Bariatric Surgery and Cardiovascular Risk Factors
2011; Lippincott Williams & Wilkins; Volume: 123; Issue: 15 Linguagem: Inglês
10.1161/cir.0b013e3182149099
ISSN1524-4539
AutoresPaul Poirier, Marc‐André Cornier, Theodore Mazzone, Sasha Stiles, Susan Cummings, Samuel Klein, Peter A. McCullough, Christine Ren Fielding, Barry A. Franklin,
Tópico(s)Cardiovascular Disease and Adiposity
ResumoHomeCirculationVol. 123, No. 15Bariatric Surgery and Cardiovascular Risk Factors Free AccessResearch ArticlePDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessResearch ArticlePDF/EPUBBariatric Surgery and Cardiovascular Risk FactorsA Scientific Statement From the American Heart Association Paul Poirier, Marc-André Cornier, Theodore Mazzone, Sasha Stiles, Susan Cummings, Samuel Klein, Peter A. McCullough, Christine Ren Fielding and Barry A. Franklin Paul PoirierPaul Poirier , Marc-André CornierMarc-André Cornier , Theodore MazzoneTheodore Mazzone , Sasha StilesSasha Stiles , Susan CummingsSusan Cummings , Samuel KleinSamuel Klein , Peter A. McCulloughPeter A. McCullough , Christine Ren FieldingChristine Ren Fielding and Barry A. FranklinBarry A. Franklin and on behalf of the American Heart Association Obesity Committee of the Council on Nutritionand Physical Activity, and Metabolism Originally published14 Mar 2011https://doi.org/10.1161/CIR.0b013e3182149099Circulation. 2011;123:1683–1701Other version(s) of this articleYou are viewing the most recent version of this article. Previous versions: January 1, 2011: Previous Version 1 The rate of obesity is rising logarithmically, especially in those with severe obesity (body mass index [BMI] >40 kg/m2). Cardiologists, endocrinologists, internists, family practitioners, and most healthcare professionals are increasingly confronted with the severely obese patient and with postoperative bariatric patients because obesity is associated with significant morbidity and increased mortality. In addition, more adolescents these days are severely obese. Substantial long-term successes of lifestyle modifications and drug therapy have been disappointing in this population. The National Institutes of Health has suggested that surgical therapy be proposed to those patients with BMI >40 kg/m2 or >35 kg/m2 with serious obesity-related comorbidities such as systemic hypertension, type 2 diabetes mellitus, and obstructive sleep apnea. When indicated, surgical intervention leads to significant improvements in decreasing excess weight and comorbidities that can be maintained over time. These include diabetes mellitus, dyslipidemia, liver disease, systemic hypertension, obstructive sleep apnea, and cardiovascular dysfunction. Recent prospective, nonrandomized, observational, or case-control population studies have also shown bariatric surgery to prolong survival in the severely obese. Different types of bariatric procedures are being performed. Historically, operative mortality was between 0.1% and 2.0% with more recent data not exceeding 1%. Early complications include pulmonary embolus (0.5%), anastomotic leaks (1.0% to 2.5%), and bleeding (1.0%). Late complications include anastomotic stricture, anastomotic ulcers, hernias, band slippage, and behavioral maladaptation. The number of bariatric operations being performed is increasing tremendously as a result of increasing medical need and the evolution of safer surgical techniques and guidelines. Currently, bariatric surgery should be reserved for patients who have severe obesity in whom efforts at medical therapy have failed and an acceptable operative risk is present.Definition and Prevalence of Severe ObesityThe terms overweight, obese, and severe obesity refer to a clinical continuum. Excess adiposity should be considered a chronic disease that has serious health consequences. An expert panel convened by the National Heart, Lung, and Blood Institute stated that "obesity is a complex multifactorial chronic disease that develops from an interaction of genotype and the environment." In 1997, the World Health Organization defined obesity as "a disease in which excess fat is accumulated to an extent that health may be adversely affected." Since 1979, the World Health Organization has listed obesity as a disease in its International Classification of Disease. Obesity has reached epidemic proportions in the United States and in much of the industrialized world.1 The standard classification of obesity is expressed in terms of BMI. Obesity is defined as a BMI ≥30 kg/m2 and may be further subdivided into classes (Table 1).2 The most rapidly growing segment of