Surgery for Obvesity Reduces Cardiovascular Events
July 24, 2008 — Bariatric surgery for obesity such as gastric banding or gastric bypass is associated with a reduction in long-term cardiovascular events, a new study suggests .
The study, published online July 21, 2008 in the American Journal of Cardiology, was conducted by a group led by Dr. John Batsis (Mayo Clinic College of Medicine, Rochester, MN).
They note that bariatric surgery is increasingly being used to induce weight loss, reduce medical comorbidities, and improve cardiovascular risk factors in obese patients, but its long-term impact on cardiovascular events and mortality is still poorly defined. They therefore tried to ascertain whether such surgery is associated with a reduced risk of cardiovascular events using various cardiovascular risk models.
Senior author Dr Francisco Lopez-Jimenez (Mayo Clinic College of Medicine, Rochester, MN) told heartwire that this study addressed two questions. First, the researchers conducted a systematic review of the literature to examine the effect of bariatric surgery on cardiovascular risk factors such as cholesterol, blood sugar, blood pressure, and body weight. And consistent with previous studies, they showed a reduction in all these parameters in patients who had undergone surgery.
The second part of the study addressed whether or not this reduction in risk factors would translate into a reduction in cardiovascular events. "Only one study of bariatric surgery actually had data on cardiovascular events at follow-up, so for the others we had to estimate event rates using well-accepted formulas such as Framingham and PROCAM risk scores. We calculated the predicted risk of cardiovascular events based on risk-factor measurements before and after surgery," Lopez-Jimenez explained. To do this accurately, it is best to use individual patient data, which the researchers had from their own study (the validation study), and for the other studies they found in the literature (the test studies) they had to use average values for the risk factors to estimate future risk. Both models showed a clear reduction in cardiovascular events after bariatric surgery.
In the study, the researchers performed a Medline search using terms associated with obesity, bariatric surgery, and cardiovascular risk factors to identify six test studies. The validation study consisted of a population-based, historical cohort of 197 patients who underwent Roux-en-Y gastric bypass and 163 control patients, identified through the Rochester Epidemiology Project. Results showed that 10-year Framingham and PROCAM risk scores for cardiovascular events were lower at follow-up in the bariatric-surgery group, and the difference between groups was significant.
Absolute 10-Year Risk (%) for Cardiovascular Disease After Bariatric Surgery Using Risk-Prediction Models in the Validation Study
Measure Nonoperative group at baseline Nonoperative group at follow-up Operative group at baseline Operative group at follow-up Intergroup p
Framingham risk score 7.1 6.5 7.0 3.5 <0.001
PROCAM risk score 4.4 3.8 4.1 2.0 <0.001
With mean data from the validation study, the trend and directionality in risk was similar in the operative group. Mean data from other studies also suggested a reduced risk of events, with estimated relative risk reductions for bariatric-surgery patients ranging from 18% to 79% using the Framingham risk score, compared with 8% to 62% using the PROCAMrisk score.
The authors conclude: "In light of the paucity of studies examining cardiovascular outcomes after bariatric surgery, we believe that this study will allow initial generalizability of using bariatric surgery as a means to decrease cardiovascular morbidity and mortality."
"I think this is very compelling data. While it is not proof that surgery reduces cardiovascular events, it is highly suggestive and therefore very encouraging," Lopez-Jimenez commented to heartwire . "Cardiovascular events are the most common cause of death in patients who are morbidly obese, but still, the decision to undergo surgery must be made on an individual basis. For example, a middle-aged obese patient who has many other risk factors such as high cholesterol and high blood pressure would have more to gain than a younger obese patient with normal cholesterol and blood pressure. I would say that while the current study is not definitive, its results could still be taken into account when weighing the pros and cons of surgery," he added.
Batsis JA, Sarr MG, Collazo-Clavell ML, et al. Cardiovascular risk after bariatric surgery for obesity. Am J Cardiol 2008; DOI:10.1016/j.amjcard.2008.05.040. Available at: www.ajconline.org.