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DMD

2009 Three-in-Five Competition

Tuesday, April 13, 10:30-12:00
Regents, The Radisson Hotel

 

"Design of a Catheter-Based Device for Performing Percutaneous Chordal-Cutting Procedures"

Presented by Alexander H. Slocum, Jr., Massachusetts Institute of Technology, Department of Mechanical Engineering

In this paper we detail the rapid design, fabrication and testing of a percutaneous catheterbased device that is envisioned to enable externally controlled manipulation and cutting of specific chordae tendinae within the heart. The importance of this work is that it (a) provides a means that surgeons may use to alleviate problems associated with some forms of mitral valve regurgitation and (b) demonstrates how a deterministic design process may be used to drive design innovation in medical devices while lowering development cost/time/resources. In the United States alone, approximately 500,000 people develop ischemic or functional MR per year. A chordal cutting procedure and device could allow many patients, who would otherwise be unable to survive open-heart surgery, to undergo a potentially life-saving operation at reduced risk. The design process has enabled us to generate a solution to this problem in a relatively short time. A deterministic design process was used to generate several design concepts and then evaluate and compare each concept based on a set of functional requirements. A final concept to be alpha prototyped was then chosen, optimized, and fabricated. The design process made it possible to make rapid progress during the project and to achieve a device design that worked the first time. This approach is important to medical device design as it reduces engineering effort, cost, and the amount of time spent in iterative design cycles. An overview of the design process will be presented and discussed within the context of a specific case study–the rapid design/fabrication of a chordal cutting device. Experimental results will be used to assess: (i) The performance of the catheter in maneuvering into the heart and grasping various structures. (ii) The effectiveness of the catheter's RF ablation tip at cutting chordae inside of a heart. In the first experiment, the catheter was guided to the basal chordae under direct visualization, which showed that the catheter is capable of successfully grasping a chord. During the second experiment, ultrasound was shown to be a viable method of visualizing the catheter within the heart. During this experiment, once contact between the chord and RF ablator tip was confirmed, the chord was successfully ablated. We will also discuss experiments that are currently underway to visualize the catheter utilizing a Trans-Esophageal Echo probe, as well as imaging the mitral valve from the apex of the heart with a laparoscope so that video of the basal chord being grasped and cut can be acquired on a heart whose anatomical structures are intact. A brief synopsis will then be given of how the design process has been used in research and educational collaborations between MIT and local hospitals.

"A Novel Combination Therapy for Post-Operative Atrial Fibrillation"

Presented by Eric Richardson, Department of Biomedical Engineering, University of Minnesota

Atrial fibrillation (AF) is a common heart rhythm disorder, effecting about 20% of cardiac surgical patients. While often benign, it leads to a prolonged hospital stay, and potentially to malignant arrhythimas. Many anti-arrhythmic drugs have been used to both prevent and treat post-operative AF and other post-operative arrhythmias; however, they have potentially harmful side-effects (e.g., hypotension, pulmonary fibrosis). Cardioversion is often the therapy of last resort to restore a perfusable rhythm. We propose a novel, innovative concept that allows for local pharmacological and electrical therapy of the heart. We have shown in animal models that such delivery increases the efficacy of the therapy and reduces side effects. Several variations of the device have been conceived and prototypes are currently being developed. The simplest version is a multi-port infusion catheter incorporated into a temporary pacing lead. Placement of the device would be trivial for surgeons, who routinely place temporary pacing leads prior to closing the chest. Removal of the device post-operatively would be equally simple. More complex iterations include an expandable wick to maintain the infused drug in a desired location. Designs may also include epicardial defibrillation capabilities, which would lower the energy required for defibrillation. To demonstrate proof of principle, cadaver and animal investigations were performed. In a fresh cadaver, a sternotomy and pericardiotomy was performed. A catheter was placed in the pericardium, and an infusion of radio-opaque contrast was administered under fluoroscopy. The majority of the contrast collected near the pulmonary veins, which are often the origin of atrial arrhythmias. To evaluate the efficacy of drugs administered into the pericardium as compared with drugs administered through the conventional route (intravenously), animal studies in swine were performed. Results demonstrated that pericardially administered metoprolol had a greater and more lasting effect on heart rate than when given intravenously. Additionally, during pericardial delivery myocardial contractility was better preserved. Only trace amounts of metoprolol were found in the circulation. Thus pericardial delivery may enhance certain therapeutic effects of drugs while limiting side effects. Currently, studies are underway to evaluate the efficacy other pharmacologic agents delivered into the pericardium. Should our animal studies continue to show promising results, we anticipate moving into clinical trials. Development and refinement of prototype delivery devices will also continue as we pursue this promising new therapy for post-operative arrhythmias.


