Do patients in congestive cardiac failure undergoing cardiac surgery demonstrate worse outcomes compared with those with a history of cardiac failure?

OBJECTIVES: Cardiac surgery in patients with symptoms of congestive cardiac failure (CCF) carries a significant risk of mortality and morbidity. Except for emergencies and in unstable cases, the recommendation has been to delay the operation until the patient is fully recovered. The objective of this study was to determine the consequences of cardiac surgery in patients with acute decompensated heart failure and to compare their outcomes with the results of the operation in patients with previous CCF. METHODS: We compared the outcomes of patients with CCF (n = 707) at the time of cardiac surgery (valve replacement or coronary artery bypass grafting [CABG]) with those with a history of CCF (n = 1583). The EuroSCORE was significantly higher in CCF patients (P < .001). Impaired renal function was also more commonly observed in patients with CCF (P < .001). After adjusting for preoperative characteristics, we compared the 2 groups with respect to postoperative complications, postoperative creatine kinase MB values, and in-hospital mortality. RESULTS: Before adjusting for preoperative characteristics, we found that in-hospital mortality (15.5%) and postoperative complications, such as arrhythmias (31%), renal failure (19%), stroke (4.7%), and myocardial infarction (MI) (3%), were significantly higher in the CCF group than in those with a previous history of CCF. When the patients were matched for preoperative characteristics, the rates of postoperative MI and arrhythmia were the main complications that were significantly higher in the CCF group, compared with the patients with previous CCF. The 2 groups were not significantly different with respect to in-hospital mortality. The results were not affected by the type of procedure (valve or CABG), and the main factor influencing mortality was the EuroSCORE. CONCLUSION: Despite the significant risk of mortality and morbidity in patients with current CCF, cardiac surgery to reverse the cause should not be delayed in these patients, because doing so may lead to further deterioration. Other risk factors, however, should be taken into consideration on an individual basis.

A multi-centre additive and logistic risk model for in-hospital mortality following aortic valve replacement.

OBJECTIVE: To develop a multivariate prediction model for in-hospital mortality following aortic valve replacement. METHODS: Retrospective analysis of prospectively collected data on 4550 consecutive patients undergoing aortic valve replacement between 1 April 1997 and 31 March 2004 at four hospitals. A multivariate logistic regression analysis was undertaken, using the forward stepwise technique, to identify independent risk factors for in-hospital mortality. The area under the receiver operating characteristic (ROC) curve was calculated to assess the performance of the model. The statistical model was internally validated using the technique of bootstrap resampling, which involved creating 100 random samples, with replacement, of 70% of the entire dataset. The model was also validated on 816 consecutive patients undergoing aortic valve replacement between 1 April 2004 and 31 March 2005 from the same four hospitals. RESULTS: Two hundred and seven (4.6%) in-hospital deaths occurred. Independent variables identified with in-hospital mortality are shown with relevant co-efficient values and p-values as follows: (1) age 70-75 years: 0.7046, p<0.001; (2) age 75-85 years: 1.1714, p<0.001; (3) age>85 years: 2.0339, p<0.001; (4) renal dysfunction: 1.2307, p<0.001; (5) New York Heart Association class IV: 0.5782, p=0.003; (6) hypertension: 0.4203, p=0.006; (7) atrial fibrillation: 0.604, p=0.002; (8) ejection fraction<30%: 0.571, p=0.012; (9) previous cardiac surgery: 0.9193, p<0.001; (10) non-elective surgery: 0.5735, p<0.001; (11) cardiogenic shock: 1.1291, p=0.009; (12) concomitant CABG: 0.6436, p<0.001. Intercept: -4.8092. A simplified additive scoring system was also developed. The ROC curve was 0.78, indicating a good discrimination power. Bootstrapping demonstrated that estimates were stable with an average ROC curve of 0.76, with a standard deviation of 0.025. Validation on 2004-2005 data revealed a ROC curve of 0.78 and an expected mortality of 4.7% compared to the observed rate of 4.1%. CONCLUSIONS: We developed a contemporaneous multivariate prediction model for in-hospital mortality following aortic valve replacement. This tool can be used in day-to-day practice to calculate patient-specific risk by the logistic equation or a simple scoring system with an equivalent predicted risk.

Intestinal ischaemia following cardiac surgery: a multivariate risk model.

