiovascular disease is the leading cause of death in the United States and represents more than a half trillion dollar business in research and treatment here.
In vivo validation of the model is the next step.
“This will take us closer to the clinical work to help develop new, noninvasive procedures for new drugs,” Hossain says.