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Bariatric surgery reduced the risk of a second heart attack or other major cardiovascular event (MACE) in patients with severe obesity, authors of a cohort study reported.

The study compared 509 patients with a prior myocardial infarction (MI) who underwent bariatric surgery with matched controls with prior MI who did not have surgery. At a median 4.6 years of follow-up, the surgery group was significantly less likely to have a second heart attack (HR 0.24, 95% CI 0.14-0.41), said researchers led by Erik Näslund, MD, PhD, of the Karolinska Institutet in Stockholm.

Writing in the journal , Näslund and colleagues also reported the surgery group had a lower risk of any MACE (HR 0.44, 95% CI 0.32-0.61), all-cause mortality (HR 0.45, 95% CI 0.29-0.70), and new-onset heart failure (cumulative incidence 2% vs 5%, HR not calculated). However, there was no significant difference in risk for stroke or new-onset atrial fibrillation.

"Despite the relatively established effect of metabolic surgery as primary prevention of CVD [cardiovascular disease], there is minimal available data on the use of metabolic surgery for secondary prevention of CVD," the study authors wrote. If confirmed by a randomized controlled trial, "severely obese patients with a previous myocardial infarction can be suggested to undergo metabolic surgery as a secondary prevention."

Doctors have been reluctant to use bariatric surgery in post-MI patients because of concerns that the benefits will not outweigh the risk of perioperative complications and long-term side effects, Näslund's group said. In addition, there is the obesity paradox, which suggests a lower mortality risk with a higher body mass index (BMI) in patients with established CVD, they said.

"This uncertainty, together with the fact that persistent weight loss is difficult to achieve, has resulted in less focus on weight and obesity in post-MI care," they said. "However, the association between BMI and outcome in patients with CVD appears to be U-shaped, with a higher risk in those with severe obesity (BMI>35)."

Näslund and colleagues analyzed data on patients with severe obesity and a prior MI in national medical registries, including the Scandinavian Obesity Surgery Registry. Of the 509 surgery patients, 465 underwent Roux-en-Y gastric bypass and 44 underwent sleeve gastrectomy. They were matched with patients who did not have surgery in terms of sex, age, year of MI, and BMI.

Overall, the study patients were well-matched, the researchers said, except that in the surgery group there were lower proportions of patients with reduced left-ventricle ejection fraction after MI (7% vs 12%), previous heart failure (10% vs 19%), atrial fibrillation (6% vs 10%), and chronic obstructive pulmonary disease (4% vs 7%).

The median baseline BMI for surgery patients was 40. Two years after surgery, median BMI was 28 and total weight loss was 29% of body weight. Patients were followed for up to 8 years. The primary outcome was any MACE, including a second MI, stroke, and any cause of death, as the database lacked information on specific causes of death. These outcomes were also analyzed separately. Secondary outcomes included new-onset atrial fibrillation and heart failure.

Postoperative complications occurred in 42 surgery patients (8.4%), with 19 complications classified as serious (3.8%). These rates were similar to those reported for patients with severe obesity without prior MI, the study authors said.

It is unlikely that weight loss alone was the driving factor in reduced risk for cardiovascular events in the surgery patients, the researchers noted. A large proportion of these patients had clinical remission of type 2 diabetes, hypertension, and dyslipidemia. "Thus, we suggest that the observed benefit of metabolic surgery on MACE is caused not only by a larger and more sustainable weight loss, but also by other cardiometabolic effects of metabolic surgery," they said.

Limitations of the study, they noted, included a lack of information on socioeconomic status, which could have affected the outcomes. In addition, because most patients underwent Roux-en-Y and only a small proportion had sleeve gastrectomy, the study could not differentiate between these procedures, they said.

"In conclusion, this study suggests that in severely obese patients with a previous MI, metabolic surgery was associated with a low risk for serious complications, and lower risk of MACE, death, new MI, and new onset heart failure compared with no surgery. These findings need to be confirmed in a randomized, controlled trial," Näslund and colleagues said.

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