Body Mass Index, Outcomes, and Mortality Following Cardiac Surgery in Ontario, Canada

Perioperative Care of the Obese Cardiac Surgical Patient

Morbid obesity is associated with impairment of cardiovascular, pulmonary, gastrointestinal, and renal physiology with significant perioperative consequences and has been linked with higher morbidity and mortality after cardiac surgery. Cardiac surgery patients have a higher incidence of difficult airway and difficult laryngoscopy than general surgery patients do, and obesity is associated with difficult mask ventilation and direct laryngoscopy. Positioning injuries occur more frequently because obese patients are at greater risk of pressure injury, such as rhabdomyolysis and compartment syndrome. Despite the association between obesity and several chronic disease states, the effects of obesity on perioperative outcomes are conflicting. Studies examining outcomes of overweight and obese patients in cardiac surgery have reported varying results. An "obesity paradox" has been described, in which the mortality for overweight and obese patients is lower compared with patients of normal weight. This review describes the physiologic abnormalities and clinical implications of obesity in cardiac surgery and summarizes recommendations for anesthesiologists to optimize perioperative care of the obese cardiac surgical patient.

Predictors of survival in octogenarians after mitral valve surgery for degenerative disease: The Mitral Surgery in Octogenarians study

OBJECTIVES

An increasing number of octogenarians are referred to undergo mitral valve surgery for degenerative disease, and percutaneous approaches are being increasingly used in this subgroup of patients. We sought to determine the survival and its predictors after Mitral Valve Surgery in Octogenarians (MiSO) in a multicenter UK study of high-volume specialized centers.

METHODS

Pooled data from 3 centers were collected retrospectively. To identify the predictors of short-term composite outcome of 30 days mortality, acute kidney injury, and cerebrovascular accident, a multivariable logistic regression model was developed. Multiple Cox regression analysis was performed for late mortality. Kaplan-Meier curves were generated for long-term survival in various subsets of patients. Receiver operating characteristic analysis was done to determine the predictive power of the logistic European System for Cardiac Operative Risk Evaluation.

RESULTS

A total of 247 patients were included in the study. The median follow-up was 2.9 years (minimum 0, maximum 14 years). A total of 150 patients (60.7%) underwent mitral valve repair, and 97 patients (39.3%) underwent mitral valve replacement. Apart from redo cardiac surgery (mitral valve repair 6 [4%] vs mitral valve replacement 11 [11.3%], P = .04) and preoperative atrial fibrillation (mitral valve repair 79 [52.6%] vs mitral valve replacement 34 [35.1%], P < .01), there was no significant difference in terms of any other preoperative characteristics between the 2 groups. Patient operative risk, as estimated by logistic European System for Cardiac Operative Risk Evaluation, was lower in the mitral valve repair group (10.2 ± 11.8 vs 13.7 ± 15.2 in mitral valve replacement; P = .07). No difference was found between groups for duration of cardiopulmonary bypass and aortic crossclamp times. The 30-day mortality for the whole cohort was 13.8% (mitral valve repair 4.7% vs mitral valve replacement 18.6%; P < .01). No differences were found in terms of postoperative cerebrovascular accident (2% vs 3.1%; P = .9), acute kidney injury requiring dialysis (6.7% vs 13.4%; P = .12), and superficial or deep sternal wound infection (10% vs 16.5%, P = .17; 2% vs 3.1%, P = .67, respectively). The final multiple regression model for short-term composite outcome included previous cardiac surgery (odds ratio [OR], 4.47; 95% confidence interval [CI], 1.37-17.46; P = .02), intra-aortic balloon pump use (OR, 4.77; 95% CI, 1.67-15.79; P < .01), and mitral valve replacement (OR, 7.7; 95% CI, 4.04-14.9; P < .01). Overall survival for the entire cohort at 1, 5, and 10 years was 82.4%, 63.7%, and 45.5% (mitral valve repair vs mitral valve replacement: 89.9% vs 70.7% at 1 year, 69.6% vs 54% at 5 years, and 51.8% vs 35.5% at 10 years; P = .0005). Cox proportional hazard model results showed mitral valve replacement (hazard ratio, 1.88; 95% CI, 1.22-2.89; P < .01) and intra-aortic balloon pump use (hazard ratio, 2.54; 95% CI, 1.26-5.13; P < .01) to be independent predictor factors affecting long-term survival. Logistic European System for Cardiac Operative Risk Evaluation did not perform well in predicting early mortality (area under the curve, 0.57%).

