human
***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVES We sought to investigate the impact of body mass index ( BMI ) on short- and long-term outcomes after initial revascularization with percutaneous transluminal coronary angioplasty ( PTCA ) or coronary artery bypass graft surgery ( CABG ) .  BACKGROUND Equivocal results exist on the impact of BMI on the risk of in-hospital complications after PTCA or CABG , and no long-term mortality data exist from a large series of revascularized patients . METHODS From the r and omized series and observational registry of the Bypass Angioplasty Revascularization Investigation ( BARI ) , 2,108 patients who had PTCA and 1,526 patients who had CABG were evaluated by taking their BMI at study entry . They were classified as follows : low ( < 20 kg/m(2 ) ) , normal ( 20 to 24.9 kg/m(2 ) ) , overweight ( 25 to 29.9 kg/m(2 ) ) , class I obese ( 30 to 34.9 kg/m(2 ) ) and class II/III obese ( greater-than-or-equal 35 kg/m(2 ) ) . In-hospital complications and short- and long-term mortalities were compared between levels of BMI within each mode of initial revascularization . RESULTS Among patients who had PTCA , each unit increase in BMI was associated with a 5.5 % lower adjusted risk of a major in-hospital event ( death , myocardial infa rct ion , stroke , coma ) ; among patients who had CABG , no difference in the in-hospital outcome was observed according to BMI . In contrast , BMI was not associated with five-year mortality in the PTCA group ; among the CABG group , adjusted relative risks of five-year cardiac mortality according to levels of BMI were 0.0 ( low ) , 1.0 ( normal ) , 2.02 ( overweight ) , 3.16 ( class I obese ) and 4.85 ( class II/III obese ) ( linear p < 0.001 ) . CONCLUSIONS Body mass index appears to have a differential impact on short- and long-term outcomes after coronary revascularization . These results underscore the need for further research to identify factors responsible for the apparent short-term protective effect of a higher BMI in patients undergoing PTCA and to study the impact of weight reduction on the long-term survival of obese patients undergoing CABG Purpose Obesity influences risk stratification in cardiac surgery in everyday practice . However , some studies have reported better outcomes in patients with a high body mass index ( BMI ): this is known as the obesity paradox . The aim of this study was to quantify the effect of diverse degrees of high BMI on clinical outcomes after cardiac surgery , and to assess the existence of an obesity paradox in our patients . Methods A total of 2,499 consecutive patients requiring all types of cardiac surgery with cardiopulmonary bypass between January 2004 and February 2009 were prospect ively studied at our institution . Patients were divided into four groups based on BMI : normal weight ( 18.5–24.9 kg∙m−2 ; n = 523 ; 21.4 % ) , overweight ( 25–29.9kg∙m−2 ; n = 1150 ; 47 % ) , obese ( ≥30–≤34.9kg∙m−2 ; n = 624 ; 25.5 % ) and morbidly obese ( ≥35kg∙m−2 ; n = 152 ; 6.2 % ) . Follow-up was performed in 2,379 patients during the first year . Results After adjusting for confounding factors , patients with higher BMI presented worse oxygenation and better nutritional status , reflected by lower PaO2/FiO2 at 24h and higher albumin levels 48h after admission respectively . Obese patients showed a higher risk for Perioperative Myocardial Infa rct ion ( OR : 1.768 ; 95 % CI : 1.035–3.022 ; p = 0.037 ) and septicaemia ( OR : 1.489 ; 95 % CI : 1.282–1.997 ; p = 0.005 ) . In-hospital mortality was 4.8 % ( n = 118 ) and 1-year mortality was 10.1 % ( n = 252 ) . No differences were found regarding in-hospital mortality between BMI groups . The overweight group showed better 1-year survival than normal weight patients ( 91.2 % vs. 87.6 % ; Log Rank : p = 0.029 . HR : 1.496 ; 95 % CI : 1.062–2.108 ; p = 0.021 ) . Conclusions In our population , obesity increases Perioperative Myocardial Infa rct ion and septicaemia after cardiac surgery , but does not influence in-hospital mortality . Although we found better 1-year survival in overweight patients , our results do not support any protective effect of obesity in patients undergoing cardiac surgery 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 data base 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 r and omly 