Earlier this year, the American Heart
Association (AHA) released a statement that nonalcoholic fatty liver disease-an
increasingly common liver condition that affects more than one in four adult
Americans-is a risk factor for atherosclerotic cardiovascular disease.
And surprisingly, heart disease-not
progression of liver disease-is the leading cause of death in people with
nonalcoholic fatty liver disease, according to the AHA.
Investigators from the Smidt Heart Institute
at Cedars-Sinai have found that even subtle forms of liver disease directly
impact heart health. The findings, recently published in the journal Frontiers
in Cardiovascular Medicine, help further clarify the relationship between liver
disease and heart disease beyond their shared risk factors.
In the retrospective study, investigators
compared patients’ FIB-4 scores-a marker for liver fibrosis that can indicate
risk of developing severe liver disease-with heart abnormalities visible
through cardiac MRI scans. They found that elevated FIB-4 scores were
associated with abnormalities in heart function and vascular dimension.
Alan Kwan, MD, a cardiologist and cardiac
imaging researcher in the Smidt Heart Institute as well as lead and
corresponding author of the study, said it had been known that nonalcoholic
fatty liver disease was associated with cardiovascular death, but the
relationship was poorly understood and possibly obscured by risk factors the
two have in common, such as diabetes.
Previous similar studies had been limited in
scope, looking only at how cirrhosis and nonalcoholic fatty liver disease
affect the heart.
“If 25% of the population has this potential
risk factor for cardiac disease, we knew we needed to understand it more
fully,” Kwan said. “So, our overall aim with this study was to examine the
connections between the heart and the liver-a newer area of study, but one that
made sense to explore further. The liver processes cholesterol and produces
factors involved in blood clotting and inflammation-all of which can affect the
heart-so we wanted to take a closer look at these associations.”
To conduct the study, investigators reviewed
electronic medical records from the past 11 years of 1,668 patients who had
low, moderate or high FIB-4 scores within one year of having a cardiac MRI,
adjusting for standard cardiovascular risk factors. They found that nearly 86%
of patients had at least one heart abnormality.
Cardiac MRI provides a unique view of the
heart, using detailed imaging that can identify subtle changes in heart
structure, function, blood vessel size and structure, heart muscle composition,
and more.
“The abnormalities we saw were vascular
changes-enlargement of the blood vessels coming out of heart as well as an
increase in how much blood was moving,” Kwan said.
“Typically, when physicians examine the heart,
we aren’t thinking about the liver, and vice versa. We tend to be very
specialized in our own organ categories. But this study’s findings indicate
that we can and should screen for liver conditions when looking at heart
conditions-we can’t view the heart and the liver as completely separate organs
functioning on their own islands.”
The next step in the research, Kwan said, is
to further explore the impact that liver disease can have on heart health.
“Also, other questions come to light,” he
said, “such as, when treating people with nonalcoholic fatty liver disease,
could medications to treat this also help the heart? Or, when you see your
cardiologist or primary care physician and risk factors such as high
cholesterol, blood pressure, diabetes and family history are discussed, should
nonalcoholic fatty liver disease also be a standard risk factor to consider?”
Susan Cheng, MD, MPH, director of the
Institute for Research on Healthy Aging in the Department of Cardiology at the
Smidt Heart Institute and senior and co-corresponding author of the study,
agreed that there are multiple reasons to continue research in this area.
“If we can understand the basic science of how
the liver affects the heart, we can likely better understand other heart and
organ interactions,” said Cheng, who also holds the Erika J. Glazer Chair in
Women’s Cardiovascular Health and Population Science. “This could also shed
light on directions for potential future targeted therapies to prevent
cardiovascular disease in patients with liver disease.”
Reference:
Alan Kwan et al,Cardiovascular and hepatic
disease associations by magnetic resonance imaging: A retrospective cohort
study, Frontiers in Cardiovascular Medicine, DOI 10.3389/fcvm.2022.1009474