the obese population is the severely obese.3 Between 1986 and 2000, those with a BMI >30, 40, and 50 kg/m2, are reported to have doubled, quadrupled, and quintupled, respectively, in the United States.4 It is projected that in the near future, there will be at least 31 million US adults who are severely obese and may qualify for bariatric surgery.Table 1. Classification of Body Weight According to BMI in Adults and ChildrenAdults Underweight: BMI 80% of bariatric operations although the proportion is changing with the availability of the laparoscopic adjustable gastric band procedure (LAGB).7Table 2. Long-Term Deleterious Health Impacts of Severe ObesityShorter life expectancyLower quality of life with fewer economic and social opportunitiesCardiovascular diseaseType 2 diabetes mellitusStrokeHigh blood pressure/hypertensionKidney failureDyslipidemiaObstructive sleep apneaAcid reflux/gastroesophageal reflux diseaseCancerDepressionOsteoarthritisJoint painThis statement reviews the indications for bariatric surgery, the different surgical options, the complications related to bariatric surgery, and cardiovascular risk factors improvement and outcome benefits of each type of operation, as well as the postoperative management from an interdisciplinary team viewpoint.Type of Bariatric Surgical ProceduresSurgery for severe obesity has evolved over the past 50 years.8 Many surgical techniques have been described and abandoned,9 but numerous different techniques are still in use today. All techniques rely on 1 or both of 2 mechanisms: restriction of food intake and/or the malabsorption of food. Surgical techniques differ in terms of morbidity and mortality rate, magnitude of weight loss, weight loss maintenance, rate of resolution of comorbidities, and side-effects profile. No consensus exists as to which procedure offers the best option overall, nor is there established criterion or algorithm for a made-to-measure procedure for a given patient. Despite the lack of consensus, it is clear that obesity surgery today offers the only effective long-term treatment option for the severely obese patient.Bariatric surgery can be performed either through a large abdominal incision or by less invasive laparoscopy. Conventional laparotomy used to be the traditional approach to all general surgery. Laparoscopically performed operations carry the advantages of decreased pain, decreased complication rates (ie, pulmonary, thromboembolism, wound infection, hernia), and shorter recovery time with comparable efficacy. Specialized training is required for minimally invasive surgery, but laparoscopic approaches may not be possible in certain situations. Three categories of operations currently exist: restrictive operations, malabsorptive operations, and combined operations. All operations have advantages and disadvantages, with no clear evidence of one being the standard of care. There are currently no large-scale head-to-head randomized trials comparing surgical procedures. Restrictive operations have a lower mortality with a lower rate of surgical and nutritional complications compared with the malabsorptive or combination operations. However, on average, restrictive operations require more frequent postoperative outpatient visits and are associated with a slower and lesser weight loss.10 Combination operations result in the greatest weight loss but require continuous lifelong nutritional surveillance and supplementation.10Purely Restrictive ProceduresRestrictive operations induce weight loss by decreasing the amount of oral intake primarily by the small volume of the pouch and the small diameter of the opening obstructing the passage of food. Appetite suppression or early satiety may be also involved in weight loss.11 The mechanisms have been hypothesized to be vagal nerve compression or gastric hormone diminution (ie, ghrelin, peptide YY).12 Restrictive operations include the adjustable gastric band and the sleeve gastrectomy. The adjustable gastric band is an implanted silicone device that includes an inflatable band connected to a reservoir port. The topmost part of the upper stomach is encircled by the band, which prevents expansion circumferentially just below the esophagogastric junction when filled with saline injected through the reservoir port (Figure 1). The injections are performed in the office on a routine basis and result in "adjustment" of the upper stomach pouch outlet until the patient achieves optimum appetite control and satiety. Six band adjustments were reported to be the median adjustments required in the first year and