CARDIOVASCULAR JOURNAL OF AFRICA • Volume 34, No 5, November/December 2023 300 AFRICA Given the problem associated with advanced age, combined co-morbid status and subsequent risk stratification of patients presenting for CABG, RDW is increasingly being sought for the prediction of postoperative outcomes.15 RDW from a standard complete blood count is a convenient and inexpensive biochemical parameter that represents the size variability of circulating erythrocytes.14 Increased RDW indicates the presence of anisocytosis, which reflects chronic inflammation and high levels of oxidative stress, is associated with impaired erythropoiesis and erythrocyte destruction.15 Along with its extensive use in diagnostic haematology, RDW has been associated with the presence and complications of a wide variety of human pathologies, including cardiovascular disease, over the past decade.13 Although the link between RDW and cardiovascular diseases has not been fully defined, previous studies have shown that RDW correlates with markers of chronic inflammation (such as IL-6, IL-8, IL-12, IL-17, IL-18, interferon and TNF).15 Kılıçgedik et al. reported in their retrospective study that increased RDW values were a predictor of AF developing after CABG.16 Likewise, Geçmen et al. found in their study with 94 patients operated on for isolated CABG surgery with CPB, who were followed up until discharge from the cardiovascular intensive care unit (ICU), that RDW independently predicted the risk of POAF.17 Previous studies have attempted to demonstrate the effect of inexpensive, simple and routinely measured RDW on predicting the onset of POAF. However, the prognostic value of RDW after AF in critically ill patients who underwent isolated CABG with CPB is largely unknown. The aim of our study was to predict the development of POAF in critically ill patients and investigate the potential clinical importance of RDW in predicting in-hospital mortality and morbidity in those with AF. Methods The medical records of a total of 1 096 patients who underwent isolated CABG between January 2015 and December 2021 were reviewed retrospectively. The operations were performed at the same centre by the same surgical team. We enrolled 790 (72.1%) patients with pre-operative normal sinus rhythm who underwent isolated CABG with CPB. Two different populations were created: group 1 (n = 183) including patients who developed AF in the first 72 hours postoperatively; and group 2 (n = 607), including patients who remained in normal sinus rhythm. AF diagnosis was based on the criteria proposed by the American Heart Association/American College of Cardiology/Heart Rhythm Society (AHA/ACC/HRS) 2019 guidelines for AF.18 AF was defined as the demonstration of AF for a minimum duration of 30 seconds using electrocardiography (ECG) recordings. Patients with pre-operative non-sinus rhythm, a history of paroxysmal or chronic AF, an implanted cardiac device or electrophysiological ablation were excluded from the study. In addition, also excluded from the study were patients who had valvular heart disease, systemic inflammatory diseases, chronic obstructive pulmonary disease, malignancy, haematological proliferative diseases, autoimmune diseases, endocrinological disorders, left ventricular systolic function disorder (left ventricular ejection fraction ≤ 30%), advanced age (> 75 years), chronic kidney disease, patients with low pre-operative haemoglobin levels (≤ 10 g/dl), patients with a left atrial diameter > 4.5 cm in echocardiography, the presence of signs of clinical infection [fever > 37.5°C, CRP ≥ 5 mg/dl, erythrocyte sedimentation rate (ESR) > 20 mm/h or leukocyte count > 11 000 cells/μl] before surgery, emergency operations, patients who required intra-aortic balloon pump, patients who were re-operated on due to haemodynamic instability or bleeding, patients who were operated on a beating heart or redo CABG. Demographic data, pre-operative–postoperative clinical and biochemical parameters, and intra-operative and operative information of the patients were obtained retrospectively from the hospital’s software system. We also recorded age, gender, smoking (defined as continuous or cumulative smoking for ≥ six months or at least six months every day; passive smoking, which refers to non-smokers inhaling the smoke from smokers’ breath for at least 15 minutes per day for more than one day per week), history of statin use, diabetes (including history of diabetes mellitus or newly diagnosed diabetes), hypertension (defined as history of hypertension or newly diagnosed hypertension), dyslipidaemia [defined as low high-density lipoprotein cholesterol (HDL-C) and high triglyceride levels; the cut-off values were selected at HDL-C < 40 mg/dl (1.04 mmol/l) and triglycerides ≥ 200 mg/dl (2.26 mmol/l) in both men and women), left ventricular ejection fraction (LVEF), left atrial diameter, laboratory parameters (haemoglobin, haematocrit, leukocyte count, thrombocyte count, RDW, and total cholesterol, triglyceride, serum creatinine, urea, ESR and CRP levels), operation information, the number of grafts used, duration of CPB and aortic cross-clamp (ACC), use of blood products and length of stay in the ICU and hospital. The pre-operative basal heart rates of the patients were obtained by analysing 12-lead ECG records. At days one, three and seven after surgery, additional ECGs and blood samples were obtained for standardised postoperative follow up. Fasting venous blood samples were routinely obtained from patients, both pre-operatively and on the first, third and seventh postoperative days for complete blood count (CBC), CRP and ESR analysis. Approximately 5 to 7 ml venous blood samples were placed into a sterile tube with EDTA. Haematological parameters were calculated by an automated blood count device (Abbott CELL-DYN 3700; Abbott Laboratory, Abbott Park, Illinois, USA) following a waiting time of one hour. Serum levels of total cholesterol, low-density lipoprotein cholesterol (LDL-C), HDL-C and triglycerides were determined in all specimens using an automatic multichannel biochemical analyser (Hitachi-7450, Hitachi, Tokyo, Japan) following routine laboratory procedures. Levels of CRP were determined using immune-enhanced nephelometry. The patients were followed in the ICU and in-patient room with continuous ECG monitoring for the first 48 hours. In the absence of any contra-indication, oral 50 mg/day metoprolol was started in all patients on the first postoperative day. During the in-patient clinic follow up of the patient’s rhythm ECG, pulse and arterial blood pressure measurements were performed at maximum intervals of four hours. A patient’s complaint of cardiac arrhythmia or palpitation was detected by standard 12-lead ECG recording. A diagnosis of AF was made with ECG recording. Intravenous (IV) metoprolol (5–10 mg) was administered to control heart rate in the treatment of AF. All required patients
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