CONCLUSIONS

In octogenarians, mitral valve repair for degenerative disease is associated with good survival and remains the gold standard, whereas mitral valve replacement is still associated with significant mortality. Logistic European System for Cardiac Operative Risk Evaluation was unable to predict early mortality in our cohort of patients. Larger international multicenter registries are required to optimize the decision-making process in such a high-risk subgroup.

Effect of body mass index on clinical outcome and all-cause mortality in patients undergoing transcatheter aortic valve implantation

Objectives

To assess the effect of body mass index (BMI) on outcome among patients with severe aortic stenosis (AS) admitted for transcatheter aortic valve implantation (TAVI).

Background

Being overweight or obese is associated with improved outcome following certain medical treatments, suggesting the existence of a BMI paradox. However, the relationship between BMI and mortality after TAVI remains controversial.

Methods

Patients were classified according to World Health Organisation criteria such as normal weight, overweight, or obesity according to their BMI (18.5 to 24.9 kg/m², 25.0 to 29.9 kg/m², and ≥30.0 kg/m², respectively).

Results

A total of 549 consecutive patients (age: 80.2 ± 7.5 years; logistic European system for cardiac operative risk evaluation [EuroSCORE]: 17.3 ± 9.9%) who underwent TAVI for AS were included. Of these patients, 43% (n = 237) had normal weight, 36% (n = 200) were overweight, and 20% (n = 112) were obese. There were no differences in peri-operative bleeding or vascular complication rates between the groups. All-cause mortality after 30 days, and 1 year, were higher in normal weight patients compared with overweight and obese patients (7% vs. 5 and 4%, p = 0.383, and 19% vs. 9 and 10%, p = 0.006, respectively). After adjustment for several confounding factors, overweight was associated with a decreased 30-day and 1‑year all-cause mortality outcome (hazard ratio [HR] 0.69; 95% confidence interval [CI] 0.47–0.99, and HR 0.65; 95% CI 0.45–0.94, respectively).

Conclusions

Despite the well-documented adverse effects of increased body weight on health, being overweight is associated with improved survival following TAVI when compared with normal weight.

The Relationship between Body Mass Index and the Severity of Coronary Artery Disease in Patients Referred for Coronary Angiography

Background and Aim. Obesity is associated with an increased risk of cardiovascular disease and may be associated with more severe coronary artery disease (CAD); however, the relationship between body mass index [BMI (kg/m²)] and CAD severity is uncertain and debatable. The aim of this study was to examine the relationship between BMI and angiographic severity of CAD. Methods. Duke Jeopardy Score (DJS), a prognostic tool predictive of 1-year mortality in CAD, was assigned to angiographic data of patients ≥18 years of age (N = 8,079). Patients were grouped into 3 BMI categories: normal (18.5–24.9 kg/m²), overweight (25.0–29.9 kg/m²), and obese (≥30 kg/m²); and multivariable adjusted hazard ratios for 1-year all-cause and cardiac-specific mortality were calculated. Results. Cardiac risk factor prevalence (e.g., diabetes, hypertension, and hyperlipidemia) significantly increased with increasing BMI. Unadjusted all-cause and cardiac-specific 1-year mortality tended to rise with incremental increases in DJS, with the exception of DJS 6 (p < 0.001). After adjusting for potential confounders, no significant association of BMI and all-cause (HR 0.70, 95% CI .48–1.02) or cardiac-specific (HR 1.11, 95% CI .64–1.92) mortality was found. Conclusions. This study failed to detect an association of BMI with 1-year all-cause or cardiac-specific mortality after adjustment for potential confounding variables.

Differences in Short- and Long-Term Mortality Associated With BMI Following Coronary Revascularization

BACKGROUND

The association between obesity and mortality risks following coronary revascularization is not clear. We examined the associations of BMI (kg/m2) with short-, intermediate-, and long-term mortality following coronary artery bypass graft surgery (CABG) and percutaneous coronary intervention (PCI) in patients with different coronary anatomy risks and diabetes mellitus status.

