SA JOURNAL OF DIABETES & VASCULAR DISEASE RESEARCH ARTICLE VOLUME 21 NUMBER 1 • November 2024 5 Methods This retrospective, analytical cohort included ACS patients who received elective CABG surgery as the mode of treatment between 2008 and 2014. During this period, 200 patients received CIMT evaluations, of whom 89 patients met the inclusion criteria and had complete data sets. The study was performed at the Cardiothoracic Surgery Department at Universitas Academic Hospital, Bloemfontein, the only public tertiary referral hospital in the central South African region. It mainly services patients from the Free State and Northern Cape provinces and Lesotho. Ethical clearance was obtained from the Health Science Research Ethics Committee (HSREC) of the University of the Free State (UFSHSD 2020/1708/2601) and the Free State Department of Health. This study was a sub-study of a prospective investigation conducted on all ACS patients (ETVOS NR 51/07). Eighty-nine patients were included in the study and divided into two cohorts as per genderspecific CIMT reference ranges. Group 1 included patients with normal CIMT values (CIMT < 0.07 cm) and group 2 patients had abnormal CIMT values (CIMT ≥ 0.07 cm). Patient demographics, clinical history, pre-operative risk factors, EuroSCORE II, CPB, near-infrared spectroscopy (NIRS) and postoperative outcomes and complications were recorded from the patients’ medical records and the departmental database. Ethnicity was self-identified and cross-referenced using the hospital identification system. Pre-operative results for levels of cholesterol, creatine, total creatine kinase, glucose, insulin, N-terminal-pro-B-type natriuretic peptide (NT-proBNP) and the creatinine kinase-MB (CK-MB) isoform were captured. Blood analysis was performed by the National Health Laboratory Service according to the laboratory standard operating procedures, applying local laboratory reference ranges for each parameter. Body mass index (BMI) was calculated using the Du Bois formula21 and categorised as underweight (> 18.5 kg/m2), normal or healthy weight (18.5–24.9 kg/m2), overweight (25.0–29.9 kg/m2) and obese (> 30 kg/m2).22 Hypertension was defined as isolated systolic hypertension (> 140/90 mmHg), according to the definition of Mancia et al.23 Patients with normal (120–129/80–89 mmHg) and/or high normal (130–139/85–89 mmHg) blood pressures were classified as not having hypertension. The CIMTmeasurements were performed pre-operatively one day prior to surgery. Patient positioning and the examination procedure were done according to standardised methods published in the Mannheim CIMT and plaque consensus.24 Standard equipment included a high-resolution B-mode system operating in black-andwhite mode, with linear ultrasound transducers at frequencies > 7 MHz. A Phillips EnVisor sonar machine and phased/sector array 2–8 MHz L12-3 sonar probe was used to obtain the CIMT images. Three CIMT measurements were recorded and averaged. For our study, a normal CIMT cut-off was set at < 0.07 cm for males and < 0.065 cm for females. For an abnormal CIMT the cutoff was ≥ 0.07 cm for males and ≥ 0.065 cm for females. Since there are no consistent reference guidelines for CIMT cut-off in the literature, the groups were divided based on the primary cut-off values per gender, as Youn et al. recommended.25 Due to the lack of standard reference guidelines in the literature, a second limited sub-analysis was done using a cut-off CIMT value of ≥ 0.09 cm as abnormal, irrespective of gender or age.26 However, only the intra- and postoperative outcomes and complications were compared between groups. Lactate levels were analysed at specified time intervals: (1) after the insertion of an intra-arterial catheter (T1 or baseline), (2) after intubation (T2), and (3) at approximately 15-minute intervals for the duration of surgery (T3, T4, etc). Postoperatively, lactate values were recorded at one, two, four, eight, 12, 24, 48 and 72 hours after the patient was admitted to the intensive care unit (ICU). Only peak lactate values were used for intra- and postoperative analysis. This study defines peak lactate as > 4 mmol/dl during and after surgery. Two NIRS electrodes were placed on the patient’s forehead before the patient was induced, and baseline values were set. Results were interpreted as either satisfactory (NIRS values > 50% or < 20% drop from baseline) or as compromised cerebral blood flow (NIRS values ≤ 50% or > 20% drop from baseline). It should be noted that not all patients received NIRS measurements because not all theatres were equipped with a NIRS monitor. Only 32 of the 89 patients had recorded NIRS measurements. Standard transthoracic echocardiograms (TTE) were performed on all patients in line with the British Society of Echocardiography protocol for comprehensive adult TTE studies.27 A Phillips EnVisor echocardiography machine was used and the patient’s left ventricular ejection fraction (LVEF) was calculated peri-operatively using Simpson’s method. The American Society of Echocardiography defines LVEF as the percentage of blood ejected during a left ventricular contraction of the heart, using quantitative measures. LVEF was calculated using the formula: LVEF = EDV – ESV EDV × 100 Where EDV is the end-diastolic volume and ESV is the end-systolic volume. The cut-off value for normal LVEF for our study was determined at > 55%. Statistical analysis Statistical analyses were done using R Software version 3.2.2 (2015/08/14). XLSTAT version 2016.03.30846 was used for t-tests and the calculation of confidence intervals. Data were compared using the Student’s t-test for normally distributed continuous variables, the Mann–Whitney test for continuous data that were not normally distributed, and the chi-squared or Fisher’s exact test (where cell counts were less than five) for categorical variables. Statistical significance was noted if the p-value was less than 0.05. Results Eighty-nine ACS patients received CIMT measurements prior to elective CABG surgery. Twenty-eight patients (31%) presented with a normal CIMT and 61 (69%) with an abnormal CIMT. Seventyseven (86.5%) were male and 12 (13.5%) were female patients. The mean age of the groups was comparable, and both groups presented with a preponderance of Caucasian males (80%). The mean BMI was significantly higher in group 2 compared to group 1 (29.2 vs 26.6 kg/m2) (p < 0.05). The demographic and anthropometric data are summarised in Table 1. Significantly more patients in group 2 with an abnormal CIMT presented with hypertension (p = 0.009), diabetes (p = 0.008) and an increased NT-proBNP level (p = 0.017). Low-density lipoprotein
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