Bariatric surgery may reduce the risk of developing heart failure for people living with obesity by improving blood flow through their heart muscle, according to a new study led by University College London (UCL) researchers. The study, from UCL and King's College London researchers, suggests that these harmful effects of obesity may be at least partly reversible.
"Previous research has suggested that weight loss surgery can reduce the risk of developing or dying from cardiovascular disease in people living with obesity,” explained Professor Charlotte Manisty (UCL Institute of Cardiovascular Science), who led the study. “Our work provides a new, additional explanation for the benefits of this intervention."
Researchers scanned patients' hearts before and six months after they underwent bariatric surgery. The team used quantitative perfusion magnetic resonance imaging, which allowed them to measure blood flow through the smallest vessels in the heart muscle. Before their surgery, patients had a median body mass index (BMI) of 44kg/m2. Compared to volunteers the same age and sex, and with an average BMI of 25, patients had thicker heart walls (a sign that the heart is having to work harder to pump blood) and lower blood flow through their heart muscle.
Six months after their surgery, patients had lost an average of 29 kg, and 13 of the 17 patients with type 2 diabetes before surgery were in remission at follow up.
Compared with age- and sex-matched healthy volunteers, 38 patients living with obesity had lower stress myocardial blood flow (MBF) (p=0.001) and lower myocardial perfusion reserve (p<0.001). A total of 27 participants underwent paired follow-up 6 months post-surgery. Metabolic abnormalities reduced significantly at follow-up including mean body mass index by 11 ± 3 kg/m2 (p<0.001), glycated haemoglobin by 9 mmol/mol (Q1-Q3: 4-19 mmol/mol; p<0.001), fasting insulin by 142 ± 131 pmol/L (p<0.001) and hepatic fat fraction by 5.6% (2.6%-15.0%; p<0.001).
Stress MBF increased by 0.28 mL/g/min (−0.02 to 0.75 mL/g/min; P = 0.003) and myocardial perfusion reserve by 0.13 (−0.25 to 1.1; p=0.036). The increase in stress MBF was lower in those with preoperative type 2 diabetes mellitus (0.1 mL/g/min [−0.09 to 0.46 mL/g/min] vs 0.75 mL/g/min [0.31-1.25 mL/g/min]; p=0.002). Improvement in stress MBF was associated with reduction in fasting insulin (beta = −0.45 [95% CI: −0.05 to 0.90]; p=0.03).
In addition, levels of triglycerides in patients' blood had decreased, while their levels of HDL cholesterol increased. Patients also had less fat around their livers and lower blood pressure than before their surgery.
"These promising results offer important insights into how weight loss associated with bariatric surgery could help to improve outcomes for patients living with obesity,” added Dr George Joy (UCL Institute of Cardiovascular Science), who was also involved with the study. "With trials of other approaches to weight loss, such as medications, also reporting positive effects on the heart, more research is now needed to understand whether similar mechanisms could be contributing to these effects."
The findings were reported in the paper, ‘The Impact of Bariatric Surgery on Coronary Microvascular Function Assessed Using Automated Quantitative Perfusion CMR’, published in JACC: Cardiovascular Imaging. To access this paper, please click here (log-in maybe required)
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