116 Chapter 6 Statistical analysis Variables’ normal distribution in both groups was tested using the Shapiro-Wilk statistic. Continuous variables are presented as mean ± standard deviations (SD) or median (first quartile - third quartile [Q1, Q3]), and compared using Student t-test or Mann-Whitney U test, as appropriate. Categorical variables are presented as counts (%),compared with Chi-squared test. Fisher’s exact test was used in case cell counts less than five, due to small sample size. If a difference in MBV exceeding two SD between observers occurred, data were reanalyzed for agreement. Mean values of measurements were used for further analysis. Comparison of MBV among ANOCA entities was asses by one-way ANOVA. Pearson’s correlation tested the association between MBV, the M-value and myocardial response to dobutamine-induced stress, expressed by the correlation coefficient r. Statistical analyses were performed using SPSS version 28 (IBM Corp., Armonk, NY, USA). p < 0.05 was considered statistically significant. RESULTS Study population A total of 28 ANOCA patients and 28 matched healthy controls were included. The study population included 6 (21.4%) men in both the ANOCA and the healthy control group. Mean age was 56.8 ± 8.6 years in the ANOCA group vs 56.5 ± 7.0 years in the healthy control group (p = 0.89). Across the baseline characteristics, statistically significant differences were found between ANOCA patients and controls with respect to BMI (27.6 ± 4.5 vs. 24.0 ± 2.6, respectively p < 0.001), prevalence of hypertension (57% vs. 0%, p < 0.001) and prevalence of hyperlipidemia (50% vs. 0%, p < 0.001). Furthermore, patients had a lower total cholesterol, a lower LDL-cholesterol and a higher triglyceride-level than controls (Table 1). Table 1. Baseline characteristics Total ANOCA patients Healthy controls p-value Total number of participants n = 56 n = 28 n = 28 Demographics Women, % 44 (78.6) 22 (78.6) 22 (78.6) Age, yrs 56.7 ±7.8 56.8 ±8.6 56.5 ±7.0 BMI, kg/m2 25.8 ±4.1 27.6 ±4.5 24.0 ±2.6 <0.001 Ejection fraction, % 62.9 ±5.2 62.4 ±5.6 63.4 ±5.0 0.447
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