METHODS AND RESULTS

Data from the Alberta Provincial Project for Outcomes Assessment in Coronary Heart Disease (APPROACH) registry were analyzed. Using normal BMI (18.5-24.9) as a reference, multivariable-adjusted hazard ratios for all-cause mortality within 6 months, 1 year, 5 years, and 10 years were individually calculated for CABG and PCI with 4 prespecified BMI categories: overweight (25.0-29.9), obese class I (30.0-34.9), obese class II (35.0-39.9), and obese class III (≥40.0). The analyses were repeated after stratifying for coronary risks and diabetes mellitus status. The cohorts included 7560 and 30 258 patients for CABG and PCI, respectively. Following PCI, overall mortality was lower in patients with overweight and obese class I compared to those with normal BMI; however, 5- and 10-year mortality rates were significantly higher in patients with obese class III with high-risk coronary anatomy, which was primarily driven by higher mortality rates in patients without diabetes mellitus (5-year adjusted hazard ratio, 1.78 [95% CI, 1.11-2.85] and 10-year adjusted hazard ratio, 1.57 [95% CI, 1.02-2.43]). Following CABG, overweight was associated with lower mortality risks compared with normal BMI.

CONCLUSIONS

Overweight was associated with lower mortality following CABG and PCI. Greater long-term mortality in patients with obese class III following PCI, especially in those with high-risk coronary anatomy without diabetes mellitus, warrants further investigation.

Obesity Increases Risk-Adjusted Morbidity, Mortality, and Cost Following Cardiac Surgery

BACKGROUND

Despite the epidemic rise in obesity, few studies have evaluated the effect of obesity on cost following cardiac surgery. We hypothesized that increasing body mass index (BMI) is associated with worse risk-adjusted outcomes and higher cost.

METHODS AND RESULTS

Medical records for 13 637 consecutive patients who underwent coronary artery bypass grafting (9702), aortic (1535) or mitral (837) valve surgery, and combined valve-coronary artery bypass grafting (1663) procedures were extracted from a regional Society of Thoracic Surgeons certified database. Patients were stratified by BMI: normal to overweight (BMI 18.5-30), obese (BMI 30-40), and morbidly obese (BMI >40). Differences in outcomes and cost were compared between BMI strata and also modeled as a continuous function of BMI with adjustment for preoperative risk using Society of Thoracic Surgeons predictive risk indices. Morbidly obese patients incurred nearly 60% greater observed mortality than normal weight patients. Moreover, morbidly obese patients had greater than 2-fold increase in renal failure and 6.5-fold increase in deep sternal wound infection. After risk adjustment, a significant association was found between BMI and mortality (P<0.001) and major morbidity (P<0.001). The risk-adjusted odds ratio for mortality for morbidly obese patients was 1.57 (P=0.02) compared to normal patients. Importantly, risk-adjusted total hospital cost increased with BMI, with 17.2% higher costs in morbidly obese patients.

CONCLUSIONS

Higher BMI is associated with increased mortality, major morbidity, and cost for hospital care. As such, BMI should be more strongly considered in risk assessment and resource allocation.

Association of body mass index and visceral fat with aortic valve calcification and mortality after transcatheter aortic valve replacement: the obesity paradox in severe aortic stenosis

BACKGROUND

Previous studies showed that metabolic syndrome is associated with aortic valve calcification (AVC) and poor outcomes in aortic stenosis (AS). However, if these associations change and how body fat impacts the prognosis of patients in late stage of the disease have been not yet explored.

AIMS

To determine the association of body mass index (BMI) and visceral fat with AVC and mortality after transcatheter aortic valve replacement (TAVR).

METHODS

This was a prospective cohort of 170 severe AS patients referred to TAVR. We quantified AVC mass score and fat depots including epicardial adipose tissue, intrathoracic fat, and abdominal visceral (VAF) and subcutaneous fats by computed tomography. Fat depots were indexed to body surface area. All-cause and cardiovascular-related deaths after TAVR were recorded over a median follow-up of 1.2 years.

RESULTS

Higher AVC mass was independently associated with low BMI and low VAF. All-cause mortality risk increased with the decrease of BMI and increment of VAF. A stratified analysis by obesity showed that in non-obese, VAF was inversely associated with mortality, whereas in obese, high VAF was associated with higher mortality (p value for interaction < 0.05). At long-term, hazard ratio [HR] with non-obese/low VAF was 2.3 (95% confidence interval [CI] 1.1-4.9; p = 0.021) and HR with obese/high VAF was 2.5 (95% CI 1.1-5.8; p = 0.031) compared with obese/low VAF patients.

