## 4 Discussion
#### Limitations  
Sample sizes should be consistent, despite the difficulty in maintaining the dimensions of cardiac tissues due to their inhomogeneity. This task is quite challenging as the interatrial septum consists of both the thinner and thicker regions. Moreover, it is important to grip all the samples at the same location when mounted on the tensile test machine. This is not practically achievable in the case of some biological samples, as the thickness of the septum varies from heart to heart. In the tensile test, FO was securely fixed at one end using a static fixture. A similar fixture was not used during the indentation test. However, the sample was almost the size of the Petri dish, which resisted FO from moving during the test. A fixture setup may be used to hold the tissue more effectively. During the test, one cannot predict what part of the sample will rupture initially as this depends on the thickness of the sample. Therefore, the plots for such tissue samples tend to show significant variation. Due to these limitations, five samples out of twenty failed during the test. With respect to the tensile test experiments, only the uniaxial boundary condition was considered. A limitation of biaxial testing is that the system cannot record the actual region of interest loads. These could be lower than the applied loads measured by the load cells. To overcome challenges with such experimental methods, optical imaging methods could be considered to determine the strain in FO. Literature studies suggest using finite element methods to calculate a correction factor, which could be used to calculate the experimental stresses at the region of interest. A combination of experimental and finite \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline  & \multicolumn{3}{c}{**Available Data from Previous Studies**} \\ \hline
**No. of Hearts** & **Heart Weight (g)** & \begin{tabular}{c} **BRK Neede Size and Tip** \\ **Geometry** \\ \end{tabular} & \
\begin{tabular}{c} **Average Puncture** \\ **Force (N)** \\ \end{tabular} &
\begin{tabular}{c} **Methodology** \\ \end{tabular} \\ \hline
55 & 428 130 & 4F (Tapered Tip) & 2.33–2.73 &
\begin{tabular}{c} Puncture Testing of Fossa \\ Ovalis [21] \\ \end{tabular} \\ \hline
2 & Not specified & \begin{tabular}{c} 3.2F (Trocar Neede) \\ 3.8F (Bevel-Tip Neede) \\ \end{tabular} & \
\begin{tabular}{c} \textless{}1.5(Trocar) \\ \textless{}0.8 (Bevel) \\ \end{tabular} &
\begin{tabular}{c} Needle Insertion into Porcine \\ Hearts [10] \\ \end{tabular} \\ \hline \hline \multicolumn{4}{c}{**Recorded Data for Current Study**} \\ \hline
**No. of Hearts** & **Heart Weight (g)** & \begin{tabular}{c} **BRK Neede Size and Tip** \\ **Geometry** \\ \end{tabular} & \
\begin{tabular}{c} **Average Force (N)** \\ \end{tabular} &
\begin{tabular}{c} **Methodology** \\ \end{tabular} \\ \hline
14 & 430.2 17.5 & 3.8F (Bevel Tip) & \
\begin{tabular}{c} 15.57 (Hemispherical) \\ 5.47 (BRK) \\ \end{tabular} &
\begin{tabular}{c} Indentation on Fossa Ovalis \\ \end{tabular} \\ \hline
15 & 430.2 17.5 & - & 10.51 &
\begin{tabular}{c} Tensile Testing of Fossa \\ Ovalis \\ \end{tabular} \\ \hline \hline \multicolumn{4}{c}{**Available Data from Previous Studies**} \\ \hline
**Objective** & \begin{tabular}{c} **FO Diameter Range (mm)** \\ \end{tabular} & \begin{tabular}{c} **FO Shape** \\ \end{tabular} \\ \hline Morphological study of fossa ovalis [2] & 12.60–14.53 & \
\begin{tabular}{c} Oval (82\%) \\ \end{tabular} \\ \hline Overview of trans-septal punctures; & 12.6–14.5 &
\begin{tabular}{c} Oval (86\%) \\ \end{tabular} \\ \hline \hline \multicolumn{4}{c}{**Recorded Data for Current Study**} \\ \hline
**Objective** & \begin{tabular}{c} **FO Diameter Range (mm)** \\ \end{tabular} & \
\begin{tabular}{c} **FO Shape** \\ \end{tabular} \\ \hline Dissection of fossa ovalis for the purpose of mechanical testing & 8.2–15.0 (Vernier Calipers) &
\begin{tabular}{c} Oval \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Diameter data comparison.