frequently asked questions

what is the simulation request process and how to interpret outcome?

When a physician requests a simulation, they will receive:

• Simulation reports comparing two or more EVAR strategies (e.g., different Endurant sizes, landing zones, or introduction sides, or a combination of these).
• An ERI (Endoleak Risk Index) associated with each simulation.
• A link to iView Colour, with apposition gaps between the graft and aortic wall, providing direct access to the platform and allow the visualisation of 3D simulation from different devices.
• Three levels of support: Clinical support, Technical and peer-to-peer discussion between surgeons.

How are the cross section shown in the report ?

In the new version of the report, 12 cross-sections per simulation are now provided, supporting the physicians in their EVAR strategy choice. Transversal cross-sections are displayed every 2mm along the proximal neck, starting from the landing zone and extending up to 18 mm distally (shown in blue). In addition, two extra cross-sections are provided: one at the midpoint of the third stent and another at the midpoint of the fourth stent.

These cross-sections highlight the apposition and any potential gap between the graft (depicted in black) and the aortic inner wall (depicted in red). It is important to note that thrombus is not represented in these cross-sections; only the inner aortic wall, excluding thrombus, is shown in red.

How good apposition but high ERI should be handled/ interpreted?

Even when the distance color map suggests an apparently good apposition between the endograft and the aortic wall, there can still be a significant risk of type 1A endoleak. This discrepancy arises because the Endoleak Risk Index (ERI) is not limited to the evaluation of apposition alone. Instead, it integrates additional anatomical and procedural factors that play a crucial role in sealing effectiveness.

Among these, graft oversizing and the detailed morphology of the aortic neck are particularly important. Features such as conicity and circularity of the proximal neck may substantially influence the ERI results despite seemingly optimal contact.

With the new ERI 2, the occurrence of double reds has decreased significantly, but they are still present. Why?

With the introduction of ERI2, the number of double red cases—where both simulated strategies predict ahigh risk of type 1A endoleak—has dropped by approximately 59%.

This improvement is largely due to the expansion of the training and validation datasets (now 117 patients in the training set and 56 in the validation set), which has led to a better balance between sensitivity and specificity.

Despite this progress, a non-negligible proportion of double red cases remains—about 1 in 5. There are two main reasons for this:

• False Positives: Even with improved algorithm robustness, some double red results are due to false positives. In recent analyses, when ERI 2 was applied to previously archived double red cases, more than half had at least one simulation with a low ERI (unlikely or highly unlikely), suggesting that the new version reduces, but does not eliminate, false positives.
• Challenging Anatomies: Some patient anatomies are inherently unsuitable for EVAR, regardless of the device or strategy simulated. In these cases, the ERI will consistently indicate a high risk, reflecting the true clinical challenge rather than a limitation of the algorithm.

Therefore, while ERI 2 significantly reduces the frequency of double red cases, their continued presence highlights both the complexity of certain anatomies and the inherent limitations of any predictive model.

In practice, double red results should prompt careful clinical review, and we are happy to support you in this process

Does ERI consider infolding?

Infolding has been analysed in a few (3-4) retrospective patients who experienced this complication. For some of them, the infolding was visible on the simulation, for others not.

To design and validate a predictive model of infolding based on simulation, we would need to gather a significant number of patients with infolding, simulate them, and validate that this complication is also seen on the simulation; as it stands, the system does not look at potential infolding of the device.

ERI behaviour with excessive oversizing (beyond values in practice) is uncertain: 

ERI was trained on a cohort of real patients with oversizing values typically used in clinical practice (no more than 35%). In simulations where oversizing exceeds this threshold, ERI values may not be meaningful. In such cases, most clinical experts would find it difficult to predict outcomes.

How do you handle simulations outside of IFU?

As shown in EnduSim, only 2/3 of patients with type 1A endoleak were inside IFU. As more complex patients with hostile necks are being considered for EVAR, a dedicated tool to help prediction of type 1A endoleak is vital. 

Nevertheless, when a case is outside IFU, SmartPlanPro will provide a second opinion to assure that the physician can make an informed decision and that the patient will receive the best possible treatment. However, we do not want to promote use outside of IFU. Therefore, in these cases the following legally approved statement will be added to the case planning notes of the Predisurge simulation and 3Mensio report:

"Please note that this case is outside of the device’s Instructions for Use (IFU) and Medtronic does not recommend to use the device for indications outside the scope of those specified in the labelling and IFU as it has not been tested and validated for safety and efficacy under these circumstances. The physician is solely responsible for all decisions and any medical judgment relating to patient diagnosis and treatment, including case selection and sizing of the device."

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