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 BACKGROUND In China , there have been few large prospect i ve studies of the associations of body mass index ( BMI ) with overall and cause-specific mortality that have simultaneously controlled for biases that can be caused by pre-existing disease and smoking . METHODS Prospect i ve cohort study of 224 064 men , of whom 40 700 died during follow-up between 1990 - 91 and 2006 . Analyses restricted to 142 214 men aged 40 - 79 years at baseline with no disease history and , to further reduce bias from pre-existing disease , at least 5 years of subsequent follow-up , leaving 17 800 deaths [ including 4165 stroke , 1297 coronary heart disease ( CHD ) , 3121 chronic obstructive pulmonary disease ( COPD ) ] . Adjusted hazard ratios ( HRs ) and 95 % confidence intervals ( 95 % CIs ) per 5 kg/m(2 ) calculated within either a lower ( 15 to < 23.5 kg/m(2 ) ) or higher ( 23.5 to < 35 kg/m(2 ) ) range . RESULTS The association between BMI and all-cause mortality was U-shaped with the lowest mortality at ∼22.5 - 25 kg/m(2 ) . In the lower range , 5 kg/m(2 ) higher BMI was associated with 14 % lower mortality ( HR 0.86 , 95 % CI 0.82 - 0.91 ) ; in the upper range , it was associated with 27 % higher mortality ( HR 1.27 , 95 % CI 1.15 - 1.40 ) . The absolute excess mortality in the lower range was largely accounted for by excess mortality from specific smoking-related diseases : 54 % by that for COPD , 12 % other respiratory disease , 13 % lung cancer , 11 % stomach cancer . The excess mortality in the upper BMI range was largely accounted for by excess mortality from specific vascular diseases : 55 % by that for stroke , 16 % CHD . In this range , 5 kg/m(2 ) higher BMI was associated with ∼50 % higher mortality from stroke ( HR 1.61 , 95 % CI 1.36 - 1.92 ) and CHD ( HR 1.48 , 95 % CI 1.12 - 1.95 ) . CONCLUSIONS For China , previous evidence may have overestimated the excess mortality at low BMI but underestimated that at high BMI . The main way obesity kills in China appears to be stroke BACKGROUND A debate exists whether obesity is a risk factor for operative mortality after  coronary artery bypass graft surgery ( CABG ) . The contradictory findings in the literature may largely be attributable to the variety of method ological approaches used to model the association between body mass index ( BMI ) and post-CABG outcomes . This study aims to investigate this association , and to uncover possible explanations for the lack of consensus across prior studies . METHODS Data were prospect ively collected on 80,792 patients who underwent a CABG procedure during a 14-year period at the 45 Department of Veterans Affairs cardiac surgery programs .  Generalized additive models were used to estimate the relationship of BMI and outcomes after a CABG procedure . RESULTS We found that the relationship of BMI with post-CABG mortality and morbidity is U-shaped with the minimum risk located around a BMI of 30 kg/m2 , indicating that patients classified as overweight have the lowest risk , and those in the lower end of the obese range do not have seriously elevated risk . This U-shape relationship is significantly nonlinear and robust to adjustment for other risk factors . CONCLUSIONS This study demonstrates that BMI is an independent predictor of mortality and morbidity after CABG surgery . Previous studies that model BMI linearly or as categories can not accurately capture this U-shaped relationship and are unlikely to find a significant contribution by including BMI . Further research is needed to determine the mechanisms of risk for patients with low and high BMI and whether interventions to modify BMI may improve patient outcomes OBJECTIVES To up date the European System for Cardiac Operative Risk Evaluation ( EuroSCORE ) risk model . METHODS A dedicated website collected prospect i ve risk and outcome data on 22,381 consecutive patients undergoing major cardiac surgery in 154 hospitals in 43 countries over a 12-week period ( May-July 2010 ) . Completeness and accuracy were vali date d during data collection using m and atory field entry , error and range checks and after data collection using summary feedback confirmation by responsible officers and multiple logic checks . Information was obtained on existing EuroSCORE risk factors and additional factors