[The impact of morbid obesity on the peri- and postoperative course after aortocoronary bypass surgery]

Relationship of body mass index with total mortality, cardiovascular mortality, and myocardial infarction after coronary revascularization: evidence from a meta-analysis

OBJECTIVE

To investigate the relationship of body mass index (BMI) with total mortality, cardiovascular (CV) mortality, and myocardial infarction (MI) after coronary revascularization procedures (coronary artery bypass grafting [CABG] and percutaneous coronary intervention [PCI]).

PATIENTS AND METHODS

Systematic search of studies was conducted using PubMed, CINAHL, Cochran CENTRAL, Scopus, and the Web of Science databases. We identified studies reporting the rate of MI, CV mortality, and total mortality among coronary artery disease patients' postcoronary revascularization procedures in various BMI categories: less than 20 (underweight), 20-24.9 (normal reference), 25-29.9 (overweight), 30-34.9 (obese), and 35 or more (severely obese). Event rates were compared using a random effects model assuming interstudy heterogeneity.

RESULTS

A total of 36 studies (12 CABG; 26 PCI) were selected for final analyses. The risk of total mortality (relative risk [RR], 2.59; 95% CI, 2.09-3.21), CV mortality (RR, 2.67; 95% CI, 1.63-4.39), and MI (RR, 1.79; 95% CI, 1.28-2.50) was highest among patients with low BMI at the end of a mean follow-up period of 1.7 years. The risk of CV mortality was lowest among overweight patients (RR, 0.81; 95% CI, 0.68-0.95). Increasing degree of adiposity as assessed by BMI had a neutral effect on the risk of MI for overweight (RR, 0.92; 95% CI, 0.84-1.01), obese (RR, 0.99; 95% CI, 0.85-1.15), and severely obese (RR, 0.93; 95% CI, 0.78-1.11) patients.

CONCLUSION

After coronary artery disease revascularization procedures (PCI and CABG), the risk of total mortality, CV mortality, and MI was highest among underweight patients as defined by low BMI and CV mortality was lowest among overweight patients.

Effect of obesity on short- and long-term mortality postcoronary revascularization: a meta-analysis

OBJECTIVE

Overweight and obesity are often assumed to be risk factors for postprocedural mortality in patients with coronary artery disease (CAD). However, recent studies have described an "obesity paradox" -- a neutral or beneficial association between obesity and mortality postcoronary revascularization. We reviewed the effect of overweight and obesity systematically on short- and long-term all-cause mortality post-coronary artery bypass grafting (CABG) and post-percutaneous coronary intervention (PCI).

METHODS

We searched the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, Scopus, and Web of Science to identify cohort, case control, and randomized controlled studies evaluating the effect of obesity on in-hospital/short-term (within 30 days) and long-term (up to 5 years) mortality. Full-text, published articles reporting all-cause mortality between individuals with and without elevated BMI were included. Two reviewers independently assessed studies for inclusion and performed data extraction.

RESULTS

Twenty-two cohort publications were identified, reporting results in ten post-PCI and twelve post-CABG populations. Compared to individuals with non-elevated BMI levels, obese patients undergoing PCI had lower short- (odds ratio (OR) 0.63; 95% confidence interval (CI) 0.54-0.73) and long-term mortality (OR 0.65; 95% CI 0.51-0.83). Post-CABG, obese patients had lower short-term (OR 0.63; 95% CI 0.56-0.71) and similar long-term (OR 0.88; 95% CI 0.60-1.29) mortality risk compared to normal weight individuals. Results were similar in overweight patients for both procedures.

CONCLUSIONS

Compared to non-obese individuals, overweight and obese patients have similar or lower short- and long-term mortality rates postcoronary revascularization. Further research is needed to confirm the validity of these findings and delineate potential underlying mechanisms.

Cardiac procedures in patients with a body mass index exceeding 45: outcomes and long-term results

BACKGROUND

Obesity has become a public health crisis. Although prior studies in obese patients undergoing cardiac surgical procedures have shown variable effects on outcomes, data are limited for extremely obese patients (body mass index [BMI] > or = 45). We undertook this study to evaluate outcomes in this cohort.

METHODS

A retrospective analysis was performed on 14,571 patients in our database who underwent cardiac operations from 1992 to 2005. Patient demographics, comorbidities, and outcomes were recorded. A univariate analysis between two groups: BMI 21 to 34.9 and BMI 45 or more was performed. Logistic regression models were used to identify independent risk factors for 30-day mortality. Long-term follow-up of the extreme obese group was achieved.

RESULTS

We identified 128 extreme obese patients, and 480 patients with a BMI of 21.0 to 34.9 were randomly selected for comparison. Univariate analysis showed significant differences in age, gender, and multiple comorbidities, as well as in cardiopulmonary bypass and cross-clamp times, operative procedure, and transfusion requirements. Extreme obese patients had a higher incidence of infection, acute renal failure, and 30-day mortality. Logistic regression analysis showed BMI, preoperative renal insufficiency, and transfusion status to be independent risk factors for 30-day mortality. Follow-up data did not reveal significant functional improvements. Long-term survival was 33.6% at 12 years.

