Bariatric Surgery Prompts Visceral Fat Reduction, Cardiac Changes

Heidi Splete

October 10, 2022

Weight loss after bariatric surgery was linked with visceral fat reduction as well as reduced blood pressure, fasting glucose, and left ventricular remodeling, based an imaging study in 213 patients.

"We found that ventricular function measured by strain imaging improved in both the left and right sides of the heart, but function measured in the traditional method using endocardial motion [in other words, ejection fraction] actually worsened," senior investigator Barry A. Borlaug, MD, said in an interview.

Although previous studies have shown positive effects of weight loss on the heart after bariatric surgery, most have been short term and have not specifically examined the effects of visceral fat reduction, wrote the investigators.

"We are in the middle of an increasing epidemic of obesity worldwide, but particularly in the United States, where it is currently projected that one in two adults will be obese by 2030," added Borlaug of Mayo Clinic, Rochester, Minn. "Heart failure with preserved ejection fraction (HFpEF) is growing in tandem, and numerous recent studies have shown that obesity is one of the strongest risk factors for developing HFpEF, and that the severity of HFpEF is intimately linked to excess body fat. This suggests that therapies to reduce body fat could improve the cardiac abnormalities that cause HFpEF, which was our focus in this study," he explained.

In the study, published in the Journal of the American College of Cardiology, the researchers reviewed echocardiography data from 213 obese patients before and more than 180 days after bariatric surgery. They also measured abdominal visceral adipose tissue (VAT) of 52 patients via computed tomography. The average age of the patients was 54 years, the average body mass index was 45 kg/m2, and 67% were women. Comorbidities included hypertension, diabetes, dyslipidemia, and obstructive sleep apnea.

The primary outcome was changes in cardiac structure and function.

After a median follow-up of 5.3 years, patients overall averaged a 23% reduction in body weight and a 22% reduction in BMI. In the 52 patients with abdominal scans, the VAT area decreased by 30% overall. Changes in left ventricular mass were significantly correlated to changes in the VAT.

Epicardial adipose thickness decreased by 14% overall. Left and right ventricular longitudinal strains improved at follow-up, but left atrial strain deteriorated, the researchers noted.

Although the mechanism of action remains unclear, the results suggest that left ventricular remodeling was associated with visceral adiposity rather than subcutaneous fat, the researchers wrote.

They also found that right ventricular strain was negatively correlated with VAT, but not with body weight or BMI.

"These findings suggest that weight loss, particularly reduction in visceral adiposity, benefits [right ventricular] structure and function in a manner akin to that observed in the [left ventricle]," the researchers noted.

Some Surprises and Limitations

Borlaug said he found some, but not all, of the results surprising. "Earlier studies had shown evidence for benefit from weight loss on cardiac structure and function, but had been limited by smaller sample sizes, shorter durations of evaluation, and variable methods used," he said in an interview.

The findings that strain imaging showed both left and right ventricular function improved while EF declined "shows some of the problems with using EF, as it is affected by chamber size and geometry. We have previously shown that patients with HFpEF display an increase in fat around the heart, and this affects cardiac function and interaction between the left and right sides of the heart, so we expected to see that this fat depot would be reduced, and this was indeed the case," Borlaug added.

In the current study, "visceral fat was most strongly tied to the heart remodeling in obesity, and changes in visceral fat were most strongly tied to improvements in cardiac structure following weight loss," Borlaug told this news organization. "This further supports this concept that excess visceral fat plays a key role in HFpEF, especially in the abdomen and around the heart," he said.

However, "The biggest surprise was the discordant effects in the left atrium," Borlaug said. "Left atrial remodeling and dysfunction play a crucial role in HFpEF as well, and we expected that this would improve following weight loss, but in fact we observed that left atrial function deteriorated, and other indicators of atrial myopathy worsened, including higher estimates of left atrial pressures and increased prevalence of atrial fibrillation," he said.

This difference emphasizes that weight loss may not address all abnormalities that lead to HFpEF, although a key limitation of the current study was the lack of a control group of patients with the same degree of obesity and no weight-loss intervention, and the deterioration in left atrial function might have been even greater in the absence of weight loss, Borlaug added.


Larger Numbers Support Effects

Previous research shows that structural heart changes associated with obesity can be reversed through weight loss, but the current study fills a gap by providing long-term data in a larger sample than previously studied, wrote Paul Heidenreich, MD, of Stanford (Calif.) University in an accompanying editorial).

"There has been uncertainty regarding the prolonged effect of weight loss on cardiac function; this study was larger than many prior studies and provided a longer follow-up," Heidenreich said in an interview.

"One unusual finding was that, while weight loss led to left ventricle reverse remodeling (reduction in wall thickness), the same effect was not seen for the left atrium; the left atrial size continued to increase," he said. "I would have expected the left atrial changes to mirror the changes in the left ventricle," he noted.

The findings support the greater cardiac risk of visceral vs. subcutaneous adipose tissue, and although body mass index will retain prognostic value, measures of central obesity are more likely predictors of cardiac structural changes and events and should be reported in clinical studies, Heidenreich wrote.

However, "We need a better understanding of the factors that influence left atrial remodeling and reverse remodeling," Heidenreich told this news organization. "While left ventricular compliance and pressure play a role, there are other factors that need to be elucidated," he said.

Studies in Progress May Inform Practice

The current data call for further study to test novel treatments to facilitate weight loss in patients with HFpEF and those at risk for HFpEF, and some of these studies with medicines are underway, Borlaug said in the interview.

"Until such studies are completed, we will not truly understand the effects of weight loss on the heart, but the present data certainly provide strong support that patients who have obesity and HFpEF or are at risk for HFpEF should try to lose weight through lifestyle interventions," he said.

Whether the cardiac changes seen in the current study would be different with nonsurgical weight loss remains a key question because many obese patients are reluctant to undergo bariatric surgery, Borlaug said. "We cannot assess whether the effects would differ with nonsurgical weight loss, and this requires further study," he added.

As for additional research, "Randomized, controlled trials of weight-loss interventions, with appropriate controls and comprehensive assessments of cardiac structure, function, and hemodynamics will be most informative," said Borlaug. "Larger trials powered to evaluate cardiovascular outcomes such as heart failure hospitalization or cardiovascular death also are critically important to better understand the role of weight loss to treat and prevent HFpEF, the ultimate form of obesity-related heart disease," he emphasized.

The study was supported in part by grants to lead author Hidemi Sorimachi of the Mayo Clinic from the Uehara Memorial Foundation, Japan, and to corresponding author Borlaug from the National Institutes of Health. Borlaug also disclosed previous grants from National Institutes of Health/National Heart, Lung, and Blood Institute, AstraZeneca, Corvia, Medtronic, GlaxoSmithKline, Mesoblast, Novartis, and Tenax Therapeutics; and consulting fees from Actelion, Amgen, Aria, Axon Therapies, Boehringer Ingelheim, Edwards Lifesciences, Eli Lilly, Imbria, Janssen, Merck, Novo Nordisk, and VADovations. Heidenreich had no financial disclosures.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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