External validity of the Society of Thoracic Surgeons risk stratification tool for deep sternal wound infection after cardiac surgery in a UK population.

OBJECTIVES: Deep sternal wound infection (DSWI) is a devastating complication of cardiac surgery, with a historical incidence of 0.4-5%. Predicting which patients are at higher risk of infection may help instituting various preventive measures. Risk calculations for mortality have been used as surrogates to estimate the risk of deep sternal wound infection, with limited success. The Society of Thoracic Surgeons (STS) 2008 Risk Calculator modelled the risk of DSWI for cardiac surgical patients, but it has not been validated since its publication. We sought to assess the external validity of the STS-estimated risk of DSWI in a United Kingdom (UK) population. METHODS: Using our prospectively captured database, we retrospectively calculated the risk of DSWI for 14 036 patients undergoing valve, coronary artery bypass grafts or combined procedures between February 2001 and March 2010. DSWI was identified according to the Centre for Disease Control and Prevention definition. The receiver operator characteristic (ROC) curve was employed to test the performance of the model using the area under the ROC curve (AUROC). The calibration of the model was interrogated using the Hosmer-Lemeshow test for Goodness of Fit. RESULTS: A total of 135 (0.95%) patients developed DSWI. Although there was a statistically significant difference in the calculated risk of patients who contracted DSWI (0.44% ± 0.01) vs those who did not (0.28% ± 0.00, P < 0.0001), the AUROC of 0.699 (95% confidence interval: 0.6522-0.7414) denoted a modest discriminatory power, with the Hosmer-Lemeshow Goodness of Fit statistic (P < 0.001) suggesting poor calibration. A risk-adjusted modifier improved the calibration (P = 0.08). CONCLUSIONS: The STS risk calculator lacks adequate discriminatory power for estimating the isolated risk of developing deep sternal wound infection in a UK population. The discrimination is similar to the tool's validation c-statistic and may have a place in an integrated calculator.

Does the outcome improve after radiofrequency ablation for atrial fibrillation in patients undergoing cardiac surgery? A propensity-matched comparison.

OBJECTIVES: Preoperative atrial fibrillation (AF) significantly reduces the survival rate post cardiac surgery. It has been shown that patients in persistent or paroxysmal AF have higher mid- and long-term mortality post cardiac surgery compared with those in sinus rhythm. In this study we aimed to assess whether radiofrequency (RF) ablation during cardiac surgery in these patients improves the survival. METHODS: For a period of 5 years (2005-10), we studied all the patients who underwent ablation for AF during cardiac surgery for persistent/paroxysmal AF in our institution. We used RF ablation on 113 patients who had AF for <5 years and where the atrial dimension measured <5.5 cm. A 1:2 propensity matching was performed to adjust for the preoperative and operative characteristics with a group in persistent/paroxysmal AF, who had cardiac surgery during the same period of time (2005-10) and did not undergo ablation. We compared the postoperative outcome and survival rates between the two groups. RESULTS: Before and after adjusting for the preoperative and operative characteristics, inotropic support, renal failure, stroke, intensive care unit and hospital stay, as well as in-hospital mortality were similar between the two groups. After 5 years the difference in the survival was significant between the groups; 91.1 and 83.2%, with and without ablation, respectively (P value = 0.038). CONCLUSIONS: Despite, the similar postoperative outcome with or without ablation in persistent/paroxysmal AF, 5-year survival was found to be significantly higher with the ablation during cardiac surgery. This improvement can be due to the fall in the incidence of cerebro-vascular events or bleeding with AF or warfarin. Ablation during cardiac surgery is a simple and quick procedure and should be considered if indicated.

Choice of conduit for coronary artery bypass grafting in poor ventricles.

BACKGROUND: advantages in the use of arterial grafts for coronary artery revascularizations have been reported previously. OBJECTIVES: we aimed to compare the outcome and survival rates of different conduits in patients with poor ventricular function (ejection fraction<30%). METHODS: in a 10-year period, 979 patients with an ejection fraction<30%, who underwent isolated first-time coronary artery bypass grafting, were divided into in 3 groups: (A) total arterial grafts (n=257), (B) total vein grafts (n=76), and (C) left internal mammary artery and vein grafts (n=610). Multivariate logistic regression was used to assess the effect of graft type on mortality, while adjusting for patient and disease characteristics. Hospital mortality and 5-year survival rates were compared among the groups. RESULTS: hospital mortality was 8.9% for group A, 11.8% for group B, and 5.7% for group C. Mortality at 5 years was 27.2% for group A, 42.3% for group B, and 28.7% for group C. After risk adjustment, hospital mortality and mid- and long-term mortality showed no significant differences among the groups. CONCLUSIONS: patients with poor ventricular function have a high mortality rate in both the short- and long-term with any type of conduit. Mortality rates with total arterial grafts and vein plus arterial grafts were comparable before and after risk adjustment.

Outcomes and predictors of prolonged ventilation in patients undergoing elective coronary surgery.

