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February 2011 Supplement
The Role of Simulation in Aortic Endografting
How this tool can be used effectively to train the next generation of vascular clinicians.
By Alan B. Lumsden, MD; Jean Bismuth, MD; and Michael A. Donovan, BS
Endovascular training for vascular surgeons began in the mid 1990s, and at that time, the use of glass and plastic flow models was considered “state of the art.” The Society of Clinical Vascular Surgery, under the direction of Dr. Kim Hodgson, was first to run what were considered cutting-edge, hands-on courses using these models and portable C-arms to teach basic catheter and wire skills. Now considered rudimentary, these models served to educate a generation of vascular trainees. Supplemented by mini-fellowships and device-specific multiday courses, the endovascular transformation of vascular surgery had begun, and these modules all played an important role. Fast-forward 15 years, and one can reasonably ask the question, “Where are we now?” An increased number of devices, more complex devices, shortened resident work hours, and competition from multiple specialties are all factors that confound endovascular training. Endografts represent some of the most complex devices ever developed for the endovascular space, and with the emergence of branched vessels, they also represent significant training challenges. This article addresses the role of simulation for endograft training.
DEFINITION OF MEDICAL SIMULATION
Medical simulation is defined as “a person, device, or set of
conditions that attempts to present (education and) evaluation
problems authentically.” Multiple types of simulator
exist, each with their particular role. The students or trainees
are required to respond to the simulated problems as they
would under natural circumstances. Frequently, the trainees
receive performance feedback as if they were involved in a
real situation.1,2 One elemental question remains: how much
realism is actually necessary? Some of the common characteristics
of most simulation technologies are:
- Cues and consequences that are very close to reality
- Ability to simulate complex situations
- Limitations in technology (eg, the endosimulator's inability to learn, reliability of haptics)
- High costs
- Varying formats that can be either interactive or individualistic, inanimate (ie, anatomical model), or computerbased (ie, endosimulators).
The Agency for Healthcare Research and Quality report from 2007 essentially supports the effectiveness of simulation training “especially for psychomotor skills (eg, procedures) and communication skills.”3 However, this support is limited by data that are weak due to the small number of suitable trials and the lack of quantitative data.
SIMULATION AND AORTIC DISEASE
Interestingly, we now see a move back to the models and
flow circuit-based simulation, albeit in a much more sophisticated
environment compared to the models of 1995. This
has been pioneered by a group of European surgeons working
with the European Society for Vascular Surgery to create
complex models that can be used for both endovascular
training and for practicing and measuring technical capabilities
for open aortic repair (Figure 1). Taught annually in
Pontresina, Switzerland, students under the supervision of senior surgeons practice open aneurysm
repair in a flow model environment. The
European Board of Vascular Surgery has
developed a validated method of testing
vascular surgery skills that is now required
for their board certification.4 No such
program exists in the United States or in
other parts of the world, although fledgling
programs are beginning to quantitate
the value of simulation in training.5,6
Introducing this type of training to the
United States and to the international surgery
community will help to standardize
the workforce, increase the level of expertise
among cardiovascular surgeons, and
potentially shorten the learning curve for
developing these skills. The American
Board of Internal Medicine has developed
Medical Knowledge Modules,
which include interventional cardiology
simulation. This is a pilot program in
which simulation permits the candidate
to accrue points toward maintenance of
certification.
The Pontresina endovascular tower (Figure 2) permits groin puncture and device delivery into flowing glass models under video control (replacing C-arms) in a radiation-free environment. The real advantage of these towers is that actual stent grafts are delivered and deployed, providing the trainee with the tactile feedback associated with delivery of different types of devices. Also, adjustable pulsatile flow gives the model an even greater sense of realism.
One real challenge in the evolution of a true simulation experience for aortic endografts has been the disconnect between simulation companies and the device manufacturers. The device companies have long been uncertain about the real value in simulation and consequently have been reluctant to invest in the development of simulation modules. With fewer cash reserves, the simulation companies have not had the resources or desire to develop these simulated aortic environments alone. Both believe that hospitals should appreciate the potential role of simulation in credentialing and recredentialing. But, to date, no matrices exist by which hospitals can use these expensive simulators to credential, refuse credentialing, or remove credentialing for physicians based on their performance in aortic simulation or in any other endovascular models.
This complex situation of who owns the simulator versus who owns the training module led to a bitter experience for our institution in which we leased and housed the simulator but were denied access to the most recently developed and most exciting modules. This led to a situation in which the standard modules were rapidly used and little additional value in the simulator was perceived. We learned that we needed continuously updated material of increasing complexity with built-in complications.
