Percutaneous transcatheter one-step mechanical aortic disc valve prosthesis implantation: a preliminary feasibility study in swine

How Transcatheter Aortic Valve Implantation (TAVI) Was Born: The Struggle for a New Invention

This story is about the invention of transcatheter aortic valve implantation (TAVI), and the people who transformed it from a concept and primitive device to a breakthrough lifesaving treatment for hundreds of thousands of patients with aortic valve stenosis. It is an inspirational example of a new disruptive technology that began with an idea most dismissed. The story describes the ups and downs from idea, design, construction, animal testing, proof-of-concept, scientific publication hurdles, a patent, license agreement, cooperation with several companies, fighting in patent courts in Europe and USA and finally how multinational companies financially bypassed the inventor. It is also a story about the struggles and battles the inventor experienced when injected into a world of lawyers and patent fights. I hope my personal story and journey can provide an inspiration and word of caution for new inventors.

Reverse endoventricular artificial obturator in tricuspid valve position. Experimental feasibility research study

The concept of vena contracta space reduction in tricuspid valve position was tested in an animal model. Feasibility of specific artificial obturator body (REMOT) fixed to the right ventricular apex and interacting with tricuspid valve leaflets was evaluated in three different animal studies. Catheter-based technique was used in three series of experiment in 7 sheep. First acute study was designed for evaluation if the screwing mode of guide wire anchoring to the right ventricular apex is feasible for the whole REMOT body fixing. Longer study was aimed to evaluate stability of the REMOT body in desired position when fixing the screwing wire on its both ends (to the right ventricular apex and to the skin in the neck area). X-ray methods and various morphological methods were used. The third acute study was intended to the REMOT body deployment without any fixing wire. In all of 7 sheep the REMOT was successfully inserted into the right heart cavities and then fixed to the right ventricular apex area. When the REMOT was left in situ more than 6 months it was stable, induced adhesion to the tricuspid valve leaflet and was associated with a specific cell invasion. Releasing of the REMOT from the guiding tools was also successfully verified. Deployment of the obturator body in the aim to reduce the tricuspid valve orifice is feasible and well tolerated in the short and longer term animal model. Specific cell colonization including neovascularization of the obturator body was observed.

Development of transcatheter aortic valve implantation (TAVI): a 20-year odyssey

The development of transcatheter aortic valve implantation (TAVI) by our group has been a 20-year odyssey. In 1993, postmortem studies validated the concept of intravalvular stenting in calcific aortic stenosis. The first prototypes of balloon-expandable valves were tested in an animal model in 2000. The first-in-man implantation was performed in Rouen in 2002, rapidly followed by two prospective series in compassionate cases in our centre. TAVI took flight in 2004 in the hands of Edwards Lifesciences, with major improvements in devices and approaches. At the same time, the self-expanding CoreValve was launched. Thousands of high-surgical-risk patients were enrolled in feasibility studies, leading to the Conformité Européenne (CE) mark being granted in 2007 for the two devices. A number of postmarketing registries have shown dramatic improvements in procedural and midterm results and decreased complication rates, with more experience and improved technology. The results of the randomized PARTNER study in the USA recently confirmed the important place of TAVI in non-operable and high-surgical-risk patients. To date, more than 50,000 patients have benefited from TAVI worldwide (2300 patients in 33 centres in France in 2011) and the number is consistently increasing. An optimal multidisciplinary collaboration and formally trained experienced physicians are the keys to success. An extension of indications to lower-risk patients might be expected in the coming years but should be cautiously investigated. Ten years after the first-in-man case, TAVI is here to stay and the future is promising.

A new cone-shaped aortic valve prosthesis for orthotopic position: an experimental study in Swine

The aim of this experimental study was to evaluate a newly designed cone-shaped aortic valve prosthesis (CAVP) for one-step transcatheter placement in an orthotopic position. The study was conducted in 15 swine using either the transcarotid (11 animals) or the transfemoral (4 animals) artery approach. A 12- or 13-Fr sheath was inserted via arterial cutdown. The CAVP was deployed under fluoroscopic control and its struts, by design, induced significant native valve insufficiency. CAVP function was evaluated by aortography and aortic pressure curve tracing. In 11 of 15 swine the CAVP was properly deployed and functioned well throughout the scheduled period of 2-3 h. In three swine the CAVPs were placed lower than intended, however, they were functional even in the left ventricular outflow tract position. One swine expired due to inadvertent low CAVP placement that caused both aortic regurgitation and immobilization of the anterior mitral valve leaflet by the valve struts. We conclude that this design of CAVP is relatively easy to deploy, works well throughout a short time period (2-3 h), and, moreover, seems to be reliable even in a lower-than-orthotopic position (e.g., infra-annulary space). Longer-term studies are needed for its further evaluation.

Development and evaluation of a novel artificial catheter-deliverable prosthetic heart valve and method for in vitro testing

BACKGROUND

This work presents a novel artificial prosthetic heart valve designed to be catheter or percutaneously deliverable, and a method for in vitro testing of the device. The device is intended to create superior characteristics in comparison to tissue-based percutaneous valves.

METHODS

The percutaneous heart valve (PhV) was constructed from state-of-the-art polymers, metals and fabrics. It was tested hydrodynamically using a modified left heart simulator (Lhs) and statically using a tensile testing device.

RESULTS

The PhV exhibited a mean transvalvular pressure gradient of less than 15 mmhg and a mean regurgitant fraction of less than 5 percent. It also demonstrated a resistance to migration of up to 6 N and a resistance to crushing of up to 25 N at a diameter of 19 mm. The PhV was crimpable to less than 24 F and was delivered into the operating Lhs via a 24 F catheter.

CONCLUSION

An artificial PhV was designed and optimized, and an in vitro methodology was developed for testing the valve. The artificial PhV compared favorably to existing tissue-based PhVs. The in vitro test methods proved to be reliable and reproducible. The PhV design proved the feasibility of an artificial alternative to tissue based PhVs, which in their traditional open-heart implantable form are known to have limited in vivo durability.

Catheter-based modification of heart valve diseases: from experimental to clinical application

Efforts to modify cardiac valve defects using catheter-based techniques are increasing at the present time. We present observations on cardiac valve morphology and disease and review the progress being made to address valve defects with these innovative methods. Some new procedures developed through animal experimentation have already been put to use in clinical practice, but the newness of these techniques and the small number of cases in which they have been applied to date precludes an evaluation of their long-term durability. Although at the present time cardiac surgery remains the standard for treating most cases of valve disease, in certain situations a catheter-based treatment might provide a reasonable alternative, even if only temporary, especially for individuals with serious disease who are not suitable candidates for surgery.

Percutaneous Technique for Creation of Tricuspid Regurgitation in an Ovine Model

Experimental models of tricuspid regurgitation (TR) are needed to study the percutaneous placement of prosthetic atrioventricular valves. The purpose of this study was to develop an appropriate simple and reproducible percutaneous experimental model for creation of tricuspid regurgitation. Tricuspid regurgitation was successfully created through papillary muscle avulsion using a guide-wire loop in seven sheep with regurgitation documented on right ventricular angiograms and a significant increase in heart rate and right atrial pressures. Acute onset of tricuspid regurgitation was poorly tolerated in one animal that died. Autopsy examinations showed avulsion of one papillary muscle in four animals and two papillary muscles in three animals.