## 3 Results
### Electrocardiogram Monitoring and Histological Changes of the Heart  
Figure 3 shows the ECG changes characteristic for all groups included in the study. The results of the interpretations of the ECGs are presented in Table 1.  
Administration of ISO induced important ECG changes, such as reduced RR intervals, increased HR (heart rate) and QT and QTc intervals, QRS complex prolongation, ST-segment elevation, and reduced R-wave amplitude (Figure 3b, Table 1). These changes are characteristic of ISO-induced AMI. The administration of STZ caused a lengthening of the RR interval and a decrease in HR, but also a prolongation of the QRS complex. Both ISO and STZ did not affect the PR segment (Figure 3, Table 1). Conventional curcumin and NC increased the RR interval and decreased HR in all groups (Figure 3e-h, Table 1), with significantly better NC than CC (Table 1, \(p=0.0021\)). \begin{table}
\begin{tabular}{l l l l l l l l l} \hline \hline
**Abbreviation** & **RR(ms)** & **HR(b/min)** & **PR(ms)** & **QRS(ms)** & **QT(ms)** & **QTc(ms)** & **R(mV)** & **ST(mV)** \\ \hline C & 209 (7.0) & 287 (9.6) & 44 (2.1) & 35 (2.2) & 75 (4.4) & 64 (3.7) & 3 (0.11) & 0.00 (0.00) \\ AMI & 180 (3.1) & 333 (5.7) & 45 (2.2) & 53 (2.3) & 103 (3.6) & 94 (3.0) & 1.3 (0.10) & 0.09 (0.01) \\ T1 DM & 239 (8.7) & 252 (9.4) & 43 (1.7) & 42 (1.3) & 85 (3.6) & 68 (2.4) & 2.1 (0.13) & 0.00 (0.00) \\ T1 DM-AMI & 191 (3.0) & 314 (5.0) & 44 (2.6) & 57 (2.0) & 113 (3.0) & 100 (2.7) & 1.2 (0.08) & 0.10 (0.02) \\ S-T1 DM-CC- AMI & 223 (3.6) & 269 (4.3) & 43 (1.5) & 42 (2.2) & 99 (2.5) & 81 (1.6) & 1.2 (0.13) & 0.08 (0.01) \\ CC-T1 DM-CC-AMI & 226 (6.6) & 266 (7.7) & 43 (1.5) & 40 (1.3) & 94 (2.9) & 76 (3.1) & 1.4 (0.13) & 0.08 (0.02) \\ S-T1 DM-NC-AMI & 249 (6.1) & 241 (5.8) & 44 (1.7) & 37 (1.7) & 88 (1.7) & 68 (1.2) & 1.7 (0.17) & 0.05 (0.01) \\ NC-T1 DM-NC-AMI & 250 (3.4) & 240 (3.4) & 44 (1.4) & 37 (1.6) & 87 (2.7) & 67 (2.1) & 2.1 (0.17) & 0.02 (0.01) \\ \hline \hline \end{tabular} The values in the table represent the mean and standard deviation (in round brackets): HR—heart rate; C—control; AMI—acute myocardial infarction; T1 DM—type 1 diabetes mellitus; S—saline (0.09%); CC—conventional curcumin solution (200 mg/Kg bw); NC—solution of curcumin nanoparticles (200 mg/Kg bw).  
\end{table} 
Table 1: ECG interpretation for each group. Figure 3: ECG changes characteristic of each group. (**a**) C, (**b**) AMI, (**c**) T1 DM, (**d**) T1 DM-AMI, (**e**) S-T1 DM-CC-AMI, (**f**) CC–T1 DM-CC-AMI, (**g**) S-T1 DM-NC-AMI, (**h**) NC–T1 DM-NC-AMI. Increased RR interval (black arrow), reduced RR interval (purple arrow), lengthening of the QRS complex (orange arrow), increased QT interval (red arrow), ST-segment elevation (green arrow), reduced amplitude of the R wave (yellow arrow). C—control; AMI—acute myocardial infarction; T1 DM—type 1 diabetes mellitus; S—saline (0.09%); CC—conventional curcumin solution (200 mg/Kg bw); NC—solution of curcumin nanoparticles (200 mg/Kg bw). NC was more effective than CC in preventing elongation of the QRS complex (Figure 3e-h, Table 1, \(p\leq 0.0057\)), without statistically significant differences between the two groups that received NC (\(p>0.05\)). Curcumin nanoparticles more effectively prevented the prolongation of QT and QTc intervals after AMI induction, compared to conventional curcumin (Figure 3e-h, Table 1, \(p\leq 0.0026\)), without statistically significant differences between the two groups that had received NC (\(p>0.05\)). The administration of NC most effectively prevented the R-wave amplitude reduction prior to T1 DM induction (Figure 3, Table 1, \(p\leq 0.0048\))  
Curcumin nanoparticles effectively reduced ST-segment elevation (Figure 3g-h, Table 1, \(p\leq 0.0021\)). The best effect for reducing ST-segment changes was obtained for NC administered before T1 DM induction (Figure 3h, Table 1, \(p\leq 0.0066\)).