CARDIOVASCULAR JOURNAL OF AFRICA • Volume 35, No 2, May – August 2024 AFRICA 107 Tablets containing 10 mg active EMPA (Jardiance, Boehringer Ingelheim) and 25 mg AMT (100 mg/kg, Laroxyl 25 mg, Roche), which weighed nearly 257 mg and 194.6 mg with other supplemental products, respectively, were dissolved in physiological serum to yield a concentration of 5 mg/ml and 50 mg/ml, respectively. According to the weight of each rat, the suspended drug solution was completed to 2 ml with physiological serum. All subjects were anaesthetised intraperitoneally with ketamine (40 mg/kg; Ketalar, Pfizer) and xylazine hydrochloride (4 mg/kg; Alfazyne 1, Ege Vet, Alfasan International BV). After the subjects were placed in a prone position, ECG recordings were taken from the D2 lead with needle electrodes (Fig. 1B). ECG recordings were evaluated with the Biopac MP36 system. RR and QT intervals and heart rates (HR) were measured by ECG recordings at baseline, and at the first and second hour, respectively. Heart rate was calculated as 1 500 per number of small squares between consecutive R waves. After the QT interval and HR measurements were performed, the corrected QT (QTc) was calculated with the Bazzet formula (QT/RR1/2). QTc prolongation, measured by serial ECG, was the accepted main endpoint. In a similar previous experimental model, researchers showed that the QTc difference of rats two hours after drug administration was 43 ms between the control and amitriptyline groups.12 It is generally accepted that a 20-ms change in QTc interval is significant.13 Therefore, in order to detect a difference of 20 ms in QTc interval between the groups, six rats per group would be required for a total of 24 rats to be able to reject the null hypothesis with a probability (power) of 0.8. The type I error probability associated with this test of the null hypothesis was 0.05. Statistical analysis Statistical analyses were performed with SPSS 22 (IBM Corp, Armonk, NY, USA). The mean and median QT, HR and QTc durations of all groups were calculated. The Shapiro–Wilk test was used to evaluate whether the data fitted a normal distribution. All ECG parameters at all available time points (baseline, first and second hours) were compared with repeated measurements of one-way analysis of variance (ANOVA), followed by Tukey’s or Tamhane post hoc tests. ECG parameters of all of the study groups at each time point (baseline, first and second hours) were also separately compared. Data without a normal distribution are expressed as median and interquartile range (IQR) and were compared by Kruskal–Wallis analysis (HR at first hour). Data with a normal distribution are expressed as mean ± standard deviation (SD) and were compared using ANOVA, followed by Tukey’s test for post hoc analysis (for other parameters). Differences of p < 0.05 were considered significant. Results After anaesthesia, ECG recordings of the four groups at baseline, and first and second hours were obtained and compared between all groups (Table 1). The measurements of the control group were within normal limits and consistent with the literature.13 In the control group, QT was 77.33 ± 9.02 ms at baseline, 73.50 ± 2.26 ms at the first hour, and 78.17 ± 6.18 ms at the second hour. The QTc calculation was 165.42 ± 18.34 ms at baseline, 166.63 ± 17.92 ms at the first hour, 184.65 ± 12.86 ms at the second hour (Table 1). ECG findings of the EMPA group were within normal limits and similar to the control group (Table 1). Although baseline HR were different between the groups, after anaesthesia all HR became similar and consistent with the literature (Table 1). The durations of QT interval and QTc were found to be statistically longer in the AMT group than in the control group at the first and second hours (p ≤ 0.001) (Table 1, Fig. 2). EMPA significantly ameliorated AMT-induced QT and QTc prolongation. The durations of the QT interval were significantly lower at the first (p < 0.001) and second hours (p < 0.01) in the AMT+EMPA group compared to the AMT group. Moreover, the QTc calculation was significantly lower in the AMT+EMP group than in the AMT group at the first and second hours (p < 0.01) (Table 1). ECG comparisons of all groups for one second within the second hour can be seen in Fig. 3. When the changes in baseline, and first and second hours of the QT intervals of the groups were compared with repeated measurements ANOVA, there was a significant difference between time points (p < 0.001). Moreover, there was a significant difference between the AMT group and all the other groups (p < 0.01). In addition, when the changes in baseline, and first and second hours of the QTc intervals of the groups were compared with repeated measurements ANOVA, there was a significant difference between time points (p < 0.001). There was also a significant difference between the AMT group Fig. 1. A. Drug administration to the animals via an oral tube. B. ECG recording of the rats from the D2 lead in a supine position with the Biopac MP36 system. A B
RkJQdWJsaXNoZXIy NDIzNzc=