CONCLUSIONS

Extreme obese patients undergoing cardiac surgical procedures have higher perioperative morbidity and mortality compared with a lower BMI group. BMI and preoperative renal insufficiency increase mortality in both groups, whereas transfusion does so only in the extreme obese. These patients can realize acceptable outcomes from cardiac procedures, but continue to suffer from the comorbidities of obesity.

Association of bodyweight with total mortality and with cardiovascular events in coronary artery disease: a systematic review of cohort studies

BACKGROUND

Studies of the association between obesity, and total mortality and cardiovascular events in patients with coronary artery disease (CAD) have shown contradictory results. We undertook a systematic review to determine the extent and nature of this association.

METHODS

We selected cohort studies that provided risk estimates for total mortality, with or without cardiovascular events, on the basis of bodyweight or obesity measures in patients with CAD, and with at least 6 months' follow-up. CAD was defined as history of percutaneous coronary intervention, coronary artery bypass graft, or myocardial infarction. We obtained risk estimates for five predetermined bodyweight groups: low, normal weight (reference), overweight, obese, and severely obese.

FINDINGS

We found 40 studies with 250,152 patients that had a mean follow-up of 3.8 years. Patients with a low body-mass index (BMI) (ie, <20) had an increased relative risk (RR) for total mortality (RR=1.37 [95% CI 1.32-1.43), and cardiovascular mortality (1.45 [1.16-1.81]), overweight (BMI 25-29.9) had the lowest risk for total mortality (0.87 [0.81-0.94]) and cardiovascular mortality (0.88 [0.75-1.02]) compared with those for people with a normal BMI. Obese patients (BMI 30-35) had no increased risk for total mortality (0.93 [0.85-1.03]) or cardiovascular mortality (0.97 [0.82-1.15]). Patients with severe obesity (> or =35) did not have increased total mortality (1.10 [0.87-1.41]) but they had the highest risk for cardiovascular mortality (1.88 [1.05-3.34]).

INTERPRETATION

The better outcomes for cardiovascular and total mortality seen in the overweight and mildly obese groups could not be explained by adjustment for confounding factors. These findings could be explained by the lack of discriminatory power of BMI to differentiate between body fat and lean mass.

Is Obesity a Risk Factor for Mortality in Coronary Artery Bypass Surgery?

Background— The published articles examining obesity and CABG surgery contain conflicting results about the role of body mass index (BMI) as a risk factor for in-hospital mortality.

Methods and Results— We studied 16 218 patients who underwent isolated CABG in the Providence Health System Cardiovascular Study Group database from 1997 to 2003. The effect of BMI on in-hospital mortality was assessed by logistic regression, with BMI group (underweight, normal, overweight, and 3 subgroups of obesity) as a categorical variable or transformations, including fractional polynomials, of BMI as a continuous variable. BMI was not a statistically significant risk factor for mortality in any of these assessments. However, using cumulative sum techniques, we found that the lowest risk-adjusted CABG in-hospital mortality was in the high-normal and that overweight BMI subgroup patients with lower or higher BMI had slightly increased mortality.

Conclusions— Body size is not a significant risk factor for CABG mortality, but the lowest mortality is found in the high-normal and overweight subgroups compared with obese and underweight.

Current determinants of operative mortality in 1400 patients requiring aortic valve replacement

BACKGROUND

Determinants of operative mortality after aortic valve replacement vary with a changing patient population due to advances in operative management and increasing life expectancy. In order to predict current groups of high risk patients, a statistically valid large study population base recruited over a short period of time is required.

METHODS

Between January 1996 and June 2001, 1408 aortic valves were replaced in 1400 patients (572 of them with simultaneous coronary artery bypass grafting). The data were analyzed by multivariate logistic regression to evaluate the operative risk. Mean age of the study population was 68 +/- 11 years (range 19 to 90 years old, 44% female).

RESULTS

Overall operative mortality (within 30 days) was 3.8%. Independent predictive factors for operative mortality were previous bypass surgery, emergency operation, simultaneous mitral valve replacement, renal dysfunction, more than 80 years old, simultaneous bypass surgery in female patients with a body mass index greater than 29 kg/m(2), and height smaller than 1.57 m for patients more than 71 years old. Simultaneous coronary artery bypass grafting in general (p = 0.6), previous aortic valve replacement (p = 0.59), and implantation of stented bioprostheses (p = 0.39) or stentless bioprostheses (p = 0.7) were not identified as independent risk factors.

CONCLUSIONS

Certain groups of patients with a high operative risk were identified: patients more than 80 years old, women with a body mass index greater 29 kg/m(2) undergoing simultaneous coronary artery bypass surgery, and "small" patients more than 71 years old.