OBJECTIVE: Intestinal ischaemia following cardiac surgery is a serious complication, which carries a high mortality rate. Several studies have examined pre-operative and intra-operative risk factors. We aimed to develop a multivariate risk model to identify those patients at highest risk of intestinal ischaemia. METHODS: Data was prospectively collected for 10,976 consecutive cardiac surgery patients from our institution between April 1997 and March 2004. Fifty (0.5%) patients developed post-operative intestinal ischaemia. A forward stepwise multivariate logistic regression analysis was undertaken to identify predictors of developing intestinal ischaemia. Intra-operative and post-operative variables were censored at the time of onset of intestinal ischaemia. RESULTS: The predictors of post-operative intestinal ischaemia were: post-op inotrope and dialysis support (OR 6.7; p < 0.001), post-op ventilation >48 h (OR 5.1; p < 0.001), age at operation (OR 1.06 [for each additional year]; p < 0.001), post-op atrial fibrillation (OR 2.3; p = 0.014) and blood loss in intensive care unit (ICU) >700 ml (OR 2.0; p = 0.037). The predictive ability of this model was very good with an area under the receiver operating characteristic curve of 0.93. In-hospital mortality for the patients who developed intestinal ischaemia was 94% (47/50) compared to 3.6% (390/10,926) for the other patients (p < 0.001). CONCLUSIONS: Although the incidence of intestinal ischaemia following cardiac surgery is low, the prognosis for these patients is very poor. We have identified several risk factors, and developed a multivariate prediction tool, which may be useful in identifying patients at high-risk of developing intestinal ischaemia.

Impact of avoiding cardiopulmonary bypass for coronary surgery on perioperative cardiac enzyme release and survival.

OBJECTIVE: This study examines the association between avoiding the use of cardiopulmonary bypass (CPB) for coronary surgery and postoperative cardiac enzyme (CE) release, and its subsequent impact on survival. METHODS: Between January 1999 and September 2002, 3734 consecutive patients underwent either off-pump or on-pump coronary surgery. Patient characteristics and postoperative cardiac enzyme release were collected prospectively. Logistic regression was used to assess the effect of off-pump coronary surgery on cardiac enzyme release. All analyses were adjusted for preoperative characteristics and number of grafts. All patients were followed up at 1 year to assess survival. RESULTS: Nine hundred and sixty (25.7%) patients had off-pump coronary surgery. Seven hundred and twenty-six (19.4%) patients had cardiac enzyme release three to six times the upper limit of the reference range, while 266 (7.1%) patients had cardiac enzyme release more than six times the upper limit of the reference range. After adjusting for patient characteristics, off-pump surgery was associated with less release (cardiac enzyme release three to six times, adjusted odds ratio 0.43, p<0.001; cardiac enzyme release more than six times, adjusted odds ratio 0.59, p=0.005). Risk adjusted survival at 1 year was 97.5% for the on-pump group and 97.0% for the off-pump group (p=0.33). CONCLUSIONS: Avoiding cardiopulmonary bypass significantly reduces early cardiac enzyme release following coronary artery bypass grafting (CABG). However, it does not result in improved survival compared to coronary surgery using cardiopulmonary bypass. This absence of survival benefit may be due to higher mortality rates experienced by the fewer patients with high (>6 times the upper limit of range) cardiac enzyme release following coronary artery bypass surgery without cardiopulmonary bypass.

Effect of risk-adjusted, non-dialysis-dependent renal dysfunction on mortality and morbidity following coronary artery bypass surgery: a multi-centre study.

OBJECTIVE: As little is known about the impact of non-dialysis-dependent renal dysfunction on short- and mid-term outcomes following coronary surgery we have conducted a large multi-centre study comparing patients with no history of renal dysfunction to those with preoperative renal dysfunction. METHODS: Data was prospectively collected on 19,625 consecutive patients undergoing isolated coronary surgery between 1997 and 2003 from four institutions. Sixty-seven patients had a history of dialysis support prior to coronary surgery, and were excluded from the main analysis of the study. The remaining 19,558 patients were divided into two groups based on preoperative serum creatinine level, patients with preoperative renal dysfunction with serum creatinine levels >200 micromol/L without dialysis support and control patients with preoperative serum creatinine levels <200 micromol/L. Case-mix was accounted for by developing a propensity score, which was the probability of belonging to the non-dialysis-dependent renal dysfunction group, and included in the multivariable analyses. RESULTS: There were 19,172 patients with preoperative serum creatinine levels <200 micromol/L and 386 patients with serum creatinine levels >200 micromol/L without dialysis support. The propensity score included sex, body mass index, co-morbidity factors (respiratory disease, diabetes, cerebrovascular disease, hypertension, and hypercholesterolemia), ejection fraction, left main stem stenosis, emergency status, prior cardiac surgery, off-pump surgery, and the logistic EuroSCORE. After adjusting for the propensity score, patients with preoperative non-dialysis-dependent renal dysfunction had significantly higher in-hospital mortality (adjusted odds ratio 3.0, p < 0.001), stroke (adjusted odds ratio 2.0, p = 0.033), atrial arrhythmia (adjusted odds ratio 1.5, p = 0.003), prolonged ventilation (adjusted odds ratio 2.1, p < 0.001), and post-op stay > 6 days (adjusted odds ratio 2.6, p < 0.001). One thousand one hundred and eighty-three (6.1%) deaths occurred during 58,062 patient-years follow-up. After adjusting for the propensity score, the adjusted hazard ratio of mid-term mortality for non-dialysis-dependent renal dysfunction was 2.7 (p < 0.001). CONCLUSIONS: Patients undergoing coronary surgery with non-dialysis-dependent renal dysfunction have significantly increased perioperative morbidity and mortality. Mid-term survival is also significantly reduced at 5-years.

