Preoperative anaemia is an independent predictor of 30-day mortality post-CABG and improves de predictive accuracy of EuroScore II

Background

The impact of preoperative anaemia on the results of cardiovascular surgery has already been demonstrated by some authors. Some of the studies observed worse surgical results in anaemic patients, however, in others, no difference was observed. In addition, the impact that the inclusion of anaemia or haemoglobin would have as a predictor in a risk model such as EuroScore II is not yet known.

Purpose

To evaluate the impact of preoperative anaemia on 30-day mortality post-CRM and compare the predictive accuracy of EuroScore II with and without the inclusion of haemoglobin levels in the model.

Methods

Single center cohort with 2168 patients consecutively included between January 2010 and December 2020. All procedures were performed with cardiopulmonary bypass. 32 baseline and operative characteristics were assessed. The primary outcomes were 30-day mortality and the EuroScore II predictive accuracy. Patients were stratified into two groups according to anaemia status. WHO Classification – haemoglobin: men <13 g/dL and women <12 g/dL. No Anaemia Group (1301–60.1%) – Anaemia Group (867–39,9%). Univariate analysis was performed to compare the characteristics of the groups, the occurrence of death in 30 days and to verify variables associated with mortality. Logistic regression analyses were used to assess predictors of mortality and generate a set of probabilities for assessing the predictive accuracy of EuroScore II with and without the addition of haemoglobin in the model. The probabilities generated through the regressions were analysed by ROC curves, which in turn were compared using the DeLong test. The level of significance was 5% and the statistical analysis was performed using Python 3.0.

Results

The anaemic patients were older and had higher prevalence of conditions, such as: diabetes, renal impairment, smoking, HF class III or IV, RBC transfusion and highest mean of EuroScore II (p<0.05 for all conditions). When comparing mortality in the groups, a significantly higher rate was observed in the anaemic group (2.2% vs 5.4%; p<0.001). In view of the heterogeneity of the groups, an adjusted logistic regression model was applied. The results of the multivariate model demonstrated that preoperative anaemia was an independent risk predictor for the occurrence of death in 30 days after CABG (B: 0.597; SE: 0.27; Wald: 5.2; OR: 1.82; 95% CI 1.09–3.04; p=0.022). In addition, we were able to verify that the addition of preoperative haemoglobin to EuroScore II resulted in a significantly higher predictive accuracy when compared to the predictive accuracy of the isolated score (AUCs: 0,732 vs 0.709; p=0.032).

Conclusions

Preoperative anaemia was an independent risk predictor for the occurrence of death in 30 days after CABG. We were also able to verify that the addition of the preoperative haemoglobin levels to EuroScore II resulted in a significantly higher predictive accuracy, improving the performance of the surgical risk model.

Funding Acknowledgement

Type of funding sources: None. Figure 1. Haemoglobin vs 30-day mortalityFigure 2. Predictive accuracies – EuroScore II

EuroScore II is the best predictive model for the off pump coronary artery bypass graft surgery

Background

Coronary artery bypass graft surgery (CABG) is the most common cardiac surgery performed in the world and a significant part of these surgeries are performed without cardiopulmonary bypass (off pump). Although none of the main surgical risk scores include pump use in their prediction model, the scores are widely used in risk stratification, including for patients who will be submitted to off pump CABG.

Purpose

To analyse and compare the predictive accuracy of EuroScore I, EuroScore II and STS Score for 30-day mortality after off pump CABG.

Methods

Single-centre cohort with 943 patients consecutively submitted to off pump CABG between January 2010 and December 2020. 31 baseline and operative variables were analysed. The primary outcome was the occurrence of death in the first 30 days after the surgery. Descriptive analysis, normality for quantitative data and univariate inference were performed to compare proportions and means between the survival group (n=930) and death group (n=13). Next, three logistic regression models were performed. Each of them had 30-day mortality as a dependent variable and one of the scores as an independent variable. The probabilities generated by the three models were saved and analysed by ROC curves. Thus, it was possible to assess the predictive accuracy of each of the scores. Finally, the values of the areas under the curves were compared using the DeLong test. The level of significance was 5% and the analysis was performed using the Python 3.0 programming language.

Results

The mean age of the general group was 63 years old and there was a predominance of male patients (68.4%). The means of the three evaluated risk scores were significantly higher in the Death group (p<0,05). This pattern confirmed the findings of higher prevalence of several comorbidities in the death group. The 30-day mortality rate was 1.37%. Through the analysis of regressions and the probabilities generated through them, it was possible to verify that the predictive accuracy of EuroScore II was significantly higher than that of the other two scores. While the predictive accuracy of EuroScore II was 77.3%, the accuracy of two other scores was in the range of 69% (AUC EsI: 0.697; AUC EsII: 0.773; AUC STS: 0.695; p=0.029).

Conclusion

EuroScore II seems to be the most adequate surgical risk score for the assessment of mortality risk of patients who will undergoing to off pump CABG. The score had a predictive accuracy of 77.3%, almost 8% more than the other two scores. Therefore, although EuroScore II does not include in its model the use of cardiopulmonary bypass, it has a satisfactory accuracy to be used in clinical-surgical practice. On the other hand, the EuroScore I and the STS Score showed predictive accuracy not adequate for this type of surgery.

Funding Acknowledgement

Type of funding sources: None. Predictive accuracies of risk scores

Results of on-pump and off-pump coronary artery bypass graft surgery in 30 days: an analysis by propensity score matching

Background

The results of coronary artery bypass graft surgery (CABG) performed with and without the support of cardiopulmonary bypass have already been widely discussed and studied, including through a few large randomized clinical trials. Despite the efforts, the findings of these studies still generate controversy and doubts about the outcomes achieved by the two techniques. One of the contested points is the heterogeneity of the degree of specialization in the off-pump technique in relation to the surgical groups that participated in the studies.

Purpose

To compare the results in 30 days of on-pump and off-pump CABG.

Methods

A single centre cohort with 1,767 patients undergoing isolated CABG was initially evaluated (January 2013 – December 2018). 397 patients undergoing off-pump CABG and 1,370 patients undergoing on-pump surgery were identified. To obtain two completely homogeneous study groups, a propensity score matching was applied. For this, a logistic regression model was built with the variable use of CPB support as dependent variable. In the group of independent variables, 14 baseline and operative characteristics were included. The probabilities generated for each patient were used as scores to establish the match. To establish a pair, it was necessary to have three squares after the comma, with the fourth decimal place being the tiebreaker criterion in the pairing. In this way it was possible to obtain 332 pairs (N=664). The paired groups, on and off-pump, were compared by descriptive and univariate analysis and later a logistic regression model was applied to identify possible risk predictors and to verify the impact of CPB support on 30-day mortality. The level of significance was 5% and the analysis was performed using Python 3.0.

Results

None of the 29 baseline and operative characteristics showed a significant difference between the groups, demonstrating a high degree of homogeneity obtained from the propensity score matching, which enabled a solid comparison between the incidences of outcomes in 30 days. None of the analysed outcomes showed any difference between the groups on and off-pump, including AMI, stroke, major reoperation and death (1.5% vs 2.4%; p=0.401). Through regression analysis it was possible to establish that the use of CPB was not an independent predictor of risk for the occurrence of death (p=0.246).

Conclusion

After matching by propensity score, patients who underwent surgery with and without CPB had similar incidences of 30-day mortality. In addition, it was possible to verify that the use of CPB was not an independent predictor of risk for the occurrence of death in 30 days.

Funding Acknowledgement

Type of funding sources: None. Propensity score adjustment by group30-day outcomes vs CABG technique