OBJECTIVES Despite the seriousness of prolonged mechanical ventilation (PMV) as a postoperative complication, previously proposed risk prediction models were met with limited success. The purpose of this study was to identify perioperative variables associated with PMV in elective primary coronary bypass surgery. PMV was defined as the need for intubation and mechanical ventilation for >72 h, after completion of the operation. METHODS Between April 1997 and September 2010, 10 ,977 consecutive patients were retrospectively reviewed. A series of two multivariate logistic regression analyses were carried out to identify preoperative predictors of prolonged ventilation and the impact of operative variables. RESULTS PMV occurred in 215 (1.96%) patients; 119 (55.3%) of these underwent tracheostomy. At multivariate analysis, predictors included NYHA higher than class II (odds ratio [OR], 1.77; 95% confidence intervals [CI], 1.34-2.34), renal dialysis (OR, 5.5; 95% CI, 2.08-14.65), age at operation (OR, 1.04; 95% CI, 1.02-1.06), reduced FEV(1) (OR, 0.99; 95% CI, 0.98-0.99), body mass index >35 kg/m(2) (OR, 1.73; 95% CI, 1.14-2.63). On serial logistic regression analyses, operative variables added little to the discriminatory power of the model. Kaplan-Meier survival curves showed reduced survival among PMV patients (P < 0.001) with an improved survival in the tracheostomy subgroup. CONCLUSIONS PMV after coronary bypass is associated with a reduction in early and mid-term survival. Risk modelling for PMV remains problematic even when examining a more homogenous lower risk group.

Impact of chronic obstructive pulmonary disease severity on surgical outcomes in patients undergoing non-emergent coronary artery bypass grafting.

OBJECTIVES: Although the association between chronic obstructive pulmonary disease (COPD) and adverse surgical outcomes has been previously demonstrated, the impact of COPD severity on postoperative mortality and morbidity remains unclear. Our objective was to analyse the prognostic implication of COPD stages as defined by the Global Initiative for Chronic Obstructive Lung Disease. METHODS: Between September 1997 and April 2010, 13,638 patients undergoing first time isolated CABG were retrospectively reviewed, of whom 2421 patients were excluded due to lack of spirometry records or restrictive pattern on spirometry. The remaining 11,217 patients were divided into three groups: group 1 (including patients with normal spirometry and patients with mild COPD (FEV1/FVC ratio<70%, FEV1≥80% predicted), group 2 (moderate COPD: FEV1/FVC ratio<70%, 50%≤FEV1<80% predicted) and group 3 (severe COPD: FEV1/FVC ratio<70%, FEV1<50% predicted). Logistic regression was used to examine the effect of COPD severity on early mortality and morbidity, after adjusting for differences in patient characteristics. RESULTS: Early mortality in the three groups was 1.4, 2.9 and 5.7% respectively (P<0.001). Similarly, a consistent trend of increasing frequency of postoperative complications with advanced COPD stage was noted. On multivariate analysis, severe COPD was found to be significantly associated with early mortality [adjusted OR, 2.31 (95% CI) (1.23-4.36)], P=0.01. CONCLUSIONS: The severity of COPD as defined by spirometry can be a prognostic marker in patients undergoing CABG. Spirometric criteria may help refining currently used operative risk scores.

Monitoring cardiac output trends with end-tidal carbon dioxide pressures in off-pump coronary bypass.

The optimum method of intraoperative monitoring in patients undergoing off-pump coronary bypass remains debatable. Using capnography and end-tidal carbon dioxide pressure may be a helpful method of monitoring cardiac output trends, especially when grafting posterior and lateral vessels. After repositioning the heart, End-tidal carbon dioxide pressures that continue to trend down usually indicate decreased cardiac output and precede hemodynamic and electrical instability. The advantages of this method include simplicity, universal availability, and a short response time to changes in cardiac output.

Comparing the outcome of on-pump versus off-pump coronary artery bypass grafting in patients with preoperative atrial fibrillation.

OBJECTIVES: Around 5-15% of patients undergoing coronary artery bypass grafting (CABG) suffer from preoperative/pre-existing atrial fibrillation (PAF). This is a benign arrhythmia but can affect the outcome of the surgery. The aim of this study was to assess the effect of PAF on the immediate postoperative course of patients undergoing on-pump (ONCAB) vs. off-pump (OPCAB) CABG. METHODS: Over a 10-year period, data were prospectively entered into the database of our institution. A total of 10,461 patients underwent CABG, of whom 477 (4.6%) were in PAF. We analyzed these patients in two separate groups: group A (n=310) who underwent ONCAB and group B (n=167) who underwent OPCAB. After 4:1 propensity matching and adjusting for the preoperative and operative characteristics of these two groups with patients in SR (sinus rhythm), early, mid- and long-term outcomes of PAF patients were analyzed. RESULTS: After adjusting for preoperative characteristics, postoperative complications were significantly higher in patients who had ONCAB when there was PAF compared to those in SR (P<0.001). In the OPCAB patients, on the other hand, there was no statistically significant difference in the postoperative complications between the patients with preoperative SR or PAF. In-hospital and short-term mortality were no different in the PAF group undergoing OPCAB compared to those in SR; however, the mid- and long-term survival rates in PAF patients who underwent OPCAB/ONCAB were worse compared than was seen in SR. CONCLUSIONS: PAF is associated with a higher incidence of postoperative complications. Our results have demonstrated that patients in PAF undergoing ONCAB are more susceptible to the postoperative complications compared to those in SR. However, there were no differences in mid- and long-term outcomes.