"A Wireless Insufflation System for Capsular Endoscopes"

Presented by Jenna L. Toennies, Vanderbilt University

Swallowable capsule-based cameras (e.g., the Given Imaging PillCam and competitors) are rapidly becoming the gold standard for diagnosis in the gastrointestinal (GI) tract. However, definitive diagnosis is still often precluded by the inability to control capsule position and orientation. This has inspired a number of active positioning strategies including augmenting the capsule with legs or other appendages, or incorporating magnets which can apply forces and torques in response to an external magnetic field. Furthermore, the loose, mucous coated, elastic intestine is generally deflated during capsule passage, making it challenging to view the entire internal surface adequately without the insufflation that is relied upon in traditional endoscopy. To address these challenges, we propose a new fluid-powered system that permits insufflation from a wireless capsule platform. This is accomplished by carrying a small reservoir of biocompatible liquid onboard the capsule which vaporizes and expands when released through a small onboard solenoid valve. The internal components of the capsule consist of two 3V Lithium coin cell batteries (VL621, Panasonic, Inc.) which charge 3 Tantalum capacitors (TAJB157M006R, AVX Corporation, Inc.) that fire the solenoid valve (S120, Lee Company, Inc.). In our initial proof-of-concept study, we have packaged all components in a 26 mm long by 11 mm diameter capsule. The fluid used in initial experiments is biocompatible Perfluoropentane, although any of a variety of biocompatible fluids that can be liquefied with light pressurization may be used. Perfluoropentane, developed for lung lavage, is a liquid at room temperature and becomes gaseous at body temperature. We note that pneumatic pressure produced in this way may be used for a variety of objectives, including powering biopsy collection devices or other mechanisms within the capsule, or being vented to inflate the intestine. In initial experiments, we have harnessed the pressure to inflate a balloon at the front of the capsule which can distend tissue and thereby improve image quality. In experimental tests, only 0.2 ml of fluid was consumed in inflating the balloon to sufficient pressure to distend porcine intestine (see http://research.vuse.vanderbilt.edu/MEDLab for images of these experiments). Optimization of the capsule body and electrical components is currently underway. Including a wireless camera, all components are expected to fit within the dimensions of a commercial PillCam.

 

Panel Judges:

Sarah Audet - Medtronic, Inc.
Sarah Audet received her Bachelor of Science degree from the State University of New York at Upstate Medical Center in the area of Medical Technology, Master’s of Science Degree in Electrical Engineering from Boston University, and her PhD in Electrical Engineering from the Technical University of Delft, the Netherlands.

Buzz Benson - Sightline Partners
Buzz Benson is a Managing Director of SightLine Partners LLC, a venture capital firm that invests in emerging growth medical technology companies.  Mr. Benson also serves as a director of several private companies.  

Joe Biller - Sightline Partners
Joe Biller is an Associate at SightLine Partners LLC, a venture capital firm that invests in emerging growth medical technology companies. Joe is a graduate from the University of Wisconsin at Eau Claire and holds the Chartered Financial Analyst designation (CFA).

David Boudreault - Stanford Biodesign, UCSF General Surgeon
David is a general surgery resident at UCSF East Bay and finishing his second year at the Biodesign program at Stanford.  His focus is Emergency Medical Services and Stroke.  He is also the consulting CMO for the latest start-up from The Foundry in Menlo Park.

Doug Johnson, University of Minnesota

Trevor McCaw - Aegis Medical
Trevor McCaw received his MBA from Harvard and is now President of Aegis Medical Innovations.

Tom Savard - St. Jude Medical, Director of R&D
Tom currently directs Technology Development at St. Jude Medical, Cardiovascular Division. He has developed technologies for cardiovascular, diabetes, patient monitoring, automotive, and aerospace applications. He has a BA from St. John’s University and a Ph.D. in physics from Duke University.


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