Does off-pump surgery offer benefit in high respiratory risk patients? A respiratory risk stratified analysis in a propensity-matched cohort.

OBJECTIVE: The role of off-pump surgery in high respiratory risk patients remains unclear. In this study, we aim to evaluate the effect of off-pump surgery on high respiratory risk patients. METHODS: To achieve comparative groups, a five digit propensity score matching with 18 pre-operative variables was performed on 4406 consecutive CABG patients operated between January 2000 and September 2003. Respiratory risk stratification was performed with the following variables: (1) FEV(1)<65% of predicted, (2) patients>75 years old, (3) history of current smoking, (4) body mass index more than 40 kg/m(2) and (5) NYHA class IV dyspnoea in combination with current respiratory medication. The presence of two or more variables defined high risk. The primary end point was post-operative ventilation time. We also compared alveolar arterial gradients (A-a gradient) on admission to ITU, 2 and 4h using Friedman rank time analysis. RESULTS: We matched 1353 off-pump patients with 1353 unique on-pump patients. Respiratory risk stratified selection resulted in 73 off-pump and 55 on-pump high-risk patients. In the off-pump group, four (5.5%) patients had more than two selection criteria, compared to one (1.8%) for on-pump patients (p=0.29). The off-pump group had more patients with FEV1<65% compared to on-pump: 65 (89.0%) versus 40 (72.7%); p=0.017. The median ventilation time was significantly shorter for off-pump patients (7h [IQR: 5-14] vs 12h [IQR: 7-18], p=0.003). In the off-pump group, three (4.1%) patients had a ventilation time>48 h compared to eight (14.6%) in the on-pump group, p=0.037. A-a gradient measurements on admission to ITU were lower in off-pump patients (median: 182.3 [IQR: 126.6-216.2]) compared to on-pump patients (median: 194.7 [IQR 139.7-245.4], p=0.064). CONCLUSION: Off-pump surgery offers benefit to high respiratory risk patients by reducing post-operative ventilation time. Off-pump patients also have lower A-a gradients in the early post-operative period but this failed to reach significance.

Total arterial revascularisation: effect of avoiding cardiopulmonary bypass on in-hospital mortality and morbidity in a propensity-matched cohort.

OBJECTIVE: The combination of total arterial revascularisation and avoidance of cardiopulmonary bypass may provide additional benefits to patients receiving complete arterial grafting with cardiopulmonary bypass. We performed a propensity-matched cohort study of complete arterial off-pump and on-pump coronary surgery and examined differences in in-hospital mortality and morbidity. METHODS: Three hundred and sixty patients who underwent off-pump coronary surgery with complete arterial grafting between April 1997 and September 2002 were matched to 360 patients who received coronary surgery with cardiopulmonary bypass and complete arterial grafting. To match off-pump with unique on-pump patients, logistic regression was used to develop a propensity score for off-pump surgery. The C statistic for this model was 0.79. Off-pump patients were matched to unique on-pump patients with an identical 5-digit propensity score. If this could not be done, we then proceeded to a 4-, 3-, 2-, or 1-digit match. RESULTS: Patient characteristics were well matched. There was no difference in in-hospital mortality between the groups. Off-pump patients were less likely to develop sternal wound infections compared to the on-pump group (2.5 versus 5.8%; P=0.03), and had significantly lower blood loss (675 versus 780 ml; P<0.001), red blood cell unit transfusion (8.6 versus 38.9%; P<0.001), enzyme rises (13 versus 23 U/l; P<0.001), inotrope support (11.9 versus 28.9%; P<0.001), and ventilation times (5 versus 8 h; P<0.001). Intensive care unit and hospital stay were also significantly lower in the off-pump patients. CONCLUSIONS: Off-pump coronary surgery with complete arterial revascularisation can significantly reduce in-hospital morbidity and lengths of stay compared to conventional on-pump coronary surgery.