CONCLUSIONS

In AS patients submitted to TAVR, BMI and VAF were inversely associated with AVC. Pre-intervention assessment of VAF by computed tomography may provide a better discrimination of mortality than BMI alone.

Impact of Body Mass Index on Short-Term Outcomes in Patients Undergoing Percutaneous Coronary Intervention in Newfoundland and Labrador, Canada

Background and Aim. Obesity (BMI ≥ 30 kg/m²) is associated with advanced cardiovascular disease requiring procedures such as percutaneous coronary intervention (PCI). Studies report better outcomes in obese patients having these procedures but results are conflicting or inconsistent. Newfoundland and Labrador (NL) has the highest rate of obesity in Canada. The aim of the study was to examine the relationship between BMI and vascular and nonvascular complications in patients undergoing PCI in NL. Methods. We studied 6473 patients identified in the APPROACH-NL database who underwent PCI from May 2006 to December 2013. BMI categories included normal, 18.5 ≤ BMI < 25.0 (n = 1073); overweight, 25.0 ≤ BMI < 30 (n = 2608); and obese, BMI ≥ 30.0 (n = 2792). Results. Patients with obesity were younger and had a higher incidence of diabetes, hypertension, and family history of cardiac disease. Obese patients experienced less vascular complications (normal, overweight, and obese: 8.2%, 7.2%, and 5.3%, p = 0.001). No significant differences were observed for in-lab (4.0%, 3.3%, and 3.1%, p = 0.386) or postprocedural (1.0%, 0.8%, and 0.9%, p = 0.725) nonvascular complications. After adjusting for covariates, BMI was not a significant factor associated with adverse outcomes. Conclusion. Overweight and obesity were not independent correlates of short-term vascular and nonvascular complications among patients undergoing PCI.

Prognostic value of body mass index and body surface area on clinical outcomes after transcatheter aortic valve implantation

BACKGROUND

Inverse associations between Body Mass Index (BMI) and Body Surface Area (BSA) with mortality in patients after Transcatheter Aortic Valve Implantation (TAVI) have been reported. This "obesity paradox" is controversial, and it remains unclear which parameter, BMI or BSA, is of greater prognostic value. The aim of this study was to investigate the association of BMI and BSA on short- and mid-term outcomes after TAVI.

METHODS AND RESULTS

This prospective, observational study consisted of 917 consecutive patients undergoing TAVI at our center from 2011 to 2014. The association between BMI/BSA and mortality (at 30 days and 1 year) was assessed using restricted cubic spline functions in propensity-adjusted (by Society of Thoracic Surgeons (STS) risk factors) logistic and Cox proportional models, respectively. The median age of the patients was 82.6 years, with a mean STS Predicted Risk of Mortality (STS-PROM) of 6.6 ± 4.3 %. Throughout the study period (mean follow-up time was 297 days), 150 (16.4 %) patients died; 72 (7.9 %) patients died within 30 days of TAVI. After risk adjustment, the association between body constitution and 30-day mortality was not significant for either measure (BMI p = 0.25; BSA p = 0.32). However, BMI (p = 0.01), but not BSA (p = 0.13), was significantly associated with 1-year survival. There was no association between stroke, vascular complications, or length of stay with BMI or BSA.

CONCLUSIONS

BMI was associated with survival at 1-year after TAVI. Despite the trend towards implementing BSA in risk score calculation, BMI may be more suitable for the assessment of TAVI patients.

Severe Obesity Is Associated With Increased Risk of Early Complications and Extended Length of Stay Following Coronary Artery Bypass Grafting Surgery

Background

Better understanding of the relationship between obesity and postsurgical adverse outcomes is needed to provide quality and efficient care. We examined the relationship of obesity with the incidence of early adverse outcomes and in‐hospital length of stay following coronary artery bypass grafting surgery.

