Patients with obesity who had bariatric surgery had a lower risk of having a major adverse cardiovascular event (MACE) or dying from all causes during a median 7-year follow-up, compared with similar patients who did not undergo surgery.
These findings, from a province-wide retrospective cohort study from Quebec, follow two recent, slightly shorter similar trials.
Now we need a large randomized clinical trial (RCT), experts say, to definitively establish cardiovascular and mortality benefits in people with obesity who have metabolic/bariatric surgery. And such a trial is just beginning.
Philippe Bouchard, MD, a general surgery resident from McGill University in Montreal presented the Quebec study in a top papers session at the annual meeting of the American Society for Metabolic & Bariatric Surgery.
The findings showed that, among obese patients with metabolic syndrome, bariatric/metabolic surgery is associated with a sustained decrease in the incidence of MACE and all-cause mortality of at least 5 years, Bouchard said.
“The results of this population-based observational study should be validated in randomized controlled trials,” he concluded.
In the meantime, “we believe our study adds to the body of evidence in mainly two ways,” Bouchard told this news organization in an email.
It has a longer follow-up than recent observational studies, “a median of 7 years, compared to 3.9 years in a study from the Cleveland Clinic, and 4.6 years in one from Ontario, he said.
“This allows us to [estimate] an absolute risk reduction of MACE of 5.11% at 10 years,” he added. This is a smaller risk reduction than the roughly 40% risk reduction seen in the other two studies, possibly because of selection bias, Bouchard speculated.
“Second, most of the larger cohorts are heavily weighted on Roux-en-Y gastric bypass,” he continued. In contrast, their study included diverse procedures, including sleeve gastrectomy, duodenal switch, and adjustable gastric banding.
“Given the rise in popularity of a derivative of the duodenal switch – the single-anastomosis duodenal-ileal bypass with sleeve gastrectomy (SADi-S) – we believe this information is timely and relevant to clinicians,” Bouchard said.
RCT on the Subject Is Coming
“I totally agree that we need a large randomized controlled trial of bariatric surgery versus optimal medical therapy to conclusively establish” the impact of bariatric surgery on cardiovascular outcomes, said the assigned discussant, Mehran Anvari, MD. And their research group is just about to begin one.
In the absence of RCT data, clinicians “may currently not refer [eligible] patients for bariatric surgery because of the high risk they pose,” said Anvari, professor and director of the Centre for Minimal Access Surgery of McMaster University, Hamilton, Ont., and senior author in the Ontario study.
Furthermore, an important point is that the current trial extended the follow-up to 7 years, he told this news organization in an email.
That study included patients with diabetes and hypertension, he added, whereas his group included patients with a history of cardiovascular disease and/or heart failure.
“We hope these studies encourage general practitioners and cardiologists to consider bariatric surgery as a viable treatment option to prevent and reduce the risk of MACE in the obese patients [body mass index >35 kg/m2] with significant cardiovascular disease,” he said.
“We have embarked on a pilot RCT among bariatric centers of excellence in Ontario,” Anvari added, which showed the feasibility and safety of such a study.
He estimates that the RCT will need to recruit 2,000 patients to demonstrate the safety and effectiveness of bariatric surgery in reducing MACE and cardiac and all-cause mortality among patients with existing cardiovascular disease.
This “will require international collaboration,” he added, “and our group is currently establishing collaboration with sites in North America, Europe, and Australia to conduct such a study.”
Patients Matched for Age, Sex, Number of Comorbidities
Quebec has a single public health care system that covers the cost of bariatric surgery for eligible patients; that is, those with a BMI greater than 35 kg/m2 and comorbidities or a BMI greater than 40 kg/m2.
Using this provincial health care database, which covers over 97% of the population, the researchers identified 3,637 patients with diabetes and/or hypertension who had bariatric surgery during 2007-2012.
They matched the surgery patients with 5,420 control patients with obesity who lived in the same geographic region and had a similar age, sex, and number of Charlson Comorbidity Index comorbidities, but did not undergo bariatric surgery.
The patients had a mean age of 50 and 64% were women.
Half had zero to one comorbidities, a quarter had two comorbidities, and another quarter had at least three comorbidities.
Most patients in the surgery group had type 2 diabetes (70%) and 50% had hypertension, whereas in the control group, most patients had hypertension (82%) and 41% had diabetes.
The most common type of bariatric surgery was adjustable gastric banding (42% of patients), followed by duodenal switch (24%), sleeve gastrectomy (23%), and Roux-en-Y gastric bypass (11%).
The primary outcome was the incidence of MACE, defined as coronary artery events (including myocardial infarction, percutaneous coronary intervention, and coronary artery bypass graft), stroke, heart failure, and all-cause mortality,
After a median follow-up of 7-11 years, fewer patients in the surgical group than in the control group had MACE (20% vs. 25%) or died from all causes (4.1% vs. 6.3%, both statistically significant at P < .01)
Similarly, significantly fewer patients in the surgical group than in the control group had a coronary artery event or heart failure (each P < .01).
However, there was no significant between-group difference in the rate of stroke, possibly because of the small number of strokes.
The risk of MACE was 17% lower in the group that had bariatric surgery than in the control group (adjusted hazard ratio, 0.83; 95% confidence interval, 0.78-0.89), after adjusting for age, sex, and number of comorbidities.
In subgroup analysis, patients who had adjustable gastric banding, Roux-en-Y gastric bypass, or duodenal switch had a significantly lower risk of MACE than control patients.
The risk of MACE was similar in patients who had sleeve gastrectomy and in control patients.
However, these subgroup results need to be interpreted with caution since the surgery and control patients in each surgery type subgroup were not matched for age, sex, and comorbidities, said Bouchard.
He acknowledged that study limitations include a lack of information about the patients’ BMI, weight, medications, and glycemic control (hemoglobin A1c).
Bouchard and Anvari have no relevant financial disclosures.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.