Timing of intra-aortic balloon pump support and 1-year survival.

OBJECTIVE: The relationship between the timing of intra-aortic balloon pump (IABP) support and surgical outcome remains a subject of debate. Peri-operative mechanical circulatory support is commenced either prophylactically or after increasing inotropic support has proved inadequate. This study evaluates the effect timing of IABP support on the 1-year survival of patients undergoing cardiac surgery. METHODS: From April 1997 to September 2002, 7698 consecutive cardiac surgical procedures were performed. This included 5678 isolated coronary artery bypasses (CABGs), 1245 isolated valve procedures and 775 simultaneous CABG and valve procedures. IABP support was required in 237 patients (3.1%). Twenty-seven patients (0.35%) were classed as high-risk and received preoperative IABP support, 25 patients (0.32%) were haemodynamically compromised and required preoperative IABP support, 120 patients (1.56%) required intra-operative IABP support, and 65 patients (0.84%) required post-operative IABP support. Multiple variables were offered to a Cox proportional hazards model and significant predictors of 1-year survival were identified. These were used to risk adjust Kaplan-Meier survival curves. RESULTS: 1-year follow-up was complete and 450 deaths (5.8%) were recorded. The significant independent predictors of increased mortality at 1-year (P<0.05, HR=hazard ratio) were post-operative renal failure (HR=3.5), increasing EuroSCORE (HR=1.2), post-operative myocardial infarction (HR=3.7), post-operative IABP (HR=4.1) intra-operative IABP (HR=2.8), post-operative stroke (HR=2.5), increasing number of valves (HR=1.6), ejection fraction <30% (HR=1.3) and triple-vessel disease (HR=1.3). After risk-adjustment, 1-year survival for patients who required intra-operative IABP support was significantly greater than for those patients who required IABP support in the post-operative period. CONCLUSIONS: Patients who warrant IABP support in the post-operative setting have a significantly increased mortality at 1-year when compared to any other group. Therefore, earlier IABP support as part of surgical strategy may help to improve the outcome.

Effect of peri-operative red blood cell transfusion on 30-day and 1-year mortality following coronary artery bypass surgery.

OBJECTIVE: The purpose of this study was to examine the effect of peri-operative red blood cell (RBC) transfusion on 30-day and 1-year mortality following coronary artery bypass grafting (CABG). METHODS: We retrospectively analysed 3024 consecutive patients who underwent isolated CABG between January 1999 and December 2001. Patient records were linked to the National Strategic Tracing Service, which records all mortality in the UK. Thirty-day and 1-year mortality were derived from Kaplan-Meier curves. Confounding variables were controlled for by constructing a propensity score for the probability of receiving a transfusion from core patient characteristics including the lowest recorded laboratory haemoglobin (LL Hb) from a clinical chemistry database (C statistic 0.81). The propensity score and the comparison variable (transfusion versus no transfusion) were included in a Cox proportional hazards analysis, allowing calculation of adjusted hazard ratios (HR) and Kaplan-Meier survival curves. RESULTS: Nine hundred and forty (31.1%) patients received RBC transfusion during or within 72h of surgery. Predictors of the need for transfusion were LL Hb and lower body mass index, use of cardiopulmonary bypass, female sex, number of grafts, renal dysfunction, increased age, extent of disease, and prior CABG; these factors were all included in the propensity score. After 1-year of follow-up, 122 (4.03%) deaths occurred. The crude HR for 1-year mortality in patients transfused was 3.0 (P<0.001). After adjusting for the propensity score, re-operation for bleeding, peri-operative blood loss and post-operative complications, the adjusted 30-day mortality was 1.9% in transfused patients compared to 1.1% in patients not transfused (P<0.05). The adjusted HR for 1-year mortality in patients transfused was 1.88 (P<0.01). CONCLUSIONS: Peri-operative RBC transfusion after CABG is associated with an increased risk of mortality during a 1-year follow-up period, with a large proportion of deaths occurring within 30-days.

Effect of preoperative aspirin use in off-pump coronary artery bypass operations.

