While it had previously been known that nonalcoholic fatty liver disease was associated with cardiovascular death, the relationship was poorly understood, said researcher Dr. Alan Kwan. He is a cardiologist and cardiac imaging researcher in Cedars-Sinai Medical Center’s Smidt Heart Institute, in Los Angeles.
The relationship may also have been partly obscured by risk factors the two diseases often have in common, such as diabetes.
In this study, researchers compared scores of a marker for liver fibrosis (FIB-4 scores) that can indicate risk of developing severe liver disease. The investigators compared these FIB-4 scores with heart abnormalities that could be seen on cardiac MRI scans. They found that elevated FIB-4 scores were associated with abnormalities in heart function and vascular dimension.
The study authors noted that the American Heart Association earlier this year released a statement that nonalcoholic fatty liver disease is a risk factor for cardiovascular disease, and that heart disease was the leading cause of death in people with nonalcoholic fatty liver disease, not progression to liver disease.
About one in four American adults have nonalcoholic fatty liver disease — a condition in which excess fat builds up in the liver, and the buildup is not caused by heavy alcohol use.
“If 25% of the population has this potential risk factor for cardiac disease, we knew we needed to understand it more fully,” Kwan said in a Cedars-Sinai news release. “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.”
The research team reviewed electronic medical records from the past 11 years of more than 1,600 patients who had low, moderate or high FIB-4 scores within one year of having a cardiac MRI, which provides a detailed imaging of the heart structure, function and its blood vessels. The team found that nearly 86% of patients had at least one heart abnormality.
“The abnormalities we saw were vascular changes — enlargement of the blood vessels coming out of the 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,” Kwan added.
Future studies could ask whether treating people with medications for nonalcoholic fatty liver disease could also help the heart and whether fatty liver disease should be considered a risk factor for heart disease.
Senior and corresponding study author, Dr. Susan Cheng, is director of the Institute for Research on Healthy Aging in the department of cardiology at the Smidt Heart Institute. She said, “If we can understand the basic science of how the liver affects the heart, we can likely better understand other heart and organ interactions. This could also shed light on directions for potential future targeted therapies to prevent cardiovascular disease in patients with liver disease.”
The findings were published recently in the journal Frontiers in Cardiovascular Medicine. The study was supported by the Doris Duke Charitable Foundation.
The U.S. National Library of Medicine has more on nonalcoholic fatty liver disease.
SOURCE: Cedars-Sinai Medical Center, news release, Dec. 8, 2022
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