proven to influence risk from research conducted since the original model . The primary outcome was mortality at the base hospital . Secondary outcomes were mortality at 30 and 90 days . The data set was divided into a developmental subset for logistic regression modelling and a validation subset for model testing . A  logistic risk model ( EuroSCORE II ) was then constructed and tested . RESULTS Compared with the original 1995 EuroSCORE data base ( in brackets ) , the mean age was up at 64.7 ( 62.5 ) with 31 % females ( 28 % ) . More patients had New York Heart Association class IV , extracardiac arteriopathy , renal and pulmonary dysfunction .  Overall mortality was 3.9 % ( 4.6 % ) . When applied to the current data , the old risk models overpredicted mortality ( actual : 3.9 % ; additive predicted : 5.8 % ; logistic predicted : 7.57 % ) . EuroSCORE II was well calibrated on testing in the validation data subset of 5553 patients ( actual mortality : 4.18 % ; predicted : 3.95 % ) . Very good discrimination was maintained with an area under the receiver operating characteristic curve of 0.8095 . CONCLUSIONS Cardiac surgical mortality has significantly reduced in the last 15 years despite older and sicker patients . EuroSCORE II is better calibrated than the original model yet preserves powerful discrimination . It is proposed for the future assessment of cardiac surgical risk BACKGROUND Mediastinitis is a devastating complication of cardiac surgery . Previous studies have often observed small population s , been retrospective in design , and used a variety of definitions for mediastinitis . AIM To identify risk factors for mediastinitis , and strategies to minimize its incidence . METHODS A prospect i ve cohort study of 4883 adult patients who underwent cardiac surgery between October 2003 and February 2009 , comparing pre- and 
    Output:
    
agent
In the present series , overweight and obese patients had similar or slightly lower in-hospital mortality rates after cardiac surgery compared with normal-weight individuals .
Conversely , postoperative complication rates increased with higher BMI levels .
Most studies included in the review showed that overweight and obese patients had at least the same mortality rate as normal-weight patients , or even a lower death risk .
Pooled- data of the meta- analysis provided evidence on the association between higher BMI levels and a lower all-cause in-hospital mortality rate after cardiac surgery
***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVES We sought to investigate the impact of body mass index ( BMI ) on short- and long-term outcomes after initial revascularization with percutaneous transluminal coronary angioplasty ( PTCA ) or coronary artery bypass graft surgery ( CABG ) .  BACKGROUND Equivocal results exist on the impact of BMI on the risk of in-hospital complications after PTCA or CABG , and no long-term mortality data exist from a large series of revascularized patients . METHODS From the r and omized series and observational registry of the Bypass Angioplasty Revascularization Investigation ( BARI ) , 2,108 patients who had PTCA and 1,526 patients who had CABG were evaluated by taking their BMI at study entry . They were classified as follows : low ( < 20 kg/m(2 ) ) , normal ( 20 to 24.9 kg/m(2 ) ) , overweight ( 25 to 29.9 kg/m(2 ) ) , class I obese ( 30 to 34.9 kg/m(2 ) ) and class II/III obese ( greater-than-or-equal 35 kg/m(2 ) ) . In-hospital complications and short- and long-term mortalities were compared between levels of BMI within each mode of initial revascularization . RESULTS Among patients who had PTCA , each unit increase in BMI was associated with a 5.5 % lower adjusted risk of a major in-hospital event ( death , myocardial infa rct ion , stroke , coma ) ; among patients who had CABG , no difference in the in-hospital outcome was observed according to BMI . In contrast , BMI was not associated with five-year mortality in the PTCA group ; among the CABG group , adjusted relative risks of five-year cardiac mortality according to levels of BMI were 0.0 ( low ) , 1.0 ( normal ) , 2.02 ( overweight ) , 3.16 ( class I obese ) and 4.85 ( class II/III obese ) ( linear p < 0.001 ) . CONCLUSIONS Body mass index appears to have a differential impact on short- and long-term outcomes after coronary revascularization . These results underscore the need for further research to identify factors responsible for the apparent short-term protective effect of a higher BMI in patients undergoing PTCA and to study the impact of weight reduction on the long-term survival of obese patients undergoing CABG Purpose Obesity influences risk stratification in cardiac surgery in everyday practice . However , some studies have reported better outcomes in patients with a high body mass index ( BMI ): this is known as the obesity paradox . The aim of this study was to quantify the effect of diverse degrees of high BMI on clinical outcomes after cardiac surgery , and to assess the existence of an obesity paradox in our patients . Methods A total of 2,499 consecutive patients requiring all types of cardiac surgery with cardiopulmonary bypass between January 2004 and February 2009 were prospect ively studied at our institution . Patients were divided into four groups based on BMI : normal weight ( 18.5–24.9 kg∙m−2 ; n = 523 ; 21.4 % ) , overweight ( 25–29.9kg∙m−2 ; n = 1150 ; 47 % ) , obese ( ≥30–≤34.9kg∙m−2 ; n = 624 ; 25.5 % ) and morbidly obese ( ≥35kg∙m−2 ; n = 152 ; 6.2 % ) . Follow-up was performed in 2,379 patients during the first year . Results After adjusting for confounding factors , patients with higher BMI presented worse oxygenation and better nutritional status , reflected by lower PaO2/FiO2 at 24h and higher albumin levels 48h after admission respectively . Obese patients showed a higher risk for Perioperative Myocardial Infa rct ion ( OR : 1.768 ; 95 % CI : 1.035–3.022 ; p = 0.037 ) and septicaemia ( OR : 1.489 ; 95 % CI : 1.282–1.997 ; p = 0.005 ) . In-hospital mortality was 4.8 % ( n = 118 ) and 1-year mortality was 10.1 % ( n = 252 ) . No differences were found regarding in-hospital mortality between BMI groups . The overweight group showed better 1-year survival than normal weight patients ( 91.2 % vs. 87.6 % ; Log Rank : p = 0.029 . HR : 1.496 ; 95 % CI : 1.062–2.108 ; p = 0.021 ) . Conclusions In our population , obesity increases Perioperative Myocardial Infa rct ion and septicaemia after cardiac surgery , but does not influence in-hospital mortality . Although we found better 1-year survival in overweight patients , our results do not support any protective effect of obesity in patients undergoing cardiac surgery 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 data base 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 r and omly 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 BACKGROUND In China , there have been few large prospect i ve studies of the associations of body mass index ( BMI ) with overall and cause-specific mortality that have simultaneously controlled for biases that can be caused by pre-existing disease and smoking . METHODS Prospect i ve cohort study of 224 064 men , of whom 40 700 died during follow-up between 1990 - 91 and 2006 . Analyses restricted to 142 214 men aged 40 - 79 years at baseline with no disease history and , to further reduce bias from pre-existing disease , at least 5 years of subsequent follow-up , leaving 17 800 deaths [ including 4165 stroke , 1297 coronary heart disease ( CHD ) , 3121 chronic obstructive pulmonary disease ( COPD ) ] . Adjusted hazard ratios ( HRs ) and 95 % confidence intervals ( 95 % CIs ) per 5 kg/m(2 ) calculated within either a lower ( 15 to < 23.5 kg/m(2 ) ) or higher ( 23.5 to < 35 kg/m(2 ) ) range . RESULTS The association between BMI and all-cause mortality was U-shaped with the lowest mortality at ∼22.5 - 25 kg/m(2 ) . In the lower range , 5 kg/m(2 ) higher BMI was associated with 14 % lower mortality ( HR 0.86 , 95 % CI 0.82 - 0.91 ) ; in the upper range , it was associated with 27 % higher mortality ( HR 1.27 , 95 % CI 1.15 - 1.40 ) . The absolute excess mortality in the lower range was largely accounted for by excess mortality from specific smoking-related diseases : 54 % by that for COPD , 12 % other respiratory disease , 13 % lung cancer , 11 % stomach cancer . The excess mortality in the upper BMI range was largely accounted for by excess mortality from specific vascular diseases : 55 % by that for stroke , 16 % CHD . In this range , 5 kg/m(2 ) higher BMI was associated with ∼50 % higher mortality from stroke ( HR 1.61 , 95 % CI 1.36 - 1.92 ) and CHD ( HR 1.48 , 95 % CI 1.12 - 1.95 ) . CONCLUSIONS