BACKGROUND: The effect of preoperative aspirin use until the day of operation on mortality rate and bleeding risks in patients who had on-pump coronary artery bypass operation has been well documented. However, the effect of aspirin use in patients undergoing off-pump coronary artery bypass operation (OPCAB) with regard to postoperative blood loss and morbidity has not been studied. We aimed to determine the effects of continuing aspirin therapy preoperatively. METHODS: We performed a retrospective study of 340 patients who had first-time OPCAB between January 1998 and September 2001. A propensity score for receiving aspirin until the day of operation was constructed from core patient characteristics. All aspirin users (n = 170) were matched with unique 170 nonaspirin users by identical propensity score. The primary outcome measures were in-hospital mortality rate and hemorrhage-related outcomes (postoperative blood loss in the intensive care unit, reexploration for bleeding, and blood product requirements). Secondary outcome measures were stroke, myocardial infarction, gastrointestinal bleeding, and sternal wound infections. RESULTS: There were no differences in patient characteristics between aspirin users and nonaspirin users. The average postoperative blood loss (845 mL versus 775 mL; p = 0.157) and the rate of reexploration for bleeding (3.5% versus 3.5%; p > 0.99) were similar in aspirin users and nonaspirin users. We found no significant difference between blood product requirements for the two groups. Similarly, we found no significant difference in the incidence of the secondary outcomes. CONCLUSIONS: Preoperative aspirin did not increase bleeding-related complications, mortality rate, or other morbidities in patients who had off-pump coronary artery operation.

Coronary surgery in patients with peripheral vascular disease: effect of avoiding cardiopulmonary bypass.

BACKGROUND: An increasing number of patients with peripheral vascular disease are undergoing coronary artery bypass grafting. Such patients have an increased risk of adverse outcomes. Our aim was to quantify the effect of avoiding cardiopulmonary bypass in this group of patients. METHODS: Between April 1997 and March 2002, 3,771 consecutive patients underwent coronary artery bypass grafting performed by five surgeons. Four hundred and twenty-two (11.2%) had peripheral vascular disease and of these, 211 (50%) received off-pump surgery. We used multivariate logistic regression analysis to assess the effect of off-pump surgery on in-hospital mortality and morbidity, while adjusting for treatment selection bias. Treatment selection bias was controlled for by constructing a propensity score, which was the probability of receiving off-pump surgery and included core patient characteristics. The C statistic for this model was 0.8. RESULTS: Off-pump patients were more likely to have preoperative renal dysfunction, previous gastrointestinal surgery, and less extensive disease. The left internal mammary artery was used more in off-pump compared to on-pump cases (90.1% vs 82.9%; p = 0.033). In the univariate analyses, off-pump patients were less likely to have a postoperative stroke (p = 0.007), and had shorter postoperative hospital stays (p < 0.001). However, the incidence of new atrial arrhythmia was higher (p = 0.028). After adjustment for differences in case-mix (propensity score), avoidance of cardiopulmonary bypass was still associated with a significant reduction in postoperative stroke (adjusted odds ratio 0.09 [95% confidence interval 0.02 to 0.50]; p = 0.005), and shorter postoperative hospital stay (p = 0.001). CONCLUSIONS: Off-pump coronary surgery is safe in patients with peripheral vascular disease, with acceptable results. The incidence of postoperative stroke is substantially reduced when avoiding cardiopulmonary bypass in patients with peripheral vascular disease.

Neurological outcomes in coronary surgery: independent effect of avoiding cardiopulmonary bypass.

BACKGROUND: Recent studies examining neuroprotective effects of off-pump coronary artery bypass grafting (CABG) have shown inconsistent results. We examined our database to quantify the independent effects of avoidance of cardiopulmonary bypass (CPB) and aortic manipulation on neurologic outcomes after CABG. METHODS: A total of 2,327 consecutive cases undergoing isolated CABG between April 1997 and May 2001 were identified at our two institutions. Patients were divided into three groups: on CPB, off-pump with aortic manipulation, and off-pump without aortic manipulation. To control for the confounding effects of other risk factors, we performed a multivariate logistic regression analysis. Potential covariates considered in the logistic model included age, sex, redo operations, diabetes, chronic obstructive pulmonary disease, neurologic disease, peripheral vascular disease, ejection fraction, and priority of operation. RESULTS: A total of 1,210 cases were performed on CPB, compared with 520 off-pump with aortic manipulation, and 597 off-pump without aortic manipulation. The incidence of focal neurologic deficit was 1.6% (n = 19) in the on-pump group, 0.4% (n = 2) in the off-pump with aortic manipulation group, and 0.5% (n = 3) for the off-pump without aortic manipulation group (p for trend = 0.027). The results of the multivariate logistic regression analysis demonstrated that use of CPB was a risk factor for focal neurologic deficit, with an odds ratio of 3.82 (95% confidence interval, 1.41 to 10.34; p = 0.005). Aortic manipulation did not significantly influence neurologic outcome in off-pump patients. CONCLUSIONS: Off-pump operation, with or without aortic manipulation, reduces adverse neurologic outcomes compared with on-pump procedures.

