Tiny bubbles too small to see with the human eye are the newest, and perhaps best, defense against heart disease for patients at The Nebraska Medical Center. Called “micro-bubbles,” they help doctors see blood flowing through a patient’s arteries and veins. When combined with ultrasound, the bubbles can predict heart disease even more precisely—and at a much lower cost—than nuclear imaging. To date, The Nebraska Medical Center has the most experience in the country with micro-bubbles.
Thomas Porter, M.D., a cardiologist, UNMC professor of medicine and Theodore F. Hubbard Distinguished Chair of Cardiology, began studying micro-bubbles in 1994. Six years later, he began human trials. From 2000 to 2003, more than 1,500 patients went through micro-bubble testing at The Nebraska Medical Center. What Dr. Porter found was not only a way to assess the health of the heart muscle, but also to monitor blood flow.
“When blood flow slows down, we know there’s a blockage. Catching that early enough allows us to treat the blockage and hopefully prevent a heart attack,” said Dr. Porter.
Just how big are the bubbles? They measure 3 to 4 microns, which makes them about 85 times smaller than the dot punctuating the end of this sentence. Injected into the blood stream, these bubbles, filled with fluorocarbons, act as a red blood cell tracer. The
fluorocarbon filling lights up on ultrasound, detecting changes in blood flow and problems with the heart muscle—both of which are indicators of heart disease, blockages and even an impending heart attack.
Precision and Cost Savings
“The resolution achieved with this technique is more precise than nuclear imaging and traditional ultrasound,” Porter noted. “The bubbles pose no risk to patients, add no time to a conventional echocardiogram, and are significantly less expensive than traditional testing.”
Standard nuclear tests cost around $1,500; an angiogram can run more than $5,000. By contrast, the micro-bubbles cost about $120 and are used in conjunction with an echocardiogram which costs about $500. So the cost savings is significant and the test is more precise than any other.
Bubbling Through the Body to Diagnose or Medicate
Made of a lipid or albumin shell, the bubbles are filled with fluorocarbons that the body naturally expels through the lungs. The bubbles are injected into the blood stream where they naturally follow the red blood cells through the body. The fluorocarbon in the bubbles makes them easy to find on ultrasound. They help doctors determine the rate of blood flow and spots where that rate slows down or even stops—thus spotting a blocked artery, vein or even capillary. Once the bubbles enter the heart, doctors can see the heart’s border and thickness, which helps them determine if the heart is enlarged (another sign of heart disease). The bubbles then travel into the lungs, where they are breathed out without the patient even knowing.
“The micro-bubble can go beyond diagnostics to treatment,” explained Dr. Porter. “If we detect a blockage or scarring in the wall of a blood vessel, we can coat a micro-bubble with medication that prevents further injury. Once injected into the blood stream, that medication gets exactly where it’s needed.”
The Nebraska Medical Center is the only site for human trials on that use of the micro-bubbles.
“I can see many uses for the micro-bubble in the future that go far beyond cardiology,” said Dr. Porter, who presented his research to the American Heart Association meeting in New Orleans in November and will present to the American College of Cardiologists in Orlando, Fla. in March.