## 4 Use Case
### Systematic Approach for SCVAD Modeling
#### 4.3.1 Adverse Process Modeling  
Each PFS was transcribed into an interpreted PN based on the process modeling resources presented in Section 2.3, titled Formalisms for Process Modeling of Complex Systems. A legend in each PN references the elements used, namely, a discrete transition, discrete place, oriented arc, and enabling arc. The enabling arcs are used to represent data \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Guide** & **Deviation** & **Cause** & **Detection** & **Consequence** & **Recommended Actions** \\ \hline Yes & \begin{tabular}{c} Symptoms of HF \\ or persistent low \\ flow \\ \end{tabular} & \begin{tabular}{c} Medical \\ evaluation \\ \end{tabular} & \begin{tabular}{c} Evaluate and correct hypovolemia, \\ arrhythmia, or hypertension \\ \end{tabular} \\ \hline Less & \begin{tabular}{c} Slow decrease in \\ blood flow \\ \end{tabular} & \begin{tabular}{c} Post-pump \\ Thrombosis \\ \end{tabular} & \begin{tabular}{c} Outflow blood flow \\ \end{tabular} & \begin{tabular}{c} Perturbation of \\ outflow blood flow \\ \end{tabular} \\ \hline Yes & \begin{tabular}{c} Outflow \\ obstruction \\ \end{tabular} & \begin{tabular}{c} Imaging \\ diagnosis \\ \end{tabular} & \begin{tabular}{c} Surgery for stent placement with carotid \\ protection if obstruction confirmed \\ \end{tabular} \\ \hline Yes & \
\begin{tabular}{c} Anastomosis \\ stenosis \\ \end{tabular} &
\begin{tabular}{c} Surgery for stent placement if stenosis in the \\ anastomosis is confirmed \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 6: HAZOP table for post-pump thrombosis (AE1.3). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Guide Word** & **Deviation** & **Cause** & **Detection** & **Consequence** & **Recommended Actions** \\ \hline More & \begin{tabular}{c} Increase power \\ consumption \\ \end{tabular} & \begin{tabular}{c} Device alarms \\ \end{tabular} & \begin{tabular}{c} Thromolysis, re-evaluation, and oral \\ anticoagulation \\ \end{tabular} \\ \hline Yes & \begin{tabular}{c} Presence of the \\ third harmonic \\ \end{tabular} & \begin{tabular}{c} Intra-pump \\ Thrombosis \\ \end{tabular} & \begin{tabular}{c} Acoustic \\ analysis \\ \end{tabular} & \begin{tabular}{c} Device malfunction \\ \end{tabular} & \begin{tabular}{c} \\ \end{tabular} \\ \hline Yes & \begin{tabular}{c} Symptoms of HF \\ severe hemolysis \\ \end{tabular} & \
\begin{tabular}{c} Medical \\ evaluation \\ \end{tabular} &
\begin{tabular}{c} Pump exchange surgery \\ \end{tabular} \\ \hline \end{tabular}
\end{table} 
Table 5: HAZOP table for intra-pump thrombosis (AE1.2). flow with the external environment, and a table of inputs (transitions) and outputs (places) for the PN is provided in Appendix A to aid understanding. The transitions and places have been named as necessary to maintain a clean and clear design in the figures. Figure 9 presents the digital adverse event diagnosis model (DMAD), which supports the specification of diagnostic modules for adverse processes associated with known adverse events. The 'adverse process diagnosis module AE1' presented in Figure 10 was developed through the HAZOP study for risk identification detailed in Section 4.2 and was further elaborated into three adverse activities:  
* The PFS model 'pre-pump thrombosis AE1.1' is presented in Figure 11, with the corresponding PN in Figure 12.
* The PFS model 'intra-pump thrombosis AE1.2' is presented in Figure 13, with the corresponding PN in Figure 14.
* The PFS model 'post-pump thrombosis AE1.3' is presented in Figure 15, with the corresponding PN in Figure 16.  
Figure 11: PFS and detailing of the adverse activity ‘pre-pump thrombosis AE1.1\({}^{\prime}\). Figure 12: PN corresponding to the adverse activity ‘pre-pump thrombosis AE1.1\({}^{\prime}\). Figure 13: PFS and detailing of the adverse activity ‘intra-pump thrombosis AE1.2\({}^{\prime}\).