Foreword of the TAVI Atlas
Taken from the original PCR Valve Atlas app
Developing TAVI has been a fascinating 20-year-long odyssey with a happy ending. Following in the footsteps of the transcatheter treatment of congenital pulmonic (1979) and congenital aortic (1983) valvular stenosis, and subsequently of mitral valvuloplasty (1984) and aortic valvuloplasty (1985) in adults, TAVI emerged in 2002 to profoundly alter the landscape of cardiovascular medicine. This new "disruptive" technology is among the most important medical breakthroughs to date. It evoked scepticism and criticism in the beginning but, thanks to innumerable clinical trials and evidence-based investigations, it is now widely accepted by the medical community, and this acceptance is continuing to grow.
In the last decade, TAVI has been performed in around 150,000 patients worldwide and its use keeps growing by 40% annually. The field of TAVI is rapidly evolving, with major refinements in technology, procedural techniques, patient selection and biomedical engineering. With the development of better devices, new approaches and new implantation strategies, TAVI has become much simpler and safer. Indications were initially limited to elderly aortic stenosis (AS) patients with multiple comorbidities. These same indications are now cautiously, but appropriately growing to include a broader population of patients with lower surgical risk, degenerated surgical bioprosthesis, and even patients with other valvular diseases such as pure aortic or even mitral insufficiency. There are few examples of clinical fields in medicine that match the rapid and careful evolution of TAVI.
In addition to the noble task of helping patients, TAVI has catalysed a medical culture of dynamic multidisciplinary physician collaboration within the framework of the "Heart Valve Team". This new culture has not only altered the previous way of practising medicine but has also broken down many professional barriers. Cardiologists and interventional cardiologists, cardiac and vascular surgeons, anaesthesiologists, imaging specialists and other specialists, in addition to nurses and technicians, are all involved at one stage or another of the process, in the best interest of the patient's care, whether it be at the stage of patient's screening or procedural completion. The assistance of multimodality imaging in diagnosis, case planning and intraprocedural decision-making has been a key to procedural success and good clinical outcome.
Where are we today, and what is the future of TAVI? Most of our knowledge is founded on the extensive experience acquired with two devices, the balloon-expandable Edwards Sapien 3 device (Edwards Lifesciences, Irvine, CA, USA) and the self-expanding Medtronic CoreValve® prosthesis (Medtronic, Minneapolis, MN, USA), which, outside of USA, have been implanted in equal numbers. FDA approval was obtained for the Edwards device based on the results of the pivotal "Placement of Aortic Transcatheter Valve (PARTNER) Trial", a randomised US trial published in 2011 and 2012 (for non-surgical patients and high-risk patients, respectively) and for the CoreValve device in 2014, after the results of the Extreme Risk Study of the US Pivotal Trial (for non-surgical patients). The CoreValve US Pivotal Trial, which was published early this year, has notably shown the superiority of TAVI over surgery on mortality at one year in high-risk patients. Indications for TAVI were specified in the European and US Guidelines in 2012 and 2014, respectively. Briefly, TAVI can be performed in patients with severe AS without a surgical option, and as an alternative to surgery in high-risk patients in whom TAVI is favoured by the Heart Team based on individual risk profiles and anatomic suitability. Based on these guidelines, TAVI is currently indicated in about 20% of all AS patients, with two-thirds of the patient population being sent for surgery, and the remaining third left with medical treatment.
To my mind, the expansion of clinical indications and the further growth of the procedure can be anticipated in the not too distant future. Advances in four main areas will determine the verity of this prediction: improved safety profile, application in lower-risk patients, assessment of long-term device durability and decreased costs.
Addressing the issue of procedural complications remains a priority. New models of valves, which need smaller size delivery systems, have recently been launched and have already had a favourable impact on the incidence of the two leading and potentially life-threatening complications, paravalvular aortic regurgitation (AR) and vascular complications. It is too early to say that these complications will be non-existent, but these new devices, together with a better appraisal of valve sizing, will markedly decrease their incidence. Strokes, multifactorial in origin, might possibly be improved by embolic protection devices and new anticoagulation strategies which are currently under investigation.
Lower-risk patients and other subsets of patients
An increasing number of lower-risk patients have already been included in many clinical trials. Several studies (Bermuda trial, Switzerland trial, France 2 registry etc.) have clearly shown a better outcome in this subset of patients. The eagerly awaited results of the randomised PARTNER 2 trial (USA) with the Edwards XT valve, and of the SURTAVI trial (EU) with the Medtronic CoreValve will further highlight the evidence-based comparison of TAVR versus surgery in this patient population, with enormous consequences for the future of TAVI. Several hundred patients have already been included in the Valve-In-Valve registry in which TAVI is used for treating degenerated surgical bioprosthesis. TAVI is clinically efficient but valve malpositioning, ostial coronary obstruction and residual stenosis are persistent issues which might be solved by advanced TAVI technologies. New types of valves and devices (JenaValve; JenaValve Technology GmbH, Munich, Germany; Boston Scientific's ACURATE TA™; and the Helio transcatheter aortic dock with the SAPIEN XT valve (Edwards Lifesciences) are currently being investigated for the treatment of pure aortic insufficiency, with promising results. Finally, transcatheter mitral valve replacement has commenced and the first successful human cases already reported.
Assessment of long-term durability of valve cusp and platform
This is still a missing piece of the jigsaw that needs to be further assessed before offering TAVI to younger/lower-risk patients. However, valve deterioration has so far very rarely been reported in this elderly population and we have, in our personal series, seen no case since 2002. As an anecdote, one of our patients has notably seen eight years of follow-up without any change in valvular function. The question of a potentially higher incidence of valvular calcification in younger patients, however, remains.
Device and procedural costs
Device and procedural costs are the main factors impeding a widespread utilisation of TAVI across the world. The amortised costs of R&D, increased sales, concurrent devices and cost-effective procedures are expected to make TAVR more accessible in the near future. In this regard, the "minimalist strategy" for TF-TAVI (local anaesthesia, pre-closing techniques and early patient discharge), an increasingly accepted and safe approach, has been shown to lower the costs due to a shorter length of stay and less resource utilisation. The advent of lower size devices for TAVR should further expand the use of this "stent-like" strategy in the near future. Read more about Devices
As a matter of fact, like many other investigators, I am quite optimistic about the future of TAVI. It is likely that the next 10 years will see this technology become the dominant therapy for aortic stenosis. Is it too far-fetched to speculate that surgical valve replacement will eventually be reserved for patients with contra-indication to TAVI?
For all those like me, who have been passionate observers or actors in the development of transcatheter valve interventions over the last few decades, the latest session of the PCR London Valves Course will certainly be a unique and fascinating event and a great "state-of-the-art" platform. Complementing outstanding didactic sessions, workshops and live demonstration cases, the participants of 2014 was offered this comprehensive Atlas (the PCR Valve Atlas app) which covers all matters related to TAVI. It is prepared for the iPad and is rich in visual illustrations. There is no doubt that this Atlas will be a remarkable asset for everyone, particularly for the intermediate practitioners, young physicians, nurses and technicians as well as all those individuals interested in setting up their own TAVI programmes. They will find in it a wealth of information on the anatomy of the aortic valve complex, the appropriate modalities of imaging, the many currently used valves, delivery systems and accessories, the details of procedures, the prevention and treatment of complications and the role of the Heart Valve Team and nurses.
A wide selection of the PCR Valve Atlas app contents is now available on the website.