# Temporary Pacing Simulator: A Training Tool for Clinicians
## 3 Experimental Results
### Pacing Failure Scenarios  
This subsection details the analysis of various pacing failure modes simulated by the TCPS. Understanding the behavior of different pacing modes is crucial for clinicians, but it is equally important to understand pacing failure modes. Clinicians must be able to detect different types of pacing failures, comprehend their causes, and respond quickly by adjusting settings to correct them. Each pacing failure mode impacts the signals differently, and detection is not always straightforward. The TCPS simulates four major types of pacing failures: ALOC, VLOC, undersensing, and oversensing, all of which will be described in this section. Figure 17 illustrates a simulated scenario of intermittent VLOC in DOO pacing mode at a rate of 80 bpm. In this failure mode, the TCPS delivers pacing spikes that successfully capture the atria, but the ventricular spikes fail to generate a ventricular contraction. This is most evident in the ECG signal, where pacing spikes are visible without the subsequent QRS complexes, indicating that the electrical impulse from the TP is not depolarizing the ventricles. As a result, VLOC leads to decreased cardiac output, which is reflected in the ABP and CVP signals. Similarly, the TCPS-simulated ALOC manifests in a comparable way, but in this case, the loss of capture occurs in the atria. Figure 18 presents an ALOC scenario in DOO mode with a pacing rate of 75 bpm. In this scenario, pacing spikes are visible on the ECG signal before the first three R peaks, followed by a flat line indicating the lack of atrial conduction. However, unlike VLOC, ALOC does not significantly affect the blood pressure signals, as the loss of atrial capture has a less pronounced impact on overall cardiac output compared to the loss of ventricular capture. Sensing failure modes manifest differently compared to capture failure modes. In the case of undersensing, as shown in Figure 19, the TP fails to detect intrinsic cardiac events appropriately. While the ECG signal maintains its typical waveform, with clearly identifiable P waves, QRS complexes, and T waves, pacing spikes are observed at inappropriate times. In the scenario of atrial undersensing, depicted in Figure 20, pacing spikes are erroneously superimposed on the P-waves. These spikes occur during the atrial depolar  
Figure 16: Example of the signal displayed when the user selects the baseline signal, in this case, SR, and chooses the DDI pacing mode with a pacing rate under 70 bpm, causing the intrinsic conduction to show on the signals and the inhibition of the pacing spikes in both the atria and the ventricles, where intrinsic conduction occurs. ization phase--a time when the atria are naturally contracting. Normally, the pacemaker should inhibit pacing upon detecting an intrinsic P-wave, but the failure to sense this atrial activity results in unnecessary pacing stimuli. This disruption in atrial sensing can lead to asynchronous atrioventricular contractions, potentially causing hemodynamic inefficiency. In the case of ventricular undersensing, shown in Figure 21, pacing spikes are incorrectly placed on the T-waves, which follow the QRS complexes. These sharp, narrow deflections during the ventricular repolarization phase indicate the TP's failure to detect intrinsic ventricular activity. Pacing during this phase is particularly dangerous, as it can lead to arrhythmias by interfering with the heart's recovery phase. Normally, pacing spikes should precede the QRS complex when pacing the ventricles, but this failure to properly sense ventricular activity results in pacing during an inappropriate phase of the cardiac cycle. In DDI pacing mode, undersensing can occur in both the atria and ventricles simultaneously. The TCPS simulates both scenarios simultaneously, as shown in Figure 22.  
In oversensing, the pacemaker incorrectly detects electrical signals (noise or other non-cardiac signals) as heartbeats, leading to inappropriate inhibition of pacing, which can cause the heart to miss needed beats.