# Calculation of Intracoronary Pressure-Based Indexes with JLabChart
## 3 Results and Discussion  
JLabChart was tested on pressure measurements obtained in the interventional cardiology laboratory of the University Hospital of Catanzaro on 65 patients divided into two datasets: (i) 58 patients (102 _runs_) and (ii) 39 patients (102 _runs_), with an overlap of 32 patients between the two groups, where both FFR and iFR measurements were available, for a total of 600 _cardiac cycles_. A cardiac cycle is a pressure cycle between two consecutive diastolic points. A run is a 6 second time interval. Two types of experimental tests were performed to measure JLabChart's calculated values in terms of quality and reliability compared to commercial software. Starting from 600 cardiac cycles, JLabChart identified:  
* 595 recognized cycles in the distal pressure signal;
* 600 recognized cycles in the proximal pressure signal. Figure 9: JLabChart Software tool. User interface with various visual and numerical signal analyses. FFR and iFR values calculated with JLabChart and commercial software show that the JLabChart results are reliable and comparable with those obtained by the commercial system. A statistical analysis was performed in order to find the correlations between measures. The analysis included: (i) a correlation plot (Figures 10a and 11a), (ii) a Youden plot (Figures 10b and 11b), and (iii) a Bland-Altman plot (Figures 10c and 11c). These plots report both the FFR and iFR indexes. The correlation plots in Figures 10a and 11a confirm the strong correlation between the results obtained with the two systems. This is demonstrated by (i) the dissemination degree of the points in the diagram, (ii) a high value of the correlation coefficient (FFR: \(R_{p}=0.96\), iFR: \(R_{p}=0.998\)), and (iii) a value of the intraclass correlation coefficient (FFR: \(R_{IC}=0.96\), iFR: \(R_{IC}=0.9796\)), implying an excellent reproducibility of the measurements. Both plots confirm that JLabChart has a robust correlation with commercial software and a high reproducibility between measurements. In Figures 10b and 11b we report two Youden plots, a type of scatter plot used to visually plot measurement results from multiple instruments on the same graph in order to uncover any bias in measurements and make it easy to detect any differences between JLabChart and the commercial software. The Youden plots showed that the FFR and iFR values from the two tools lay on the bisector line of the first and third quadrants, which proves that the JLabChart FFR (or iFR) values and commercial software FFR or (iFR) values were statistically similar. This means that the FFR and iFR values calculated by JLabChart agreed with the commercial tool. \begin{table}
\begin{tabular}{c c c c c} \hline
**ID\_Patient** & **FFR\({}_{c}\)** & **FFR\({}_{j}\)** & **iFR\({}_{c}\)** & **iFR\({}_{j}\)** \\ \hline
1 & 0.77 & 0.79 & 0.90 & 0.91 \\
2  
Figure 11: Statistical analysis results for the iFR index between commercial software and JLabChart. Figure 10: Statistical analysis results for the FFR index between commercial software and JLabChart. Lastly, the Bland-Altman plots, also known as difference plots, reported in Figures 10c and 11c plot the FFR and iFR values calculated by JLabChart and the commercial software in order to analyze the agreement between the two different groups of measures. In fact, any two methods designed to measure the same parameter (or property) should have a good correlation when a set of samples is chosen such that the property to be determined varies considerably. Figures 10 and 11 show that the values obtained by using JLabChart are comparable with those of the commercial system, since the data points are around the mean value and are delimited by the standard deviation. The four graphs shown in Figure 12 report our investigation into irregular cardiac frequency recognition, with the aim of identifying the presence of noise as well as extra-systoles or tachycardias (thus, cycles with irregular cardiac frequency were filtered out from the analysis).