are critical to successful weight loss. No cutting or stapling of stomach or intestine is involved. The gastric band is associated with less loss of fat-free mass compared with other operations but on average also with the slowest and least weight loss13 (Table 3). The sleeve gastrectomy involves resection of the greater curvature of the stomach, ≈75 of the stomach. The smaller reservoir provides early satiety, and the remnant stomach is associated with a decrease in ghrelin and peptide YY levels.14Download figureDownload PowerPointFigure 1. Gastric banding.Table 3. Impact of the Type of Weight Loss Surgery on Weight, Lipid Profile, Systemic Hypertension, Diabetes Mellitus, and Side EffectsProceduresRestrictiveHybridWeight↓↓↓ Fat mass↓↓↓ Fat-free mass↓↓↓Lipid profile LDL cholesterol→→ HDL cholesterol↑↑ Triglycerides↓↓↓Systemic hypertension→ or ↓→ or ↓Diabetes mellitus↓↓↓Side effects+++↓ indicates decrease; LDL, low-density lipoprotein; →, no change; HDL, high-density lipoprotein; ↑, increase.Plus signs indicate seriousness of side effects.Hybrid ProcedureA combination of restriction and malabsorption is represented by the RYGB (Figure 2).15 This operation involves reducing the size of the stomach to 15 mL by cutting off the topmost upper portion and connecting it to the small intestine further down in the digestive system. The stomach remains viable but is bypassed of all food intake, and the new stomach has a dramatically smaller capacity; the duodenum is bypassed of all food intake, resulting in decreased macronutrient absorption, which may modulate postprandial hormonal responses.16,17 The reduction of appetite may be partially explained by modulations in serum peptide YY and glucagon-like peptide.18 Bypassing the duodenum also contributes to decreased micronutrient absorption such as iron and calcium, making lifelong supplementation a necessity.7Download figureDownload PowerPointFigure 2. Roux-en-Y gastric bypass. ① indicates alimentary; ②, biliopancreatic; and ③, common.The biliopancreatic diversion (BPD) involves resection of the lower two thirds of the stomach, leaving a 250-mL stomach capacity associated with an intestinal bypass, whereby one half of the jejunum and ileum are disconnected from the alimentary tract and reconnected near the terminal ileum (Figure 3A). With delayed entry of digestive enzymes into the alimentary tract, the majority of fat and a significant proportion of the protein content ingested are excreted as a result of reduced digestion. Dramatic rapid weight loss results, but many micronutrients are not absorbed and supplementation is required.7 A modification of the BPD procedure is the BPD–duodenal switch procedure in which the stomach construction is made up of a sleeve gastrectomy with a less drastic intestinal bypass (Figure 3B).19,20 The advantage of the BPD–duodenal switch is the preservation of the pylorus that connects the stomach to the beginning portion of the small intestine. In addition, the length of the small intestine available for absorption is increased to 100 cm. As a result of these adjustments, this variant procedure carries fewer complications but achieves comparable or even greater weight loss.21–23 In very high-risk patients, staged approaches may be required in which 1 operation, either gastrectomy or intestinal bypass, is "followed by" the other operation in 2 separate surgical procedures.Download figureDownload PowerPointFigure 3. A, Biliopancreatic diversion. B, Biliopancreatic diversion duodenal switch. ① indicates alimentary; ②, biliopancreatic; and ③, common.Complications of Bariatric Surgical ProceduresMortalityOperative (30-day) mortality for bariatric surgery ranges from 0.1% to 2%.10,24,25 Mortality rates depend on several factors: complexity of the operation, patient comorbidities, patient body habitus, and experience of the surgeon and the center. Gastric banding typically has the lowest mortality rate of 0.1%.24,25 Gastric bypass and sleeve gastrectomy mortality is 0.5%, and malabsorptive operations tend to carry a higher average mortality rate of 1%. More recent data reported a 30-day mortality rate not exceeding 0.3%.26 The improved mortality rates are secondary to laparoscopic approaches, better anesthesia, and better monitoring and oversight. These numbers can be lower, however, when taking into account healthier patients with lower BMI who have operations performed by an experienced surgeon at an experienced center. Indeed, in the Longitudinal Assessment of Bariatric Surgery Consortium study, none of the 1198 patients who had undergone LAGB