For China , previous evidence may have overestimated the excess mortality at low BMI but underestimated that at high BMI . The main way obesity kills in China appears to be stroke BACKGROUND A debate exists whether obesity is a risk factor for operative mortality after  coronary artery bypass graft surgery ( CABG ) . The contradictory findings in the literature may largely be attributable to the variety of method ological approaches used to model the association between body mass index ( BMI ) and post-CABG outcomes . This study aims to investigate this association , and to uncover possible explanations for the lack of consensus across prior studies . METHODS Data were prospect ively collected on 80,792 patients who underwent a CABG procedure during a 14-year period at the 45 Department of Veterans Affairs cardiac surgery programs .  Generalized additive models were used to estimate the relationship of BMI and outcomes after a CABG procedure . RESULTS We found that the relationship of BMI with post-CABG mortality and morbidity is U-shaped with the minimum risk located around a BMI of 30 kg/m2 , indicating that patients classified as overweight have the lowest risk , and those in the lower end of the obese range do not have seriously elevated risk . This U-shape relationship is significantly nonlinear and robust to adjustment for other risk factors . CONCLUSIONS This study demonstrates that BMI is an independent predictor of mortality and morbidity after CABG surgery . Previous studies that model BMI linearly or as categories can not accurately capture this U-shaped relationship and are unlikely to find a significant contribution by including BMI . Further research is needed to determine the mechanisms of risk for patients with low and high BMI and whether interventions to modify BMI may improve patient outcomes OBJECTIVES To up date the European System for Cardiac Operative Risk Evaluation ( EuroSCORE ) risk model . METHODS A dedicated website collected prospect i ve risk and outcome data on 22,381 consecutive patients undergoing major cardiac surgery in 154 hospitals in 43 countries over a 12-week period ( May-July 2010 ) . Completeness and accuracy were vali date d during data collection using m and atory field entry , error and range checks and after data collection using summary feedback confirmation by responsible officers and multiple logic checks . Information was obtained on existing EuroSCORE risk factors and additional factors proven to influence risk from research conducted since the original model . The primary outcome was mortality at the base hospital . Secondary outcomes were mortality at 30 and 90 days . The data set was divided into a developmental subset for logistic regression modelling and a validation subset for model testing . A  logistic risk model ( EuroSCORE II ) was then constructed and tested . RESULTS Compared with the original 1995 EuroSCORE data base ( in brackets ) , the mean age was up at 64.7 ( 62.5 ) with 31 % females ( 28 % ) . More patients had New York Heart Association class IV , extracardiac arteriopathy , renal and pulmonary dysfunction .  Overall mortality was 3.9 % ( 4.6 % ) . When applied to the current data , the old risk models overpredicted mortality ( actual : 3.9 % ; additive predicted : 5.8 % ; logistic predicted : 7.57 % ) . EuroSCORE II was well calibrated on testing in the validation data subset of 5553 patients ( actual mortality : 4.18 % ; predicted : 3.95 % ) . Very good discrimination was maintained with an area under the receiver operating characteristic curve of 0.8095 . CONCLUSIONS Cardiac surgical mortality has significantly reduced in the last 15 years despite older and sicker patients . EuroSCORE II is better calibrated than the original model yet preserves powerful discrimination . It is proposed for the future assessment of cardiac surgical risk BACKGROUND Mediastinitis is a devastating complication of cardiac surgery . Previous studies have often observed small population s , been retrospective in design , and used a variety of definitions for mediastinitis . AIM To identify risk factors for mediastinitis , and strategies to minimize its incidence . METHODS A prospect i ve cohort study of 4883 adult patients who underwent cardiac surgery between October 2003 and February 2009 , comparing pre- and 
    Output:
    