Diagnosing cardiac disease by looking for structural defects in the heart itself, says Jagat Narula, MD, PhD, is like analyzing highway traffic by examining the road.
Dr. Narula is director of cardiovascular imaging at Mount Sinai School of Medicine in New York. There, researchers use a variety of imaging techniques to measure the blood flow as it leaves the heart—studying fluid mechanics instead of muscle mechanics.
The researchers believe that the eddies and whirls of blood flow as it exits the left ventricle can reveal heart disease that doesn’t show up in images of the heart itself.
“With visualization, we are looking at the ultimate measure of the efficiency of the heart: how the blood is brought in and how it is sent out,” Dr. Narula said, as quoted in a Mount Sinai news release. He continued:
Today, cardiologists place great weight on a gauge called the squeeze fraction or ejection fraction—the portion of blood pumped from the ventricle with each heartbeat. What we are doing is a complete departure from the view of the heart as a squeezing, pressure-generating chamber.
Mount Sinai researchers and their collaborators have used several imaging techniques but are focusing on forms of ultrasound imaging known as echocardiographic particle imaging velocimetry. They detail their findings in an article in the May issue of JACC: Cardiovascular Imaging. Dr. Narula is senior author.
“The most effective technique involves injecting a stream of bubbles that behave exactly like red blood cells and using echocardiography to track their path through the left ventricle,” said Partho Sengupta, MD, director of cardiac ultrasound research at Mount Sinai and an author of the article.
Computer-enhanced video shows the blood flow in detail, complete with arrows plotting the direction as the bubbles swirl through the heart chamber. Said Dr. Sengupta:
Not only are you following the path of the blood, but you can actually identify the amount of energy that is being distributed. Like other forms of ultrasound, that means low-cost heart tests using this technology could be performed on a simple outpatient basis.
Blood flow into, inside, and out of the heart is very complex. The researchers are just beginning to tease out the significance of specific disturbances and abnormalities. Even assuming that the technique proves its worth and that research reveals which flow patterns are normal and which indicate trouble, reading the images will not be easy.
“We have started using these imaging techniques in clinical trials,” said Dr. Narula. “They will require careful evaluation.”
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