CARDIOVASCULAR JOURNAL OF AFRICA • Volume 34, No 5, November/December 2023 AFRICA 303 The results of univariate and multivariate regression analysis of patients who developed AF in the early postoperative period are shown in Tables 5 and 6. In multivariate analysis, the variables that were found to be statistically significantly associated with POAF in univariate analysis were increased pre-operative RDW (p = 0.0001), CRP (p = 0.0001) and ESR (p = 0.0001) levels; increased postoperative first-, third- and seventhday RDW (p = 0.0001) levels; postoperative first-, third- and seventh-day ESR (respectively; p = 0.03, p = 0.0001, p = 0.03), and CRP (respectively; p = 0.0001, p = 0.04, p = 0.0001) levels. These were found to be independent predictors of early POAF. The receiver operating characteristic (ROC) curves for pre-operative and postoperative first-, third- and seventh-day RDW were in association with POAF following isolated CABG (Fig. 1). The area under the curve (AUC) for the pre-operative RDW was 0.885 (95% CI: 0.856–0.915; p = 0.0001). Using a cut-off value of 14.55, the pre-operative RDW predicted POAF with a sensitivity of 83.1% and specificity of 80.2%. The AUC for the postoperative first-day RDWwas 0.805 (95% CI: 0.767–0.843; p = 0.0001). Using a cut-off value of 14.35, the postoperative first-day RDW predicted POAF with a sensitivity of 77.2% and specificity of 72.7%. The AUC for the postoperative third-day RDW was 0.802 (95% CI: 0.769–0.835; p = 0.0001). Using a cut-off value of 14.15, the postoperative third-day RDW predicted POAF with a sensitivity of 77.1% and specificity of 69.9%. The AUC for the postoperative seventh-day RDW was 0.865 (95% CI: 0.837–0.893; p = 0.0001). Using a cut-off value of 13.85, the postoperative seventh-day RDW predicted POAF with a sensitivity of 83.1% and specificity of 75.9%. The pre-operative RDW level of the patients who underwent isolated CABG and died within one month postoperatively was 15.35 ± 0.94%, while it was 13.74 ± 0.78% for the patients who survived, which was statistically significantly different (p = 0.0001). Likewise, postoperative first-, third- and seventh-day RDW levels were significantly different between patients who died (respectively; 15.84 ± 0.95, 14.93 ± 0.87, 14.58 ± 0.82%) and who survived (respectively; 14.58 ± 0.86, 13.87 ± 0.79, 13.68 ± 0.71%) (p = 0.0001). Moreover, the pre-operative RDW level was 15.54 ± 0.97% in patients who developed neurological events within one month postoperatively, and 13.62 ± 0.75% in patients who did not, which showed a statistically significant difference (p = 0.0001). Also, the RDW levels of the patients who developed neurological events on the first, third and seventh days postoperatively (respectively; 15.72 ± 0.91, 14.76 ± 0.84, 14.42 ± 0.78%) compared to those who did not (respectively; 14.66 ± 0.81, 13.72 ± 0.77, 13.54 ± 0.70%) were statistically significantly different (p = 0.0001). Discussion In this study, we found that increased RDW in the pre-operative and early postoperative period was associated with early POAF and adverse events after isolated CABG. Again, we found a relationship between the increase in CRP and ESR levels, which are other easily measurable routine markers of inflammation in the pre-operative and early postoperative period, and early POAF after isolated CABG. In addition, we found that increased RDW and increased CRP and ESR levels in the pre-operative and early postoperative period were also valuable in predicting the development of POAF. To our knowledge, this is not the first study to evaluate the relationship between RDW and AF after CABG surgery but one of the few studies to demonstrate the relationship of RDW with the adverse effects of POAF. Despite advanced treatment options, CABG remains the gold-standard treatment method for the treatment of patients with multivessel coronary artery disease.2 CABG is a high-risk procedure and many patients may experience postoperative complications that can cause significant morbidity and mortality.19 Despite advances in surgery, CPB and cardioplegic arrest techniques, the incidence of AF after cardiac surgery has increased significantly and remains relevant.20 POAF, which is a short-lived and self-limiting arrhythmia that usually begins two to four days after surgery, is an important complication with a frequency of 20–40% in cardiac surgical procedures and 10–20% in non-cardiac thoracic operations.21 Luo et al. reported that the incidence of POAF was 23.36% in patients aged 60 years and older who underwent isolated CABG with CPB.22 POAF most commonly occurs between the second and fourth postoperative days and is self-limiting in most patients.9 POAF is known to be a transient and benign complication of CABG, but recent studies have reported an association between POAF and increased early mortality and morbidity rates, including stroke, renal and respiratory failure, increased length of ICU and hospital stay, and hospital costs.7 Reducing POAF can result in significant savings; therefore, recently there has been increasing interest in identifying risk factors that could enable the implementation of preventative strategies.9 In our study, we found that POAF developed in 23.2% of patients after isolated CABG surgery, which is in accordance with the literature. The exact pathophysiology of POAF after cardiac surgery has not been fully elucidated.3 Identified potential predisposing factors include age, presence of myocardial ischaemia, type of cardiac surgery, atrial distension and pre-existing cardiac Sensitivity 1 – Specificity 0.0 0.2 0.4 0.6 0.8 1.0 1.0 0.8 0.6 0.4 0.2 0.0 Source of the curve Pre-operative RDW Postoperative 1-day RDW Postoperative 3-day RDW Postoperative 7-day RDW Reflective line Fig. 1. ROC curve analysis of pre- and postoperative RDW to predict postoperative AF.
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