Novel, intermediate‐fidelity simulator for aortic arch surgery for the cardiothoracic surgical trainee

Training cardiothoracic surgeons in open aortic surgery is challenging due to limited operator experience, low patient volume and technically demanding skills to be performed within a deep thoracic cavity. Surgical simulation has become a cornerstone of cardiothoracic surgical training and has been shown to improve skill acquisition and performance in the operating theatre. Due to the complexity of aortic surgery, there is a paucity of simulators that are concomitantly accessible and of sufficient fidelity. The purpose of this study was to develop a reproducible, intermediate‐fidelity simulator for aortic surgery.


Introduction
Training in open aortic surgery is innately a challenge due to limited operator experience, low frequency of exposure, the threedimensional anatomy of the aortic root and aorta, and complex techniques that are to be performed within a deep thoracic cavity, while under time pressure with high stakes outcomes.Surgical simulation has increasingly been used in cardiothoracic surgical training and has been shown to improve skill acquisition and performance in the operating theatre. 1,2However, despite the complexity of aortic surgery, there is a paucity of simulators that are concomitantly accessible and of sufficient fidelity.The paper reports on an inexpensive, reproducible, intermediate-fidelity simulator for aortic surgery.

Materials and methods
Plastic storage containers (13.5 Â 46 Â 29.5 cm) purchased from Kmart were used to act as the bounds of the thoracic cavity.Three small holes were drilled into the top of the storage container by Dr Cole in an arrangement based on the dimension and special arrangement from the CT scan of a patient who required an aortic arch replacement (Fig. 1).One hole was drilled into the right-hand side, $2 cm from the top of the container.In these holes, graft pieces were placed, simulating the arrangement of the head vessels and distal arch (Fig. 2).Synthetic Dacron polyester grafts were used to maximize model fidelity.The head vessels and aorta grafts were $1 and 3 cm in diameter, respectively, to replicate the real-life vessel diameters (Fig. 2).A porcine or bovine heart was used for the simulation of aortic root replacement and anastomosis to the distal arch graft (Fig. 3).This model was reproduced for the wet-lab training session of Australian cardiothoracic trainees.This project was exempted from ethics review due to its negligible risk.

Results
The simulator was utilized during the Royal Australasian College of Surgeons Cardiothoracic Surgery Trainee meeting.The first task was to anastomose a branched arch graft to the 'subclavian', 'common carotid' and 'innominate' arteries, and then perform an open distal anastomosis.The second task was to perform an aortic root replacement on a porcine or bovine heart and attach this to the distal arch graft.The trainees were assigned pairs, a junior with a senior trainee, to perform a timed open distal anastomosis.Consultant surgeons provided direct observation and instruction.Feedback was obtained from attendees through a questionnaire, who reported that the simulator was 'confidence building', 'a good opportunity to practise the anastomosis repeatedly' and 'an excellent opportunity to practise a procedure they are unlikely to encounter as a primary surgeon, being a trainee, with the benefit of immediate feedback'.The simulator enabled surgical trainees to learn and practise technically demanding procedures, maximizing fidelity through using industry-provided Dacron grafts and porcine and bovine hearts.

Discussion
'See one, do one, teach one' has been the long-held mantra for surgical skill acquisition, based on an apprenticeship model of training. 3However, certain procedures do not occur frequently enough for adequate opportunity for trainees to achieve proficiency.Teaching and assessment of procedural proficiency is hindered by the time-pressured clinical environment where supervisors are often expected to balance patient care with teaching responsibilities. 3As such, the surgical education paradigm has shifted towards including simulation as a means of skill acquisition.
Simulation has been demonstrated to improve trainee confidence and technical performance in the operating theatre. 4,5Despite the technical challenge of cardiothoracic surgery, there are a lack of training models that are of sufficient fidelity.][8] The basis of our design is a reproducible, intermediate to high fidelity model.High fidelity simulations such as those involving cadaveric specimens are becoming less feasible and accessible, due to its resource-intensive and high-cost nature.The utilization of Dacron grafts and tissue hearts significantly increase the fidelity of the model, by almost close approximation of tissue and graft properties expected in surgery, allowing the strength and integrity of the anastomosis to be tested.While attaining high quality graft  material is a potential limitation to this model, graft material may be substituted, and the materials required for the rest of the simulator is easily accessible at a low-cost.Additionally, the model is portable, quick to construct and easy to use, while providing the experience of working within a deep thoracic cavity.The model has been tested by Australian cardiothoracic trainees and yielded highly positive feedback.Coupled with wet-lab workshops and consultant guidance, this intermediate-fidelity model provides trainees with an invaluable opportunity to develop and practise the technical skills required in aortic surgery.

Conclusion
This is a cost-effective, easily reproducible, intermediate-fidelity simulator for aortic surgery, attested to by Australian cardiothoracic surgical trainees.As the surgical education paradigm shifts towards include simulation, this model provides an effective avenue to equip the trainee for the operating room.It is a feasible method of surgical training that can be considered by training supervisors and colleges.

Fig. 1 .
Fig. 1.Three holes were drilled on top of the storage container to replicate the arrangement of the aortic arch branches.

Fig. 2 .
Fig. 2. Dacron graft pieces placed in an arrangement simulating the head vessels and distal arch.

Fig. 3 .
Fig. 3. Porcine or bovine heart was used for a wet-lab skills training session for Australian cardiothoracic surgical trainees.