CARDIOVASCULAR JOURNAL OF AFRICA • Volume 34, No 4, September/October 2023 208 AFRICA Statistical analysis The SPSS program was used to perform all statistical analyses (version 20.0 for Windows, SPSS Inc, Chicago, IL). The data were compared in terms of the groups and evaluated by a normal distribution of the Shapiro–Wilk test and QQ plots. Continuous variables with normal distribution are expressed as mean ± standard deviation, non-normal distribution is expressed as median and interquartile range (IQR), and categorical variables are expressed as percentages when appropriate. The student’s t-test was used to analyse continuous variables with a normal distribution. The paired samples t-test and Mann–Whitney U-test compared numerical variables between the two groups. The chi-squared test was used to compare categorical variables between the two groups. A p-value of < 0.05 was considered statistically significant. Results A total of 155 patients were included in our study. While 77 of these patients were in the MINOCA group, 78 patients were in the control group. In the MINOCA patients, a total of 41 (53.24%) had plaque disruption, 21 (27.27%) had microvascular dysfunction and slow flow, four had (5.19%) vasospasm and three (3.89%) had spontaneous coronary dissection. Conventional imaging could not determine the diagnosis in eight (10.38%) patients. There were no statistically significant differences between the groups concerning gender, age, diabetes mellitus, hypertension, previous CAD and echocardiographic parameters. C-reactive protein (CRP) level (21.38 ± 43.87 vs 4.06 ± 2.60 mg/l, p < 0.001) and white blood cell (WBC) count (10.09 ± 3.70 × 103 vs 7.95 ± 5.08 × 103 cells/µl, p = 0.003), which are inflammatory markers in laboratory examinations, were statistically significantly higher in the MINOCA group. Clinical characteristics, laboratory examinations and echocardiographic features of the patients with MINOCA and the control subjects are shown in Table 1. There was no statistically significant difference between the two groups in terms of MPV ECG score, a new and valid electrocardiographic predictor of atrial arrhythmia (1.95 ± 1.03 vs 1.68 ± 1.14, p = 0.128). P-wave voltage, P-wave morphology and P-wave duration, which are components of MVP ECG score, were not statistically significantly different. The total P-wave duration was significantly higher in the MINOCA group than in the control group (110.87 ± 17.78 vs 104.36 ± 19.10 ms, p = 0.030). In addition, the PR interval was found to be statistically significantly lower in the MINOCA group than in the control group (156.95 ± 22.99 vs 167.08 ± 30.33 ms, p = 0.021). Electrocardiographic variables used for prediction of atrial arrhythmia are shown in Table 2. The QRS complex duration (90.21 ± 14.87 vs 82.99 ± 21.59 ms, p = 0.017), ST interval (271.95 ± 45.91 vs 302.31 ± 38.40 ms, p < 0.001), corrected QT interval (438.17 ± 43.80 vs 421.41 ± 28.39 ms, p = 0.005) and QT dispersion (60.75 ± 22.77 vs 34.19 ± 12.95, p < 0.001) were statistically significantly higher in the MINOCA group than in the control group. The Tpeak–Tend (89.53 ± 32.16 vs 65.22 ± 18.11, p < 0.001), Tpeak–Tend/QT interval (0.2306 ± 0.0813 vs 0.1676 ± 0.0470, p < 0.001) and Tpeak–Tend/corrected QT interval (0.2043 ± 0.6997 vs 0.1551 ± 0.4310, p < 0.001) ratios were also significantly higher in patients with MINOCA than in the control group. Electrocardiographic parameters used for prediction of ventricular arrhythmia are shown in Table 3. Discussion In this trial, our primary finding was that the risk of AF, as indicated by the MVP ECG score, was not statistically significantly higher in the MINOCA patient group compared to the control group. Furthermore, the corrected QT interval, QT dispersion, Tpeak–Tend, Tpeak–Tend/QT interval and Tpeak–Tend/ corrected QT interval ratios were statistically significantly higher in the MINOCA patients than in the control group. Table 1. Baseline clinical, laboratory and echocardiographic characteristics Characteristics MINOCA (n = 77) Control (n = 78) p-value Age (years) 54.85 ± 13.64 56.92 ± 11.69 0.078 Women, n (%) 40 (51.9) 31 (39.7) 0.127 Diabetes mellitus, n (%) 18 (23.4) 24 (30.8) 0.300 Hypertension, n (%) 32 (41.6) 47 (60.3) 0.200 Previous coronary artery disease, n (%) 6 (7.8) 7 (9) 0.791 White blood cell count, × 103 cells/µl 10.09 ± 3.70 7.95 ± 5.08 0.003 C-reactive protein 21.38 ± 43.87 4.06 ± 2.60 < 0.001 Creatinin clearance (MDRD) 81.48 ± 22.14 84.70 ± 15.18 0.095 Left ventricular ejection fraction, % 58.05 ± 8.47 60.07 ± 5.10 0.073 Left ventricular end-diastolic diameter, mm 48.21 ± 5.12 47.87 ± 6.32 0.350 Left atrial diameter (parasternal long axis), mm 36.03 ± 6.32 37.33 ± 6.7 0.810 Left ventricular diastolic function, n (%) Normal 47 (61.03) 45 (57.69) 0.570 Stage 1 28 (36.36) 30 (38.46) Stage 2 2 (2.59) 3 (3.84) Stage 3 0 0 Stage 4 0 0 Numerical variables with normal distribution are shown as mean ± standard deviation. Categorical variables shown as numbers (%). MDRM: Modification of Diet in Renal Disease. Table 2. Comparison of atrial arrhythmia predictors in electrocardiography Predictors MINOCA (n =77) Control (n = 78) p-value Heart rate, bpm 81 ± 26.40 72 ± 23.50 0.001 PR interval, ms 156.95 ± 22.99 167.08 ± 30.33 0.021 PR segment, ms 62.57 ± 26.40 69.23 ± 30.77 0.151 P-wave duration, ms (%) 110.87 ± 17.78 104.36 ± 19.10 0.030 < 120 41 (53.2) 47 (60.3) 0.590 120–140 31 (40.3) 28 (35.9) > 140 5 (6.5) 3 (3.8) P-wave voltage, mV (%) > 0.20 28 (36.4) 26 (33.3) 0.827 0.10–0.20 45 (58.4) 49 (62.8) < 0.10 4 (5.2) 3 (3.8) P‐wave morphology, n (%) No inter-atrial block 29 (37.7) 38 (48.7) 0.284 Partial inter-atrial block 42 (54.5) 37 (47.4) Advanced inter-atrial block 6 (7.8) 3 (3.8) MVP ECG score 1.95 ± 1.03 1.68 ± 1.14 0.128 Low (0–2), n (%) 51 (66.2) 54 (69.2) 0.577 Intermediate (3–4), n (%) 25 (32.5) 24 (20.8) High (5–6), n (%) 1 (1.3) 0 (0) Numerical variables with normal distribution are shown as mean ± standard deviation. Categorical variables shown as numbers (%). MVP ECG: morphology–voltage–P‐wave duration electrocardiography.
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