Swedish researchers at Karolinska Institutet and Danderyd Hospital, examining the risk of additional myocardial infarctions and early death in patients with severe obesity who undergo metabolic surgery following a myocardial event, have reported a lower risk of additional myocardial infarctions and improved survival that cannot be simply attributed to the loss of weight in this group of patients. The study, ‘Association of Metabolic Surgery With Major Adverse Cardiovascular Outcomes in Patients With Previous Myocardial Infarction and Severe Obesity: A Nationwide Cohort Study’, was published in the journal Circulation.
The teams looked at 509 individuals who underwent surgery was matched with people of the same gender, age and BMI (the average BMI of both groups was 40), and who had suffered a myocardial infarction in the same year but not undergone metabolic surgery (total n=1,018 individuals) between 2007 and 2018.
They then cross-referenced the quality registries SOReg (Scandinavian Obesity Surgery Registry) and SWEDHEART (for people who have suffered myocardial infarction) between 1995 and 2018, the researchers were able to identify individuals with severely obesity who underwent a gastric bypass or gastric sleeve procedure as a treatment for their obesity after suffering a myocardial infarction.
"It is well known that obesity is associated with an increased risk for Type 2 diabetes and heart disease," said the study's first author, Erik Naslund, professor at the Department of Clinical Sciences, Danderyd Hospital, Karolinska Institutet and consultant surgeon at Danderyd Hospital. "It has also been shown that weight-reduction surgery can improve Type 2 diabetes and cardiovascular disease. What has yet to be proven is: if you have had a heart attack, can weight-reduction surgery reduce your risk of having another heart attack, which was the focus of our study."
The study reported that:
- Weight-reduction surgery was associated with a lower risk of heart attack and a lower risk of new onset heart failure, yet there was no statistical difference in the risk of stroke between the surgery and non-surgery groups.
- The patients who had weight-reduction surgery had half the risk of death compared to those who did not have surgery.
- The rate of serious surgical complications was similar to that seen among weight-reduction surgery patients without prior heart attacks.
- While patients' weight in the surgery group was markedly lower one year after surgery (median BMI was 29 after one year), researchers note that the weight loss alone was likely not the driving force in the association between surgery and decreased risk.
- A large number of surgery patients had significant improvements in sleep apnoea (67% remission) as well as improvement in hypertension (22 % remission), cholesterol and triglyceride levels (29 % remission); and
- More than half of the patients with Type 2 diabetes experienced clinical remission of the disease after the weight-reduction surgery.
According to the researchers, it is unlikely the weight loss is the only reason for the study's observed correlation between metabolic surgery and a lower risk of cardiopathic events, such as stroke, myocardial infarction or early death. One theory is that metabolic surgery per se has a positive impact on cardiometabolic risk factors, which is to say physiological conditions that increase the risk of cardiovascular disease.
"We found that individuals operated on for their obesity were at a much lower risk of suffering another myocardial infarction, of death and of developing heart failure," added Naslund. "These data suggest that severely obese people who suffer a myocardial infarction should be offered metabolic surgery for their obesity as a secondary prevention. Many of the patients who underwent metabolic surgery in this study had clinical remission of type 2 diabetes, hypertension and dyslipidaemia. An earlier study, Look AHEAD, demonstrated that long, intensive non-surgical lifestyle intervention in patients with type 2 diabetes resulted in weight loss of 6 per cent, but did not lower the risk of myocardial infarction."
The study authors did not have information about the socioeconomic status of patients, and there was no data on weight beyond the two-year follow-up mark for the group who had surgery, and no follow-up weight data for the non-surgery group. Additionally, within the surgery group, there was a substantially higher number of patients who had gastric bypass, thus, any difference in outcomes between gastric bypass patients and the patients who had the sleeve gastrectomy procedure could not be evaluated.
The researchers were also unable to assess if the timing between each surgery group patient's heart attack and weight-reduction surgery was a key factor for complications.
Before the results of the study can become part of clinical praxis, more research is needed in which patients with severe obesity who have suffered myocardial infarction are randomly assigned to either surgery or to regular post-infarction care to confirm the results of this study.
This study was supported by grants from the Region Örebro County and Stockholm County Council in Sweden.