Heart injury reduced after bariatric surgery but not lifestyle intervention

"Obesity is a global problem that is closely linked to the development of cardiovascular disease," said lead author Dr Magnus N. Lyngbakken, a PhD candidate at the University of Oslo in Norway. "Morbidly obese patients are at high risk of heart attack, heart failure and diabetes."

Approximately one in five western Europeans are obese and have a body mass index (BMI) over 30 kg/m², while around 2 to 3% are morbidly obese (BMI over 35 to 40 kg/m²).

The study published today investigated whether weight loss by bariatric surgery could reduce levels of high-sensitivity cardiac troponin I (hs-TnI) in morbidly obese patients, which would indicate reduced cardiac stress and chronic subclinical cardiac injury. Cardiac troponins are traditionally used to diagnose acute ischaemic injury and confirm that a patient had a heart attack. The more recent high-sensitive test also identifies low-grade, chronic cardiac damage in patients who do not have established cardiovascular disease.

Concentrations of hs-TnI were compared between 74 morbidly obese patients who had a type of bariatric surgery called Roux-en-Y gastric bypass, 62 morbidly obese patients who exercised and restricted their calorie intake, and a control group of 30 people with normal weight.

At the beginning of the study, hs-TnI levels were 2.40 ng/L in the bariatric surgery group, 2.35 ng/L in the lifestyle intervention group, and 0.90 ng/L in the normal weight group. At 12 months after the intervention, hs-TnI levels decreased significantly in the surgery group (p<0.001) but not in the lifestyle group (p=0.087).

As reported previously, the surgery group lost 30% of their body weight on average while the lifestyle intervention group lost an average of 8% (p<0.001). "The extensive weight loss that we saw with the surgery group was associated with a drastic reduction in hs-TnI levels," said Dr Lyngbakken. "The group that exercised and ate less showed no such significant reduction in levels of hs-TnI."

Interestingly, after 12 months hs-TnI levels in the surgery group were not significantly different from the normal weight group (1.30 vs 0.90ng/L, p=0.54). In the lifestyle intervention group, however, hs-TnI levels remained significantly higher than in the control group (2.15 vs 0.90 ng/L, p=0.003).

"Twelve months after surgery levels of hs-TnI were the same in the surgery group as in the control group of normal weight," said Dr Lyngbakken. "It's too early to tell, but if this translates into less heart failure, heart attacks and cardiovascular deaths, then this could mean that morbidly obese patients who have bariatric surgery obtain a cardiovascular risk comparable to a normal weight population."

"This is one of the first studies showing that an intervention can reduce mildly elevated cardiac troponin levels," said author Professor Torbjørn Omland, professor of medicine at the University of Oslo. "High-sensitivity troponin I is a good marker of how much stress the heart is exposed to. Marked weight loss induced by bariatric surgery seems to have a direct effect on the health of the heart and reduces strain to normal levels."

Subsequent analysis showed that changes in body weight and serum triglycerides may mediate the change in hs-TnI achieved with surgery. Professor Omland said: "Bariatric surgery reduces the stress on the heart through a reduction in body weight. It also improves the cardiometabolic milieu of the body, as reflected by the drop in triglycerides, which has beneficial effects on heart muscle cells."

Professor Omland concluded: "Our findings and those of other studies all point to bariatric surgery being superior to lifestyle intervention with regard to the beneficial effects on the heart. Much of that can be explained by the greater weight loss induced by bariatric surgery. Although lifestyle intervention leads to a transient reduction in weight, its impact in the long term is not as great as surgery."