Major finding: The incidence rate of heart failure during a median 15 years of prospective follow-up after bariatric surgery was 3.1 cases per 1,000 person-years, compared with 5.2/1,000 person-years in obese controls.
Data source: The Swedish Obese Subjects study included 2,010 obese subjects who underwent bariatric surgery in 1987-2001 and 2,037 closely matched obese controls. It is a nonrandomized, prospective, observational study.
New findings from the landmark Swedish Obese Subjects study "strongly suggest" that bariatric surgery reduces by roughly half the long-term risk of developing heart failure, Dr. Kristjan Karason reported at the annual congress of the European Society of Cardiology.
"This is the first study to look at the effect of bariatric surgery on heart failure risk," observed Dr. Karason of the University of Gothenburg (Sweden). "Our findings support a modulating role of excess body fat in the pathogenesis of heart failure."
The SOS (Swedish Obese Subjects) study has been a major driver of the growing enthusiasm for bariatric surgery, not only as a means of achieving sustained weight loss far beyond what can typically be accomplished medically, but also as a means of reducing obese patientsâ elevated risks for a variety of serious chronic comorbid diseases.
For example, the SOS investigators have previously reported that bariatric surgery reduced the long-term risk of developing type 2 diabetes by 87% compared to matched obese controls who didnât undergo weight-loss surgery (N. Engl. J. Med. 2012;367:695-704), that it reduced the risk of fatal or nonfatal acute MI or stroke by one-third during a median 14.7 years of follow-up (JAMA 2012;307:56-65), and it resulted in a 42% decrease in cancer incidence in women (Lancet Oncol. 2009;10:653-62).
The SOS is a nonrandomized, prospective, observational study involving 2,010 obese subjects who underwent bariatric surgery in 1987-2001, when they were 37-60 years old. A total of 68% of the bariatric surgery recipients had vertical band gastroplasty, 19% underwent gastric banding, and 13% had a Roux en-Y gastric bypass. They were extensively matched by 18 variables to 2,037 obese controls. The SOS study is being conducted at 25 surgical departments and 480 primary care clinics across Sweden. Follow-up is ongoing.
It has been known for more than a decade that increased body mass index is associated with greater risk of developing heart failure. The mechanism involved is not well defined but is probably multifactorial. Obesity imposes a greater hemodynamic load on the heart, both preload and afterload, with resultant left ventricular hypertrophy and diastolic dysfunction. Obesity is also associated with higher levels of cardiovascular risk factors and an increased risk of atrial fibrillation, Dr. Karason noted.
Mean weight loss after a median of 14.7 years of prospective follow-up in the SOS study was 18% in the bariatric surgery group and 1% in controls. During follow-up, 91 bariatric surgery patients and 152 controls were diagnosed with heart failure, for an incidence rate of 3.1 as compared with 5.2 cases per 1,000 person-years in the control subjects.
This translated to a 48% relative risk reduction in new-onset heart failure in a multivariate regression analysis adjusted for age, sex, baseline body mass index, waist circumference, blood glucose, lipids, prior cardiovascular disease, and smoking status.
One audience member asked how to interpret the new SOS findings in light of the heart failure obesity paradox, which is the observation in multiple studies that overweight and obese heart failure patients tends to fare better than leaner ones.
"There have been no studies of weight loss in obese patients with heart failure. There really should be," Dr. Karason replied. "But my feeling is that they would reduce their risk because they will improve several risk factors, and their hemodynamic situation is also improved. So my recommendation would be for those heart failure patients to lose weight. I donât have any studies to support that."