Blood flows differently in men and women, MRI study shows

OAK BROOK, Ill. — There’s no shortage of ways in which men and women differ, but a new study finds one more to add to the list. Researchers say that men and women show different blood flow characteristics in their hearts. Perhaps that’s why matters of the heart are so complex between the two genders.

Besides this finding’s status as a powerful piece of dinner conversation, the study’s authors believe their work may one day lead to specialized heart and blood flow standards for men and women. Such standards could bring about more accurate cardiac performance assessments.

Doctors have known that male and female hearts differ for quite some time. For example, a male heart is bigger than a woman’s, but a female heart beats faster than a man’s. Up until now, however, blood flow differences within the two genders’ hearts wasn’t as well studied.

This time around, a 4D flow MRI machine was used to observe gender differences in the left ventricle (the heart’s main pumping chamber). In all, 20 men and 19 women consented to undergoing an MRI.

Results show differences in how the heart contracts

The results reveal some dramatic differences between the sexes. Kinetic energy, defined as a measurement of energy usage during contraction and filling of the heart, was much higher in male left ventricles. On the other hand, vorticity  — “a measure of regions of rotating flow that form during different points of the cardiac cycle” — and strain (another measure of left ventricle functioning) were both higher among women.

“Using the MRI data, we found differences in how the heart contracts in men and woman,” says lead study author David R. Rutkowski, a postdoctoral researcher at the University of Wisconsin in Madison, in a release. “There was greater strain in the left ventricle wall of women and a higher vorticity in the blood volume. We hypothesize that these two things are related.”

These findings may go a long way toward explaining why male and female hearts often respond differently to various stressors and diseases.

“These blood flow metrics would be useful as reference standards because they are derived from healthy people, so we could use these to compare with someone who is unhealthy,” Dr. Rutkowski adds.

Blood flow technology proves vital for doctors

Dr. Rutkowski also says that the ability of 4D flow MRI technology to provide more exact blood flow readings is invaluable.

“There’s been a push in the last couple of decades to make MRI more quantitative,” he notes. “So instead of looking at something and saying it looks normal or different, we can get a number to go with that visual information.”

Now, researchers are using 4D flow MRI technology to examine the upper chambers of atrial fibrillation (irregular heartbeat) patients.

“The goal of our work in general is to move from qualitative MRI to more quantitative MRI,” Dr. Rutkowski concludes. “Getting blood flow and velocity information is just one more metric that is being developed to make MRI more quantitative.”

The study is published in Radiology: Cardiothoracic Imaging.

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