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Systematic review

Surgery has “impressive” effect on cardiac factors

The review says that bariatric surgery has unparallelled success at helping obese patients with cardiovascular disease. Illustration: Wikimedia / Patrick Lynch
Bariatric surgery has significant effect on hypertension, diabetes and hyperlipidemia
Ten-year risk of cardiovascular disease for a diabetic hypertensive man drops by 75%
Cardiac imaging studies show evidence of significant improvement in heart function

The largest ever systematic review of studies into the relationship between bariatric surgery and cardiovascular function has concluded that surgery has an “impressive” effect on cardiac risk factors, and that no pharmacological treatment has shown a similar effect over such short time periods.

The paper, which appears in the journal Heart, collected 73 studies involving a total of 19,543 subjects, published between 1950 and 2012. It found that resolution or improvement of hypertension occurred in 62.5% of affected patients, diabetes in 73.2% of patients, and hyperlipidaemia in 65.2% of patients.

The researchers say that based on their analysis, a woman with no cardiovascular disease, diabetes, and does not smoke, but is taking antihypertensive medication, drops her 10-year risk of developing cardiovascular disease from 8.6% to 3.9%. A man whose diabetes and hypertension resolves after bariatric surgery reduces his risk of developing cardiovascular disease from 18.4% to 4.7%.

The authors say that they did find significant publication bias in the studies measuring hypertension, diabetes, and hyperlipidaemia, meaning that it was more likely that studies finding a greater effect were more likely to be published. However, after adjusting for this, surgery’s effect on all three cardiovascular risks remained significant.

The review also found eight studies, covering 1,157 subjects, measuring levels of C-reactive peptide. It found that levels of the protein, which is thought to put patients at an increased risk of diabetes, hypertension, and cardiovascular disease, were elevated at baseline in obese individuals, but dropped by an average of 73% (from 9.1mg/l to 2.5mg/l).

Within the studies reviewed, the average age at time of operation was 41.7 years, ranging from 27-54. Women made up 76% of the population, and the mean BMI was 47.1. The mean BMI of the individual studies ranged from 30 to 60. Malabsorptive operations made up the majority of cases: 57% of procedure were either Roux-en-Y gastric bypass or biliopancreatic diversion. Most of the remaining operations – 27% – were gastric banding procedures.

The studies investigating myocardial structure also revealed improvements heart performance after surgery.

Left ventricular mass reduced by an average of 31%. There was also an improvement in the average E/A ratio – the ratio of early to late (atrial) ventricular filling, in which a greater proportion of late filling indicates diastolic heart failure – from a mean of 1.28 to 1.48. Isovolumic relaxation time reduced from a mean of 84ms to 72.9ms, bringing most patients to within the normal range.

Analysis

The authors say that their analysis adds weight to the existing body of evidence suggesting that bariatric surgery has a strong effect on cardiovascular outcomes in obese individuals. “These observations have elevated bariatric surgery beyond the realms of a cosmetic procedure and into the spectrum of interventions demonstrating efficacy in preventing cardiovascular events,” they add.

Their analysis of the Swedish Obese Subjects cohort found that the most effective predictor of how effective surgery would be at reducing cardiovascular risk was the patient’s insulin resistance at baseline, rather than their initial BMI or their excess weight loss after surgery. They say that this shows the importance of case selection, as BMI alone does not indicate the level of the patient’s adiposity, or their level of metabolic dysfunction.

“It is imperative that case selection targets individuals whose potential for long-term health gains considerably exceed operative risks,” they write.

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