'Shunt shuffle'-a simple technique of introducing intracoronary shunts for off-pump coronary artery bypass.

Intracoronary shunting is a useful method for maintaining distal perfusion as well as providing a bloodless field during off-pump coronary revascularization. Intracoronary shunts require insertion of both ends through a limited arteriotomy, which sometimes can be troublesome. We describe the 'shunt shuffle' as a simple technique, which allows rapid, atraumatic and easy insertion of intracoronary shunts.

The effect of obesity on mid-term survival following coronary artery bypass surgery.

OBJECTIVE: Several studies have shown no significantly increased risk of in-hospital mortality for obese patients after coronary artery bypass grafting (CABG). However, the effect of obesity on mid-term survival has not been adequately studied. We set out to examine whether mid-term survival following CABG is affected by obesity. METHODS: We performed a retrospective study of 4713 consecutive patients undergoing isolated CABG between April 1997 and September 2001. Body mass index (BMI) was used as the measure of obesity, with 3429 patients categorised as non-obese (BMI<30 kg/m(2)), and 1284 patients as obese (BMI> or = 30 kg/m(2)). Patient records were linked to the National Strategic Tracing Service, which records all deaths in the community, to establish current vital status. Deaths occurring over time were described using Kaplan-Meier techniques. To control for differences in patient characteristics, we used Cox proportional hazards analysis to calculate adjusted hazard ratios (HR) and 95% confidence intervals (CI). RESULTS: Three hundred and thirty (7.0%) deaths occurred during the study period, with a mean follow-up of 2.4+/-1.4 years. The crude HR of mid-term mortality for obese patients was 1.09 (95% CI 0.86-1.39; P=0.457). After adjustment for core pre-operative factors, the adjusted HR of mid-term mortality for obese patients was 1.28 (95% CI 1.01-1.64; P=0.048). The adjusted freedom from death in the obese patients at 30 days, 1, 2, 3, and 4 years was 97.9, 95.9, 94.2, 92.4 and 90.5%, respectively, compared with 98.4, 96.8, 95.5, 94.0 and 92.5% for the non-obese patients. CONCLUSIONS: Although in-hospital mortality after CABG does not seem to be adversely affected by obesity there appears to be a significant increase in mortality in obese patients during a 4-year follow-up period.

Risk factors for sternal wound infection and mid-term survival following coronary artery bypass surgery.

OBJECTIVE: To identify risk factors for sternal wound infection following coronary artery bypass surgery (CABG), and to compare early and mid-term survival outcome. METHODS: Data were prospectively collected for 4228 patients who underwent CABG surgery between April 1997 and March 2001. One hundred and nine (2.6%) patients developed sternal wound infection. We used logistic regression to identify independent risk factors associated with post-operative sternal wound infection. Patient records were linked to the National Strategic Tracing Service, which records all deaths in the UK, to establish current vital status. Deaths occurring over time were described using Kaplan-Meier techniques. To control for differences in patient characteristics, we used Cox proportional hazards analysis to calculate adjusted hazard ratios (HR) and 95% confidence intervals (CI). RESULTS: The results of the logistic regression analysis found that the independent predictors of sternal wound infection were obesity (odds ratio (OR) 2.0; P<0.001), New York Heart Association class >/=3 (OR 1.6; P=0.022), use of bilateral internal mammary arteries (OR 3.2; P<0.001), increasing number of grafts (OR 1.5; P<0.001), re-exploration for bleeding (OR 3.1; P=0.011), and increased duration of mechanical ventilation (for every 10 h (OR 1.12; P<0.001)). Three hundred and forty one (8.1%) deaths occurred during the study period with mean follow up of 3.2+/-1.3 years. The crude HR of mid-term mortality for sternal wound infection patients was 2.51 (95% CI 1.59-3.94, P<0.001). After adjustment for pre, intra and post-operative factors, the adjusted HR of mid-term mortality for sternal wound infection patients was 1.64 (95% CI 1.03-2.61, P=0.037). The adjusted freedom from death for sternal wound infections at 30 days, and 1, 2 and 4 years was 96.8, 93.7, 91.4 and 86.7%, respectively, compared with 98.1, 96.1, 94.7 and 91.7% for patients without sternal wound infections. CONCLUSIONS: In conclusion, we have identified risk factors for sternal wound infection, many of which are modifiable. We have also shown that there is a significant increase in mortality in patients with sternal wound infection during a 4-year follow-up period after CABG.