died, whereas 0.2% of the 2975 patients who had undergone laparoscopic RYGB and 2.1% of the 437 patients who had undergone open RYGB died.26 Of importance, patients who underwent open RYGB in that study had a higher BMI and more severe coexisting conditions.26 The higher end mortality rates have been correlated with visceral obesity, sex, BMI of 50 kg/m2, diabetes mellitus, sleep apnea, and older age if the patient, particularly if the operation is performed at a lower-volume center.2,10,26,27Early ComplicationsThe severely obese patient is at risk of developing several general complications. They include thromboembolism (1%), pulmonary or respiratory insufficiency (<1%), hemorrhage (1%), peritonitis (1%), and wound infection (2%). Laparoscopy has been instrumental in decreasing these rates.28 Preventive measures resulting in lower pulmonary complications, lower complications of medical care (ie, medical errors, iatrogenic hypotension), and lower wound infections have also decreased such early morbidity.29Late ComplicationsGastrointestinal obstruction can occur, but the cause of the obstruction typically depends on the type of bariatric operation performed. Gastric obstruction associated with gastric banding is due to food entrapment at the narrowed banded area, from overinflation of the band, or from band "slippage," which causes pouching over the band. Symptoms can be resolved by loosening the band, but in certain circumstances, surgical repositioning of the band is necessary.30 Gastric obstruction associated with gastric bypass or sleeve gastrectomy is due to stenosis of the gastric outlet secondary to scar tissue and may be treated with endoscopic dilation.31 Intestinal obstruction can occur after gastric bypass and malabsorptive operations and requires urgent surgical intervention.32 Marginal ulceration between the stomach pouch and the small intestine after gastric bypass surgery is relatively rare but when present is a frequent source of abdominal pain and anemia. A couple factors explain the impression that this complication may be more prevalent for the clinician33: The majority of the studies are retrospective, and because endoscopic studies have been performed only in selected symptomatic patients, no information on outcomes in the asymptomatic patients is available. A systematic review reported the rates of marginal ulcer to be 0% to 4.3%.34 More recently, Csendes et al35 published a prospective study assessing the incidence of marginal ulcer 1 month and 1 to 2 years after gastric bypass in 442 consecutive patients. Those investigators found early marginal ulcer (1 month after surgery) in 6% of patients and late marginal ulcer (1 to 2 years after surgery) in only 0.6% of patients. Tobacco, aspirin, and anti-inflammatory nonsteroidal medications should be avoided after gastric operations.31 Incisional hernias are common after open bariatric surgery and require subsequent surgical intervention. The increased use of minimally invasive techniques have significantly decreased the incidence of this complication.28 Device-related complications with the gastric band include malfunction of the band, tubing, or reservoir component. Complications are reported to be <1%.30 A leak in any of these components results in lack of weight loss and subsequently requires surgical replacement. Erosion of the band into the stomach also results in weight loss failure and necessitates removal of the device. Band infection is relatively rare, but infection of the reservoir port can be seen in high-risk patients such as patients with diabetes mellitus and smokers. Most can be treated successfully with antibiotics.30Hypoglycemia has been reported after gastric bypass and can typically be managed successfully with diet modulations. Steatorrhea, diarrhea, and bacterial overgrowth are more common with malabsorptive procedures than gastric banding. Diet modification and antibiotics can be helpful in controlling the severity of these side effects.36 The most important thing to remember is that a patient with a complication may be best served by being evaluated by an experienced bariatric surgeon. With the rapid growth of bariatric surgery, the maintenance of quality care was the impetus for the creation of Centers of Excellence in the United States. However, the health benefits of this implementation are not clear.37 A thorough nutrition evaluation can identify characteristics known to be associated with nutrition risks and/or complications of bariatric surgery. The nutrition evaluation should contain a detailed weight history, including a