Photo: UW Cardiovascular Fluid Dynamics Laboratory
Using advanced imaging technology, University of Wisconsin-Madison engineers have found significant differences in blood flow in the hearts of healthy men and women.
Their research and methods could help clinicians make better assessments of patients’ heart health based on their sex, and potentially enable earlier detection of disease.
“Our goal is to use existing technology to develop new ways of determining how sick a patient with cardiovascular disease is,” says Alejandro Roldán-Alzate, an assistant professor of mechanical engineering at UW-Madison. “This involves analyzing and quantifying the efficiency of a patient’s heart to determine how well it’s functioning. These methods also allow us to assess the effectiveness of a treatment or surgery for improving a patient’s heart function.”
But to gauge the severity of a patient’s disease, the researchers first needed to determine a baseline for “normal” cardiac efficiency—and understand how that might differ between men and women.
In a study published in the journal Radiology: Cardiothoracic Imaging in February 2020, Roldán-Alzate, postdoctoral researcher David Rutkowski, and their collaborators detail results that could be used to help establish quantitative standards for normal cardiac performance depending on sex.
The researchers used a sophisticated cardiac imaging technology called 4D flow MRI to study sex differences in the left ventricle, the heart’s main pumping chamber, of healthy volunteers.
The non-invasive imaging technology allowed the researchers to document, in real-time, characteristics of the blood flow—such as its speed and how it twists and turns as it flows through the heart.
“From about 10 minutes of imaging using this method, we can attain enough information from the MRI scans to characterize how well the heart is functioning based on the fluid dynamics of the blood flow,” Roldán-Alzate says.
For the recent study, the researchers obtained MRI scans from 20 men and 19 women, who were all between 20 and 35 years old. The team then derived various blood flow parameters from those scans and correlated them with cardiac function.
The data showed some significant cardiac performance differences between the sexes, says Rutkowski, the lead author on the paper.
Kinetic energy, which is one indicator of energy expenditure during contraction and filling of the heart, was significantly higher in the left ventricles of men.
Vorticity, a measure of swirling flow in the blood, was higher in women, as was cardiac strain, a measure of how much the heart wall contracts to pump blood.
“Using the MRI data, we found differences in how the heart contracts in men and women,” Rutkowski says.
Rutkowski says it appears the greater contraction in the heart wall of women causes more vortices to form in the blood, which helps the blood move more efficiently.
“Our hypothesis is that healthy women have a more efficient heart earlier in their life than men of the same age,” Rutkowski says. “We’d need future studies to determine if that changes with age, or how it might change in response to disease. But now we have a baseline for ‘normal’ flow in men and women to reference while making further comparisons.”
Additionally, the researchers’ results demonstrate that 4D flow MRI and their techniques can reveal discrepancies in cardiac performance between sexes that go beyond what current clinical assessments can measure.
“We believe the quantitative metrics we’re providing will show changes in heart function before changes can be detected in a standard clinical assessment,” Rutkowski says. “So the hope is that this work could help enable earlier detection of disease, allowing for earlier intervention, and also help clinicians better monitor disease progression.”
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