Risk of morbidity and in-hospital mortality in obese patients undergoing coronary artery bypass surgery.

OBJECTIVES: Obesity is often perceived to be a risk factor for adverse outcomes following coronary artery bypass graft (CABG) surgery. Several studies have been unclear about the relationship between obesity and the risk of adverse outcomes. The aim of this study was to examine the relationship between obesity and in-hospital outcomes following CABG, while adjusting for confounding factors. METHODS: A total of 4713 consecutive patients undergoing isolated CABG between April 1997 and September 2001 were retrospectively analyzed. Body mass index (BMI) was used as the measure of obesity and was grouped as non-obese (BMI <30), obese (BMI 30-35), and severely obese (BMI > or =35). Associations between obesity and in-hospital outcomes were assessed by use of logistic regression to adjust for differences in patient characteristics. RESULTS: A total of 3429 patients were defined as non-obese, compared to 1041 obese and 243 severely obese. There was no association between obesity and in-hospital mortality, stroke, myocardial infarction, re-exploration for bleeding and renal failure. Obesity was significantly associated with atrial arrhythmia (adjusted odds ratio (OR) 1.19, P = 0.037 for the obese; adjusted OR 1.52, P = 0.008 for the severely obese) and sternal wound infections (adjusted OR 1.82, P = 0.002 for the obese; adjusted OR 2.10, P = 0.038 for the severely obese). The severely obese patients were 4.17 (P < 0.001) times more likely to develop harvest site infections. Severely obese patients were also more likely to have prolonged mechanical ventilation and post-operative stays, compared to non-obese patients. CONCLUSIONS: Obese patients are not associated with an increased risk of in-hospital mortality following coronary artery bypass surgery. In contrast, there is a significant increased risk of morbidities and post-operative length of stay in obese patients compared to non-obese patients.

Limitations of additive EuroSCORE for measuring risk stratified mortality in combined coronary and valve surgery.

OBJECTIVE: To study the use of the additive and logistic European System for Cardiac Operative Risk Evaluation (EuroSCORE) to predict mortality following adult combined coronary artery bypass grafting (CABG) and valve surgery. METHODS: Data were collected prospectively, from all four centres providing adult cardiac surgery in the north west of England, on 1769 consecutive patients undergoing combined CABG and valve surgery between April 1997 and March 2002. Observed in-hospital mortality was compared to predicted mortality as determined by both additive and logistic EuroSCORE. RESULTS: Observed mortality for simultaneous CABG and valve surgery was 8.7%, compared to 6.7% (additive) and 9.4% (logistic). Sixty-five percent of patients were classified as high-risk (additive EuroSCORE >5); the observed mortality was 11.5%, compared to 8.1% (additive) and 12.8% (logistic). Discrimination was similar in both systems as measured by the C statistic (additive 0.73, logistic 0.73). CONCLUSIONS: The logistic EuroSCORE is more accurate at predicting mortality in simultaneous CABG and valve surgery, as the additive EuroSCORE significantly under-predicts in this high-risk group.

Effect of avoiding cardiopulmonary bypass in non-elective coronary artery bypass surgery: a propensity score analysis.