description of the onset, severity, and duration of obesity; a description of current eating patterns; and an assessment of overall nutrition knowledge. Because indications for bariatric surgery include failed attempts to maintain weight loss, a brief summary of self-directed, commercial plans and medically supervised programs should also be documented by the interdisciplinary bariatric surgery team. A patient's motivation for seeking bariatric surgery and knowledge of the procedure, risk, benefits, and impacts on their postsurgical diet and eating behaviors, as well as expectations about weight loss, are all part of a thorough pre–bariatric surgery nutrition evaluation. Nutritional deficiencies of micronutrients are common in obese patients seeking bariatric surgery and should be detected and corrected to avoid postoperative complications. Vitamin B12, vitamin D, folate, and trace minerals such as zinc, iron, and calcium should be screened before bariatric surgery and repleted as needed.38,39 Vitamin D deficiency is a major public health problem in the United States, and patients with obesity may be at higher risk for developing this deficiency.40,41 25-OH Vitamin D should be assessed preoperatively and repleted.39 Thiamine deficiency, especially in black and Hispanic patients with obesity, is not uncommon and should be screened and repleted.38 Reported neurological complications of bariatric surgery are peripheral neuropathy, burning feet syndrome, meralgia paresthesia, myotonic syndrome, posterolateral myelopathy, myotonic syndrome, optic neuropathy, Wernicke-Korsakoff encephalopathy, and lumbosacral plexopathy. Although encephalopathies are rare, retrospective reviews identified the prevalence of peripheral neuropathy as being between 7% and 16%.42,43 Risk factors for peripheral neuropathy included increased glycohemoglobin levels at baseline and increased triglycerides at follow-up, longer duration of hospital stay, prolonged postoperative gastrointestinal symptoms, and a lesser rate of attendance at nutritional clinics. Rate and absolute amount of weight loss were also identified but may represent a lack of appropriate nutritional follow-up.42,43No data exist to support mandatory psychological evaluation, and no predictive value has been found in a patient's psychological profile in terms of outcomes. However, psychological evaluations have become incorporated into most bariatric surgery practices. Although these evaluations often focus on screening for untreated psychopathology, they should also focus on psychoeducational matters and include an assessment of the behavioral and environmental factors that may have contributed to the development of severe obesity, as well as the potential impact of these factors on the patient's ability to make the necessary dietary and behavioral changes to experience an optimal postoperative outcome.44 Although a psychological evaluation for untreated or undiagnosed psychological conditions may be important for identifying the need for presurgery psychological treatment, the mental health professional will play a greater role in the postoperative care of patients by conducting support groups and/or providing individual psychotherapy.Regarding exercise, according to 1 report, <20% of severely obese patients engage in structured exercise before undergoing RYGB surgery.45 Common barriers to regular physical activity include frustration with contemporary exercise guidelines, hesitation to exercise in public places (walking tracks, swimming pools), excessive fatigue/dyspnea with low-level effort, and associated musculoskeletal problems that hinder balance and mobility.46 However, every patient should be counseled to engage in a preoperative exercise regimen, which may be beneficial in reducing surgical complications and enhancing postoperative recovery. Because reduced peak oxygen consumption (peak Vo2) level (<15.8 mL · kg−1 · min−1 or <4.5 metabolic equivalents [METs; 1 MET=3.5 mL · kg−1 · min−1]) is independently associated with increased short-term complications after bariatric surgery, cardiorespiratory fitness should be optimized before bariatric surgery to potentially reduce postoperative complications.47 Activities corresponding to ≥3 METs are likely to induce somatic fatigue because these aerobic requirements may exceed the ventilatory-derived anaerobic threshold in severely obese patients.48 This would suggest a training intensity of 2 to 3 METs, which approximates walking speeds of only 1 to 2.5 mph. Such training intensities, if performed in ≥20 min/d of continuous or