Consequently, it is only recently that aortic endograft simulation models have evolved. Medtronic, Inc. (Minneapolis, MN) first developed a thoracic simulation environment (Figure 3) in partnership with Medical Simulation Corporation (Denver, CO) for deployment of their Talent endograft. Interestingly, they also developed a dissection module, which would have been of immense value but was unavailable for United States physicians because this was an “off-label” indication for their device.
The absurdity of this is obvious. Module development is dependent on a device company that can only permit use of their module if it is in line with US Food and Drug Administration-approved indications for that device. Consequently, despite the fact that most physicians now believe that stent grafting is the first-line intervention for complicated type B dissections, they were denied access (on regulatory grounds) to the one training system that could have benefited them and such patients.
W. L. Gore & Associates (Flagstaff, AZ) has partnered with Simbionix Ltd. (Cleveland, OH) to develop an abdominal aortic aneurysm simulation platform for the EXCLUDER Device (Figure 4). This was created in conjunction with coauthor Dr. Jean Bismuth. One potential advantage of the Simbionix platform is the ease of performing patient-specific simulation. Computed tomography (CT) scans in DICOM format can be loaded into the simulator to provide a “patient-like” simulation. Why the distinction? Basically, these simulation scenarios are created from a contrastenhanced CT scan, whereas interventionists deploy devices using angiography. Not only do we deploy the devices using real-time angiography, but the device itself deforms the anatomy, and these device-tissue interactions are not yet modeled in simulation scenarios. Consequently, most simulation companies are not yet ready to claim the true fidelity of patient-specific scenarios. This claim may need a clinical trial approved by the US Food and Drug Administration to demonstrate true fidelity before it can be made. Nevertheless, we strongly believe that the capability of simulators to continuously modify the scenarios is an absolute prerequisite to provide value in simulation. The real value is in simulating tomorrow's case today, provided the clinician is not lured into performing the procedure because of its ease of use in a simulation environment.
Although there is clearly a difference between angiographic guidance and CT guidance, those margins are becoming increasingly hard to distinguish. Modern hybrid rooms all permit the acquisition of CT scans using the image detector. Three-dimensional (3D) reconstruction and 3D overlay are increasingly being used as guidance systems (Figure 5). Consequently, the lines of distinction between CT angiography-based simulation and the intraprocedural imaging modality are rapidly being blurred.
Management of complications, especially device-specific complications and unusual clinical scenarios, is yet another mandatory component in simulation evolution. Indeed, rehearsing these seldom-experienced situations could be one of the most important assets of simulation.
METHODIST INSTITUTE FOR
TECHNOLOGY AND EDUCATION
Depending on the ultimate goals of the individual training
center, the infrastructure can clearly vary, but either way,
a significant investment is necessary. Having perceived a
huge void, a significant investment was made in the
Methodist Institute for Technology and Education in
Houston, Texas, which has trained more than 2,500 health
care professionals across 16 different specialties since 2007.
The mission of the training center at the Methodist Hospital
is to serve as an educational resource for practicing health
care professionals seeking to maintain excellent clinical skills
and acquire new ones. Like many other training facilities, it is
intended to improve patient safety through educational pursuits and conduct research on skills acquisition and
technological development. The DeBakey Institute for
Cardiovascular Education and Training has now been developed
to support cardiovascular education, with a focus on
aortic endografting. This will be launched within our extensive
hands-on experience at the upcoming Total
Endovascular Aorta II meeting in March 2011.
CONCLUSION
Given the quickly evolving world of endovascular
therapeutics, it will be necessary for health care professionals
to train on new devices and/or develop new
techniques. Simulation is able to fill the education gap
and likely improve physician confidence and patient
outcomes. Although simulation for aortic endografting
has lagged behind endovascular simulation in general,
simulated environments for percutaneous aortic valves
to thoracic endografts to abdominal aortic endografts
are available. The expansion of simulated cases, the ability
to develop patient-like modules, and the development
of various simulated complications will greatly
increase their utility.
Alan B. Lumsden, MD, is with the Methodist DeBakey Heart& Vascular Center, The Methodist Hospital in Houston, Texas.He has disclosed that he holds no financial interest in any productor manufacturer mentioned herein. Dr. Lumsden may bereached at ablumsden@tmhs.org.
Jean Bismuth, MD, is with the Methodist DeBakey Heart &Vascular Center, The Methodist Hospital in Houston, Texas. Hehas disclosed that he holds no financial interest in any productor manufacturer mentioned herein.
Michael A. Donovan, BS, is with the Methodist DeBakeyHeart & Vascular Center, The Methodist Hospital in Houston,Texas. He has disclosed that he holds no financial interest inany product or manufacturer mentioned herein.
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