JHS Researchers study arterial health, heart disease
By Jack Mazurak
If Ervin Fox ran a smoothie stand, he’d offer customers heart-healthy drinks in three sizes: Big Gulp, Middleman and Kiddy.
But as a nationally recognized cardiologist and researcher with the Jackson Heart Study, he’s more in his element using ultrasound and pulse-wave recordings to diagnose the health of three sizes of blood vessels: large, medium and small.
Fox, professor of cardiology, used this three-size approach in designing a $3.6 million federally funded study.
In a vascular function laboratory in Jackson that he established for the study, Fox and a team of technicians, sonographers, medical students and residents are performing pulse wave tonometry – a method of recording blood flow through different parts of the circulatory system – on thousands of African-Americans enrolled in the Jackson Heart Study.
The researchers use the blood-flow recordings and other information to gauge the health of participants’ large, medium and small blood vessels.
In the big picture, the team wants to look at correlations between arterial health and heart disease. At the smallest level, they’re assessing the health of vascular endothelium, the innermost lining of blood vessels.
Endothelial cells perform many roles. They help give vessels their tone and dilating abilities, they act as gatekeepers for passage of certain cells and hormones through the vessel walls, and they work to prevent plaque buildup.
Endothelial linings can lose function and stiffen with age, disease and risk behaviors, such as smoking and poor diets. Endothelial dysfunction may lead to atherosclerosis, which can contribute to high blood pressure, stroke, heart attacks and other cardiovascular problems.
Fox and his team want to see if the health of people’s vascular endothelial linings directly link to cardiovascular and related diseases. As well, they want to determine if and what role genetics play in that link.
“We think endothelial function is a marker for atherosclerotic risk and becomes abnormal early on in the development of heart disease, before negative health outcomes occur,” Fox said. “If endothelial function in our group can be proven to be a cardiovascular risk predictor, then it might be used in the future as a tool for disease prevention and management.”
While scientists and physicians have long suspected that arterial health impacts cardiovascular health – and have used tonometry to take such measurements – Fox’s study marks the first use of a more detailed version of pulse tonometry developed by investigators in Boston in a large African-American community-based group.
Fox hopes to include 3,829 people in his study. His team began recruiting participants in early April and has already surpassed 500, he said. A five-year grant Fox received in 2011 from the National Heart, Lung and Blood Institute paid for the research.
Using a peripheral arterial tonometry device, or PAT, the team records pulse waves in the tiny vessels in participants’ fingertips. At day’s end, they e-mail those recordings to PAT expert Dr. Koby Sheffy, chief scientific officer at Itamar Medical in Israel. Sheffy processes the recordings and returns them to the Jackson team for analysis.
For mid-sized arteries, Fox’s Jackson team takes images and tonometry of participants’ brachial arteries, which are in the upper arm. Ultrasound images go to a team at Boston Medical Center, Dr. Joseph Vita, director of clinical research, and Mai-Ann Duess for processing.
Brachial tonometry recordings get sent for processing to Dr. Gary Mitchell, president of Massachusetts-based Cardiovascular Engineering, Inc.
And for large vessels, Fox and his team record waveforms in the aortic root – the base of the body’s largest artery – and perform tonometry on the femoral artery in the upper leg.
Dr. Emelia Benjamin, professor of medicine at Boston University, serves as the study’s intellectual collaborator.
“She performed tonometry for the Framingham Heart Study and serves as director of the Framingham Echocardiography and Vascular Laboratory,” he said.
Fox’s preliminary work on the study, along with prior research, helped him earn a Presidential Early Career Award for Scientists and Engineers, the highest governmental honor for young researchers. He received the award and met President Barack Obama at a ceremony in Washington D.C. in July.
With four years to go before the study is complete, Fox and his collaborators already are writing abstracts, presenting posters and beginning manuscripts based on preliminary data. And they’re looking forward to their findings, no matter if they’re sized small, medium or large.