accumulated exercise 3 to 4 times a week, may serve to increase aerobic capacity and improve quality of life and surgical outcomes.49Effects of Bariatric Surgery on Cardiovascular Risk FactorsWeightBariatric surgery provides the greatest sustainable weight loss. Bariatric surgery weight loss effectiveness is commonly expressed in terms of loss of excess weight. The excess weight loss nomenclature as a measurement of weight loss after bariatric surgery has been challenged because of several limitations.50 The term "excess weight" refers to the difference between the actual weight and "ideal weight" of a given individual. In this context, "ideal weight" is synonymous with "desirable weight," first introduced in 1943 by the Metropolitan Life Insurance Company in their standard height-weight tables for men and women of a medium frame size category. An average weight loss of 50% of excess weight at 5 years may be considered a success, although this typically varies according to the type, aggressiveness, and complexity of surgery. In a meta-analysis of 22 000 bariatric surgery patients, Buchwald et al24 found that an average percent excess body weight loss of 61% was accompanied by improvements in type 2 diabetes mellitus, systemic hypertension, obstructive sleep apnea, and dyslipidemia. In another meta-analysis,51 bariatric surgery resulting in a weight loss of 20 to 30 kg maintained up to 10 years was associated with a reduction of comorbidities with an overall mortality rate 50%.53 In addition, a recent meta-analysis found a composite percent excess weight loss of 49.4% for LAGB versus 62.6% for laparoscopic gastric bypass. The authors found percent excess weight loss outcomes for laparoscopic gastric bypass to be significantly superior to those for LAGB at all 3 time points examined (1, 2, and >3 years).54Weight loss after malabsorptive bariatric surgery reaches a nadir at ≈12 to 18 months with an average of 70% excess body weight loss and 35% decrease in BMI7 with an approximate 10% weight regain over the next decade.55 RYGB similarly nadirs at 18 months with a 70% excess body weight loss and may have a weight regain after 3 years of up to 15%, for an average of 55% excess body weight loss out to 15 years.7,55 Sleeve gastrectomy has weight loss patterns similar to RYGB.Diabetes MellitusThe vast majority of people with type 2 diabetes mellitus are overweight, with up to 50% to 60% qualifying as obese or severely obese.56 The presence of diabetes mellitus is associated with a significant 3- to 4-fold increase in the risk of microangiopathy and large-vessel atherosclerosis as manifested by myocardial infarction, stroke, or lower-extremity claudication.57 There have been significant advances in the management of hyperglycemia and prevention of complications of diabetes mellitus over the past several decades. However, even with currently available approaches, efficacy is incomplete, and the need for multiple medications and intensive medical follow-up leads to considerable expense and poor patient compliance. In addition, in a subset of patients with type 2 diabetes mellitus, currently available therapies are poorly effective and associated with substantial weight gain. Weight loss has long been regarded as the first approach to prevent diabetes mellitus in high-risk subjects and to manage the metabolic derangements of established diabetes mellitus. The attractiveness of weight control as a therapeutic target and the limited efficacy of producing medically induced weight loss have led to increased interest in the effect of surgically produced weight loss to correct the metabolic abnormalities in patients with established diabetes mellitus and to prevent diabetes mellitus in high-risk individuals.Weight loss prevents the emergence of diabetes mellitus in a significant portion of high-risk patients (eg, those with insulin resistance, impaired glucose tolerance, or impaired fasting glucose).58,59 In the Diabetes Prevention Program, lifestyle intervention with diet and exercise produced a 5.6-kg weight loss and reduced the emergence of diabetes mellitus by 58% with an average 2.8 years of follow-up.58 Bariatric surgery with its substantial weight loss reduces the appearance of diabetes mellitus in overweight insulin-resistant subjects. In 1 study55 in which patients underwent bariatric surgery or conventional treatment, the odds ratio for developing diabetes mellitus in the surgical group was 0.14 (95% confidence interval, 0.08 to 0.24) at 2 years and 0.25 (95% confidence interv
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