Discussion

The survey was performed with the intention of disclosing the current status of neurointerventional training models particularly in regard to the incidence of animal models applied and training environments preferred. To our knowledge, this survey is the first to report the experience in different neurointerventional training environments in European countries. Including answers of 71 neurointerventional participants from 25 different countries, it can be considered as representative of European neurointerventional practice.

In neurointerventional practice, training environments are important in facilitating the safe use of existing and new devices, particularly with regard to intraprocedural complications.3 4 8 10 Therefore, a structured neurointerventional education with the possibility of hands-on training in artificial surroundings is necessary. For learning diagnostic angiography as a beginner, participants of our survey most favorably rated angiography simulators (figure 1A). To learn more complex interventional procedures such as coil embolization of cerebral aneurysms, implantation of a flow diverter, and acute endovascular stroke intervention (figure 1B-D) both animal-based training and the use of vascular models or angiography simulators were more commonly rated as suitable applications. In our opinion, one of the reasons why simulators were rated as less suitable for more complex procedures may be the lack of direct, ‘true’ tactile feedback. This type of tactile feedback can be experienced in vascular models and animal-based training, and certainly contributes significantly to the learning curve associated with procedures such as flow diverter implantation, which require intimate control over the movement of the pusher wire and associated catheters to allow adequate device positioning. Therefore, further refinement of vascular models should be focused on improving the reproduction of these more complex interventions, which would both address the need for an adequate training environment reflected by our study’s respondents as well as increase the likelihood of actually replacing animal experiments. Interestingly, in addition to their suitability for less complex interventions, angiographic simulators were also rated as particularly suitable for training lesser-experienced physicians. These findings may be helpful, e.g. for designing a tiered-stage training curriculum incorporating both simulators and vascular models.

Our survey confirms that in several European countries, animal-based training is still quite frequently utilized for teaching neurointerventional procedures and is generally regarded as suitable, particularly for training more complex interventional procedures (see also figure 1). Coil embolization and acute endovascular stroke intervention were the most commonly practiced procedures, both being associated with relatively high reported frequencies of animal based-training. These procedures therefore qualify as particularly valuable targets for the development of improved vascular models when aiming to reduce animal experiments. Physicians with expertise in using animal-laboratory training rated this type of training modality as suitable for beginners to learn distinct neurointerventional procedures, whereas respondents without experience working on animal models heterogeneously assessed its eligibility (see figure 4). Remarkably, a majority of participants rated animal-based training as moderately- or even very well-suited for beginners, without these participants themselves being experienced in the use of animal-laboratory training. Although the reasons for the aforementioned heterogeneities remain unknown, these results can be interpreted as a general need for a more standardized neurointerventional training curriculum and the principal support for the use (and therefore the development) of vascular models offering an adequate training environment resembling human structures, which may offer an ethically preferable alternative to animal experiments.

The results of our survey furthermore show that the participants’ level of experience seems to affect the preferred training environment. Animal-based training was rated preferably to learn and improve operator skills by less experienced respondents, whereas the more experienced physicians evaluated animal-based training as less suitable (see figure 3). This relationship may point at the shortcomings of animal-based training. Animal models include constant bloodflow with its typical hemodynamic forces and representative haptics of the vessel walls as well as the possibility for thrombosis and vasospasm.¹⁴ Participants might appreciate the awareness of operating on a living creature, generating a more realistic setting. However, animal models are poorly predictive regarding clinical complications¹⁶ and carry inherent limitations such as the non-human anatomy (which often poorly reflects the disease process being simulated, particularly for coil embolization) or unrealistic device behavior, such as the strong microcatheter pulsation often observed in the rabbit elastase aneurysm model.9 10 14–17 An alternate interventional training method using silicone models based on 3D printing technology might be a feasible approach to overcome some of the important limitations of animal-based training and has been shown to be a crucial part of the education for neuroradiologists so far.9 17 3D printing of vascular structures offers the possibility of testing endovascular devices in different patient-specific conditions, ranging from simple straight vessel anatomy over severe curvature or stenoses to the multitude of different real aneurysm morphologies. From an educational standpoint, the ability to theoretically rehearse a challenging case based on DSA and video recordings and afterwards perform training in an anatomically identical vessel model, is unique to this training environment and certainly exciting.

Our results might indicate that the shortcomings of animal-based training are more evident to more experienced physicians. The future improvement of vascular training models should therefore aim at overcoming some of these limitations of animal-based training while trying to increase acceptance, particularly among lesser-experienced physicians.

As our survey reveals some disparities regarding training modalities and preferences, it points out the central issue of lacking a standardized neurointerventional curriculum in Europe at once. The general concept of neurointerventional in-vitro training to test new devices prior to clinical use and to teach neuroangiographic skills as a part of specialty and subspecialty training was strongly supported by the majority of our respondents, although hardly any queried training programs (angiography simulators, vascular models, or animal training) were rated as mandatory before performing interventional procedures in patients for the first time. Most of the physicians are trained by observing and gradually performing tasks independently before performing diagnostic and interventional procedures in patients. Furthermore, European comparison relating to the different neurointerventional types of training centers offering educational hands-on courses revealed wide imbalances (see also figure 5). Neurointerventional education seems to be well-developed in central Europe, showing the highest total numbers of academic centers and offering a sufficient number of hands-on courses per million inhabitants at the same time. However, it must be conceded that not all neurointerventions are done and therefore trained in academic hospitals and that health structures differ between countries. Comparing the regional distribution of state-owned and company-owned educational centers considerable homogeneities with overall insufficient numbers of training centers could be observed, indicating the high demand for widening these educational structures. The critical issue of major worldwide differences regarding the organization of neurointerventional training was reported earlier.18 19 Hence a structured approach for different neurointerventional training concepts is needed, aiming to improve operators’ technical skills. European differences must be overcome to provide a thriving education for all neurointerventionalists independent of their origin. Apart from providing the required theoretical background, an adequate educational curriculum should include skill-based training in a dedicated training environment. Performing a fixed number of procedures in a training environment or passing certain skill-based assessments might be considered before working with patients and simultaneous observation of real interventions in the angiosuite should be guaranteed. There is the need for future research to determine which training environment is most-suited, but we believe that a combination of angiography simulators and vascular models can be utilized to design a well-rounded training curriculum and would support this approach from an ethical point of view. In our opinion, and supported by the survey results, angiography simulators might be most useful for learning and practicing the basic steps of angiography and interventional procedures. Subsequently, vascular flow models are necessary to offer a higher degree of realism in terms of catheter and device haptics, and detailed vascular anatomy. Several opportunities for resident training in surgery comprising vascular surgery simulation laboratories are already in use, successfully showing that simulator training can increase practical skills.20–22 The endorsement of simulation to augment practical training and the benefit of developing a standardized simulation curriculum was already reported earlier by Duran et al who surveyed 183 surgical trainees about the educational value in simulation training.22 We therefore conclude that not only the reduction of animals applied in interventional training settings, but moreover a standardized educational curriculum, is appropriate to train neurointerventionalists.

The survey had several limitations. As the ESMINT served 344 members in good standing at the time of distributing the survey link, the response rate was only moderate (21%). Although it cannot be guaranteed that all replies were from actual ESMINT members, all participants confirmed to work as practicing neurointerventionalists. Near-complete or incomplete datasets were relatively frequent (n=21). We didn’t ask for the average number of performed neurointerventions per year, which might have shown an association with the individual opinion on training opportunities. Additionally, we did not assess the participant’s formal background in terms of medical specialty or subspecialty training. As our data was only acquired from European centers it cannot be directly applied to other countries.