Methods and Results

We analyzed data from 7560 patients who underwent coronary artery bypass grafting. Using body mass index (BMI; in kg/m²) of 18.5 to 24.9 as a reference, the associations of 4 BMI categories (25.0–29.9, 30.0–34.9, 35.0–39.9, and ≥40.0) with rates of operative mortality, overall early complications, subgroups of early complications (ie, infection, renal and pulmonary complications), and length of stay were assessed while adjusting for clinical covariates. There was no difference in operative mortality; however, higher risks of overall complications were observed for patients with BMI 35.0 to 39.9 (adjusted odds ratio 1.35, 95% CI 1.11–1.63) and ≥40.0 (adjusted odds ratio 1.56, 95% CI 1.21–2.01). Subgroup analyses identified obesity as an independent risk factor for infection (BMI 30.0–34.9: adjusted odds ratio 1.60, 95% CI 1.24–2.05; BMI 35.0–39.9: adjusted odds ratio 2.34, 95% CI 1.73–3.17; BMI ≥40.0: adjusted odds ratio 3.29, 95% CI 2.30–4.71). Median length of stay was longer with BMI ≥40.0 than with BMI 18.5 to 24.9 (median 7.0 days [interquartile range 5 to 10] versus 6.0 days [interquartile range 5 to 9], P=0.026).

Conclusions

BMI ≥40.0 was an independent risk factor for longer length of stay, and infection was a potentially modifiable risk factor. Greater perioperative attention and intervention to control the risks associated with infection and length of stay in patients with BMI ≥40.0 may improve patient care quality and efficiency.

Obesity and postoperative atrial fibrillation in patients undergoing cardiac surgery: Systematic review and meta-analysis

INTRODUCTION

Post-operative atrial fibrillation (POAF) is one of the most common complications following cardiac surgery. However, it is unclear whether there is a relationship between obesity and POAF. We thus assessed all available evidence investigating the association between obesity and POAF, also considering any link between POAF and other post-operative conditions such as mortality, stroke, myocardial infarctions and respiratory complications.

METHODS

Five electronic databases were searched and relevant studies were identified. Data was extracted and meta-analyzed from the identified studies.

RESULTS

We found that obese patients had significantly higher odds of POAF when compared with non-obese patients (P=0.006). There was also significant heterogeneity among the identified studies. POAF when compared with no-POAF was associated with an increased risk of stroke (P<0.0001), 30-day mortality (P=0.005) and respiratory complications (P<0.00001). However, we found no significant link between POAF and myocardial infarctions (P=0.79).

CONCLUSIONS

Our findings suggest that obesity is associated with a moderately higher risk of POAF. While POAF is also associated with an increased incidence of stroke, 30-day mortality and respiratory complications, further studies must be conducted before conclusions can be made about the long-term outcomes.

Impact of Body Mass Index on Outcomes in Cardiac Surgery

OBJECTIVES

Body mass index (BMI) commonly is used in obesity classification as a surrogate measure, and obesity is associated with a cluster of risk factors for cardiovascular disease. The aim of this study was to investigate the impact of BMI on short-term outcomes after cardiac surgery.

DESIGN

A retrospective cohort study.

SETTING

University teaching hospital, 2 centers.

PARTICIPANTS

The study comprised 4,740 patients who underwent cardiac surgery at 2 hospitals-from July 1, 2001, to June 30, 2013, in 1 hospital and from September 1, 2003, to August 31, 2014, in a second hospital.

INTERVENTIONS

No changes to standard practice were required.

MEASUREMENTS AND MAIN RESULTS

Patients were assigned into 6 BMI groups as follows: underweight (BMI<18.5 kg/m(2)), normal weight (≥18.5 to<25 kg/m(2)), overweight (≥25 to<30 kg/m(2)), class I obese (≥30 to<35 kg/m(2)), class II obese (≥35 to<40 kg/m(2)), and class III obese (BMI≥40 kg/m(2)). Short-term major postoperative complications (postoperative stroke, cardiac arrest, new atrial fibrillation/flutter, permanent rhythm device insertion, deep sternal infection, sepsis, prolonged ventilation, pneumonia, renal dialysis, renal failure, intensive care unit readmission, total intensive care unit hours, and readmission in 30 days, and mortalities (in-hospital mortality, 30-day mortality, surgical mortality) were compared among various BMI groups after cardiac surgery. Age, sex, surgery type, family history of coronary artery disease, diabetes, hypertension, heart failure, and lipid-lowering medication were the risk factors for early outcomes. Multiple logistic regression analysis indicated that the underweight and class III obese BMI groups demonstrated significant, adverse differences in some short-term outcomes, including deep sternal infection, prolonged ventilation, new atrial fibrillation/flutter, and renal failure. However, being in the overweight or class I obese group demonstrated a positive effect on discharge and surgical mortality.

CONCLUSIONS

The results of this study demonstrated that extreme obesity and underweight were significantly associated with early major adverse clinical outcomes. However, there was an "obese paradox" in short-term mortality after cardiac surgery.