OBJECTIVE: Non-elective coronary artery surgery (emergent/salvage or urgent) carries an increased risk in most risk-stratification models. Off-pump coronary surgery is increasingly used in non-elective cases. We aimed to investigate the effect of avoiding cardiopulmonary bypass on outcomes following non-elective coronary surgery. METHODS: Of the 3771 consecutive coronary artery bypass procedures performed by five surgeons between April 1997 and March 2002, 828 (22%) were non-elective and 417 (50.4%) of these patients had off-pump surgery. Multivariate logistic regression was used to assess the effect of off-pump on in-hospital outcomes, while adjusting for treatment selection bias. Treatment selection bias was controlled for by constructing a propensity score from core patient characteristics, which was the probability of avoiding cardiopulmonary bypass. The C statistic for this model was 0.8. RESULTS: Off-pump patients were more likely to be hypertensive, stable, had less extensive disease and better left ventricular function. The left internal mammary artery was used in 91.8% (n=383) of off-pump patients compared to 79.3% (n=326) of on-pump cases (P<0.001). After adjusting for the propensity score, no difference in in-hospital mortality was observed between off-pump and on-pump (adjusted odds ratio (OR) 0.83 (95% confidence intervals (CI) 0.36-1.93); P=0.667). Off-pump patients were less likely to require intra-aortic balloon pump support (adjusted OR 0.44 (95% CI 0.21-0.96); P=0.039), less likely to have renal failure (adjusted OR 0.44 (95% CI 0.22-0.90); P=0.025), and have shorter lengths of stay (adjusted OR 0.51 (95% CI 0.37-0.70); P<0.001). Other morbidity outcomes were similar in both groups. CONCLUSIONS: In this experience, off-pump coronary surgery in non-elective patients is safe with acceptable results. Non-elective off-pump patients have a significantly reduced incidence of renal failure, and shorter post-operative stays compared to on-pump coronary artery bypass surgery.

Off-pump coronary artery bypass surgery does not reduce gastrointestinal complications.

OBJECTIVES: Gastrointestinal (GI) complications following on-pump coronary artery bypass grafting (CABG) are rare, but carry a high mortality rate. Prolonged cardiopulmonary bypass (CPB) has been associated with a higher incidence of such complications. Little is known about the effect of avoiding CPB on GI complications. Our hypothesis was that off-pump CABG might reduce such complications. METHODS: A total of 2327 consecutive cases undergoing isolated CABG between April 1997 and May 2001 were identified from four consultants' practice at the two cardiothoracic centres involved in this study. We performed a multivariable logistic regression analysis to identify the risk factors for development of post-operative GI complications. Potential risk factors considered in the logistic model were age, sex, angina, ejection fraction, peripheral vascular disease, renal dysfunction, redo operations, previous GI complications, priority of surgery and the use of CPB. RESULTS: A total of 1210 cases were performed on CPB, compared to 1117 off-pump. The incidence of GI complications was 1.2% (n = 14) in the on-pump group and 1.6% (n = 18) in the off-pump group (P = 0.347). The incidence of in-hospital mortality, in the patients who had a GI complication, was 28.6% (n = 4) and 22.2% (n = 4), respectively (P = 0.681). The results of the logistic regression analysis showed that renal dysfunction, advancing age and previous history of GI surgery are significant risk factors for GI complications after coronary bypass surgery whether CPB is used or not. CONCLUSIONS: Our study suggests that off-pump and on-pump techniques are similar in the rates of GI complications. We suggest that a properly designed randomized control trial is needed to verify our findings.

Comparison of the EuroSCORE II and Society of Thoracic Surgeons 2008 risk tools.

OBJECTIVES: Risk stratification in cardiac surgery is uniquely detailed, led latterly by the EuroSCORE and the Society of Thoracic Surgeons (STS) risk calculators. The recently published EuroSCORE II (ES2) algorithms update estimated mortality in a broad spectrum of cardiac procedures. The 2008 STS tool, in comparison, predicts multiple outcomes for specific procedures. We sought to identify and compare the external validity of both contemporaneous tools in our population. METHODS: Data from our hospital database were collated for the period February 2001 to March 2010. Logistic regression coefficients from the risk calculations were applied to the data and the results presented as receiver-operating characteristic (ROC) curves. Statistical analyses were performed using the area under the ROC curve (AUROC) and the Hosmer-Lemeshow (H-L) goodness-of-fit test, with comparisons using the DeLong method. RESULTS: A total of 15 497 procedures were identified, of which 14 432 were appropriate for STS risk scoring (i.e. valve and/or graft procedures with no tricuspid valve operations etc.). For all procedures, ES2 and STS were equivalent (AUROC 0.818 vs 0.805, respectively, P = 0.343). For procedures appropriate for STS risk scoring, results were similar (AUROC ES2 vs STS, 0.816 vs 0.810, P = 0.714), whereas for procedures excluded by STS, the result was marginally worse (AUROC ES2 vs STS, 0.773 vs 0.784, P = 0.751). Goodness of fit in all cases was poor, primarily where risk was higher than 15% (H-L P < 0.0001). CONCLUSIONS: EuroSCORE II and STS both provide equivalent discrimination in predicting mortality in a British population, including those undergoing procedures for which the STS does not normally predict. Accounting for decile-grouped Hosmer-Lemeshow tests not being ideal for the assessment of calibration, both tools show good calibration for patients with low to moderate risk, with divergence from ~15% predicted risk.